north american conference on pesticide spray drift management - amazon...

1

Proceedings of the

North American Conference onPesticide Spray Drift Management

March 29 - April 1, 1998Holiday Inn By the Bay

Portland, Maine

Donna Buckley, Editor

Sponsored by theMaine Board of Pesticides Control

and the University of Maine Cooperative ExtensionPest Management Office

2

Published and distributed in furtherance of Acts of Congress of May 8 and June 30, 1914 by the University of Maine CooperativeExtension,the Land Grant University of the State of Maine and the United States Department of Agriculture cooperating. Coop-erative Extension and other agencies of the USDA provide equal opportunities in programs and employment.

To carry out a project of this size, both the conference itself and the proceedings, is no smalltask and many people have to help to make it a success. I want to thank all the speakers for their timeand effort in making this conference so successful. I also want to thank our moderators, scribes, andhotel staff. Finally, of course, accolades go to the above list of sponsors/committee members. Iespecially want to thank Donna Buckley and Don Barry for their months of time spent in gettingthese proceedings ready. Thanks Maine Board of Pesticides Control. Thanks UMCE Pest Manage-ment Office! James F. Dill

Pest Management Specialist

Acknowledgements

Sponsored byMaine Board of Pesticides Control (MBPC)University of Maine Cooperative Extension

Pest Management Office (UMCE)

Committee Members

Don Barry, UMCE Paul Gregory, MBPCRobert Batteese, MBPC Tammy Gould, MBPCDonna Buckley, UMCE Henry Jennings, MBPCJames Dill, UMCE Clay Kirby, UMCEGary Fish, MBPC Jennifer Paul, MBPC

3

Dedication

Dean began working for us in December 1990 working as Enforcement Specialist and Coor-dinator of Field Activities, which he continued until his death. Specifically, he handled the day-to-day management of field activities, tracked inspections & investigations and carried out any result-ing enforcement actions. While Dean came to us with very little pesticide related experience he wasa natural fit for the position. He learned the pesticide program quickly and his abilities helped usdevelop a better program. His quiet, calm, but firm demeanor was especially valuable in dealing withthose involved in enforcement cases and handling tense situations our field staff encountered. Deanwas an extemely organized, intelligent, adaptable and likable person. He was respected by everyoneand is missed by all. Our loss is great but we continue by following his example.

Dean RadabaughSouth Dakota Department of Agriculture

Pierre, South Dakota

DDDDDean Radabaugh, 67, Pierre, died of a massive coronary Monday, March 30, 1998,in Portland, Maine. Visitation will be from 3 to 9 p.m. Friday with a 7 p.m. prayerservice at Feigum Funeral Home. His funeral service will be at 10 a.m. Saturday atSt.. Peter & Paul Catholic Church in Pierre with Father Darrell Lamberty officiating.Interment will be at 3:30 p.m. Saturday at Fulton. Dean Vinton Radabaugh was bornFeb. 15, 1931, in Mitchell to Charles Vinton and Marjorie (Dowdell) Radabaugh. Hegrew up on the family farm near Fulton. He attended rural school and graduatedfrom Fulton High School in 1949. In 1953 he graduated from South Dakota StateCollege with a bachelor’s degree in animal husbandry. He enlisted in the U.S. Armyand served in Japan. After his discharge he worked for the Extension Service inDavison County. On June 11, 1956, he married Arlene June Sullivan in Mitchell.They returned to SDSC where Dean earned his master’s degree in 1958. He joinedZip Feed Mills and worked for 31 years as vice president of animal nutrition. In 1991they moved to Pierre where he worked for the South Dakota Department of Agricul-ture in regulatory service until his death. He was a member of Alpha Zeta, a CubScouts leader, and a Boy Scout Master for Troop 45 in Sioux Falls. He was activewith the Sioux Falls Farm Show for many years and was its chairman for one year.He was an Honorary Pork Producer and served on the board of the agriculturecommittee of the Sioux Falls Chamber of Commerce and as Grand Knight of theKnights of Columbus Council in Sioux Falls. He was active with the Fourth DegreeKnights of Columbus in Sioux Falls and Pierre. He served as president of the SiouxFalls Exchange Club, as king of Mardi Gras in Sioux Falls, and as a member of St..Peter & Paul Catholic Church in Pierre where he was rector and communion minis-ter. Survivors include his wife Arlene; four sons, Michael Radabaugh and his wifeGwen of Metairie, La., Charles Radabaugh and his wife Kathy of Wichita, Kan., JohnRadabaugh and his fiancee Kristi of Sioux Falls, and Steven Radabaugh, a studentat South Dakota School of Mines and Technology in Rapid City; three daughtersand their husbands, Laura and Don Elliott of Sioux Falls, Linda and Craig Elsen ofEagan, Minn., and Julie and LeRon Ellis of Sioux Falls; 13 grandchildren, and twosisters, Aruta Dutt and her husband Harry of Bakersfield, Calif., and Jane DeWaldand her husband Les of Fulton.

He was preceded in death by his parents and a brother, Robert.

4

Table of Contents

Program Agenda ................................................................................................................................. 6

Speaker Profiles ................................................................................................................................ 10

Poster Abstracts ................................................................................................................................ 15

Computer Modeling ......................................................................................................................... 25 David Esterly

Practical Applications of G.P.S. Technology: Differential GPS Spray Aircraft Guidance ...... 31 Harold W. Thistle, Jr., Anthony Jasumback, William Kilroy

Pesticide Drift and Organic Certification ...................................................................................... 39 Miles McEvoy

Legal Liability Issues - Liability of Public Employees .................................................................. 45 Theodore A. Feitshans

Case Studies on Controversial Drift Problems .............................................................................. 51 Jay Ellenberger

Drift Laws .......................................................................................................................................... 57 Theodore A. Feitshans

Weather Effects on Drift - Meteorological Factors and Spray Drift: An Overview .................. 64 Harold W. Thistle, Jr., Milton E. Teske, Richard C. Reardon

The Importance of Nozzle Selection and Droplet Size Control in Spray Application ............... 75 Andrew J. Hewitt

Concurrent Sessions: Application Equipment & Drift

Aerial - Fixed Wing Application and Drift ................................................................................ 86 Dennis R. Gardisser Managing Spray Drift from Aerial Fixed-Wing Applications ................................................. 88 I. W. Kirk Aerial-Rotary Application Equipment and Drift .................................................................... 101 David L. Valcore, Milton E. Teske Air-Blast/Air-Assisted Application Equipment and Drift ...................................................... 108 Robert D. Fox, Richard C. Derksen, Ross D. Brazee Boom Application Equipment and Drift .................................................................................. 130 Robert E. Wolf High Volume Sprayers for Treating Trees: Managing Drift and Exposure ......................... 146 Bruce R. Fraedrich

5

Drift Happens: A National Public Interest Perspective ............................................................. 153 Norma Grier

Risk Perception and Communication ........................................................................................... 161 Vincent T. Covello

Chemistry and Drift Management: A Biologist’s Perspective .................................................. 187 Roger A. Downer, Franklin R. Hall

Changing Pilot Behavior ................................................................................................................ 196 Niels C. Andrews

Summary of Research in Ohio including the Laboratory for Pest Control ApplicationTechnology (LPCAT) ..................................................................................................................... 200 Robert D. Fox, Frank R. Hall, H. Erdal Ozkan, Roger A. Downer, Richard C. Derksen, Charles R. Krause, Michael G. Klein, Ross D. Brazee

Reducing Drift from Air Assisted Sprayers Using Timing Targeting and Towers .................. 221 Gary R. Van Ee

Insurance Issues .............................................................................................................................. 224 Mike Kelly

The Measurement and Prediction of Spray Drift - Work at the Silsoe Research Institute ..... 229 Paul S. Miller

Summary of Small Group Concurrent Sessions: Developing Drift Management Practices

Aerial-Fixed Wing ...................................................................................................................... 245 Aerial-Rotary Application Equipment & Drift ....................................................................... 250 Airblast/Air-Assisted Application Equipment & Drift ........................................................... 252 Boom Application Equipment and Drift .................................................................................. 254 High Volume Sprayers for Treating Trees: Managing Drift and Exposure ......................... 256

Summary of Spray Drift Task Force Pesticide Registration Work ........................................... 259 David Johnson

A Summary of Spray Drift Research in Canada ......................................................................... 260 Christopher M. Riley

Update from Spray Drift Coalition ............................................................................................... 266 Paul Kindinger

List of Attendees ............................................................................................................................. 268

6

Saturday, March 28

3:00 - 7:00 Registration

Sunday, March 29


11:30 - 1:15 Lunch and Keynote AddressThe Honorable John E. Baldacci, Member of the House Agriculture and Small BusinessCommittees, United States House of Representatives

1:25 - 1:30 Moderator Call to Order and Announcements

1:30 - 2:00 Introduction & Purpose, 1984 Conference RevisitedJohn Impson, Cooperative State Research, Education & Extension Service (CSREES),USDAJay Ellenberger, Associate Director, Field & External Affairs Division, Office of PesticidePrograms, US EPAJames Dill, University of Maine Cooperative ExtensionThomas Saviello, Chair, Maine Board of Pesticides Control

2:00 - 3:00 Computer ModelingDavid Esterly, Spray Drift Task Force

3:00 - 3:45 Practical Applications of G.P.S. TechnologyHarold W. Thistle, Jr., Ph.D., Missoula Technology and Development Center, USDA-ForestService

3:45 - 4:15 Break/Visit Posters and Displays

4:15 - 5:00 Pesticide Drift and Organic CertificationMiles McEvoy, Organic Program Manager, Washington State Department of Agriculture

6:00 - 9:00 Mixer and Hors d’Oeuvres at the Portland Museum of Art

Monday, March 30

7:00 - 7:55 Continental Breakfast



8:00 - 8:45 Legal Liability IssuesTheodore A. Feitshans, J.D., Extension Specialist and Lecturer, North Carolina StateUniversity, Department of Agricultural & Resource Economics

Program Agenda

7

8:45 - 9:30 Case Studies on Controversial Drift Problems and EPA’s Goals on DriftReductionJay Ellenberger, Associate Director, Field & External Affairs Division, Office of PesticidePrograms, US EPA

9:30 - 10:15 Drift LawsTheodore A. Feitshans, J.D., Extension Specialist and Lecturer, North Carolina StateUniversity, Department of Agricultural & Resource Economics


10:45 - 11:30 Weather Effects on DriftHarold W. Thistle, Jr., Ph.D., Missoula Technology and Development Center, USDA-ForestService

11:30 - 12:15 The Importance of Nozzle Selection and Droplet Size Control in SprayApplicationDr. Andrew J. Hewitt, Spray Drift Task Force/Stewart Agricultural Research Services

12:15 - 1:30 Lunch/Visit Posters and Displays

1:30 - 2:45 Five Concurrent Sessions: Application Equipment and Drift

Aerial-Fixed Wing Application Equipment and DriftDennis Gardisser, Extension Ag Engineer, University of Arkansas

Aerial-Rotary Application Equipment and DriftDavid L. Valcore, Dow AgroSciences

Airblast/Air-Assisted Application Equipment and DriftRobert D. Fox, Agricultural Engineer, USDA-ARS

Boom Application Equipment and DriftDr. Robert E. Wolf, Extension Specialist, Agricultural Engineering Department,University of Illinois

High Volume Sprayers for Treating Trees: Managing Drift and ExposureDr. Bruce R. Fraedrich, VP Research, Bartlett Tree Research Laboratories.



3:15 - 4:15 Drift Happens: A National Public Interest PerspectiveNorma Grier, Executive Director, Northwest Coalition for Alternatives to Pesticides

4:15 - 5:30 Risk Perception and CommunicationVincent T. Covello, Ph.D., Director, Center for Risk Communication

6:00 - 9:00 Optional Bus Trip to Freeport and L.L. Bean

8

Tuesday, March 31



8:00 - 8:45 Chemistry and Drift Management: A Biologist’s Perspective,Roger Downer, Research Associate, Ohio State University

8:45 - 9:30 Changing Pilot Behavior,Niels C. Andrews, Chairman, Aerial Application Committee, Helicopter Association Interna-tional and PAASS Program Technical Advisor

9:30 - 10:30 Summary of Research in Ohio including the Laboratory for Pest ControlApplication Technology (LPCAT),Robert D. Fox, Agricultural Engineer, USDA-ARS


11:00 - 11:30 Reducing Drift from Air Assisted Sprayers Using Timing, Targeting andTowers,Gary R. Van Ee, Professor, Agricultural Engineering Dept., Michigan State University

11:30 - 12:15 Insurance Issues,Mike Kelly, Farmland Insurance, Des Moines, Iowa

12:15 - 1:25 Lunch/Visit Posters and Displays


1:30 - 2:30 The Measurement and Prediction of Spray Drift - Work at the SilsoeResearch Institute,Professor Paul Miller, Silsoe Research Institute

2:30 - 5:00 Small Group Concurrent Sessions: Developing Drift ManagementPractices

Aerial-Fixed WingDennis Gardisser, Extension Ag Engineer, University of Arkansas

Aerial-Rotary Application Equipment and DriftDavid L. Valcore, Dow AgroSciences

Airblast/Air-assistedRobert D. Fox, Agricultural Engineer, USDA-ARS

Boom SprayersDr. Robert E. Wolf, Extension Specialist, Agricultural Engineering Department,University of Illinois

Handheld-Powered,Dr. Bruce R. Fraedrich, VP Research, Bartlett Tree Research Laboratories

5:15 - 6:15 Social Hour/Visit Posters and Displays

9

Wednesday, April 1



7:45 - 9:00 Summary of Spray Drift Task Force Pesticide Registration WorkDavid Johnson, Stewart Agricultural Research Services, Inc. and Spray Drift Task Force

9:00 - 10:00 A Summary of Spray Drift Research in CanadaChristopher M. Riley, Manager Spray Technology, New Brunswick Research andProductivity Council

10:00 - 10:30 Break

10:30 - 11:30 Update from Spray Drift CoalitionPaul Kindinger, President/CEO, Agricultural Retailers Association & Co-Chair, NationalCoalition to Minimize Spray Drift

11:30 - 12:45 Small Group Reports (15 minutes each)

12:45 - 1:00 Wrap-up

1:30 - 4:30 Optional Bus Trip to Freeport and L.L. Bean

10

Speaker Profiles

Niels C. AndrewsNiels Andrews has been involved with aerial application in the Salinas Valley of California for over

twenty-five years. He has worked extensively with drift and urban encroachment issues on a regional, stateand national level. Mr. Andrews has served a President of the National Agricultural Research and EducationFoundation and currently sits on their Board of Directors. Mr. Andrews is also the principal architect ofPAASS - Professional Aerial Applicators Support System - a program that approaches accident and incidentsin aerial application from the human error perspective as a partnership approach involving the entire industry.

The Honorable John E. BaldacciRepresentative Baldacci serves Maine’s Second District— the largest Congressional district east of

the Mississippi River. He sits on the House Agriculture Committee and Small Business Committee where hehas lent support to programs which benefit growers, environmentalists and business people. Among these isthe Environmental Quality Incentives Program which, on a voluntary basis, assists farmers and ranchers whowish to preserve watersheds. Representative Baldacci was also instrumental in the establishment of U.S.D.A.Wildlife Habitat Incentives Program which helps landowners protect ecosystems on private property, and thecreation of U.S.D.A. forums for fostering dialogue between farmers and federal officials.

Prior to his election to congress in 1994, Representative Baldacci served the Maine State Senate.

Vincent T. Covello, Ph.D.Dr. Vincent T. Covello is a nationally and internationally recognized expert in risk communications:

the art and science of communicating effectively in high concern/low trust situations. He is currently servingas Director of the Center for Risk Communication in New York City.

Over the past twenty-five years, Dr. Covello has held numerous positions in academia and govern-ment, including Associate Professor of Environmental Sciences and Clinical Medicine at Columbia Univer-sity. Prior to his joining the faculty at Columbia, Dr. Covello was a senior scientist at the White HouseCouncil on Environmental Quality in Washington, D.C., a Study Director at the National Research Council/National Academy of Sciences in Washington, D.C., Director of the Risk Assessment Program at the Na-tional Science Foundation, and a professor at Brown University.

James F. Dill, Ph.D.Dr. Dill is a Maine native, receiving both his B.S. and M.S. from the University of Maine. He

received his Ph.D. in entomology from Purdue University through the guidance of Dr. John Osmun in 1979.Dr. Dill is currently the Pest Management Specialist with the University of Maine Cooperative

Extension. His responsibilities include Pesticide Applicator Training and Integrated Pest Management. Hewas an Operation Safe certified technician and has conducted some drift studies in Maine under the guidanceof Norm Akesson. Previously, Jim worked at Rutgers University.

Roger DownerRoger Downer was born and raised in southern England. His interest in pesticide application was

generated during his 20 years with ICI Agrochemicals (now Zeneca) where he was employed primarily as anentomologist but with a significant input and interest in pesticide application. In the early 1980’s the develop-ment of ICI’s electrostatic sprayer took Roger to many parts of the world, including Asia, Africa and theUSA, carrying out development field trials primarily against the cotton pest complex. In 1989 Roger joinedthe team working at the Laboratory for Pest Control Application Technology at The Ohio State Universitywhere he has been involved in a wide range of projects involving many aspects of pesticide applicationincluding the Impact of Drift Management Adjuvants on Spray Delivery.

11

Jay EllenbergerMr. Ellenberger is the Associate Director, Field and External Affairs Division of U.S. EPA’s Office

of Pesticide Programs and the program lead for pesticide spray drift. As such, he is responsible for regulatoryoversight of EPA’s spray drift activities, including working with the industry Spray Drift Task Force, theCoalition on Drift Minimization, and labeling and communication initiatives. Mr. Ellenberger also hasexperience with and current responsibilities for a diversity of national and international pesticide regulatory programs.

David M. EsterlyDave Esterly is a Senior Research Engineer, Global Technology with DuPont Agricultural Products.

Mr. Esterly joined DuPont as a research engineer in 1974 at the Chambers Works Site in New Jersey and hasheld numerous positions since then, ranging from plant design, construction and operation.

In 1982, Mr. Esterly transferred to DuPont Agricultural Products Department where he has heldassignments in plant design, venture qualification and application technology. Mr. Esterly joined the SprayDrift Task Force in 1990 to assist in the study of atomization and spray systems. This activity lead to theChairmanship of the Modeling Subcommittee.

In 1992 Mr. Esterly transferred to the Environmental Fate working group to provide environmentalfate modeling for new product registrations.

Theodore A. (Ted) Feitshans, J.D.Ted Feitshans graduated from Georgetown University Law Center, cum laude, in 1986. He also holds

a master’s degree in agricultural economics from the University of Minnesota and a bachelor’s degree inanimal science from Cornell University. He is a member of the North Carolina and New York bars. Mr.Feitshans teaches two undergraduate law courses - Agricultural Law and Environmental Law and EconomicPolicy - and conducts an extension education program on various legal issues in agriculture and the environment.

Before beginning his legal career, Mr. Feitshans served as an economist with the federal governmentin Washington, D.C. Serving first at the Department of Agriculture, Mr. Feitshans worked on many commod-ity support and conservation programs. Mr. Feitshans’ federal service also included service with the U.S.Patent and Trade Office where he developed means for measuring the impact of automation on the agency’s procedures.

Robert D. FoxDr. Fox is a graduate of Michigan State University with a degree in Agricultural Engineering. He

joined the USDA/Agricultural Research Service, Application Technology Research Unit at Wooster, Ohio in1968 and is still there. Research areas include: micro-meteorology, turbulent transport of spray droplets,airjets/airblast sprayers, and drift from orchard sprayers.

When asked what he would like to accomplish while in Maine, Dr. Fox replied, “I would like toprovide useful information on orchard/nursery crop spraying and to share and learn techniques to reduce driftwhile spraying orchards.”

Dr. Bruce R. FraedrichDr. Bruce Fraedrich is Vice President of Research and a plant pathologist at Bartlett Tree Research Laborato-ries in Charlotte, North Carolina. Dr. Fraedrich has been involved with research and extension responsibilitiesin shade tree disease management and general arboriculture with emphasis on fertilization, pruning, treegrowth regulators, hazardous tree evaluation and management, and computerized tree management plans.

The F.A. Bartlett Tree Expert Co. is a commercial arboriculture firm involved with tree care and utility lineclearance. Founded in 1907, Bartlett now operates in approximately 25 states in the Eastern United States,Midwest and California with the corporate headquarters in Stamford, Connecticut. The Bartlett Tree ResearchLaboratories is the technical support branch for the Bartlett Company located in Charlotte, North Carolina.

12

Dennis Gardisser, Ph.D., P.E.Dr. Gardisser has worked for the University of Arkansas Cooperative Extension Service since 1982

and is currently an Extension Agricultural Engineer, Power and Machinery Specialist. His primary emphasisareas are agricultural chemical applications (pesticides and plant nutrients - aerial and ground), processing(grain storage, drying and handling), precision agriculture GIS/GPS, and agricultural fencing systems. Dr.Gardisser is also president of WRK of Arkansas and responsible for agricultural chemical application re-search, testing, product development, drift evaluations, training seminars, fly-in clinics, literature develop-ment and education.

When asked what he would like to accomplish while in Maine, Dr. Gardisser replied: “Convey thatdrift is manageable! with proper training and decision making.”

Norma GrierNorma Grier is the Executive Director of the Northwest Coalition for Alternative to Pesticides

(NCAP), a position she had held since 1983. Norma was active in one of the rural community groups thatfounded NCAP in 1977.

NCAP is a multi-state grassroots organization that promotes sustainable resource management,prevention of pest problems, use of alternatives to pesticides, and the right to be free of pesticide exposure.

Dr. Andrew J. HewittDr. Hewitt graduated in England with B.S., M.S. and Ph.D. degrees in aerial and ground pesticide

application technology/spray droplet size research. His spray research employment has been equally dividedbetween industry and academia in the U.S., Europe, Central America and Africa. he has been working for theSpray Drift Task Force (SDTF) for the past four years, at Stewart Agricultural Research Services, Missouri,where his major responsibilities include atomization studies, data analysis, report preparation and co-ordina-tion/facilitation of SDTF Technical Committee activities. Dr. Hewitt is Chairman of the Institute for LiquidAtomization and Spray Systems (LASS) Agricultural Sprays Committee and serves on the Board of Directorsof ILASS-Americas. Dr. Hewitt is on the editorial board of the journal, Atomization and Sprays. He alsoleads the American Society for Testing and Materials (ASTM) sub-group on laser diffraction techniqueswithin ASTM Committee E29.04.

John W. ImpsonDr. Impson is the National Program Leader; Health, Environmental and Pesticide Safety Education,

USDA Cooperative State Research, Education and Extension Service (CSREES) in Washington D.C. Hereceived his Ph.D. in Entomology from Louisiana State University. In 1967 he joined the staff of the L.S.U.Cooperative Extension Service as the Pesticide Coordinator and was instrumental in the state’s developmentof the first PAT program. He also served on the national committee that developed the first private applicatortraining program.

From 1980 to 1991 he served as State Entomologist and Assistant Commissioner of Agriculture withthe Louisiana Department of Agriculture and Forestry. In this position, he was responsible for regulatoryprograms involving Pesticides, Fertilizer, Feed, Seed, and Horticulture and Quarantine programs. Prior to hismove to Washington in 1992, he worked for the Texas Water Commission as manager of agricultural pro-grams. As manager, he was responsible for the development of regulatory initiatives resulting from agricul-tural impacts of nutrients, animal waste and pesticides on ground and surface water.

13

David JohnsonDr. Johnson holds graduate degrees in soils from Iowa State University and crop physiology from the

University of Guelph. He spent seven years at the University of Missouri with responsibilities for teachingand research in soybean physiology and production. In 1977, he joined Stewart Agricultural ResearchServices, Inc., a field research and management company in northeast Missouri. After thirteen years ofconducting and managing efficacy and registration studies for agricultural chemical companies, he becamethe Project Manager for the Spray Drift Task Force. He was responsible for coordinating all Task Forceactivities, acting as Study Director for all studies, directly supervising the conduct of the field studies, andwriting reports.

Mike KellyMike Kelly is an agronomist for Farmland Insurance of Des Moines, Iowa. Previously, he has worked

as a crop management specialist for Farmland Industries of New Sharon, Iowa. Mike also is a member of theNational Coalition for Drift Minimization.

Paul E. KindingerPaul E. Kindinger has served as President/CEO of the Agricultural Retailers Association (ARA) since

January 1993. He was raised on a farm in Michigan and holds a doctorate in agricultural economics fromCornell University. He was Director of Agriculture for the State of Michigan from 1983 to 1989 until beingnamed Director of Public Affairs and Special Assistant to the Secretary at USDA from 1989 to 1991. Justprior to joining ARA, Kindinger was a lobbyist and governmental relations advisor specializing in agricul-tural and environmental issues for the California- and Washington-based firm of Kahn, Soares & Conway.Kindinger has and continues to serve on many state, regional and national boards and committees dealingwith agricultural and related issues.

Miles McEvoyMiles McEvoy received a BA/BS from Evergreen State College in 1985 and a MS in Entomology

from Cornell University in 1988. Since 1988 he has been working with the Washington State Department ofAgriculture’s Organic Food Program which establishes organic standards and certifies over 400 growers,processors and handlers of organic food. Mr. McEvoy works with state and private organic certificationagencies to establish common standards for the organic food industry.

Professor Paul MillerProfessor Paul Miller leads the Chemical Application Group at Silsoe Research Institute - a group

that is involved with many aspects of agricultural chemical application including the management of spraydrift from boom and air-assisted sprayers, nozzle performance, dose control and patch spraying.

Professor Miller is an agricultural engineering graduate and a visiting Professor of Cranfield Univer-sity in the UK. He has been working with agricultural pesticide application since 1984 and has a wide experi-ence of both research approaches and the link to commercial development.

Christopher M. RileyChris Riley is Manager of Spray Technology with RPC, a non-government contract research organi-

zation based in Fredericton, New Brunswick. He is a graduate of Cranfield Institute of Technology and hasworked extensively with aircraft and the application of silvicultural pesticides. Over that last sixteen yearsMr. Riley has evaluated drift from over two hundred experimental and operational spray applications and hasworked with Canadian regulatory agencies and the U.S. Spray Drift Task Force.

14

Thomas B. Saviello, Ph.D.Dr. Saviello began his professional career as a research forester in 1978 for International Paper. In

that position he carried out research for the effective use of pesticides in forestry and established the herbi-cide program presently being used by International Paper in Maine. In 1991 he moved to IP’s AndroscogginMill in Jay, Maine as Superintendent, Environmental Services.

Dr. Saviello was appointed to the Maine Board of Pesticides Control in 1983 and has served aschairman since 1990. During Dr. Saviello’s tenure with the Board, he has been involved with the adoption ofMaine’s spray drift regulations (1987).

Harold W. Thistle, Jr., Ph.D.Dr. Thistle is an engineer and program leader at the USDA Forest Service Missoula Technology and

Development Center in Missoula, Montana. He is also a certified consulting meteorologist by the AmericanMeteorological Society.

Dr. Thistle received his Ph.D. in 1988 from the University of Connecticut in Plant Science with aspecialization in Forest Meteorology.

David L. ValcoreDavid Valcore works as a Senior Scientist with DowAgroSciences, Packaging and Delivery Systems

Engineering Lab in Indianapolis, Indiana. Mr. Valcore serves as Co-Chair of the National Coalition on DriftMinimization and as Chairman of the Atomization Subcommittee of the Spray Drift Task Force. He is amember of ILASS and is active on ASAE standard development for Spray Drop Size Quality. Since 1989,Mr. Valcore’s project areas have included spray drift studies, chemigation, closed transfer, in-line injection,spray droplet sizing and DowElanco Spray Drift Model development.

Gary R. Van EeGary Van Ee grew up on an Iowa farm and obtained his B.S., M.S. and Ph.D. from Iowa State

University. Since 1980, he has held a teaching and research appointment with the Agricultural EngineeringDepartment of Michigan State University in East Lansing. His primary areas of teaching are engineeringdesign and fluid power hydraulics; of research, fruit and vegetable mechanization and air assisted spraying.

Previously, Professor Van Ee also worked for Iowa State University, John Deere and USDA-ARS.

Robert E. Wolf

Dr. Robert E. Wolf is an Extension Specialist in the Agricultural Engineering Department, Universityof Illinois in Urbana. Dr. Wolf splits responsibilities in extension, research, and teaching in the area ofchemical application equipment. His major responsibility is with developing training materials and trainingcommercial operators and applicators for certification to apply pesticides in the state.

Dr. Wolf is concentrating his efforts in areas of application and calibration, drift control, electronics,and safety for both the agricultural ground and aerial applicators and turf industries. He has prepared severalvideos, has helped write several pesticide training manuals, and is involved with the development of com-puter training modules for pesticide applicators.

15

Title: 1994 - 1996 Airborne Spray Drift Results

Author and Address:Brian StorozynskyAlberta Farm Machinery Research Centre3000 College DriveLethbridge, Alberta T1K 1L6

Abstract: Field trials were conducted to measure airborne spray drift from conventional and highspeed, high clearance sprayers. The conventional sprayer was tested with shrouds using extendedrange 80 degree 015 nozzle tips. The high clearance sprayer was tested using extended range, wideangle and low drift 110 degree 02 nozzle tips. In addition, an air assisted spraying accessory wasinstalled and tested on each sprayer. The shrouds reduced off-target spray drift by 50 to 80%. In 12mph crosswind, airborne spray drift from a high clearance sprayer using extended range, wide angleand low drift nozzles was 15, 8 and 8%, respectively. The air assisted system on the conventionalsprayer had minimal effectiveness. The air system on the high clearance sprayer had adverse effects,increasing spray drift by 5%. Airborne spray drift levels were high spraying at 20 mph and 24 inchesabove the target when compared to conventional spraying.

Submitted by:Brian StorozynskyAlberta Farm Machinery Research Centre3000 College DriveLethbridge, Alberta T1K 1L6E-mail: [email protected]

Poster Abstracts(alphabetically)

16

Title: A Compulsory Sprayer Inspection to Improve Overall Spray Results and Reduce Drift

Author and Address:J. LangenakensMinistry of Small EnterprisesTraders and AgricultureAgricultural Research CentreGhent, Belgium.

Abstract: Back in 1995 the Belgian government decided by Ministerial Decree to establish a compul-sory inspection for all sprayers to improve their general condition. The inspection was set up in firstinstance to inform, educate and advise farmers about their own sprayer and about spray applicationtechniques. Through the latter application errors, e.g. excessive spray pressures or a too large a dis-tance between nozzles and spray object, are corrected.

Since the inspection is compulsory, all users of sprayers, farmers as well as others, are contacted andmade aware of the need to improve their sprayer and sprayer technique. This compulsory sprayerinspection is one of the actions taken by the Belgian government in their battle to reduce the use ofpesticides and hence pollution of the environment through drift or other losses of pesticides.

After two years of inspection the system seems to lead to positive results. The agricultural world hasrealized that besides the pesticides proper, the application technique has a major influence on sprayingresults and on environmental pollution. A tenfold increase in the application of drift-reducing factorshas been observed after analyzing sales statistics. These factors concern mainly a better nozzle selec-tion and other systems such as air assistance.

Water samples taken in the past year from watercourses have shown for the first time a status quo in theamounts of pesticides after many years of consecutive increases in pesticide concentrations. This fa-vorable trend can possibly be attributed to actions associated with the compulsory inspection of spray-ers.

Submitted by:J. LANGENAKENSResearch Station of Agricultural EngineeringVan Gansberghelaan 115,B-9820 Merelbeke, BelgiumFax.: +32 9 252 42 34

17

Title: Controlling Pesticide Drift Using Conservation Easements

Authors and Addresses:Joseph K. Sowers, Research AssistantL. Leon Geyer, ProfessorDept. of Agricultural and Applied EconomicsVirginia Polytechnic Institute and State University

Abstract: Pesticide usage in high intensity agriculture is unavoidable considering current productionlevels necessary for profitable agribusiness. The pesticide drift which results from these operationscauses conflict with environmental interests as well as neighboring land holders who suffer from thisexternality of the agricultural industry. One method of shaping land use in areas of problematic drift,such as adjacent to streams or proximal to residential/urban areas, is the conservation easement. Thisland policy tool entails placing a deed restriction on a parcel of land, restricting usage to low intensityagriculture or other low impact use. Creating buffer zones has been an effective method to diminishproblematic pesticide drift, yet economically infeasible due to loss of profitability on land parcelsunder scrutiny. Conditions exist which make use of conservation easements to control land-use eco-nomically feasible. The restriction placed on the land deed represents diminishment of land value. Inperforming a conservation easement, this value is donated to a non-profit organization which monitorsthe land use. The value is then deducted from the income taxes of the land-owner, amortized over 6years. These tax-savings can then be carefully invested, diminishing economic loss due to the landrestriction.

Submitted by:Joseph Sowers420 N Main AvenueBlacksburg, VA 24060Tel: 540.961.1463E-mail: [email protected]

18

Title: Estimating the Potential Exposure of Ponds to Spray Drift Using Satellite Imaging Data

Authors and Addresses:Waller, Martin E. J. (1)Travis, Kim Z. (1)Holmes, Chris (2)

(1) Zeneca Agrochemicals, Jealott’s Hill Research Station, Bracknell, Berks., RG42 6ET UK

(2) Compliance Services International, 1112 Alexander Avenue, Tacoma, WA 98451-4102

Abstract: Integrating remote-sensing data, for example satellite imaging, into environmental expo-sure and risk assessments is a great challenge of today. The ability to obtain detailed remote-sensingdata is growing fast and already outstrips our ability to make good use of it. Thisposter uses the example of potential spray drift exposure to ponds and lakes and shows one option forhow remote sensing data can be used to provide more refined potential exposure estimates. 30m reso-lution land-use data around ponds and lakes in Yazoo County, MS, was captured in a geographicalinformation system (GIS). The potential spray drift from aerial application of pesticides to crops wasbased on the AgDRIFT model written by the Spray Drift Task Force. For each of eight wind directions,potential drift from each pixel of crop onto each pixel of pond/lake was estimated. Results from thisanalysis include:

- variation in potential drift deposition across the pond- total potential drift deposition- effect of wind direction on potential drift deposition- potential drift reducing effect of trees around the pond.

Submitted by:Martin E. J. WallerZeneca AgrochemicalsJealott’s Hill Research StationBracknellBerkshireRG42 6ETUKTel: +44 1344 414629 (UK)Fax: +44 1344 413688E-mail: [email protected]

19

Title: Evaluation of Spray Drift From Three Insecticide Sprayers Commonly Used in Production ofLowbush Blueberry in Maine.

Authors and Addresses:F.A. Drummond and J.A. CollinsDepartment of Biological Sciences, Entomology Program, University of Maine, Orono, Maine, USA04469

Abstract: In 1996 and 1997 we evaluated the relative spray coverage, crop canopy penetration, andspray drift for three sprayer types: boom, airblast, and fixed wing aircraft sprayer. The tests wereconducted in lowbush blueberry during both mid-season and late season (times when sprays forblueberry maggot are applied). Moisture sensitive paper cut in rectangles (3.75 x 5.0 cm) and stapledto wooden stakes so that the rectangles could be positioned within and above the blueberry canopywere used to measure spray droplet distribution. Our results suggest that drift was less in the boomsprayer compared to the airblast and aerial fixed wing application and that drift deposition fell offgeometrically from desired target area. Crop canopy penetration of the spray was higher with theboom and airblast sprayer than with the aerial application.

Submitted by:Francis A. DrummondUniversity of MaineDepartment of Biological Sciences5722 Deering Hall, Room 305Orono, ME 04469-5722Tel: (207)581-2989E-mail: [email protected]

20

Title: Evaluation of the AgDRIFT_ Model

Authors: S.L. Bird, S.G. Perry, S. Ray, M. Teske, P. Scherer

Abstract: Simulated results from AgDRIFT_, a windows-driven modeling package for evaluatingoff-site drift of pesticides, was compared to data developed in 180 aerial field trials performed by theSpray Drift Task Force in 1992 and 1993. Model simulations were performed using drop size distribu-tions measured in a wind tunnel and on-site meteorological measurements. Comparisons of modeledand measured deposition were made using a variety of techniques including box plots, QQ plots, andanalysis of the model/field ratio. In addition, an evaluation of the model performance relative to thefield results with respect to the impact of mitigation options _ i.e. establishment of buffer zones, windspeed limitations, and restrictions on drop size categories _ was performed. The model and fieldresults are consistent in the near-field. The model predicts higher deposition than measured in the fieldat distances beyond 100 m under highly evaporative conditions. There is no effective difference in theestimation of buffer widths required to reduce the deposition down to a specific (0.10, 0.05, 0.01, and0.005) fraction of the application rate between observed and simulated results. AgDRIFT_ simulationsare consistent with field results for use in estimating near-field exposure from aerial spray applicationsand the effectiveness of proposed exposure mitigation strategies.

Submitted by:Sandra BirdU.S. Environmental Protection AgencyE-mail: [email protected]

21

Title: Modeling Spray Drift in Orchards

Authors and Addresses:David R. Miller, Bing Ouyang, Thomas Soughton - University of ConnecticutDonald E. Aylor - Connecticut Agriculture Experiment StationWilliam E. Steinke - University of CaliforniaEllis W. Huddleston - New Mexico State University

Abstract: This paper will outline the drift process and present a numerical model to predict the move-ment and deposition of spray droplets in tree canopies. The model requires input of the sprayer andproduct characteristics, the local meteorology, and the canopy arrangement and drop catching charac-teristics. These provide the boundary conditions and forcing mechanisms for a model that simulatesthe movement of droplets in and out of the orchard canopy. The output is spatially distributed, timedependent quantities of drift and field deposit.

Submitted by:David R. Miller, ProfessorUniversity of ConnecticutCollege of Agriculture and Natural ResourcesDepartment of Natural Resources, Management and Engineering1376 Storrs Road, U-87Storrs, Connecticut 06269-4087Tel: 860-486-2840Fax: 860-486-5408

22

Title: Spray Drift From A High Volume Air-Assisted Sprayer

Authors and Addresses: Bernard Panneton (1)

Marlene Piche (1)Roger Theriault (2)

(1) Agriculture and Agri-Food Canada, 430 Boul. Gouin, St-Jean-sur-Richelieu, Que.CANADA, J3B 3E6

(2) Department of Soil Science and Agri-Food Engineering, Laval University,Ste-Foy, Que. CANADA, G1K 7P4.

Abstract: Drift measurements 10 m away from the end of an air-assisted boom were performed using8 rotary samplers deployed between 0.5 and 8 m above ground. Meteorological conditions (windspeed,turbulence intensity, stability) were measured using 3 propeller anemometers at 2, 4 and 8 m aboveground and a sonic anemometer-thermometer at 4 m. The ground was covered with short grass and theterrain flat. Only windspeed showed a significant correlation with drift data. Air-assistance was veryeffective in reducing drift. This is in line with published results although the air-assisted sprayer usedhad an airflow rate 3 times higher than the one that can be obtained with commercially availablemodels.

Submitted by:Bernard Panneton, Research ScientistAgriculture and Agri-Food Canada - HRDC430 Boul. GouinSt-Jean-sur-Richelieu, Que.CANADAJ3B 3E6Tel: 514-346-4494 ext. 205Fax: 514-346-7740E-mail: [email protected]

23

Title: Spray Drift Under Unstable Weather Conditions

Authors and Addresses:Masoud Salyani (1)Richard Cromwell (2)

(1) University of Florida, Citrus Research and Education Center, Lake Alfred, FL 33850

(2) University of Florida, Agricultural and Biological Engineering Dept., Gainesville, FL 32611

Abstract: The objectives of this study were to: a) investigate the variability of drift deposits underunstable weather condition, and b) to determine the effects of an invert emulsion oil and a polymericspray additive on drift reduction.

Spray mixtures were applied horizontally (at about 1.5 m above ground level) from rearside of a sprayer.Spray drift was sampled at eight location around the course of application. Mylar plastic sheets and high

volume air samplers were used for fallout and airborne drift measurements, and the residues werequantified by fluorometry. Applications were made in three replications. Weather data, including airtemperature, relative humidity, wind velocity, and wind direction were recorded during the applica-tions.

There were substantial variations in drift deposits among replications of each treatment and the depos-its were measurable in all sample locations. This indicated that the one-directional sampling of driftmay not reliably define the movement of the spray cloud and could result in underestimation of driftdeposits in places other than the assumed downwind locations.

Addition of the adjuvants had significant effects on drift reduction. Overall, tank mixes containing theinverting oil generated the least amount of drift deposits at all sample locations. Averaged over samplelocations and target distances, mean deposits of water alone, water plus polymer, and water plus invert-ing oil were: 13.0a, 4.4 ab, and 1.5b (fallout) and 331.6a, 210.6a, and 32.6b (airborne), respectively.

Submitted by:Masoud SalyaniAssociate Professor of Agricultural EngineeringUniversity of Florida, CREC700 Experiment Station RoadLake Alfred, FL 33850Tel: 941-956-1151 Fax: 941-956-4631Email: [email protected]

24

Title: Wind Tunnel Studies of Spray Drift Potential

Author and Address:Ivar LundDanish Institute of Agricultural ScienceDept. of Agricultural Engineering, Research Centre BygholmDK-8700 Horsens, Denmark

Abstract: The spray drift was studied in a wind tunnel, because there it was possible to control andrepeat the spraying conditions.

The wind tunnel has a 2.75 x 2.75 m cross section and a 5 m long test section.

Flow visualization was obtained by making an image of the spray cloud by using a laser sheet based ona 300 mW laser. The laser sheet was placed vertically in the same direction as the windspeed. Thevisualized droplets were video taped, and afterwards they were analyzed on acomputer with a commercial software.

The droplet size, velocity and volume in the spray were analyzed by use of a Dantec PDA-analyzer.

A flat fan nozzle was tested in the wind tunnel at a test pressure of 250 kPa and a wind speed of 2 m/s.Afterwards, drift reducing equipment (air assistance) was used, and the visualized picture could becompared with the pictures without air assistance. The differences in droplets sizes, velocities andspectra were studied afterwards.

It was concluded that it was possible to make repeatability tests by using a wind tunnel. The visualiza-tion of the droplet gave good information of the behaviour of the spray cloud and the droplet sizinggave information of the behaviour of the single droplets just after the droplet generation and in differentvertical and horizontal distances from the nozzle.

Submitted by:Ivar LundDanish Institute of Agricultural ScienceDept. of Agricultural EngineeringResearch Centre BygholmP. O. Box 536DK-8700 Horsens, DenmarkTel: +45 75 60 22 11Fax: +45 75 62 48 80E-mail: ivar.lund@

25

SUNDAY, MARCH 29 1998

Computer ModelingDavid Esterly, Dupont Agricultural Products

Wilmington, DE

AgDRIFTA Tiered Approach for the Assessment of Spray drift of Pesticides

Program Overview

AgDRIFT incorporates a proposed overall method for evaluating off-site deposition of aerial and groundapplied pesticides, and acts as a tool for evaluating the potential of buffer zones to protect sensitive aquaticand terrestrial habitats from undesired exposures.

Program Overview

The methodology is built into the Microsoft Windows based personal computer program called AgDRIFTand is provided to the U. S. Environmental Protection Agency’s (EPA) Of Office of Pesticide Programs as aproduct of the Cooperative Research and Development Agreement (CRADA) between the EPA’s Office ofResearch and Development and the Spray Drift Task Force (SDTF), a coalition of pesticide registrantsformed to develop a comprehensive database of off-target drift information in support of pesticide registra-tion requirements.

Application Method - Aerial

Tier I Preset model results4 droplet size classes (BCPC)

Tier II Limited input conditionsDrop size library and Drop-Kick

Tier III Complete input conditionsaircraft and material properties libraries

Application Method - Ground Sprayer

Tier I Curvefit from field data2 boom heights

Tier II No current model

Tier III No model

Application Method - Orchard Airblast

Tier I Curve fit from field data3 orchard types (11 for plotting)

Tier II No model

Tier III No model

26

Experience

AgDRIFT relies on an understanding of many concepts and ideas. It spans three Tiers of increasingcomplexity.

Tier I Variables are preset; this Tier requires little knowledge of actual application conditions or theproduct’s properties

Tier II Increased knowledge of the application equipment, environment, site and product

Tier III Free access to all model variables; assumes user is an application specialist

Tier I Assessment

Features available in Tier I, Pull Down Menu

FileEditView[Run]ToolboxHelp Can be reached for any field with F1 key

Selection with the Radio Buttons

Aerial: By Drop Size DistributionGround Sprayer: By boom height & Number of SwathsOrchard Airblast: By Orchard Type

Aerial

A quick look at the BCPC drop size distribution categories.

27

Tier I Aerial Default Values - Meteorology

Wind Speed: 4.47 m/s ( 10 mph)Wind Direction: Normal to Flight PathSurface Roughness: 0.0075 m to 0.005 mStability: NeutralRelative Humidity: 50%Temperature: 30° C (86 ° F)

Test Substance / Application

Specific Gravity: 1.0Nominal Application Rate: 100 ng/cm2 (0.25 lb/ac)Swath Width: 18.29 m (60 R)Nonvolatile Fraction: 0.03Number of F1 Flight Lines: 20

Ground

Select one of two boom height settings90th percentile deposition curve(curve-fitted) SDTF field studies

Orchard Airblast

Select one of three orchard types:(Normal, Dense, Sparse) Depositioncurve from the SDTF field studies

28

FILE

New: Refresh the Tier with its default valuesOpen: Open an input file saved from a previous AgDRIFT run (saved in Tier II or Tier III)Save:Save As:Load Field Trial Data:Export: Here we can select:

Drop Size Distribution - IncrementalDrop Size Distribution- CumulativeDepositionPond-Integrated DepositionVertical Profile1 Hour Average Concentration

Print Preview: To see what could be notedPrint Setup: Select Printer, Orientation Paper Size, etc.Print: [Print EPA Standard Form]

EDIT

Cut, Copy, Paste

Preferences: Selecting: Starting Tier (I, II, III)Units (English or metric)Interpolation Method: DropKick.Warn on Tier changePause before calculatingSuppress Calculation Warnings

VIEW - The Control Center of AgDRIFT

NotesInput SummaryNumerical ValuesCalculation LogSelect Tier 1, 11, IIIDrop Size Distribution plot Incremental or CumulativeDeposition plotPond-Integrated Deposition plotVertical Profile plot1 Hour Average Concentration plotCoefficient of Variation plot

Under Toolbox we can reach - Work Center

Aquatic Assessment To recover level of deposition on a sensitive area downwindDispersion Distance To recover the distance downwind where a specific deposition level occurs,

and vice-versaSpray Block Assessment To develop a plot of buffer zone distance as a function of number of flight

lines (or swaths)[Drop Distance][Effective Swath Width]

29

EPA-Defined Water Body

The default Downwind Water Body Width is 63.61 m (208.7 ft) - the square side of 1 ac. An “EPA WaterBody” has by definition a surface area of 1 ha = 10000 m 2 Therefore, the default length of the water body inthe flight line direction is 157.21 m (515.8 ft). Looking down:

Dispersion Distance

TOP SECTION:

Enter: Fraction of AppliedAnswer: Distance (Downwind from the Edge of the Field) — for both Deposition and Pond Deposition

BOTTOM SECTION:

Enter: Distance (Downwind from the Edge of the Field)Answer: Fraction of Applied — for both Deposition and Pond-Integrated DepositionResource: Deposition curve selected by the user on the Tier I screen, or computed by AgDRIFT

in Tier II or Tier III

30

DSD - Drop Size Distribution

User Defined(4) BCPCDropKickLibrary

Tier III

Adds Four Areas of Control:- Spray Material- Aircraft- Nozzle Placement- Advanced Settings

Tier III - Spray Material

User Defined- Specific Gravity- Evaporation Rate- Spray Rate- Active Rate- Novol. Rate

Tier III - Nozzles

Number of NozzlesBoom Vertical PositionBoom Forward PositionHorizontal Distribution

Tier III - Aircraft

Library of 73 Commercial AircraftOr Build Your Own

Tier III - Advanced Settings

All The Things You Should Not Touch- Vortex Decay Rate- Aircraft Drag Coefficient- Propeller Efficiency- Model Operation- etc.

Summary

The Important Parameters:- Release Height- Wind Speed- Drop Size Distribution

Function Key F1 = Help

Contents Accesses the Help file indexUsing Help Microsoft Help informationAgDRIFT User Guide The user manual on-lineAgDRIFT User Information The disclaimerAgDRIFT A brief history of time

Tier II

From the View Pull Down MenuSelect Tier II

Tier II - Where you will do most of your work!

Input are considered:MeasurableControllableEnforceable

Tier II

Set Limits on MeteorologyDefine Spray MaterialSelect Aircraft TypeControl SwathDefine Drop Size Distribution

Spray Material

Nonvolatile RateActive RateSpray RateCarrier Type

Aircraft

Slow Fixed WingFast Fixed WingHelicopterBoom HeightNumber of Flight Lines

Swath Control

Swath width - default 1.2 times Wing spanSwath Displacement:- 112 Swath Width-1 Swath Width- Fixed Distance- Fixed Percentage

31

Practical Applications of G.P.S. Technology: Differential GPSSpray Aircraft Guidance

Harold W. Thistle, Jr.Anthony Jasumback

William KilroyMissoula Technology & Development Center

USDA Forest ServiceMissoula, Montana

Abstract. Since 1990, DGPS spray aircraft guidance has made a dramatic entrance into the arena ofaerial spraying. This technology provides the aerial applicator with absolute spatial accuracy at a pointof 2 m or better, along with update rates on the order of 1 Hz - .5 Hz (1-2 sec.). The ability to knowlocation at this level of exactness aids in finding targets, recording position while spraying, and infinding the shortest route home or to refueling and reloading, among many other pilot functions. Thefuture of this technology is in control systems and in interfacing with Geographic Information Systems(GIS). The electronic positioning data can be used to turn spray on and off, chart course, or (in con-junction with other data), to alter spray system parameters.This paper is based on one submitted to the Journal of the American Mosquito Control Association.

Introduction

The lack of accurate positional information for aircraft pilots has long been a source of error inaerial pesticide application (Barry, 1977). This problem is exacerbated when the pilot cannot rely onvisual cues to demarcate an application target. When flying over an expanse of forest, it is often verydifficult to accurately know position. In some instances, block marking might account for over half ofproject costs (Clymer and Omer, 1994). The benefits of Differential GPS technology to aerial sprayingextend beyond guiding the pilot on an optimized route to the spray target area and delineating the area.This technology can also (Thistle et al., 1995):

• Provide aircraft tracking and guidance that allows the spray material to be applied more evenly.

• Yield detailed information for quality control, record keeping, and post-operationalquestions and challenges.

• Eliminate the need for flaggers and associated safety and cost factors.

• Reduce or eliminate pilot time lost while finding home. Reduce costs associated withreturning to base for reloading and returning to the exact position where an applicationwas stopped.

• Improve the ability of the operational manager or applicator to immediately locatemisses or gaps in coverage, allowing corrective action to be taken in a timely manner.

• Allow direct upload and download to and from any digital, geo-referenced map base offlightlines, spray blocks etc.

In general, costs can be lowered, safety improved, and efficiency increased when GPS navigationsystems are integrated into pesticide application operations.

32

Technical Background and Fundamentals

The basic idea of GPS technology rests on knowing the distance to a satellite and its position. Whenthe distance and position of the satellite are known, the receivers position can be calculated. A GPSreceiver receives signals from a constellation of satellites. By processing the data string it receives, itidentifies an individual satellite, obtains satellite position from an internal electronic almanac and cal-culates the distance between the individual satellite and the receiver. When simultaneous measure-ments are made to four or more satellites, the system can resolve a highly accurate receiver position inthree dimensions. The information processing and transmission technologies involved are very ad-vanced. Satellite distance is actually calculated using the time it takes the signal to travel from thesatellite to the receiver. Since the travel speed is the speed of light, sophisticated signal processingtechniques are required to measure this small travel time increment accurately.

The idea of using man-made satellites for positioning has existed for some time. Parkinson (1994)gives an excellent overview of early work and GPS system development. The first operational satel-lite-based navigation system, Transit, was intended to aid submarine navigation. The system wasdeveloped at Johns Hopkins University and used the Doppler shift in a constant tone broadcast bysatellites orbiting the poles.

Over the last two decades, the U.S. Department of Defense (DOD) has deployed the constellation ofNAVSTAR satellites. The constellation consists of six orbital planes inclined at 55° with four satel-lites in each plane. It was declared fully operational by the Air Force in April 1995. Due to securityconcerns, the DOD has opposed civilian use of the full system capabilities. Therefore, the DOD imple-mented a policy of selective availability (SA). The signal is intentionally degraded so that the GPSpositioning available to the civilian community has an accuracy of better than 100 m (95% of the time)and 300 m (100% of the time) in horizontal positioning compared to the 16 m (or better) accuracyavailable to the military. SA is achieved by changing the signal timing (dither) and satellite ephemeris(epsilon), which introduces a fluctuating error in the indicated position.

The civilian community responded to SA by developing a differential system that eliminates the SAerror and increases the positional accuracy to 2 m or better. This is accomplished by placing onereceiver at a point with a known location (called a base or reference station). The base station data areused to calculate range corrections for other receivers (called rovers). This technique is known asdifferential GPS, and can be done in real time or with post-processing. Most aircraft navigation andguidance systems now are able to receive the differential correction message by a satellite that receivesthe message and rebroadcasts it over a wide area, largely eliminating problems of line-of -sight to aground based differential broadcast. Differential GPS is allowed by DOD and exceeds the accuracyavailable from a keyed (decrypted) military receiver. Navigation and guidance functions use the dif-ferential correction signal in real time. GPS positional data can be post-processed to achieve DGPSusing an archived record of the differential correction signal.

Over the past 6 years, the GPS and DGPS technologies have begun to be used successfully by theagricultural aviation industry. The immediate cost savings and reduction in the exposure of flaggers topesticides made this technology very attractive. As environmental concerns increase, the ability toaccurately control where an application is made and the ability to provide documentation based onautomatically stored computer records have proved important. The present state-of-the-art allows aGPS signal to be processed at 10 Hz (10 per second). An updated differential correction is typically

33

received at .5 Hz (once every two seconds). The corrected signal can be used to guide the pilot alonga pre-programmed flight path (using audio or visual indicators), and can be stored with absolute accu-racies around 2 m. It can be transmitted back to the ground and input as an overlay into geographicinformation systems (GIS), allowing an operations manager to observe the application in real time ona computer screen. The GIS capability is also valuable in analyzing coverage and efficiency. Therecord of the operation can be downloaded and input as a spatial overlay into the GIS database andspatial summary statistics can then be calculated.

Testing and Demonstration Projects

As these technologies began to be marketed to aviators and operational managers, there was interestwithin the Forest Service to validate the various claims being made and to make agency personnelaware of the power and implications of this new technology. Demonstration and testing projects werearranged to meet this need.

Initial testing involved such basic trials as marking a point on the ground in the remote New Mexicodesert and having a spray pilot log that point from the air. The marking was removed and the ability ofthe pilot to return to that location was noted. Such crude tests are difficult to quantify, but indicated thesystems could basically do what they claimed. The technology was used in boll weevil spraying inTexas in 1992. Sampson (1993) discusses successful use of this technology in aerial grasshopperspraying in North Dakota. The elimination of flaggers on a 6400-acre block and the information avail-able from the logged positional data for post-flight analysis are given as major advantages of the sys-tem. Mierzejewski et al. (1994) describes early use of DGPS guidance for forest spraying of gypsymoths in Pennsylvania. The reduction in the size of ground crews as well as increased accuracy werethe main advantages of the system.

It is very difficult to independently measure the absolute accuracy of these systems. Absolutepositions at this accuracy have never before been available, so it is difficult to find positions for com-parison. Falkenberg et al. (1994) conducted tests to evaluate the precision of this technology. One testindicated position was within 58 cm of a video-monitored swath centerline 90% of the time. Two othertests gave 90th percentile numbers of 109 and 94 cm. These authors point out that with this level ofprecision, this becomes a test of how well the pilot and aircraft can hold a line, since that variation islarger than measurement precision. The design of tests such as these force the realization that thistechnology is unmatched in terms of both accuracy and precision.

As implementation of this technology into the spray aircraft industry accelerated, field tests beganto focus on applications and logistics. Mierzejewski (undated) performed a comparison test to empha-size the need for differential correction. The DGPS navigation systems achieved accuracies on theorder of 2 m, while systems using the raw signals showed accuracies of around 25m. Mierzejewski etal. (1995) discuss a DGPS aircraft guidance system specifically designed for forestry and indicate thatthe reduction in program costs can be significant.

Thistle et al. (1995) addressed questions of the applicability of this technology in the mountainswhere both the constellation and the differential signal could be obscured by terrain. The primaryquestion was whether a pilot could locate a small block with minimum visual cues in an extensive,mountainous forest area. The program also attempted to evaluate the accuracy and precision of thebasic technology. Some conclusions drawn from this program are:

34

• The accuracy claims of DGPS navigation systems are valid. The error in position when usingDGPS technology is smaller than other positioning errors caused by spray drift, pilot skills, andknowledge of the exact location of the pest.

• It is important to obtain independent verification of system coordinates. One of the systemsflown translated coordinates into the wrong map datum. This caused the aircraft to be approxi-mately 70 m away from the actual position.

• Software that automatically calculates parallel flight lines and uses these as guidance is notalways useful in complex terrain. Parallel flight lines might not be practical in aerial sprayingin the mountains where much of the spraying is done flying contours.

• Detailed training is critical for pilots to correctly use a given system.

• The optimal use of these systems will involve integrating them into (as opposed to replacing)current practices.

As the systems become increasingly fool-proof, independent observation of these systems is less nec-essary. One of the features demonstrated during this program was the broadcast of real-time positionback to a base station. The aircraft position was received and plotted on a map so that the progress ofthe spray operation could be evaluated. The program demonstrated the technology was suitable for usein mountain spray operations (Figure 1) with very little drop out of constellation or loss of the differen-tial signal. In very rugged terrain, signals can be obscured.

Current Technologies

GPS technology advances are occurring in the areas of GIS (Geographical Information System)interfaces and control systems. The Forest Service has been involved in developing a pest manage-ment software package using GIS technology. This package is named GYPSES (Ghent et al., 1996).Though it was designed for use in gypsy moth suppression, it can be used to manage other pests. Thetechnology allows an operational manager to plot spray blocks on any convenient geo-referenced mapbase or photo.

Over the past 2 years, the GYPSES developers have been working with DGPS spray aircraft guid-ance system manufacturers. They are now able to upload and download files directly into the in-cockpit systems of four of the manufacturers. This allows the manager to copy the block coordinates ofwhatever map base is being used to a diskette. The diskette is then put into the in-cockpit system andthe blocks are displayed as overlays on the in-cockpit guidance system map displays.

Thistle et al. (1997) conducted a demonstration and test to evaluate the file transfer capabilities ofGYPSES and to address other questions about the technology. The primary objectives were to exam-ine the frequency of occurrence and the effect of loss of differential correction in complex terrain(Figure 2), and to demonstrate the interface between the onboard aerial navigation and spray guidancesystem with the ground-based GYPSES GIS program(Figure 3). Satellite broadcast differential wasvery successful in this terrain at this latitude. The signal was only briefly interrupted. File hand-offbetween the onboard system and the ground-based GIS was seamless, providing the spray managerwith detailed spray coverage analysis.

35

The second emphasis of developing technology is in the design of control systems using the real-time position provided by DGPS. Most of the systems have two visual aids for the pilot. The first is alightbar that keeps the pilot on a line, whether it is a swath or a straight line to the block or to home.This lightbar is a horizontal set of lights mounted in the field of view of the pilot. If the pilot is exactlyon course, the middle light (usually green) will be lit. As the pilot goes off course, the lateral lights willlight up, indicating that the pilot is off the line and should make a correction. If an application consistsof parallel swaths, the system will reprogram for each swath and the lightbar will guide the pilot downa new swath for each pass. The lightbar will also act as a data display device, giving the pilot basicinformation such as heading, air speed, and percent of the block completed.

The second visual aid for pilots is an actual map display of the block. The sophistication of thesedisplays varies greatly from an idealized spray block overlain by flightlines to fairly detailed mapdisplays. The pilot has a real-time plot of position and of the spray job as it is conducted. The pilot cansee potential skips as they occur, deviations from the flightlines, and know the exact point wherespraying stopped.

The control systems which are developing use these position data to provide more information tothe pilot and even automate functions. Many systems now change the color of the plotted flightlinewhen ‘spray is on’ for post spray analysis. Spray on/off can be automated to respond to a position suchas a block edge but most applicators prefer to do the spray on/off function manually. Spray systems arenow being integrated with environmental sensors that will warn the pilot of drift or will compensate forwind with system calculated swath offsets. Eventually, it may be possible to adjust the size of thedroplets in flight, based on the input from environmental sensors (big drops are less susceptible todrift).

Conclusions

DGPS aircraft guidance is widely used in the aerial spraying industry. Differentially corrected GPSnavigation systems yield absolute position with accuracies around 2 m. This technology is used inaerial spraying to improve coverage and reduce drift, and to improve project safety and save fuel. Thetechnology is increasingly being integrated into GIS systems, allowing rapid, sophisticated analysis ofan application. Electronic systems are rapidly evolving to use DGPS technology as a basic systemcomponent. This technology has tremendous potential in the world of mosquito control.

References

Barry J.W. 1977. ‘Problems Associated With Maintaining Consistent Swaths When Spraying ForestsWith Helicopters’. Agricultural Aviation 18.

Clymer D.A. and J.R. Omer. 1995. ‘GPS Sprayplane Guidance Used for 1994 Gypsy Moth/SpanwormProject on the Allegheny National Forest’ Proceedings of the 1994 Annual Gypsy Moth Review. Sa-lem, OR.

Falkenberg W.H., J.R. Hartt and A.A. Vetter. 1994. ‘The AirStar-A Precision GPS Parallel SwathGuidance and Tracking System’ IEEE Plans ‘94. The Institute of Electrical and Electronic Engineers.New York NY.

36

Ghent J.H., D.B. Twardus, S.J. Thomas and M.E. Teske. 1996. ‘GYPSES: The Gypsy Moth DecisionSupport System’ ASAE Paper #AA96-005, St. Joseph, MI.

Mierzejewski K., W. Buzzard and G. Laudermilch. 1994. ‘Operational Use of Differentially CorrectedGPS Based Aircraft Tracking Guidance & Flight Path Recording Systems in Forest Spray Projects’.Aerial Application Technology Laboratory Pub. AATL 94-1. State College PA.

Mierzejewski K. ‘Aircraft Tracking Guidance & Flight Path Recording in Forest Spray Projects: AnEvaluation Using Two Differentially Corrected GPS-Based Systems’. Undated. Aerial ApplicationTechnology Laboratory. State College PA.

Mierzejewski K., W. Buzzard and G. Laudermilch. 1995. ‘An Evaluation of the SATLOCFORESTSTAR in the 1995 Pennsylvania Forest Insect Pest Suppression Program’. Aerial Applica-tion Technology Laboratory Pub. AATL 95-2. State College PA.

Parkinson B.W. ‘GPS Eyewitness: The Early Years’. September 1994. GPS World.

Sampson M.W. ‘Getting the Bugs Out: GPS-Guided Aerial Spraying’. September 1993. GPS World.

Thistle H., A. Jasumback, W. Kilroy, K. Mierzejewski and J. Barry. 1995. ‘DGPS in Aerial Spraying inForestry: Demonstration and Testing Final Report’. Tech Rep. 9534-2848-MTDC, U.S. Dept. of Ag-riculture, Forest Service, Missoula Technology and Development Center. Missoula MT.

Thistle H. and W. Kilroy. ‘Demonstration of the Aventech Aircraft-Mounted Meteorological Measure-ment System’. 1997. Tech. Rep. 9734-2323-MTDC. U.S. Dept. of Agriculture, Forest Service, MissoulaTechnology and Development Center. Missoula MT.

Thistle H., A. Jasumback, W. Kilroy , J.Ghent, S. Thomas and B. Eav. ‘Harrisonburg Spray AircraftNavigation: Final Report’. 1997. Tech. Rep. 9734-2846-MTDC. U.S. Dept. of Agriculture, ForestService, Missoula Technology and Development Center. Missoula MT.

37

Figure 1

This block was generated by an AgNav system (Picodas Group Inc.) during a 1994 demonstration in mountain-ous terrain outside of Missoula, MT. The total block area is 43.5 acres. The system successfully delineated asmall exclusion area. Cross hatches indicate spray is on.

38

Figure 3

An A-shaped demonstration test block with a rectangular exclusion zone is shown on this surfaceimage generated by GYPSES. These block coordinates were loaded directly into the in-cockpit sprayaircraft guidance system.

Figure 2

This schematic shows the effects of terrain masking on the differential signal broadcast from a satellite.The satellite is geostationary (over the equator). Notice that as you move northward the satellite islower on the southern horizon, allowing smaller terrain features and other obstacles to obstruct thesignal.

39

Pesticide Drift and Organic Certification

Miles McEvoyWashington State Department of Agriculture

Olympia, WA

Introduction

The Washington State Department of Agriculture (WSDA) has certified organic farms since 1988.The WSDA Organic Food Program’s mission is to protect consumers and support the development ofthe organic food industry by ensuring the integrity of organic food products. The Organic Food Pro-gram (OFP) establishes organic standards and certifies organic producers, processors and handlers.The OFP also provides technical information about organic food production and assists in the develop-ment of markets for the organic food industry.

Organic crop production standards prohibit organic crops from having synthetic pesticides applied tothem. The Washington State Department of Agriculture inspects organic farms for compliance withorganic crop production standards. A component of these inspections includes collecting samples andhaving them analyzed for pesticide residues. Samples are collected in areas where contamination ismost likely to occur, namely borders between organic and conventional crop production. If pesticidedrift occurs onto an organic farm, it may jeopardize the farmer’s ability to market the crops as organic.The loss of organic markets may be a significant financial loss to the organic grower.

Growth in Organic Market

In 1988, the first year of the WSDA Organic Food Program, there were 63 certified organic farmsproducing 2.5 million dollars worth of organic food. In 1997, WSDA certified 295 farms, 73 proces-sors and 54 handlers of organic food. These 295 farms produced over 60 million dollars of organicfood including 3.6 million dollars of organic apples and pears which were exported to the EuropeanUnion. In terms of number of farms, acreage and value of production, the organic food industry isgrowing at a rate of 20-30% per year.

National organic sales are also increasing. According to the Natural Foods Merchandiser the organicfood industry was a 2.8 billion dollar industry as of 1995 and is growing more than 20 percent peryear. European and Asian consumers are also fueling the growth in the organic market. For ex-ample, organic foods reportedly make up 5 percent of all food sales in Germany.

According to the Hartman Report (1997) the market for organic food products will continue toexpand. The majority of Americans will preferentially buy organic and other eco-labeled foodproducts as long as the core purchase criteria of price, taste, quality, convenience and availability aremet. A significant segment of American consumers are also willing to pay a premium for organicfood products. Natural food superstores are the fastest growing segment of the retail food industryand will provide additional market outlets for organic foods.

40

Organic Production Standards

In general, organic food is food that is grown without the use of synthetic chemicals. Natural fertil-izers such as manure, compost, bone meal, and rock minerals are used for maintaining soil fertility.Natural insecticides and selective synthetic insecticides including Bacillus thuringiensis (Bt), roten-one, pyrethrum, insecticidal soaps, pheromones and dormant oils are used for insect pest manage-ment. Weeds are controlled by mechanical methods rather than the use of herbicides. Approveddisease control materials include sulfur and copper hydroxide. Most synthetic fertilizers and pesti-cides are prohibited from use for at least three years prior to harvest.

Organic livestock production requires that animals are fed organic feed and have access to pasture orthe outside. Antibiotics and hormones are prohibited.

Handling and Processing Organic Food

The two primary concerns in handling organic fruit are maintaining the identity of organic food andpreventing contamination with post-harvest chemicals. Organic food is identical in appearance tonon-organic food. Bin tags, labels, scale tickets, and lot control documents must clearly identify thefood as organic. Clear and consistent labeling will preclude inadvertent misidentification or com-mingling by employees. Handlers of organic food must demonstrate that they have procedures inplace to maintain the identity and segregation of organic food at all times.

Processed organic food is food that is organically grown and has not been treated with artificiallyderived preservatives, colorings, flavorings or other artificial additives. Processed organic foods thathave both organic and non-organic ingredients have specific labeling restrictions on the use of theterm “organic.”

Organic Certification

Certified organic means that an independent, third-party has verified that all the requirements oforganic crop production, processing and handling have been met.

Farmers provide information that explains the history of the production site, production practices,neighboring borders to the site, a farm map identifying the location of the site, crops and acreage inproduction, etc. When all required documentation has been received, an inspector visits the farm towalk the fields, review production and sales records, and discuss production practices with thefarmer. In addition, samples are collected and analyzed for prohibited pesticide residues. If theinspection, recordkeeping, and sample results indicate compliance with organic standards an organicfood certificate is issued.

41

Current Regulatory Framework

Twenty six states have legislation pertaining to the labeling of organic food. In most states organiccertification is voluntary. Organic certification is required for all growers, processors and handlersthat make organic claims in Texas, Idaho, New Mexico and Washington State. Under the proposedUSDA National Organic Program all growers, processors and handlers that make organic claims willbe required to obtain certification.

There are fourty-four organic certification agencies in the United States, comprised of thirty-fourprivate agencies and ten state certification programs. States with organic certification programsinclude Maryland, Kentucky, Colorado, Oklahoma, Louisiana, Texas, New Mexico, Nevada, Idahoand Washington. Most organic certification is conducted by private organic certification agencies.The largest organic certification agencies are California Certified Organic Farmers (CCOF), OregonTilth (OTCO), Quality Assurance International (QAI), and the Organic Crop Improvement Associa-tion (OCIA).

USDA’s National Organic Program proposal

The 1990 Congress passed the Organic Foods Production Act (OFPA), setting into motion theprocess for federally mandated national organic standards. The OFPA authorized the establishmentof a National Organic Standards Board (NOSB) which the US Department of Agriculture (USDA)established in 1992. The NOSB made their final recommendations to the Secretary of Agriculture in1994.

Last December, USDA published their National Organic Program (NOP) proposal. The NOPproposal largely ignored many of the NOSB recommendations. Organic food standards would beseverely weakened by this proposal. The proposal would allow many materials that are currentlyprohibited from use in organic farming such as the pesticide avermectin, toxins derived from geneti-cally engineered bacteria, inert ingredients such as benzene, formaldehyde and xylene; and fertilizerssuch as cement kiln waste and biosolids. The proposed national standards could shake consumerconfidence in organic foods and disrupt expanding export markets.

The federal proposal would also impose additional fees raising organic certification fees by 35percent. Under the NOP proposal handlers of organic fruit would pay an additional $500 per year toUSDA. Many small organic farms, handlers and processors may choose to stop producing andselling organic food products due to the added costs of certification.

To date, the USDA has received over 22,000 comments in opposition to the proposal. WSDA hassubmitted comments to USDA on how the proposal would weaken state standards, impose an unfairburden on small farms and businesses, provide loopholes for many handlers of organic food, includenumerous unenforceable sections, and would disrupt export markets. USDA Secretary DanGlickman has stated that USDA will not adopt organic standards that are not supported by theorganic food industry. It is our hope that USDA will resubmit the proposal for public comment.

42

Organic Pesticide Residue Standards

Organic food standards do not allow the use of synthetic pesticides but pesticides may cause residueson organic food from other sources. Potential sources of pesticide residues include residual soilcontamination (e.g. DDT, dieldrin), fraudulent use of prohibited materials, inadequate rinsing ofpesticide application equipment, volitization in storage, contaminated belts, brushes or water in post-harvest handling and pesticide drift.

Existing state and private organic standards generally state that if food has pesticide residues inexcess of five percent of the EPA tolerance level it cannot be sold as organic. According to theNOSB, this residue standard does not define organic food. Organic is a production claim, not aresidue-free claim. All components of organic food crop production must be complied with in orderto make an organic claim. The residue standard serves as a tool to assist state and private organiccertification agencies in assuring compliance with organic food standards.

Unavoidable Residual Environmental Contamination (UREC)

Consumers expect that organic food does not contain pesticide residues. In 1990, Jerri Thomas ofthe Washington State Office of the Attorney General wrote –

In certifying food as organic, it does not matter whether or not thesource of drift is unknown, or that the amount of drift is barely de-tectable. The purpose of the statute is to protect the consumer. Thepoint here is that a prohibited substance is detectable and present onthe crop. The bottom line is that the consumer who chooses to pur-chase organic food does not care whether or not the producer wasresponsible for the pesticide application or whether that applicationoccurred because of spray drift. In either case, the consumer wouldnot be purchasing “organic” food if food with pesticide drift wasallowed to qualify as organic just because the producer himself didnot apply the prohibited substance.

The Senate Committee Report on the OFPA stated that “on occasion, organic farmers, althoughfollowing the strict standards in this bill, may produce products with minimum residues due toinadvertent environmental contamination such as drift from a neighboring farm.” The OFPA andthe NOSB adopted the concept of unavoidable residual environmental contamination (UREC) forresidues that occur from inadvertent, uncontrollable sources. The NOSB has recommended that theUREC be established at 5 percent of the EPA tolerance level. The USDA National Organic Programproposal would establish individual, site-specific UREC levels.

Most organic produce does not contain detectable pesticide residues. The purpose of organic pesti-cide residue standards and UREC’s has been to address the situations where pesticide residues aredetected. The standards are a reasonable, enforceable standard that balances consumers interests forno residues with the practical limitations of producing organic food in a polluted world.

43

Pesticide Drift

Drift is the physical movement of particles or droplets through the air from the area where it is beingapplied to locations outside the targeted area. The NOSB defines drift as the physical movement ofprohibited pesticides or fertilizer from the intended target onto a certified organic field or farm. InWashington state we further define drift to mean that residues of prohibited substances on organicfood are in excess of 5% of the EPA tolerance level. Organic crops that are subjected to drift maynot be sold as organic. When an organic crop has been drifted upon, it results in the suspension oforganic certification on the site affected by the drift. The loss of organic certification can causesevere economic injury to an organic grower who loses access to the organic market.

The USDA National Organic Program proposal defines detectable residue level as the level of apesticide that is 5 percent or greater than the EPA tolerance level, or where there is no tolerance, theFDA action level. The proposal fails to define drift stating that although drift may be commonplace,exposure to drift does not constitute use of a prohibited substance and does not affect the integrity oforganically produced crops because the amount of prohibited substance to which the crops areexposed is negligible. USDA’s standard on pesticide drift is in opposition to the NOSB whichrecommended that organic crops which are drifted upon should not be sold as organic.

Monitoring for drift

Most private organic certification agencies do not test for pesticide residues. A component ofWSDA’s inspections includes collecting samples and having them analyzed for pesticide residues.Samples are collected in areas where contamination is most likely to occur, namely borders betweenorganic and conventional crop production. In areas where pesticide residues are detected above 5percent of the EPA tolerance level the crops cannot be sold as organic. When residues are detectedbut are below 5 percent of the EPA tolerance level we work with the grower and the adjoininglandowner to minimize any future drift problems.

Preventing Drift

Due to the liability associated with drifting onto an organic farm, the best course of action is one ofprevention. To preclude drift problems from occurring, the following practices may be helpful:I. Determine if pesticides are being applied in an area adjoining an organic farm. Contact the

local organic certification agencies and/or the state department of agriculture to obtain a listof organic farms.

II. Communicate with the management at the organic farm. Inform them of the types of materi-als you plan on using and your plans to prevent drift from occurring.

III. Be aware that some materials have much lower EPA tolerance levels on different crops. Forinstance, chlorpyrifos is labeled for use on apples and has an EPA tolerance level of 1.5 ppm,the organic tolerance level is 0.075 ppm. Chlorpyfifos is not labeled for use on pears and theEPA tolerance level is 0.01 ppm. The organic tolerance level for pears would therefore be0.0005 or 0.5 ppb, certainly below most limits of detection.

44

IV. If you will be spraying near an organic farm there are several points to consider:A. Are the boundaries of the organic site clear to you?B. What is the prevailing wind direction and is the organic farm downwind?C. Is the organic farm uphill or downhill from your application site?D. Is there a buffer strip between the organic fields and where you are applying pesticides?

Other Points to Consider:• You may want to establish a buffer zone that provides sufficient distance between the

organic fields and your target fields.• Ensure that all workers applying pesticides are aware of the adjoining organic fields

and take all necessary precautions when applying pesticides in those areas.• Use non-chemical control methods whenever practical.• Use ground application equipment rather than aerial applications, whenever possible.• Practice Integrated Pest Management principles by monitoring pest levels, knowing

the economic threshold and spraying only when necessary.

Summary

Organic food production is expanding and will become a more significant part of agricultural pro-duction. Organic food standards prohibit most synthetic pesticides. Organic food involves a produc-tion system that relies on natural materials and biological control. Organic food is a productionclaim, not a residue-free claim. Organic farms must use organic pest control programs to preventtheir farms from being sources of pests for neighboring farms. Conversely, organic farms must beallowed to prosper without being subject to chemical trespass from non-organic farms. Non-organicfarms must utilize methods to keep their pesticides on their own land and be subject to economicpenalties when they fail to do so.

45

MONDAY, MARCH 30 1998

Legal Liability Issues

Liability of Public Employees*

Theodore A. FeitshansNorth Carolina State University

Raleigh, North Carolina

Public employees have always faced the possibility of liability as a consequence of theiractions; however, there is a perception that the risks associated with public employment have in-creased. This is particularly true for extension employees. Whether public employees actually faceincreased risks of liability is difficult to measure; however, there is no doubt that litigation, overall,has increased. There are undoubtedly many reasons for this. Some of the increase is simply associ-ated with the increase in our country’s population; however, other factors seem to be at work as well.People tend to have a greater awareness of their rights and therefore are more likely to go to court.Attitudes toward litigation have changed. People are less likely to have long term relationships withthose who provide them with goods and services and are therefore less concerned about the impactthat suing those providers may have. New legislation, alone, may account for much of the increasein litigation. For example, federal environmental law scarcely existed prior to 1970; the legislationthat has been enacted since has created many additional causes of action.

Whatever the cause of increased litigation, a liability avoidance program is essential for anyorganization, public or private. There are general liability concepts that apply to all organizations.Then there are concepts relevant only to the public sector. And, lastly, there are issues that areparticularly appropriate to the unique needs of extension organizations. This paper will discuss theseissues in that order.

While it is not the purpose of this paper to present a treatise on risk management, no paperabout liability would be complete without reference to risk management concepts. Insurance and riskmanagement applies to all organizations. The table below presents a useful framework for analyzingand addressing risks.

RISK CHARACTERISTICS Low frequency High frequencyLow severity retain retainHigh severity insure insure or avoid

The characteristics of a particular risk will determine both how it is handled (retained, in-sured or avoided) and the resources used to address it. In general, risks of higher frequency andseverity are the risks toward which most risk avoidance and mitigation resources should be directed.

46

General liability concepts

There are three general sources of liability: contractual, tort, and criminal. Contractualliability arises in conjunction with contractual relationships between parties. Tort liability addressesinstances of civil wrongs. Although legally not torts, I include in this category statutorily createdrights, such as rights created by environmental or employment statutes, that, to a layperson, may beaddressed in much the same manner as common law torts. Criminal law is also of increasing con-cern because many new crimes have been created by statute, for example, in environmental protec-tion statutes.

A contract is an agreement between two or more persons that consist of a promise or set ofpromises that a court will enforce. Absent a legally recognized excuse, each party to the contract isexpected to perform fully the obligations that they undertook when they entered the contract. Per-sons who fail to perform their obligations under a contract are said to be in “breach” of the contract.The nonbreaching party may sue the breaching party for damages (money) or other remedies. Con-tracts may be either oral or written depending upon the subject matter and the duration. Oral con-tracts present particular difficulties because memories tend to be inaccurate and because of problemswith proof. Contracts may also be implied by the parties’ conduct.

In any large organization such as an extension organization, an important issue is always theauthority of an employee of that organization to enter into a contractual arrangement. There are twotypes of authority that an employee may have: actual and apparent. Actual authority is expressauthority from the organization to enter into particular contracts or particular classes of contracts.Apparent authority is the appearance of authority sufficient to lead a reasonable person to believethat the employee/agent has actual authority to enter the subject contract. An employee, who lacksactual authority to enter a contract on behalf of the employer, may nonetheless create a bindingcontractual obligation on the part of the employer, if a reasonable person would have been lead tobelieve that such authority existed. It is therefore incumbent upon employers to make clear tomembers of the public the limitations that they have placed upon the authority of their employees.

When people think of liability they usually think of tort liability. Torts are wrongs which oneperson does to another for which the law provides a remedy. The law does not provide a remedy forall wrongs. Some torts may also be crimes. The most common types of torts are those based uponnegligence theory. In order for the person suing (the plaintiff) to win, the plaintiff must prove thatthe person sued (the defendant) had a duty to the plaintiff. A duty is an obligation to either dosomething or refrain from doing something. Once the plaintiff has proven that the defendant had aduty, the plaintiff must then prove that the defendant breached the duty. A breach of duty is a failureto fulfill the obligation that comprised the duty. Finally there are two other things that the plaintiffmust prove: that the plaintiff was actually damaged (actual damages may include under appropriatecircumstances severe emotional distress), and that the damages were proximately caused by thedefendant’s breach of duty. Proximate cause means that the damages were sufficiently related to thebreach of duty that a reasonable person could find that a particular breach of duty would cause theparticular damages. A tort based upon a negligence theory may be illustrated by a simply example.Any driver has a duty to drive in a safe manner. A driver who drives at excessive speeds hasbreached that duty. That, alone, is not enough to create liability in tort. There must be actual dam-age to some other person and those damages must have been proximately caused by the driver’s

47

excessive speed. If the driver hits a pedestrian because of his excessive speed, a tort has potentiallyoccurred. However, if a person on a second floor balcony falls from the balcony because he isleaning over the rail to watch the driver speed, there is no tort. Even though the speeding is, in ascientific sense, the cause of the injuries, it is not a cause that the law will recognize because it is notof the type of injury that is a foreseeable result of driving at an excessive speed.

There are two other categories of tort with which one should be familiar. The first is strictliability torts. These are torts where liability is imposed without fault. These torts were rare atcommon law and were generally imposed only when the defendant was engaged in an ultrahazardousactivity such as blasting. Strict liability has become more important in recent years because theconcept has been incorporated into some environmental statutes. For example an owner of realproperty contaminated with hazardous waste is responsible for cleanup costs even though the ownerhad nothing to do with creating the situation. The other category is intentional torts. An intentionaltort is one which involves some element of will or intent. Trespass is an example of an intentionaltort. It consists of the entry onto the land of another without permission. Intentional torts are no-table because proof of actual damages is not required and the court or jury may award punitivedamages. Punitive damages are unrelated to the plaintiff’s actual injuries and are designed primarilyto punish the defendant.

Crimes are wrongs that so offend the public morals or so endanger the public welfare thatthese wrongs are treated as offenses against the public at large. Unlike tort and contract actions, thefederal or state governments, or their subdivisions always bring criminal actions. Criminal laws aregenerally divided into felonies and misdemeanors. Felonies are the more serious crimes and usuallycarry heavier penalties. Courts have broad powers in sentencing and may use a variety of toolsincluding incarceration, community service, probation, fines, restitution, and counseling and treat-ment.

Proof of most felonies requires that the state prove intent on the part of the defendant. Theintent that must be proven is intent to do the acts that constitute the crime, not intent to break thelaw. Whether or not the defendant was aware of the criminal nature of his or her acts is generallynot relevant to the question of guilt. However, there are some strict liability crimes for which proofof intent is not required for conviction. Strict liability crimes are historically rare and are usuallymisdemeanors. Nonetheless, there has been some movement toward legislatively creating strictliability crimes, particularly in the area of environmental protection.

Given the restrictions that courts may impose upon life and liberty, as the result of convictionof a crime, the standard of proof in a criminal case is much higher than in a civil case. To find adefendant guilty in a criminal case, the prosecution must prove its case to the jury, or the judge in abench trial, beyond a reasonable doubt. The plaintiff in a tort case need only prove his or her caseby a preponderance of the evidence. A preponderance of the evidence means anything more thanfifty percent. Thus, although it may seem anomalous to laypersons, there is no inconsistency in ajury in a criminal trial finding that the defendant is not guilty while another jury in a civil tort trialbased upon the same facts finding that the defendant created a tort.

Issues for Public Employees

Under English law of the eighteenth century the king could do no wrong. It is upon thisfoundation that the states and the federal government base the doctrine of sovereign or governmental

48

immunity. This doctrine states that the government cannot be sued without its consent. Most stateshave partially waived sovereign immunity by statute, and, in most states court decisions have furthereroded the doctrine. Even if a state is protected by sovereign immunity, the individual public em-ployee may not fall under that umbrella of protection.

Federal sovereign immunity is partially waived by the Federal Torts Claims Act. TheFederal Torts Claims Act distinguishes between policy decisions and operational decisions. Thefederal government is absolutely immune from liability arising from its policy decisions. These aredecisions made by high-level government officials. Operational decisions are the day-to-day deci-sions made by lower level employees in the routine operation of government. For example, thedecision to build a lighthouse at a site is a discretionary policy decision for which the federal govern-ment is immune from liability; however, the negligent operation of the lighthouse is an operationaldecision for which the federal government may have liability.

The approaches that states take to waivers of sovereign immunity vary greatly. It is wellbeyond the scope of this paper to address those variations. I will use North Carolina as one exampleof the approach taken to sovereign immunity and waiver. The State Tort Claims Act governswaivers of sovereign immunity. Liability of the state is limited to the greatest of $150,000 or thelimits of any liability policy purchased by the state or its governmental units. Officers of the stateare never liable in their individual capacities. An officer is anyone whose office is specificallycreated by the North Carolina Constitution or a statute. Everyone else is an employee. Publicemployees in North Carolina are afforded no protection by the doctrine of sovereign immunity.

Public employees are protected by the Defense of Employees Act. The state through theagency that employed the employee may pay up to $150,000 of any judgment. The Office of theAttorney General has the responsibility for providing the defense for the employee. The Office ofthe Attorney General may refuse to defend the employee on any one of four possible grounds: 1) theemployee’s act or omission was not within the scope of employment; 2) the suit resulted from theemployee’s actual fraud, corruption, or actual malice; 3) there is a conflict of interest between theemployee and the state; or representation of the employee is not in the best interest of the state. Aninteresting aspect of the Defense of Employees Act is that the Office of the Attorney General mayprovide a defense of the employee in a criminal action as well as a civil action.

Most state employees are further protected by the state’s umbrella liability insurance policy.This coverage is only available to an employee if the Attorney General has elected to defend theemployee. Public employees may seek additional coverage through the purchase of individual orgroup liability insurance. Agencies, counties and municipalities may also purchase their ownpolicies. The protection provided is dependent upon the terms of the policies.

There are also statutes that create liability for public employees. At the federal level theFreedom of Information Act (FOIA) provides the public with a right to most agency records. Mem-bers of the public who are denied access to records may sue to obtain them. Most states also havesimilar acts that provide access to agency records. Liability may arise in several ways. First, if theemployee releases protected information such as personnel records he or she may be liable to theperson whose records were protected. Secondly, some statutes provide or personal liability on thepart of a public employee who fails to release records which are subject to release. And finally apublic employee who collects confidential information from members of the public and erroneously

49

implies that it can be protected from release may be liable for the consequences of its release. Toavoid liability the public employee must thoroughly understand the duties and responsibilities of hisor her position.

Insurance and Risk Management

Insurance is a means by which risk may be spread over a large group of people, the insurancecompany’s policyholders. In return for payment of a premium, the insurance company agrees to payclaims related to any covered event. In order to calculate a premium, which will cover risks, payadministrative expenses and provide a profit, insurance companies employ actuaries who quantifyrisks based upon past experience. Several factors that relate to the need to quantify risk might limitthe availability of insurance. Some events occur so infrequently that they defy quantification.Other activities are so new that there is no history from which expected losses can be calculated.Other markets are small which means that there is little loss data for an actuary to work with andlimited incentives for the insurance companies because of the limited markets.

Risk management is premised upon identifying risks, avoiding those which can be avoided,and financing those that cannot be avoided. Avoiding risk includes within it the concept of mitigat-ing damages after an event occurs so as to reduce the ultimate cost of an event. Using the riskmanagement matrix described earlier in the paper, risk managers can direct resources toward thoserisks that represent the greatest threat. Risks that are retained are self-financed. Higher severityrisks may be shifted through the purchase of insurance. It may be impossible to obtain insurance forhigh severity, high frequency risks; therefore, it is important to focus on avoiding these risks.

Extension Issues

Automobiles represent one of the highest severity and highest frequency risks that Extensionemployees face. Every risk avoidance program should include automobiles and other vehicles.Many extension employees use personal vehicles for work. Many standard automobile policies donot include business use. In order to have coverage it is necessary to obtain a business use rider/endorsement (at an extra fee).

If state or county vehicles are used, the user should be thoroughly familiar with all policiesgoverning use. Particular points to consider include who is authorized to drive the vehicle and whois authorized to ride in the vehicles. Pulled vehicles present particular problems. Pulled vehiclesare not necessarily covered under the policy that insures the pulling vehicle.

Mandatory reporting is becoming an increasingly important issue for Extension employees.Many environmental, as well as other, statutes make reporting of certain violations mandatory.Failure to report may result in civil or criminal penalties or both. Reporting when reporting was notrequired may also result in liability to the person erroneously reported. Even a required report mayresult in liability if representations were made to the effect that information shared would remainconfidential.

Working with confidential private sector information, while often essential to the Extensionmission, is fraught with liability issues. Premature disclosure of patentable inventions may result inloss of national and international rights. While the frequency of such occurrences may be relatively

50

low the severity can be staggering. Shared trade secrets, business information, and mailing lists alsocarry significant liability risks. Most universities and their Extension organizations have establishedprocedures for handling third party confidential information. It is critical that the Extension employ-ees become familiar with these procedures and adhere to them carefully. Advice from universitycounsel should be sought as uncertainties arise. It is also essential that Extension clientele be madefully aware of the limitations that are placed upon the ability of Extension employees to keep theirinformation confidential, prior to the exchange of any such information.

Increasingly Extension employees must have special certification in order to conduct pro-grams in particular areas. For example, Extension employees in North Carolina who sign animalwaste management plans must now be certified as technical specialists. Extension employees mustknow when a certification is required. In addition, the Extension employee must understand thelimitations of the certification or license.

As agricultural moves into a more regulated environment, Extension employees must avoidthe unauthorized practice of law. The line between providing technical information and interpretingregulations has never been clear and is not becoming any clearer. The issue of unauthorized prac-tice of law is particularly relevant when the Extension employee provides assistance to producerswho have been cited by regulatory agencies for violations. It is important that the Extension em-ployee confines his or her efforts to providing technical information and avoids advocacy before theregulatory agency. In such situations, it is often advisable for the Extension employee to suggest tothe producer that legal counsel be retained to address he legal aspects of responding to the violationnotice.

Conclusions

To be successful a liability avoidance program must be comprehensive and inclusive. Train-ing to identify and avoid and mitigate risks is a key component of any program. Risks and benefitsmust be balanced. The matrix set forth at the beginning of this paper provides a useful frameworkfor setting priorities. Those risks with the highest severity and highest frequency should be ad-dressed first. Although that seems self-evident, it cannot be done without considerable effort toidentify and categorize risks.

References

Avoiding Organizational and Personal Liability, prepared by Ted Feitshans and Carol Schwab,NC Cooperative Extension Service Annual Conference, November 1996

J.W. Looney and Donald L. Uchtmann, Agricultural Law, Principles and Cases, 2nd Ed.,McGraw Hill, New York, 1994

William L. Prosser, Law of Torts, 4th Ed., West Publishing, St. Paul, Mn, 1971

* Disclaimer: This paper is designed to acquaint you with certain legal issues and concerns. No legal services arerendered by distribution of this paper. If you have specific questions on the issues discussed herein, please consult anattorney licensed to practice law in your state.

51

Case Studies on Controversial Drift Problems

Jay EllenbergerOffice of Pesticide Programs, U.S. Environmental Protection Agency

Washington, DC

Two years ago I remember sitting in a small conference room at USDA in Washington, D.C.with about eight others, some from state regulatory agencies, some from other offices of EPA, andsome from the pesticide applicator industry. We spent about two hours trying to come up with adefinition of “spray drift.” I think we had about four different versions! This kind of thing happenswhen people get inside the Washington beltway.

Bob and Jim, I’m glad to be here. Before I begin my talk I want to thank Bob Batteese andJim Dill for having the foresight and energy to arrange this conference. Looking over the agenda, ithas the right mix of technical and nontechnical information to be very useful for everyone.

I’m going to talk to you about why the U.S. EPA is concerned about spray drift, a couple ofclassic drift incidents, how we all need to work toward a common goal of reducing drift, and chal-lenges and opportunities that lie ahead.

1. WHY IS EPA CONCERNED ABOUT OFF-TARGET SPRAY DRIFT?

EPA, through the Offices of Pesticide Programs and Enforcement and Compliance Assur-ance, is interested in and concerned about off-target spray drift because of the potential and unneces-sary risks to people and the environment. The Agency’s concern is validated by more than 2,000annual reports of drift incidents by state regulatory agencies and insurance companies. Spray driftresults in pesticide exposures and risks to agricultural workers in neighboring fields or to otherpeople nearby, including children playing outside their homes or in schoolyards. Spray drift alsoresults in contamination of another farmer’s crops, causing illegal residues or crop damage. And,drift can impact adjacent ecosystems. We all know that all pesticide spray applications by ground orair result in some drift. This is well documented in the scientific literature and by studies in our files.

As a national regulatory agency, EPA is responsible for assuring the public that their healthand the environment are protected from adverse effects from all sources of pesticide exposure. EPAhas the opportunity meet this responsibility through its regulatory programs--registration andreregistration--and by promoting and working with others to achieve sound training and educationfor growers and applicators and compliance among all pesticide users.

As part of EPA’s scientific and regulatory assessments of pesticides, new or old, we considerall sources of pesticide exposure before deciding how or even whether a pesticide should be used.Besides relying on scientific studies we are increasing our attention to incidents in the real world,including adverse effects from drift--how many incidents reported, how serious are they, and forwhich uses and application methods.

Product labeling is a fundamental tool to dictate application strategies that can reduce driftthrough required buffer zones, lower application rates and frequencies or numbers of permitted

52

applications per year or growing season. When such mitigation measures don’t provide adequateprotection, or applicators won’t abide by these measures, EPA may further restrict or cancel the use.

But label-based measures cannot adequately address all specific and unique local conditions.Regulators and users operating in the field are better equipped to integrate the site-specific circum-stances into a reasonable mitigation approach. National regulatory guidelines need to be specificenough to provide consistency across a varied agriculture, and flexible enough to contribute tobalanced solutions that work for farmers and applicators and that adequately protect human healthand the environment.

2. DRIFT INCIDENTS

As I mentioned earlier, 1000s of drift incidents are reported each year. Many others are not.The States, through the coordination of Paul Liemandt of Minnesota’s Department of Agriculture,reported their incident records in the three years 1993 - 1995. This provides us with a good baselineof the magnitude of the problem. We need to continue measuring how we’re doing with incidents--hopefully in a downward trend. Incidents vary widely, as you know, in their magnitude of effectsand how they’re dealt with by affected parties, the regulatory agencies, and the insurance companies.I’ve selected two major drift incident cases to tell you about this morning. Both are current. I’veselected each to illustrate a number of things: how cases can be dealt in different fashions, the com-plexity of resolving the issues, and the levels of interests and costs that can be associated with driftincidents. Some of you may be familiar with one or both of these cases.

• The first case is in Puerto Rico. Here’s a summary of the facts.The drift issue was raised in 1996 by residents of a community adjacent to a corporate farmthat grows orchard crops. So, think of airblast sprayers involved here. Residents of theneighboring community began to report health effects associated with pesticide applicationsto the Puerto Rico Department of Agriculture and the Environmental Quality Board. Localenforcement efforts were unsuccessful.

The EPA Regional Office that has responsibilities for Puerto Rico was asked to becomeinvolved. EPA issued penalties for violations of FIFRA. Drift complaints continued. Nowthe U.S. Department of Justice becomes involved and the case is taken to Federal court to getthe farm owner to comply with the requirements and limitations designed to eliminate orreduce drift.

EPA continues to work with the affected community. Drift incidents continue. The Federalcourt begins imposing buffer zones ranging from 200 to 600 feet between areas of highpressure sprays and the community for individual pesticides and a 72-hour notificationperiod; a $500,000 fine imposed on the farm owners. Consultants for Justice have beencalled in to conduct a drift monitoring study and to follow-up with a risk assessment whichwill be used to set more chemical specific use limitations.

• The second ongoing case is in central California, in and around a city named Lompoc.In contrast to the case in Puerto Rico, the drift issue in Lompoc is being dealt with by aconsortium of representatives from Lompoc citizens, growers, local, state, and federalgovernment agencies. The “Lompoc Project” is seeking to understand concerns of the

53

community, collect and disseminate information, and ultimately find appropriate solutions.In 1994, Lompoc residents raised concerns about adverse health effects and pesticideexposures associated with the pesticide use on cropland surrounding this town. Lompoc islocated near the Pacific coast in a basin surrounded by hills. Some claim temperatureinversions are in part responsible for exposures from drift.

Community concerns about impacts to their health from pesticide use persist despite ademonstration of compliance and some voluntary mitigation measures by growers andapplicators.

Some concerned residents have demanded a total ban on the spraying of pesticides, saying”You’re killing our children.” Growers counter with “You’re destroying our livelihood.”Collaboration doesn’t come easy in such a climate but, those involved are seeking tounderstand and ultimately find appropriate solutions.

The State pesticide regulatory agency ultimately convened a workgroup, a consortium ofrepresentatives from citizens, growers, as well as local, state, and federal governmentpesticide and health agencies. This group is charged with studying the situation anddeveloping recommendations to present to the California Department of Pesticide.

A recently released report by the state health agency suggests a higher than the expected rateof respiratory illness in the Lompoc area. There’s a recommendation to conduct an ambientair monitoring study for pesticides. And, there’s consideration of other environmental factorsas well.

The consortium holds regular public meetings to discuss findings and seek input for furtherplanning and recommendations.

Obviously, the drift issues in these two situations are being dealt with very differently. Butin both cases there are enormous energies and costs to ultimately reduce off-target drift. There’s realinterest by the public for action and measurement of the impact and of mitigation. Obviously not alldrift incidents come to this level of effort. But, these types of cases are becoming more common.Government is expected to address these concerns. I believe we all share the interest of preventingas many of these incidents as possible, minimizing unnecessary costs, both economic and social.How we do that is complex and involves working collaboratively in ways that are new to most of us.

3. DEALING WITH DRIFT

I ask: Are the applicators doing all they can to minimize drift? Are government agencies,the pesticide companies, and research organizations doing all we can to support growers andapplicators to choose the lowest risk pesticides and practices?

How we deal with off-target drift can start with the applicator or end with the regulator. Isthe applicator using the best available technology, is he or she availing him or herself with educationand training in drift reduction strategies? And frankly, is he putting pressure on his peers to be abetter applicator? The regulator can use a number of approaches to change applicator behavior--bysupporting education programs, meeting and talking with applicators to exchange information, and ifnecessary make changes to how pesticide products are applied.

54

We know from the literature and the available studies, including the data from the Spray DriftTask Force, and from reported incidents that pesticide applications result in drift. A highly acutetoxic pesticide drifting off-site can raise red flags for regulatory agencies to take action to prevent orminimize future incidents. However, EPA prefers a proactive approach by everyone--pesticidemanufacturers or registrants, educators, and applicators to prevent drift problems. Many times, thatdoesn’t happen. Resulting incidents can be very controversial as I’ve illustrated here.

• Coalition on Drift Minimization

As you’ve heard yesterday, the Coalition on Drift Minimization is a multi partner groupfounded two years ago to identify and facilitate initiatives that will positively affect drift reduction inthe real world. One of the biggest benefits I’ve found by participating in the Coalition is thecollaboration among the varied participants, each representing a different aspect and perspective ofthe drift issue. Each member brings talent, perspective, and fresh ideas on how to reduce drift. Weare all working toward the common goal using three different tools to get there--improvedtechnology, education, and regulatory tools.

• Training programs for applicators

One of the obvious means of informing applicators about the drift issue and what they can doto minimize drift is through the many education and training programs held around the country.These include the State Pesticide Certification and Training courses, pesticide applicator workshopsoffered by organizations like the National Agricultural Aviators Association and the AgriculturalRetailers Association, and by state universities. The continuing education of applicators is importantfor introducing them to ever changing technology.

Bob Wolf from the University of Illinois has designed a wonderful demonstration he calls his“spray table.” If you haven’t seen it you should. With it, Bob does a great job of showing howdifferent nozzles, their angle, and wind direction and speed affect drift. I understand he’s taken it onthe road. In addition, I know of at least two new drift videos that have been produced this past year--one by PAASS and the other by Bob Wolf. I’ve seen both videos and I know they will be effectivein educating the applicator and changing his or her perspective and behavior.

In the case of “fly-ins” aerial applicators can actually be shown how well their plane is doingon drift and learn strategies for even additional drift reduction. Education programs impress andreinforce the importance of drift control. Let’s face it, reducing drift is to the benefit of everyone:there’s better application efficiencies, more of the pesticide lands on the target crops and less off thetarget; there’s reduction of liabilities; and there’s better product stewardship in protecting againstunnecessary exposures of pesticide to nearby people and the ecosystem.

• Better Pesticide Product Labeling

As a regulatory agency, a couple of approaches EPA is taking is developing better labelingfor pesticide products and incorporating the Spray Drift Task Force’s data base and the AgDRIFTmodel into our risk assessments. Historically EPA required all agricultural and forestry pesticides tobear the simple label statement: “Do not allow drift.” It’s easy to understand and it’s enforceable.The problem with it is it’s somewhat of an oxymoron. We all know that all applications result insome level of drift.

55

So, a few years ago, recognizing this issue and interest from within and outside of EPA, wedrafted a set of Best Management Practices, or BMPs, we thought would better serve applicators.We sought advice from the pesticide industry Spray Drift Task Force and some state regulatoryagency personnel. Later after the Coalition was formed we sought the members’ advice. Althoughwe recognized the new BMP labeling as somewhat draft, EPA began requiring it for product labelsgoing through our new registration and reregistration programs. This set of BMPs, divided intomandatory language and advisory language, is not meant to override the “Do not allow drift.”statement or state restrictions that may be more restrictive. Rather, EPA intends the BMPs to offermore realistic guidance to applicators on how to minimize drift. They’re meant to offer applicatorswith more flexibility in reducing drift, recognizing the complexity in achieving this.

Recently, we offered a review of the BMPs to a wider audience of experts, particularly thosewho deal with drift in a regulatory capacity every day, namely EPA’s regional offices and the statepesticide enforcement personnel. Some of you in the audience provided EPA with valuablecomments and suggestions for improving these BMPs. Frankly, comments ranged from “Greatest,since sliced bread.” to “These are terrible.” reflecting the variety of needs and expectations oflabeling.

I’ve asked EPA’s Pesticide Labeling Unit to get involved in refining this label language tomeet the needs of most. Clearer label language can help, though not solve all our challenges. TheLabel Unit has the skill to work through tough labeling issues like this. Given the diversity ofcomments, I want them to work the BMPs and comments through a group like SFIREG, the StateFIFRA Issues, Research Evaluation Group, and see if we can’t have a better product later this year.

• EPA Use of the Spray Drift Task Force Data and the AgDRIFT Model

Just a few years ago the Spray Drift Task Force was nearing completion of their drift studiesto satisfy data requirements to support new and continued registration of agricultural products.Looking back I believe the collaborative effort among the 30-some major U.S. pesticide companies,USDA, and EPA to complete this effort was very fruitful for a number of reasons. I believe EPA gota better data-product than had we continued to receive discrete studies from individual companies oneach of their products. I also believe this effort resulted in new, basic research while also supportingsome of the results reported in the literature. The Task Force has also been working with EPA’sOffice of Research and Development to produce or upgrade “AgDRIFT,” a mathematical model forpredictive drift estimates.

EPA has been very carefully reviewing these data and thoughtfully brought in other outsideexperts to provide their independent judgements on interpretation of the data. Additionally, EPA hastaken the aerial application sections of the Task Force data and AgDRIFT through our ScienceAdvisory Panel for their independent review. We want to assure scientific integrity of the productwe use in our risk assessments. We will soon be ready to use the Task Force data base andAgDRIFT in our risk assessments of pesticides where deposition is important. AgDRIFT is alreadybeing used by the Canadian government for their risk assessments.

56

4. CHALLENGES AND OPPORTUNITIES

Outstanding issues continue to challenge our efforts to minimize drift. The relationshipbetween science upon which risks are assessed and real world of application and its impacts continuesto challenge us. Furthermore, the variety of issues associated with drift requires consideration of manydifferent circumstances and mitigation approaches. For instance, issues pertaining to large-acreagemonocrop system are likely to raise different concerns than in cases where many more crops andpesticides are used in close proximity to non-agricultural land uses.

Data on which drift risk assessment and decisions are based have been enhanced by the workof the Spray Drift Task Force. EPA, the Coalition, and others have noted the intrinsic limitations in thescientific validation of real-world drift and has recognized that a refined regulatory response andeffective enforcement must be accompanied by complementary responses by applicators, regulators,and educators.

Professionalism and prudence must be elevated in the applicator industry. All decisionmakers must encourage integration of principles of stewardship beyond compliance with the law. Wemust continue to identify and encourage research and extension of specific areas of concern. A nationalcurriculum of standards for a regulatory applicator educational program needs to be developed. And, weneed to improve our partnership with agricultural insurers so we can better assess impacts andcommunicate concerns to the regulated community. It is likely that the coming years will also provideus with better monitoring data that will tell us how we are doing in managing drift.

It’s very important that applicators, growers, product manufacturers, regulatory agencies,and research communities continue to work together to make improvements and seek solutions.Regulatory agencies can and will take actions as they see necessary to restrict the use of certainagricultural pesticides in order to assure public health and environmental protection. The reliance onregulatory solutions can be minimized to the degree that individual applicators and the industry as awhole continue to improve their technical skills and decisions to reduce spray drift.

57

Drift Laws

Theodore A. FeitshansNorth Carolina State University

Raleigh, North Carolina

Introduction

For the purposes of this paper drift is defined as the unintentional airborne movement of pesticides ineither particulate, liquid or vapor form beyond the target area where the pesticide was applied.Analysis of the case law reveals that pesticide overspraying, the unintentional direct application ofpesticides to a non target area, is usually included within the definition of drift; therefore,overspraying is included within the definition of drift for purposes of this paper. Drift is defined asunintentional so as to distinguish it from deliberate pesticide misuse. Drift also has an immediatecharacter to distinguish it from pesticide residue damage situations. And it is airborne to distinguishit from offsite damage resulting from movement of water.

A complex mixture of federal and state law govern drift. However, since drift is primarily related touse and the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) defines state law as primaryin the regulation of use, regulation of drift is primarily a state responsibility.1 Nonetheless, FIFRAprovides the Environmental Protection Agency (EPA) to regulate use where a state regulatory au-thority has failed to act.2

EPA plays the primary role in the registration and labeling of pesticides under FIFRA.3 EPA regula-tions require analysis of the propensity of a pesticide to drift as part of the registration and labeldevelopment process.4 5 Since it is unlawful to use a pesticide in a manner inconsistent with itslabeling, EPA can, by requiring label restrictions related to drift, restrict the use of specific pesti-cides.6 EPA also requires, by interim regulation, a specific worker protection statement on the labelof most products for agricultural use that includes reference to drift.7 EPA requires that standardsfor certification of commercial applicators include knowledge of drift prevention, if appropriate.8EPA also regulates drift through its Worker Protection Standard; a discussion of drift must be in-cluded in EPA-approved pesticide safety training for workers and pesticide handlers.9 Emergencyassistance must be provided to any employee exposed to drift.10 EPA regulations further require that“no pesticide is applied so as to contact, either directly or through drift, any worker or other person,other than an appropriately trained and equipped handler.”11

As noted above, FIFRA defines regulation of pesticide use as primarily a state responsibility. Sincedrift is a result of pesticide use, drift is primarily an area for state regulation. States have, for manyyears, shown a remarkable diversity in their approaches to regulating drift.12 This diversity appearsto have increased in recent years with local governments showing an increasing propensity to at-tempt to regulate pesticides used within their borders. The body of this paper will explore theseapproaches to the regulation of drift.

58

State Prohibitions of Drift, Pesticide Overspray, and Off Site Damage

Prohibitions of drift take several forms. Some are outright prohibitions written into statutes orregulations that provide for assessment of penalties without regard to harm caused. Others are reallynot prohibitions against drift but rather prohibitions of off site damage. The difference between thetwo is that the latter requires some damage away from the target site for any liability to arise. Whilemost states have enacted these regulatory schemes through legislation or the regulatory process, afew states have adopted their approach by court decision. Some states limit their prohibitions tocertain chemicals or classes of chemicals; some limit their prohibitions geographically. Othersdifferentiate between aerial and ground applicators.

General prohibitions

The Alabama Administrative Code provides in relevant part:“(9) No person shall dispense or cause to be dispensed from aircraft engaged in custom

pesticide application any pesticide:(a) Under such conditions that the applied pesticide would drift outside the target

area to be treated and cause or create a hazard or potential adverse effect toman or the nontarget environment;

(b) Under conditions that would result in pesticide overspray;...(e) In a manner that creates a hazard to persons, property, established apiaries,

aquatic life, wildlife, and other non-target organisms.13 “

The Alabama regulation clearly distinguishes between drift and pesticide overspray by providingseparate definitions for each.14 The regulation quoted above prohibits overspray absolutely; how-ever, the prohibition on drift is modified to apply only when damage occurs to humans or the nontar-get environment. Thus the prohibition on drift is best categorized as a prohibition of off site damagecaused by drift.

California regulations provide a general prohibition against nontarget damage:“(b) Notwithstanding that substantial drift would be prevented, no pesticide application

shall be made or continued when:...(2) There is a reasonable possibility of damage to nontarget crops, animals, or

other public or private property; or(3) There is a reasonable possibility of contamination of nontarget public or

private property, including the creation of a health hazard, preventing normaluse of such property. In determining a health hazard, the amount and toxicityof the pesticide, the type and uses of the property and related factors shall beconsidered.15 “

Maryland requires pesticide applicators to:“(3) Observe all precautions in the handling, use, storage, and disposal of pesticides and

their containers so that:(a) Pesticides do not move from the intended site of application,(b) Nontarget areas or organisms, including humans, do not suffer injury, and(c) Unreasonable adverse effects on the environment do not occur or are mini-

mized...16 “

59

Massachusetts prohibits all visible drift from aerial application of pesticides.17 Minnesota prohibitsoverspraying and off site damage by statute: “A person may not direct a pesticide onto propertybeyond the boundaries of the target site. A person may not apply a pesticide resulting in damage toadjacent property.18

Mississippi defines drift such that drift not capable of causing off-site is excluded from the defini-tion:

“Drift - Shall mean the physical movement through the air at the time of application of apesticide from the site of application to any non-target site in sufficient quantities to causeinjury to the non-target site...”19

Movement by volatility is excluded from this definition.20 Drift, thus defined, is prohibited withsanctions ranging from a warning to criminal penalties, based upon the severity of the violation.21

New Jersey regulations prohibit drift generally: “No person shall make an application of a pesticideto a target site in such a manner or under such conditions that drift or other movement of the pesti-cide, which is avoidable through reasonable precautions, infringes on a non-target site.”22 NorthCarolina regulations for both provide, “No person shall apply a pesticide(s) under such conditionsthat drift from pesticide(s) particles or vapor results in adverse effect.”23 Ohio law provides that “No person shall apply pesticide at such time or under such conditions that the wind velocity willcause the pesticide to drift and cause damage.”24 Pennsylvania flatly prohibits making pesticideapplications when weather conditions are such that the pesticide can move off site, and Pennsylvaniaprohibits application in any manner that results in unwanted residue on the property of another.25

Puerto Rico prohibits off site damage.26

Withdrawal from certain areas

Arizona requires buffer zones around schools, day care centers, health care institutions and resi-dences.27 No odoriferous pesticide, including several listed by name, profenofos, sulprofos, def, andmerphos, may be applied within the prescribed buffer zones.28 A similar prohibition applies tohighly toxic pesticides (paraquat is named). The statute expressly prohibits the application of anypesticide that results in drift within the grounds of a residence, school, day care center, or health careinstitution.

Arkansas law provides broad authority to its State Plant Board to prohibit the effects of drift.29

Arkansas uses a rather elaborate zone system to prohibit the effects of drift.30 The regulationsdifferentiate between aerial and ground application, provide special rules for specific chemicals, andinclude restrictions based upon the growing season of sensitive crops. The regulations also includereference to wind conditions, distance of application from the crop canopy and equipment specificrules.

Delaware Department of Agriculture has broad authority to act to prevent drift; measures availableinclude restricting or prohibiting use of pesticides in designated areas at specific times.31 Floridaprohibits application of organo-auxin herbicides in specified counties from January 1 to may 1.32

Florida also requires that aerial and ground applicators maintain buffer zones between the target areaand susceptible crops.33 These buffer zones are greater for aerial application and for both aerial andground application increase with wind speed; above wind speeds of ten miles per hour all applica-tions are prohibited.34

60

Idaho requires a one-half mile buffer around any hazard area.35 Aerial application of methyl par-athion is prohibited in certain areas.36 Geographic restrictions on the use of phenoxy herbicides arediscussed below. Louisiana prohibits the application of seventeen specific chemicals in severalgeographic locations during parts of the year.37 Louisiana has also established buffer zones betweentarget zones and inhabited residences or susceptible crops.38 These buffer zones vary from 2 milesdownwind to 5 feet upwind, with the variables determining the width of the buffer being wind speedand whether aerial or ground equipment is used. All applications are prohibited when wind speedsexceed 10 miles per hour.39

Massachusetts requires all pesticide applicators to observe designated buffers around water supplies,surface waters, wetlands, residences and susceptible crops.40 New York requires buffers aroundvineyards; certain phenoxy herbicides may not be used within the confines.41 North Carolinaprohibits aerial application of pesticides in restricted areas that include buffer areas around resi-dences, right of ways along public roads, schools, hospitals, nursing homes, churches, or any otheroccupied building used for business or social purposes.42 Oregon provides for buffers aroundsurface waters and surface water supplies.43 Rhode Island prohibits pesticide applications in areasaround wells and requires that no drift occur where pesticides are applied in the vicinity of publicwater supplies, crops and pasture.44 Texas restricts the geographic application of certain pesticides,primarily phenoxy herbicides.45 West Virginia requires setbacks of varying distnces depending uponthe land use protected.46

Restrictions on chemicals or classes of chemicals

Arkansas prohibits all crop dusting by either aerial or ground application.47 It also prohibits the useof most esters.48 Its zone system discussed above applies special rules to certain chemicals.

Kansas is somewhat an unusual situation in that it has regulated phenoxy herbicides by judicialdecision.49 In Binder v. Perkins the Supreme Court of Kansas held that “The duty of care imposedupon the crop sprayer, however, is a matter for the courts, and the trial court in this case has charac-terized 2-4D as a dangerous instrumentality, handling of it a hazardous activity, and has imposedupon the one handling it a duty to prevent its escape.”50 Although the court applied a negligencestandard, it held that allowing drift of 2-4D constitutes negligence. Thus under the Kansas rule,compensation must be paid for any off site damage. Query whether there is any real differencebetween this standard and the application of strict liability to drift?

Idaho places substantial restrictions on the use of phenoxy herbicides.51 Use is prohibited in certainareas of the state while buffers are required in all other areas.52 Some of the buffers for certainchemicals are fixed while other buffers vary with wind speed; no applications may be made whenwind speeds exceed ten miles per hour.53 Louisiana flatly prohibits the use of “any ester compoundof phenoxy herbicide containing an aliphatic alcohol radical with less than six carbon atoms...”54

Mississippi strictly regulates the use of hormone-type (primarily phenoxy) herbicides applied byaircraft.55 A separate license to apply hormone-type herbicides is required.56 Four types of licenses,each requiring a separate examination, are offered: weed control in soybeans; weed and brush controlon right-of-ways, forest lands, and drainage ditches; weed and brush control on pasture and range-land, small grains and other farm crops except rice; and weed control in rice.57 The regulations alsoprovide specifications for equipment, inspection requirements, ground observers, seasonal and windcondition restrictions, and reporting of all treatments to the Division of Plant Industry.58

61

North Carolina regulations provide for equipment restriction for the aerial application of phenoxyherbicides, paraquat, picloram, and dicamba.59 These restrictions are in addition to the generalprohibition on drift cited above. While the general prohibitions on drift for ground and aerial appli-cation of pesticides is almost identical, additional restrictions are placed upon the application ofspecific pesticides by air.60 Oregon requires that a special permit be obtained for application ofcertain phenoxy herbicides.61

Other Regulations and Restrictions

Many states require that commercial applicators prove financial responsibility as a condition ofcertification as a commercial applicator. Financial responsibility may be demonstrated through avariety of means including insurance and bonding. Many states also require reporting of incidents.A few states, Mississippi, Kansas, North Dakota, Oregon, and Oklahoma make timely reporting bythe damaged party a prerequisite to collecting damages for drift and other off site events.

Many states require notification to neighbors and buffers between the target area and neighboringproperties. Many states require separate certification for aerial applicators. Some states authorizelocal legislation while others specifically prohibit it.

Conclusion

State regulation of drift ranges from nonexistent to extremely complex. There are no characteristicsof state regulation of drift that are universally applicable. There is not even universal agreementupon a definition for drift. In the accompanying Appendix to this article, drift laws of the fifty statesplus Puerto Rico have been excerpted. Where no reference is made to a state, no laws regulatingdrift were found. Note that some state laws and regulations may affect drift without specificallyreferencing it. For example, a financial responsibility requirement might not reference drift butwould nonetheless provide a fund from which drift damages could be paid.

1 7 U.S.C.A. § 136W-1 (1997)“State primary enforcement responsibility(a) In general

For the purposes of this subchapter, a State shall have primary enforcement responsibility for pesticide use violations during any period for which the Administrator determines that such State -(1) has adopted adequate pesticide use laws and regulations, except that the Administrator

may not require a State to have pesticide use laws that are more stringent than thissubchapter,

(2) has adopted and is implementing adequate procedures for the enforcement of such Statelaws and regulations: and

(3) will keep such records and make such reports showing compliance with paragraphs(1) and (2) of this subsection as the Administrator may require by regulation.”

2 7 U.S.C.A. § 136w-2 (1997)3 7 U.S.C.A. §§ 136a to 136a-1 (1997)4 40 C.F.R. § 158.202(g) (1997)

“Pesticide Spray Drift Evaluation.Data required to evaluate pesticide spray drift are derived from studies of droplet size spectrum and spray driftfield evaluations. These data contribute to development of the overall exposure estimate and along with data ontoxicity for humans, fish and wildlife, or plants are used to assess the potential hazard of pesticides to theseorganisms. A purpose common to all these tests is to provide data which will be used to determine the need for(and the appropriate wording for) precautionary labeling to minimize the potential adverse effect to nontargetorganisms.

62

5 40 C.F.R. § 158.20(c) (1997); 40 C.F.R. § 158.440 (1997)6 7 U.S.C.A. § 136j(G) (1997)7 40 C.F.R. § 156.206(a) (1997)

“Application restrictions. Each product shall bear the statement: ‘Do not apply this product in a way that willcontact workers or other persons, either directly or through drift. Only protected handlers may be in the areaduring application.’ This statement shall be near the beginning of the DIRECTIONS FOR USE section of thelabeling under the heading AGRICULTURAL USE REQUIREMENTS.”

8 40 C.F.R. § 171.4 (1997)“For example, practical knowledge of drift problems should be required of agricultural applicators but not ofseed treatment applicators.”

9 40 C.F.R. §§ 170.130 and 170.230 (1997); 40 C.F.R. § 170.234 (a) (1997)“The handler employer shall assure that before the handler uses any equipment for mixing, loading, transfer-ring, or applying pesticides, the handler is instructed in the safe operation of such equipment, including, whenrelevant, ... drift avoidance.”

10 40 C.F.R. §§ 170.160 and 170.260 (1997)11 40 C.F.R. § 170.210 (1997)12 Redfield, Agricultural Law Symposium: Chemical Trespass? — An Overview of Statutory and Regulatory

Efforts to Control Pesticide Drift, 73 Ky. L.J. 855, 859 (1984)13 Ala. Admin. Code 80-1-14 (1997)14 Id.,

“Drift: the drifting or movement of a pesticide by air currents or diffusion onto property beyond the boundariesof the target area to be treated with pesticide.”“Pesticide Overspray: The application of a pesticide onto property beyond the boundaries of the target areawhich is caused by the failure to control the direct flow of the pesticide or by a failure to control the applicationequipment in surrounding conditions of use and application in a manner which fails to confine the pesticide tothe target area.”

15 Cal. Code Reg. tit. 3, @6614 (1997)16 Md. Regs. Code § 15.05.01.02 (1997)17 Advisory Statement of the Massachusetts Department of Food and Agriculture Relative to Agricultural

Aerial Pesticide Applications, Approved by the Massachusetts Pesticide Board on March 8, 1988.18 Minn. Stat. § 18B.07(b) (1997)19 Memorandum of Agreement between the Agricultural Aviation Board of Mississippi and the Bureau of

Plant Industry, Mississippi Department of Agriculture and Commerce to enter into a Cooperative Drift Minimi-zation Program to reduce the number of incidents of pesticide drift by a minimum of fifty percent during 1991(1990)

20 Id.21 Id.22 N.J.A.C. tit. 7, § 30-10.3(f) (1995)23 N.C. Admin. Code tit. 2, § C9-S9L.1404 (1997); N.C. Admin. Code tit. 2, § C9-S9L.1003 (1997) (The

regulation governing aerial application reads identically except for the insertion of “aerially” before after thefirst “pesticide(s)); “Occasionally, critics will claim that North Carolina has a “zero drift” rule for pesticides thatare applied aerially. The reality is that North Carolina has restricted areas in which pesticides can not bedeposited by aerial application.”, letter, dated March 6, 1998, from the Pesticide Section, North CarolinaDepartment of Agriculture.

24 Ohio Admin. Code § 901:511.02(G) (1997)25 7 Pa. Code Ch. 128, § 103 (1987)26 P.R.R. & Regs. tit. 4, 214 (1997)27 Ariz. Rev. Stat. § 3-365 (1997)28 Id.29 Ark. Stat. § 20-20-206 (1997)

63

30 Ark. Reg. 4.9 (1997)31 Del. Code tit. 3, § 1203 (1997)32 Fla. Admin. Code § 5E-9 (1997)33 Id.34 Id.35 Idaho Code §600 (1997)36 Idaho Code §601 (1997)37 La. Admin. Code tit. 7, § 13139 (1997)38 Id.39 Id.40 333 Code Mass. Regs. § 11.04 (1997)41 NY Agric. & Mkts. Law § 321.0 to 321.3 (McKinney 1997)42 N.C. Admin. Code tit. 2, § C9-S9L.1005 (1997);43 Or. Admin. R. 629-620-400 and 629-620-800 (1997)44 Rhode Island Pesticide Control Law (1997)45 Tex. Admin. Code tit. 4, §§ 7.1 to 7.71 (1997)46 W. Va. Code § 61-12D-5 (1992)47 Ark. Reg. 4.2 (1997)48 Id.49 Binder v. Perkins, 213 Kan. 365, 516 P. 2d 1012, 1973 LEXIS 642 (1973)50 Id.51 Idaho Code § 550 (1997)52 Id.53 Id.54 La. Admin. Code tit. 7, § 13137(D) (1997)55 Regulations Governing the Application of Hormone-Type Herbicides by Aircraft, Mississippi

Department of Agriculture and Commerce (1991)56 Id.57 Id.58 Id.59 N.C. Admin. Code tit. 2, § C9-S9L.1003 (1997);60 Id.61 Or. Rev. Stat. § 634.322(10)(a) (1995)

64

Weather Effects on DriftMeteorological Factors and Spray Drift: An Overview

Harold W. Thistle, Jr.Missoula Technology and Development Center

USDA-Forest ServiceMissoula, MT

Milton E. TeskeContinuum Dynamics, Inc.

Princeton, NJ

Richard C. ReardonForest Health Technology Enterprise Team-Morgantown

USDA Forest ServiceMorgantown, WV

Abstract

A summary is given of the meteorological factors that affect spray drift. The primary factors arewind speed and direction, humidity through its influence on droplet size, and atmospheric stability.It is difficult to generically quantify and rank the effects of meteorology on spray drift due to thecomplex interactions between spray material, the application system, the target and the ambientmeteorology. An approach to dealing with this complexity is the development of computer models.Three types of models are discussed from the standpoint of the meteorology and dispersion algo-rithms.

Introduction

The amount of spray drift from a given application depends on many factors. These can roughlybe broken down into factors related to the material properties of the sprayed material, factors relatedto the application mechanism and method, and finally, factors related to the ambient environment,including both the state of the atmosphere and the nature of the target. Drift is enhanced or hindered based on the state of the ambient atmosphere through which thematerial traverses. The longer the material is in the atmosphere, the more important ambient atmo-spheric conditions become. Arguably, the single most important variable in drift is the size of thesprayed droplets. Sprayed droplets evaporate after release into the atmosphere, becoming smallerwith time and more susceptible to drift. See Bache and Johnstone (1992) and Miller et al. (1995) foroverviews of spray meteorology. This paper discusses the role of the atmosphere on a droplet. This discussion focuses on theprimary transport of the droplet, defined here as the movement of the droplet from its release into theatmosphere until it impacts a surface. Volatile chemicals will change phase and disperse as a gas.Though much of this discussion is relevant to gaseous dispersion, this phenomena is not discussed atlength here. Other spray materials are not volatile and will not evaporate. Deposited material may,under some circumstances, be re-entrained by the atmosphere. This is known as secondary drift.

65

The objective of this discussion is to provide an overview of the effect of the state of the atmo-sphere on spray. It is directed to spray applicators and managers and attempts to provide a basicunderstanding of meteorological influences on spray drift and a conceptual framework that will aidin operational decision-making.

The Machine

This paper must begin with a discussion of the spray apparatus. The meteorological variables areoften overwhelmed near the release by forces associated with the release mode and mechanism. Inmost cases of spray application, the spray material is emitted at high velocity from a pressurizedsystem or injected into a high velocity air-stream. Sometimes it is chopped by a fan or screen. Theobject is not to give an exhaustive list of release modes, but to point out that the material oftenbegins its traverse through the environment with an initial temperature, initial velocity, and in aturbulence field different from ambient conditions. In the case of aerial spraying, the material isgreatly affected by the wake of the aircraft. In many row crop applications, the wake of the aircraftis used to push material into the crop canopy. Spray released from ground sprayers will be awayfrom the energy associated with the release within a few meters. In aerial spraying, the size andstrength of the wing-tip vortices depend on the weight of the airplane and the length of the wing(Teske et al., 1994). Such a wake may influence spray for tens of meters after ti has been released.Material still aloft beyond the influence of the release mechanism is available for drift. The extentand distance of drift depends on interaction of the material with the ambient environment as deter-mined by meteorological conditions.

Wind Speed and Wind Direction

Motion in a three-dimensional fluid is a vector quantity, meaning it has speed and direction. Thefamiliar statement of wind speed and direction provide two of the most important meteorologicalvariables when considering spraying conditions. Wind direction is a highly variable quantity in bothtime and space. Standard deviations of 20° are not uncommon in a wind direction record withmeasurements every second (1Hz) at a point in space. However, a mean wind direction (10 minuteaverage for instance) will adequately determine the mean direction of the movement of the spraycloud centerline and thus the direction of drift. The wind supplies the horizontal transporting force while gravity supplies the downward force.The mean horizontal wind speed will determine how fast the droplet moves in the horizontal direc-tion. The velocity at which the droplet would fall in still air is known as droplet ‘settling velocity’.Gravitational forces that act downward are opposed by drag forces that act to slow the fall rate. Verysmall droplets (<100 m or so) fall so slowly because the downward gravitational force is almostequally opposed by drag forces. In the simplest representation of droplet movement in the atmo-sphere, we can draw a vector resultant between the downward settling velocity and the horizontalwind speed to yield a fall angle and approximate droplet speed (Figure 1). As discussed below,many factors complicate droplet movement in the atmosphere, but this simple resultant trajectorymodel is a beginning. The wind speed can also be viewed as a dilution rate when the released material is considered as avolumetric cloud. The higher the wind speed, the more fresh material is mixed into the cloud vol-ume and the more dilute the material becomes, equating to an increase in dispersion of individualdroplets. Due to the drag of the surface of the Earth and the obstacles on it, wind speed increases

66

with height. The increase with height is generally approximated as logarithmic, so aerial applicatorsneed to be aware that a wind speed measured near the surface may not represent that at the releaseheight of the spray.

Humidity and Temperature

Humidity is defined as the amount of water vapor in the air. The direct statement of this quantityis absolute humidity, H, :

H= eMW/RT (1)

where e is water vapor pressure in Pascals (Pa), MW is the molecular weight of water (kg mol-1), R isthe universal gas constant (Pa m3 mol-1 K-1) and T is temperature (K). Working through the unitsshows that this results in a measure of humidity in mass per volume or kg m-3 . Jones (1983) gives acomplete overview of this topic. Since both MW and R are constants, the relationship for H can bewritten:

H = (2.17/T)e (2)

Relative humidity (RH) is the humidity measure most often used when discussing drift. RH is ex-pressed as:

RH=100(e/es) (3)

Thus relative humidity is a measure of the ratio of e to the vapor pressure when the air is saturatedwith water vapor (es). The absolute humidity relationships shown previously indicate a problem withusing RH, and that is that es is dependent on T. This can confuse discussion of temperature vs.humidity effects. The importance of relative humidity to spray drift derives from the dependence ofspray drift on droplet size. After release into the atmosphere, the initial droplet size begins to shifttowards smaller sizes. The rate of change of droplet sizes over the entire droplet size spectrumdepends on the chemistry of the released material and the humidity of the air. Assume the spraydroplets are spherical. The volume (and thus the mass of a uniformly mixed drop) varies with thecube of the sphere diameter. A water droplet of 200 m diameter has a settling velocity of 0.705 ms-1

while a droplet of 40 m has a settling velocity of 0.047 ms-1. This is a factor of five difference indroplet diameter and a factor of 15 difference in settling velocity. Consider a release height of 15 mand a wind speed of 1 ms-1. If we ignore the effects of turbulence and assume for simplicity sake(unrealistically) that the wind is laminar, a droplet of 200 m diameter would move with the wind 21m before reaching the surface while a droplet of 40 m would move 318m. It must be emphasizedthat this is an overly simplistic portrayal of droplet movement in the atmosphere. The point is that asthe droplet evaporates, the location that the droplet impacts the surface is greatly altered and predic-tion of that point of impact becomes increasingly difficult. The physics of small droplet evaporationare discussed elsewhere (see Davies 1978 for a review article) and many aspects of this problem arestill a matter of active research (some effects of turbulence are discussed below). It can generally besaid that as the droplet becomes smaller, it will spend more time in the atmosphere, other thingsbeing equal because of lower settling velocity.

67

Atmospheric Stability

Atmospheric stability is simply the change of temperature in the atmosphere with height. Theuniversal gas law:

PV=nRT (4)

where P is pressure, V is volume, n is moles, R is the universal gas constant and T is temperaturedictates a relationship between pressure and temperature. The equation for this relationship in theatmosphere is more complex than equation 4 however the basic relationship holds. When the tem-perature/pressure relationship is the primary control of the temperature profile in the atmosphere,indicating that no other important sources or sinks of thermal energy are affecting it, the profile issaid to be neutral and follows the adiabatic lapse rate which is a 3.6°F/1000ft temperature drop withincreasing height in a dry atmosphere. The temperature profile is commonly expressed as dT/dz ortemperature change with respect to change in height. Forecast meteorologists analyze a deep atmo-spheric layer to forecast weather. They use a term called potential temperature, , that accounts forthe pressure temperature relationship so that d /dz = 0 in a neutral atmosphere. In general, the nearsurface layer where pesticide spraying occurs is sufficiently shallow so that a conversion to is notuseful and tends to complicate the discussion. If high release heights are necessary, conversion tomay simplify interpretation. Three primary factors cause the atmospheric stability to tend away from neutral. The first isdirect input of air with different thermal properties moving laterally (advection), the second is phasechanging of atmospheric moisture. Evaporation and melting store sensible heat, while condensationand freezing release sensible heat. These effects are so ubiquitous in the atmosphere that meteorolo-gists define a moist adiabatic lapse rate (5.5°F/1000 ft) for saturated atmospheres. The third factor is the thermal energy input by solar radiation. An introductory discussion ofstability effects with regard to pesticide dispersion is given in Thistle (1996). Briefly, solar energyradiated from the sun is of a short wavelength as dictated by the temperature of the radiating body.The atmosphere of the Earth is relatively transparent to this short wavelength energy so it passesthrough the atmosphere and is absorbed at the surface. The surface then reradiates energy at a muchlonger wavelength than the sun due to its lower temperature. The atmosphere is a reasonably effec-tive absorber at these longer wavelengths and the atmosphere is heated from below. The relevance to the problem of pesticide drift is a result of the control that the resulting tem-perature profiles exert on atmospheric mixing. Warm air is not as dense as cold air and is thereforelighter. When the surface is heated, during a sunny afternoon for instance, the air near the surfacewants to rise through the colder air over it. This is known as an unstable surface layer. At night, thesurface is again the active radiation surface and loses heat faster than the air above it. Therefore, atnight the surface is colder and air adjacent to it gets cold through conductive heat loss. This cold airis heavier than the air above it and tends to stay in place. This is known as a stable surface layer.Three states of atmospheric stability are defined:

1) Neutral - the temperature change with height follows the adiabatic lapse rate relationships.

2) Unstable - warm air under cold air (or slight cooling with height but less than the adiabatic rates)

3) Stable - cold air under warm air (cooling with height is greater than the adiabatic lapse rate)

In the air layer from 50 m above the surface to the surface, we will simplify this discussion byignoring the lapse rate and discussing increasing temperature with height (stable), decreasing tem-

68

perature with height (unstable) and no change (neutral). Consider a parcel of air at a given layer. Inan unstable situation (Figure 2), the parcel is lighter than the air above it and heavier than the airbelow it. Therefore, if the parcel is moved up or down it will keep moving away from its point oforigin. A small perturbation results in substantial mixing, and is characterized by large ‘bubbles’ ofair lifting off the surface. These are the thermals that aviators are familiar with. This type of motioncan result in cumulus formation (even initiating cumulonimbus or thunderhead formation). Near thesurface, the liftoff of some air causes other air to rush in to replace it, resulting in the intermittentwinds of variable direction characteristic of many summer afternoons. Now consider a parcel of air in a stable layer (Figure 3). If this parcel is displaced upward it isheavier than the air in the layer above and will sink back to its layer of origin. If it is displaceddownward, it is lighter than the air below it and will return to its layer of origin. Thus, a smallperturbation in a stable layer will be damped out and mixing is suppressed. This situation typicallyexists on a cool, clear morning when the air is still. With some exceptions, these conditions depend on two factors. These gradients will not estab-lish themselves in strong winds. If there is macro-scale activity (such as a frontal passage) in theatmosphere and the wind is blowing, the surface layer tends to mix and the stability tends towardneutral. Surface heating and cooling are restricted by cloud cover. If cloud cover is present, surfaceheating will be damped and nocturnal surface cooling will also be lessened. The effectiveness ofcloud cover in limiting surface temperature depends on the thickness and extent of cloud cover. Themain exceptions to this rule are areas near large bodies of water (coastal settings) where the waterprovides a lateral source of air with markedly different characteristics, and sloped terrain whereupslope and downslope flows develop in non-neutral atmospheres.(See Barr and Clements, 1984, for a discussion of both coastal and complex terrain effects on atmo-spheric dispersion.) In conventional air pollution modeling, short term, single point maximum downwind concentra-tions typically occur under stable conditions. This is because the low mixing under stable conditionsallows the pollutant plume to remain relatively concentrated. Other considerations affect spraydroplets as well. The low velocity typical of the stable situations discussed above will give thedroplets more time to settle out of the air and deposit. Thus, if the plume were integrated across adownwind vertical plane, the total amount still airborne would probably be less than in higher windconditions. Increased residence time in the atmosphere leads to smaller drops. There is an explicitcovariance with humidity because the stable layer is relatively cooler. Under low mixing conditions,humidity is typically higher near the surface around plant canopies. Higher humidity will reduceevaporation.

Turbulence

Turbulence can be loosely defined as the variance in a given fluid flow. If the mean wind speedis described as , the measurement of this speed at a given time will include the mean speed and somedeviation from it. Thus, if the speed is u:

u = u+u’ (5)

the term u’ is the difference at any instant between the instantaneous wind speed and the mean windspeed (Figure 4). If we take the absolute value of this quantity ( |u’|) then a turbulence intensity (TI)can be stated as:

TI =|u’|/u (6)

69

where the overbar indicates an average, alternatively, the u’ term could be formulated as a standarddeviation. Panofsky and Dutton (1984) is an excellent text discussing turbulence in the atmosphere.These authors state that a generally accepted definition of turbulence does not exist, so turbulence isdescribed by its qualities. The system of fluid dynamics equations that describe a turbulent fluid areknown as the fluctuating Navier-Stokes equations. Constantin and Foias (1988) provide a detailedmathematical treatment of these equations. These equations are the basis for much ongoing work influid dynamic research. Turbulence can generally be thought of as overlying rotational motions that range in size in theatmosphere from a minimum of a few millimeters in diameter to a maximum wavelength determinedby the system. For instance, in an unstable atmosphere the maximum vertical eddy size is on theorder of the length of the highest rise of surface-generated thermals (that range up to thousands ofmeters in height). These big rotational motions break down in a very regular way (known as acascade) into little eddies, the smallest of which are dissipated by the fluid (air in this case) viscosity. The mean motion in the atmosphere away from the surface tends to be perpendicular to atmo-spheric isobars (lines of equal pressure). The turbulent eddies translate along with the larger mo-tions. Turbulence tends to increase near the surface where the fluid encounters the drag of a roughsurface. Plant canopies tend to have very high TI both because the canopy elements shed eddies andbecause mean flows () are relatively lower there because they lose energy to friction with the canopy. Turbulence influences spray drift in various ways. Since the airflow is not in a straight line, theconceptual model of a vector resultant between the settling velocity and the mean wind speed needsto be modified to include rotational motions in the atmosphere. Because individual turbulent mo-tions are random in time, the droplet will move up and down. The turbulent eddies tend to develop arelatively strong downward component in stronger winds and might be useful in pushing materialinto taller canopies. Also, the downward vertical component of the larger eddies may generally helpto impact droplets onto a target surface. There is also a return flow from these eddies, but it tends tobe composed of smaller eddies somewhat analogous to waves after they break on the beach. How-ever, in an unstable atmosphere, strong updrafts may develop as discussed above. These may becapable of transporting droplets to remarkable heights. Spraying in very unstable conditions shouldprobably be avoided because these large thermal eddies make the spray hard to control. Regarding the plume of droplets as a whole, the variance or turbulence controls the spread of theflow. In air pollution modeling, a dispersion coefficient of some type based on a measure of theatmospheric turbulence is used to calculate plume spread. Eddies bigger than the plume will movethe plume in a meandering motion. Eddies very small relative to the plume will cause a smallamount of ‘diffusive’ plume spread, while eddies the size of the plume are probably most influentialin determining plume width. The final influence of turbulence on drift discussed here is more subtle. When consideringdroplet evaporation, the droplet can be considered as moving in the flow and the air around thedroplet moves with it. The air adjacent to the droplet will thus have a higher humidity in the case ofan evaporating water droplet than the free air away from the droplet. This layer of air with propertiesdue to the droplet will slow evaporation. In more turbulent conditions, this boundary layer effect isweakened. Thus turbulence tends to facilitate droplet evaporation.

Canopy

A detailed discussion of canopy meteorology is beyond the scope of this paper (see Kaimal andFinnigan, (1994) and Stull(1988) for more complete discussions). Some generalizations can bemade and are important to consider since the canopy is often the application target and, in the case oforchard spraying for instance, may influence most of the spray dispersion domain. Canopies areusually moister (higher humidity) than open areas. Wind speeds tend to be lower due to drag by thecanopy elements. Turbulent intensity tends to be higher because of eddy shedding off of canopyelements. The canopy intercepts solar radiation. Under closed canopies, a stable layer (inversion)can exist in the middle of the day due to shading.

70

Modeling

There are generally three types of models currently widely used in pesticide dispersion and driftapplications. The first is a Gaussian approach that follows an established, conventional method usedin regulatory air pollution. It is most appropriate for gaseous diffusion. The second focuses on themachine energy, both of the pressurized system and of the release vehicle wake. It uses simplemeteorological transition and transport models. The third is a physical approach often based onNavier-Stokes techniques applied in the atmosphere. The first type of model assumes that the wind direction determines plume centerline and thecrosswind distribution is a Gaussian or bell-shaped curve as shown in Figure 5 (See Turner (1970)for discussion of Gaussian techniques) . Gaussian models are mass conservative and steady state.The plume is narrower near the source and becomes wider downwind. The maximum airborneconcentration is highest near the source and decreases downwind. A crosswind slice of equal thick-ness at any distance downwind will integrate to the same mass if no depletion of the plume materialis considered. The rate of plume spread is determined by dispersion coefficients that vary withstability and also can be varied to consider cases of very large surface roughness such as tall build-ings. Gaussian models have proven very robust in dispersion applications. The model forces theconcentrations to decrease with distance (at least away from source influences or source elevationeffects) from the source and to decrease laterally from the plume centerline. This also helps thesemodels show high correlations because correlation evaluates sameness of shape as opposed to aresidual measure between observed and predicted. This type of model has never been of muchinterest to researchers because it is effectively a statistical model. The down and crosswind distribu-tion of pollutant mass (expressed as concentration) is input a priori in the model so there is not muchnew to be learned from a theoretical standpoint from these models. The second type of model focuses on the wake of the machine. The most commonly used modelof this type is used in simulating aerial spraying and uses the weight of the airplane and wingspan tocalculate the strength and location of wake vortices that entrain the spray droplets. (See Bilanin etal. (1989) for the basic formulation now widely used in pesticide dispersion work and Thistle etal.(1998) for a list and description of currently available models using this approach. ) The dropletsthen travel in the atmosphere in these swirling vortices until the vortical energy is dissipated eitherby the surface or by ambient wind and turbulence. This type of model focuses on the droplets andconsiders ambient temperature and humidity for a droplet evaporation algorithm. It explicitly con-siders droplet settling velocity and considers the ambient wind and turbulence to calculate vorticedecay and to use as a transport mechanism after the machine energy has dissipated. These modelsare physically based. Some models used in the research community are full physics, numericalmodels incorporating the state-of-the-art in fluid dynamics theory. The models commonly used inagricultural spraying are greatly simplified, but are used in some research applications. The final class of models generally use the Navier-Stokes equations to describe the atmosphericdynamics and interface those equations with a full physical description of the aircraft wake. TheNavier-Stokes equations describe motion in a turbulent fluid and attempt to give a four-dimensionalrepresentation (three spatial dimensions and time). The equations use a velocity vector, pressure,fluid (air) viscosity and a stability term to calculate how the fluid will move and change with time.The equations cannot be solved without making assumptions about the flow that impart uncertaintyinto the solution. These assumptions and approaches to this problem are areas of ongoing researchand there are a number of this type of model in existence (though only a few couple the ambientenvironment and the wake energy in a physical model).

Discussion

It is difficult to summarize this topic in a short review paper. The question of what is the mostimportant meteorological variable depends on circumstances. In many situations, wind direction

71

may be the most important variable as it is critical to keep spray out of sensitive areas that lie in acertain direction. When all the variables included in spraying are examined in a sensitivity study,droplet size may be important variable in determining the amount of drift. It follows from this thathumidity plays a crucial role that is a controlling role in certain circumstances. Wind speed is ofobvious import. Some of the more mysterious cases of off-target damage can be traced to stabilityor, more specifically, a concentration of fine droplets in a stable atmospheric layer.

Conclusions

Meteorological conditions will increasingly be considered in pesticide labeling so that constraintswill be set from a regulatory perspective. Effective use of pest control agents requires that thematerial be on the target. Thus, off-target drift is a loss from both the standpoint of efficacy andeconomics and from the standpoint of the surrounding environment. The interactions of the vari-ables involved are complicated. In response to this complexity, computer models have been devel-oped and used to simulate spraying of pesticide. These models are used to plan, train and analyzecompleted application operations.

References

Bache D.H. and D.R. Johnstone. 1992. Microclimate and Spray Dispersion. Ellis Horwood Series inEnvironmental Management, Science and Technology.

Barr S. and W.E. Clements. 1984. ‘Diffusion Modeling: Principles of Application’, AtmsphericScience and Power Production. Ed. Darryl Randerson. DOE/TIC-27601.

Bilanin A.J., M.E. Teske, J.W. Barry and R.B. Ekblad. 1989. ‘AGDISP: The Aircraft Spray Disper-sion Model, code development and experimental validation’. 32.

Constantin P. and C. Foias. 1988. Navier-Stokes Equations. Chicago Lectures in Mathematics,University of Chicago Press. Chicago, IL.

Davies C.N. 1978. ‘Evaporation of Airborne Droplets’, Fundamentals of Aerosol Science Ed. D.T.Shaw. John Wiley and Sons. New York, NY.

Kaimal J.C and J.J. Finnigan. 1994. Atmospheric Boundary Layer Flows: Their Structure and Mea-surement. Oxford University Press. New York.

Jones H.G. 1983. Plants and Microclimate: A Quantitative Approach to Environmental Plant Physi-ology. Cambridge University Press. New York, NY.

Miller D.R., R.C. Reardon and M.L. McManus. 1995. An Atmospheric Primer for Aerial Sprayingof Forests. USDA Forest Service FHM-NC-07-95. Morgantown, WV.

Panofsky H.A. and J.A. Dutton. 1984. Atmospheric Turbulence: Models and Methods for Engineer-ing Applications. John Wiley and Sons. New York, NY.

Stull R.B. 1988. An Introduction to Boundary Layer Meteorology. Atmospheric Sciences Library,Kluwer Academic Publications. Boston, MA.

Teske M.E., J.W. Barry and H.W. Thistle. 1994. ‘Aerial Spray Drift Modeling’. EnvironmentalModeling Vol. II: Computer Methods and Software for Simulating Environmental Pollution and itsAdverse Effects. Ed. P. Zanetti. Computational Mechanics Publications. Boston MA.

72

Figure 1. The simplest model of droplet fall angle calculates a resultant based on settling velocity(down) and mean horizontal wind speed (horizontal). Aircraft wake vortices and turbulence in theatmosphere cause the actual droplet trajectory to be much less regular.

Thistle H.W. 1996. ‘Atmospheric Stability and the Dispersion of Pesticides’. Journal of the Ameri-can Mosquito Control Association. 12(2).

Thistle H.W., M.E. Teske and R.C. Reardon. 1998. ‘Modeling of Aerially Released Sprays’. Pro-ceedings of the GIS’98/RT’98 Conference. GIS World, Inc. Ft. Collins CO.

Turner D.B. 1970. Workbook of Atmospheric Dispersion Estimates. PHS Publication No. 999-AP-26. U.S. Department of Health, Education and Welfare. National Air Pollution Control Administra-tion. Cincinnati, OH.

73

Figure 2. In an unstable atmo-sphere, a parcel of air will moveaway from its level of origin, thusincreasing turbulence and enhanc-ing mixing in the atmosphere.

Figure 3. In a stable atmosphere, aparcel of air will tend to return to itslevel of origin when perturbedvertically. This damps out turbu-lence and suppresses mixing in theatmosphere.

74

Figure 4. Turbulence can be described by the fluctuations in the wind speed. The magnitude ofthese fluctuations relative to the mean wind speed is referred to as turbulent intensity.

Figure 5. A simple family of dispersion models are known as Gaussian models. The direction ofplume movement is determined by the wind direction and material distribution is Gaussian (normalor bell-shaped) in the crosswind direction. The vertical distribution is complicated by interactionwith the ground surface but is usually also based on a Gaussian in this type of model.(Figure adapted from Turner (1970).

75

The Importance of Nozzle Selection and Droplet Size Control in Spray Application

Andrew J. HewittStewart Agricultural Research Services

Macon, Missouri

DISCLAIMER

Commercial names are given in this paper for example only. The mention of a particular product doesnot constitute a recommendation or endorsement of that product by the author of this paper, nor does itimply different behavior from other products with similar design.

ABSTRACT

Nozzles and atomizers are an essential part of any spray application system. A large range ofnozzles and atomizers is available for use in spraying operations. These nozzles produce sprays withdifferent droplet size, velocity, trajectory and buoyancy characteristics. Well-established techniquesare available for measuring these factors, and for classifying the resultant sprays. Performancedepends on the type and design of nozzle, the orifice diameter(s), the spray pressure, nozzle angle,and the application conditions at the time of spray emission, such as sprayer speed, airstream veloc-ity and turbulence. The physical characteristics of the spray mixture are important, especially thesurface tension, shear viscosity, extensional viscosity and density. However, nozzle type and appli-cation conditions are more important than spray mixture physical properties.

Droplet size spectra can be measured using laser-based instruments in spray chambers or windtunnels. The measured spectra can be described using the entire distributions or discrete parameterssuch as average droplet size or spray volumes contained in specific size class ranges. Sprays can beclassified using schemes developed by the British Crop Protection Council and American Society forAgricultural Engineers. These schemes allow nozzles to be classified by droplet size for operationalparameters, and drift potential for non-conventional types. Literature sources and models providedroplet size data. Droplet size is a useful pesticide label item, and is a ready input for drift and otherspray application models.

INTRODUCTION

The droplet size spectrum produced by an agricultural sprayer at the time of the field application ofan agricultural or biological spray has an important influence on the behavior of that spray in theenvironment into which it is released, it’s collection on natural surfaces, and dose-transfer to thetarget (usually a pest). A review of the different interests that can affect the selection of applicationparameters, such as nozzle type and use, for a given spraying operation, was given by Matthews(1992) and Hewitt (1997). The minimization of the incidence and impact of spray drift requires

76

careful consideration of many factors, including the droplet size spectrum at emission throughnozzles, and after any subsequent evaporation (which tends to reduce droplet size), coalescence(which can increase droplet size). Many other factors also can affect the likelihood of droplets todrift. These include the height at which the spray is released above the ground; the position wheredroplets are released with respect to the wake and vortices around sprayers; the meteorologicalconditions (especially wind speed and direction) from the time of spray release to spray deposition;and canopy effects. The present paper explains the role of nozzles in the spraying process and themeasurement and description of sprays produced by agricultural nozzles. Devices for distributingsolid particles such as dust and granules are not discussed in this paper.

THE ROLE OF NOZZLES IN SPRAYING

Nozzles and atomizers provide the means by which agricultural chemicals are atomized. Nozzles areavailable as many different orifice sizes and designs within several major types. The designs alsooften include features for providing specific spray distribution patterns. Some nozzles, such as thosemanufactured by CP Products, Inc. (Mesa, AZ), include multiple orifice and deflector settings,giving the equivalent of several nozzle tips within one adjustable unit.

NOZZLE TYPES

Nozzles can be described according to the type of energy that is used to atomize the liquid intodroplets. The major types include hydraulic, rotary, twin-fluid air-assist, airblast and electrostatic.Another type of nozzle using sonic energy has application in other spray application fields, but is notcommon in agricultural spraying.

Hydraulic Nozzles

Hydraulic nozzles include the most commonly-used types in agricultural spraying in the U.S. Liquidis atomized by being forced under pressure (hydraulic energy) through the nozzle tip. Atomizationtypically occurs by the disintegration of sheets or ligaments of liquid into droplets. The major typesof hydraulic nozzle are as follows:

Disc-core: Used for applications of pesticides at a wide range of flow rates and pressures.Examples include all D-swirl plate series from Spraying Systems Company(Wheaton, IL), e.g. D8-46; RD series from Delavan (Delavan-Delta, Inc.,Lexington, TN)

Solid stream: Used in aerial applications where large droplets are required to minimizepotential spray drift. Examples include all D series from Spraying SystemsCompany; Through Valve Boom (TVB) series (Waldrum Specialties, Inc.),Accu-Flo series (Bishop Engineering), Lund series (Lund Flying Services,Inc., Ritzville, WA).

Hollow cone: Used for broadcast applications of sprays such as post-emergence contactherbicides. Examples include WRW series (Delavan); RA series (Delavan);1553-18 and other tips (Hardi International).

77

Full cone: Used for broadcast applications. Examples include TG series (SprayingSystems).

Flat fan: Also known as flat spray nozzles. Widely used for ground and aerial applica-tions. Many designs are available producing different flow rates and sprayangles typically including 25, 40, 65, 80 and 110 degrees. There are manydesign variations producing different droplet size spectra – for example theextended range, Turbo Teejet, Drift Guard and other series.

Deflector: Also referred to as flooding or wide angle flat fan. Used for applications ofherbicides. Examples include TK series (Spraying Systems), TF series(Spraying Systems), RFLD series (Delavan), RegloJet series (ICI), CPnozzles (CP Products, Inc., Mesa, AZ).

Rotary Atomizers

Rotary atomizers involve the emission of liquid from a spinning surface. Ligaments may breakdown into droplets, or droplets may form directly from the zero issuing surface (e.g. teeth on spin-ning discs). At very high liquid flow rates, the surface may become flooded with liquid, causingatomization to be by sheet disintegration. The main types of rotary atomizer are as follows:

Rotary Cage: Used primarily for aerial applications in forestry and for mosquito control. Forexample, AU series (Micronair Aerial Ltd., Sandown, Isle of Wight, U.K.), A& C Hi-Tek (A & C Ltd., Macon, GA).

Rotary Drum: Used for aerial and ground applications in forestry and for mosquito control.For example, Beecomist aerial porous rotary drum (Beeco Products, Inc.,Telford, PA).

Spinning Disc: Used for ground applications, typically herbicides. For example, Micromax(Micron Sprayers, Ltd.).

Twin Fluid and Air-Assist Atomizers

Twin fluid atomizers involve the mixing of liquid and air to produce droplets that typically containmany air inclusions. The air may be drawn into the nozzle by the venturi effect (e.g. Turbo Dropnozzles, Greenleaf Inc.; AI nozzles, Spraying Systems), or may be pumped into the mixing chamberof the nozzle, for example using compressed air (e.g. SpraySmart System, Victoria, Australia).

Airblast Nozzles

Some sprayers use high volumes and velocities of air to atomize and transport spray toward thetarget. The most well-known example of this type of scenario occurs on orchard airblast sprayers,where nozzles (typically high pressure hydraulic nozzles) discharge the tank mix into a ductedairstream. The air shear effect is similar to that occurring during aerial applications, in that the airenergy causes the spray to atomize into a relatively fine spray. Some airblast sprayers includeconditions that are likely to cause relatively high air turbulence, which will affect the atomizationprocess. An example of this occurs with the use of “wobble plates” that continually change the air

78

direction to assist with spraying trees from differing directions and assist in causing leaves to flutter,thereby potentially improving the collection efficiency of leaves for the spray cloud.Electrostatic Atomizers

Electrostatic atomizers have been studied for many years. Coffee (1979) described one of the earli-est electrostatic nozzles. Matthews (1992) reviewed the three modes of charging for electrostaticatomizers: induction, ionized and direct charging. Matthews reported that deposition may be im-proved on target surfaces for electrostatic sprays; particularly for small (<100 µm diameter) droplets.

ORIFICE DIAMETER

In general, sprays become finer with smaller nozzle orifice diameter within a nozzle type (Bouse,1994; Hewitt, 1993).

MATERIAL OF MANUFACTURE

Nozzles are available in different materials, for example stainless steel, brass, nylon and differenttypes of plastic. The material can affect the manufacture process, and therefore can affect the flowrate, spray pattern and droplet size spectrum.

SPRAYER SPEED AND NOZZLE ANGLE

As the airstream velocity increases relative to the liquid velocity at a nozzle tip, sprays generallybecome finer. Airstream velocity at the nozzle tip is affected by the following variables:

• speed at which the sprayer is travelling, e.g. aircraft air speed; ground sprayer speed relativeto air (wind speed and direction may affect the air velocity at nozzle).

• fan speed for airblast sprayers.

• angle of nozzle tip in relation to airstream. At an angle of 0° straight back, the airstreamvelocity at the nozzle tip will be minimal for laminar co-flowing air. As the nozzle angleincreases from 0°, the airstream velocity will tend to increase at the nozzle tip, reaching amaximum when the nozzle tip is at 180°, i.e. straight into the airstream.

• air turbulence in the vicinity of the nozzle tip. This may be particularly important for airblastsprayers, where axial fans tend to produce more turbulent airflows than cross-flow fans.

Research showing a decrease in droplet size with higher nozzle angle to airstreams has been reportedby many scientists including Bouse (1991); Hewitt et al, (1994); Yates et al, (1983) and Kruse et al(1949).Turbulence can also affect the atomization process. The airstream emerging from axial fan airblastsprayers can be more turbulent than the airstream flowing close to nozzles on aircraft booms. Hewitt(1991) noted that the airstream velocity produced by a large axial fan sprayer ranged from 49 to 87

79

m/sec at the different nozzle positions on the air outlet ducts; and that the air was highly turbulentdue to “wobble plates” moving laterally within the air ducts.SPRAY ANGLE

Flat fan nozzles are available with different spray plume angles, designed for different applicationsdepending on the spray release height and nozzle spacings on sprayer booms. Spray angle is definedby ASTM Standard E1620 as “the plane angle formed by the profile of a spray pattern”. Although80 degree angles are commonly used in the U.S.A. and 110 degree spray angles are common inEurope and of minor use in the U.S.A., flat fan nozzles are available with spray plume angles be-tween 15 and 110 degrees for different applications. Spray plume angle is related to the liquid flowrate and the nozzle tip shape, in particular the angle and dimensions of the elliptical orifice.

Sprays generally become coarser as spray angle decreases, with the coarsest sprays often beingproduced by solid stream nozzles which have very narrow spray angles.

SPRAY PRESSURE/ LIQUID FLOW RATE

Many researchers (e.g. Bouse, 1994) have observed finer sprays with higher liquid pressure for nozzlesmounted at angles to an airstream. There are exceptions to this trend - for example, some solid streamnozzles; and rotary atomizers, where higher flow rates generally produce coarser sprays. It is therelative velocity of the liquid and the airstream; and the liquid distribution at the discharge point thatare important in affecting atomization.

Liquid pressure affects liquid flow rate, which in turn determines liquid velocity. The decrease indroplet size with higher pressure is due to an increase in the liquid velocity at emission through thenozzle orifice.

NOZZLE CARE

Given the importance of the nozzle geometry upon atomization, it is important for careful attentionto be given by nozzle users to the care of nozzles used for spraying. Changes in orifice geometrydue to temporary blockage with material, or permanent nozzle wear from abrasive materials overlong periods of time may cause changes in the flow rate, swath uniformity and droplet size spectrumthat is produced.

TANK MIX PHYSICAL PROPERTIES

The physical properties of the tank mix atomized during a spray application can affect the dropletsize spectrum, and therefore the drift potential. It should be noted that tank mix physical propertyeffects are not as important as application parameter effects such as nozzle type and use.The active ingredient, formulation type and pesticide type do not affect atomization alone; rather, itis the physical properties of the entire tank mix that affect atomization. Tank mixing is a commonpractice for enhancing spray applications and applying several products simultaneously, with savingsin total application time and cost.

80

For tank mixes that tend to produce relatively fine sprays when applied through a given nozzle, theselection of a different nozzle or application conditions can easily compensate and produce a coarserspray.

The major physical properties affecting atomization are:

· extensional viscosity, described by Effective Trouton Ratio (E)· shear viscosity at a shear rate of 8000 s-1 (SV)· dynamic surface tension at a surface lifetime age of 20 millisec. (s20)· density (r)

Extensional Viscosity

Extensional viscosity tends to resist liquid stretching, thereby affecting atomization. It has beenidentified by the Spray Drift Task Force and others (Hudson et al, 1992; Xing et al, 1994) as beingone of the principal controlling parameters of non-Newtonian liquid atomization. An increase inextensional viscosity can produce coarser sprays. Extensional viscosity can be expressed usingTrouton Ratio, E, where:

E = EVmax / Ks

EVmax is a parameter describing the maximum extensional viscosity measured over strain rates up to20,000 s-1. Ks is a shear viscosity fitting parameter at a shear rate of one reciprocal second.

Shear Viscosity

Shear viscosity is the viscosity of a liquid at a given shear rate. The Spray Drift Task Force andother studies show that an increase in this variable, as typically shown by an increase in the value ofthe viscosity at a shear rate of 8000 s-1 (SV), generally causes sprays to become coarser.

Dynamic Surface Tension

Surface tension tends to resist atomization, so an increase in surface tension tends to cause an in-crease in droplet size (Ford and Furmidge, 1967; Lefebvre, 1989; Hewitt, 1993).

Density

The density of a liquid may affect atomization, however, where density is similar for a group ofliquids (e.g. agricultural spray liquids), density may not have a significant effect on atomization(Bayvel and Orzechowki, 1993) except with rotary atomizers, where higher density causes therotation rate to decrease, with a resultant increase in droplet size (Hewitt, 1993).

THE MEASUREMENT AND DESCRIPTION OF AGRICULTURAL SPRAYS

Agricultural sprayers include many platforms and designs. Application types are commonly dividedinto four categories: aerial, ground, orchard airblast and chemigation. Within each of these types,many different designs and characteristics exist. Aerial spray applications are typically made using

81

one of three scenarios: rotary wing (typically at flight speeds of 40 to 80 mph), piston engine-pow-ered fixed wing (typically 90 to 130 mph), and turbine-engine powered fixed wing (typically >130mph). Ground applications include hydraulic and air-assisted boom sprayers. Orchard airblastsprayers include axial fan and cross-flow fan sprayers. Chemigation systems use impact, rotary andother sprinkler systems. There are many additional sprayer types, for example shielded sprayers,tunnel sprayers, electrostatic sprayers, spray guns, etc.

The characterization of sprayers using wind tunnels and spray chambers has long been recognized asan efficient method of simulating spraying processes and environments while allowing variables tobe studied. Wind tunnels have been used for research into droplet size spectra (e.g. Akesson et al,1983), spray drift (e.g. Western et al, 1989), spray deposition (e.g. Wedding et al, 1878), collectorefficiencies (e.g. Miller et al, 1989), efficacy against pests (e.g. Floore et al, 1992), aircraft vortexeffects (e.g. Jordan et al, 1978), icing research (e.g. Hovenac and Ide, 1989), and spray evaporationand trajectory research (e.g. Dodge, 1992).

Once measured, droplet size spectra can be described and compared using either the entire spraydistribution among all the droplet size classes measured by the particle size analyzer; or by discreteparameters that describe characteristics of the spectrum, such as average droplet sizes or sprayamounts (usually volume) contained in size ranges of interest to the user. Entire spectra can becompared using statistical procedures such as the Kolmogorov-Smirnoff test (Apodaca et al, 1993).Discrete parameters can be compared using various approaches such as the analysis of variance test.A discrete parameter that is commonly used in agricultural spray descriptions is the volume mediandiameter (vmd or Dv0.5). This is the droplet diameter that divides the spray cloud into two equal partsby volume – one half of the spray volume being contained in droplets with diameter larger, and onehalf in droplets with diameter smaller than the Dv0.5. The relative span is often also used to indicatethe range of droplet sizes within the spray cloud, relative to the Dv0.5. Relative span is calculated by(Dv0.9 – Dv0.1 / Dv0.5), where Dv0.9 and Dv0.1 are the droplet diameters at which 0.1 and 0.9 of the sprayvolume is contained in droplets with smaller diameter. Several researchers have described dropletsize ranges considered and measured to be most drift-prone under most application conditions.Yates et al (1985) considered 30-150 µm droplets to be the most drift-prone. Shewchuk et al (1988)cited literature references to 50-150 µm being the major drift fraction for most herbicide sprays,while the range was considered to be <150 or <200 µm by Bode (1984), and 50 - 150 µm by Byassand Lake (1977). Differences in definitions are influenced by droplet sizing techniques, evaporationrates, spray release heights, application and meteorological conditions. For example, the data givenby Bode (1984) and Byass and Lake (1977) relate to ground applications, while Yates et al (1985)referred to aerial application scenarios.

Spray classification schemes have been developed by the Applications Committee of the BritishCrop Protection Council (BCPC) in Europe (Doble et al, 1985), and the PM41 Power and MachineryCommittee of the American Society for Agricultural Engineers (ASAE) in the U.S. (Maynard et al,1996). These schemes classify sprays into discrete size categories: Very Fine, Fine, Medium,Coarse, Very Coarse and (ASAE only) Extra Coarse. The schemes allow droplet size data collectedusing different measurement systems (for example, laser diffraction, Phase-Doppler and laser imag-ing) to be compared with standard reference nozzles/ liquid pressures describing the boundariesbetween the different size classes.

82

The classification of sprays using a scheme based solely on droplet size does not take account of therelative velocity, density or trajectory of droplets in different types of spray clouds. For a given typeof nozzle (e.g. the flat fan hydraulic nozzles for which the BCPC scheme was originally developed),these factors may fall within a sufficiently narrow range to support the use of a classification basedonly on droplet size. However, many researchers have shown that such classifications do not accu-rately describe the performance of many ground spray drift-reduction nozzle systems with regard tonear field drift and/ or coverage. For example, Walklate et al (1994) showed that drift predictionsusing the BCPC percent spray volume with diameter less than 100 µm did not give a fair representa-tion for a dual-orifice flat fan nozzle, a twin fluid nozzle, and a hot gas applicator nozzle. Similarly,Miller et al (1991) showed that the drift at 8 m from a twin fluid nozzle producing a “Fine” BCPCspray, was 60 % lower than that from a conventional “Fine” BCPC flat fan nozzle.

A technique has been developed and used for assessing airborne spray volumes from various agricul-tural nozzles in wind tunnels (Western et al 1989; Miller et al 1993; Walklate et al, 1994). Thistechnique involves the use of collectors such as tubing to measure the vertical spray profile at one ormore distances downwind of the nozzles, in a low speed wind tunnel. Typically, an array of collec-tors would be positioned at a distance of 2 m from the nozzle; and the wind would be 2 m/s. Collec-tors such as polythene tubing and cotton strings have been widely used for assessing airborne sprayvolumes in field and laboratory studies for many years. More recently, phase Doppler analyses(PDA) instruments have been used in lieu of cylindrical collectors. The PDA back-scattering tech-nique has the advantage that collection efficiency and intrusive sampling factors are eliminated. ThePDA technique involves emitting a non-intrusive laser beam through the air, and assessing airbornespray from analysis of the associated signal. From measurements using eight vertical collectors orPDA sampling, a Drift Potential Index can be derived as follows (Helck et al, 1997). A determina-tion is made of the spray volume, V, and the height above the ground of the center of gravity, h, forthe drift profile. Helck et al (1997) reported good agreement between drift characteristics measuredin a wind tunnel using this approach, with field assessments of ground deposition rates for the samespray types.

The index has been adopted in the International (BCPC) Spray Classification Scheme (Southcombeet al, 1997), and has particular value for demonstrating drift patterns that might occur with groundplatform nozzle and sprayer types that are substantially different from conventional hydraulicnozzles and sprayers. Examples of such systems include sprays from rotary, twin fluid, electrostaticand air-assist atomizers; and droplets containing air inclusions.

The droplet size and drift potential factor classification schemes were developed with several antici-pated end users. There was particular interest in the field of spray drift modeling. Therefore, theoptions for selecting droplet size input in terms of BCPC category have been incorporated into thespray deposition model, AgDRIFTTM (Teske et al, 1997). If input is selected using BCPC categories,the associated worst-case droplet size spectrum is utilized for the model analysis. For example, if a“Medium” spray is selected, the model assumes the droplet size spectrum that divides the “Medium”and “Fine” categories (i.e. the M/F reference boundary curve). Many major nozzle manufacturershave included the categories in their nozzle catalogues, for specific operational parameters. Abooklet has been produced that contains tables showing the BCPC size categories associated withdifferent nozzles and spray pressures. In the U.S.A., the National Agricultural Aviation AssociationResearch and Education Foundation (NAAREF) is finalizing a manual containing similar informa-tion for the major parameters affecting atomization for aerial applications. Models can also predictthe droplet size spectra produced by specific nozzle types (Hewitt et al, 1997).

83

It is probable that many pesticide labels may include reference to BCPC/ ASAE spray categories orother droplet size descriptors that should be used for different applications and with different bufferzones. For example, the label might require that, for a particular buffer zone with a given non-targetentity, the product be applied as “Medium” if sprayed alone, or as “Coarse” if tank-mixed with otherproducts.

When finalized, the drift potential factor scheme will expand the overall classification of groundsprays to more accurately represent differences in spray trajectory and velocity behavior, for describ-ing spray drift characteristics. Nozzle catalogues may indicate the drift potential factor associatedwith specific nozzles.

REFERENCES

N.B. Akesson, K. Haq and W.E. Yates, Pesticide Spray Drop Spectra Correlated With Fluid PhysicalProperties. ASAE Paper 83-1014, pp. 1-31, 1983.

M.A. Apodaca, R. Sanderson, A.J. Hewitt, M. Ortiz, E.W. Huddleston, J.B. Ross and D. Clason,Statistical Comparison of Droplet Size Spectra/ Proc. ILASS Sixth Annual Conf. Liquid Atomizationand Spray Systems, pp. 73-78, 1993.

L. Bayvel and Z. Orzechowski, Liquid Atomization, Taylor and Francis, Washington, D.C., pp. 85,1993.

L.E. Bode, Downwind Drift Deposits by Ground Applications/ Proceedings Pesticide Drift Manage-ment Symposium, South Dakota State University, pp. 50, 1984.

L.F. Bouse, Effect of Nozzle Type and Operation on Spray Droplet Size, ASAE Paper AA91-005, pp.1-24, 1991.

L.F. Bouse, Effect of Nozzle Type and Operation on Spray Droplet Size, TRANS of the ASAE vol.37(5), pp. 1389-1400, 1994.

J.B. Byass and J.R. Lake, Spray Drift From a Tractor-Powered Field Sprayer, Pestic. Sci. vol. 8, pp.117-26, 1977.

R.A. Coffee, Electrodynamic Energy – a New Approach to Pesticide Application/ Proc. Br. CropProt. Council Conf. – Pests and Diseases, pp. 777-89, 1979.

S.J. Doble, G.A. Matthews, I. Rutherford and E.S.E. Southcombe, A System for Classifying Hydrau-lic Nozzles and Other Atomizers into Categories of Spray Quality/ Proc. 1985 Brit. Crop Prot. Conf.- weeds vol. 9A-6, pp. 1125-33, 1985.

L.G. Dodge, TESS: Tool for Spray Studies, Technology Today, 1992

T.G. Floore, C.B. Rathburn, A.H. Boike, J.S. Coughlin, and M.J. Greer, Comparison of the SyntheticPyrethroids Esbiothrin and Bioresmethrin With Scourge and Cythion Against Adult Mosquitoes in aLaboratory Wind Tunnel, J. Ameri. Mosquito Control Assoc., pp. 58-60, 1992.

84

C. Helck, A. Herbst and H. Ganzelmeier, New Approaches to Determine Drift Potential fromNozzles, presented at workshop of British Crop Protection Council Spray Nozzle ClassificationScheme, Silsoe Research Institute, Silsoe, U.K., 1997.

A.J. Hewitt, Studies With Air-Assisted Rotary Atomizers for Pesticide Application, Ph.D. Thesis,London University, 260 pp, 1991.

A.J. Hewitt, Droplet Size Spectra Produced by Air-Assisted Atomizers, Journal Aerosol Science vol.24(2), pp. 155-62, 1993.

A.J. Hewitt, The Importance of Droplet Size in Agricultural Spraying, Atomization& Sprays vol. 7(3), pp. 235 - 244, 1997.

A.J. Hewitt, A.G. Robinson, R. Sanderson, and E.W. Huddleston, Comparison of the Droplet SizeSpectra Produced by Rotary Atomizers and Hydraulic Nozzles Under Simulated Aerial ApplicationConditions, J. Env. Sci. & Health, Part B, 1994.

A.J. Hewitt, C. Hermansky, D.L. Valcore and J.E. Bryant, Modeling Atomization and Deposition ofAgricultural Sprays. Proc. ILASS-Americas ‘97, 178-182, Ottawa, Canada, 1997.

E.A. Hovenac and R.F. Ide, Performance of the Forward Scattering Spectrometer Probe in NASA’sIcing Research Tunnel, NASA Technical Report 88-C-036, presented at 27th. Aerospace SciencesMeeting, AIAA, Reno, NV, 1989.

N.E. Hudson, J. Ferguson, and B.C.H. Warren, Controlled Aerosol Particle Size Generation Usingthe Steady Shear, Elongational and Molecular Properties of Polymer Solutions, Proc. XI Int. Congr.Rheology, vol. 1, pp. 472-4, 1992.

F.L. Jordan, H.C. McLemor and M.D. Bragg, NASA Agricultural Aircraft Research Program in theLangley Vortex Research Facility and the Langley Full Scale Wind Tunnel.ASAE Paper 78-1507, pp. 1-31, 1978.

C.W. Kruse, E.D. Hess and G.F. Ludwik, The Performance of Liquid Spray Nozzles for AircraftInsecticide Application, J. Nat. Malaria Soc., vol. 8, pp. 312-34, 1949.

A.H. Lefebvre, Atomization and Sprays, Hemisphere Publ. Corp., New York, 1989.

G.A. Matthews, Pesticide Application Methods, Longman, London and New York, 336 pp, 1992.

R.A. Maynard, A.R. Womac and I.W. Kirk, Nozzle Classification Factors for Ground Applications,Paper No. 961074, ASAE Annual Meeting: Phoenix, AZ, 1996.

P.C.H. Miller, C.J. Mawer and C.R. Merritt, Wind Tunnel Studies of the Spray Drift From TwoTypes of Agricultural Spray Nozzle, Aspects Applied Biology, pp. 237-8, 1989.

P.C.H. Miller, C.R. Tuck, A.J. Gilbert and G.J. Bell, The Performance Characteristics of a Twin-Fluid Nozzle Spryer, BCPC Mono. No. 46, Air-Assisted Spraying in Crop Prot., pp. 97-106, 1991.

85

P.C.H. Miller, E.C. Hislop, C.S. Parkin, G.A. Matthews and A.J. Gilbert, The Classification of SprayGenerator Performance Based on Wind Tunnel Assessment of Spray Drift/ Proc. A.N.P.P.-B.C.P.C.2nd In. Symp. Pestic. Appln. Tech., pp. 109-116, 1993.

S.R. Shewchuk, K. Wallace and J. Maybank, A Review of Methodology for Measuring the Drift andDeposition of Herbicides and Insecticides for Forestry Applications, Technical Report No. 220,Saskatchewan Research Council, 1988.

E.S.E. Southcombe, P.C.H. Miller, H. Ganzelmeier, J.C. Van de Zande, A. Miralles and A.J. Hewitt,The International (BCPC) Spray Classification System Including a Drift Potential Factor, Proc. Br.Crop Prot. Conf. Vol. 5A-1, pp. 371-380, 1997.

M.E. Teske, S.L. Bird, D.M. Esterly, S.L. Ray and S.G. Perry, A User’s Guide for AgDRIFTTM 1.0:A Tiered Approach for the Assessment of Spray Drift of Pesticides, Technical Note No. 95-10, CDI,Princeton, NJ, U.S.A., 1997.

P.J. Walklate, P.C.H. Miller, M. Rubbis and C.R. Tuck, Agricultural Nozzle Design for Spray DriftReduction/ Proc. ICLASS-94, Rouen, France, pp. 851-858, 1994.

Wedding, J. B. and Kim, Y. J. (1986) Wind Tunnel Characterization of Aerial Spray Nozzles Usingthe Laser Particle Spectral Analyzer. Optical Engng. 25, 556-60

N.M. Western, E.C. Hislop, P.J. Herrington and E.I. Jones, Comparative Drift Measurements forBCPC Reference Hydraulic Nozzles and for an Airtec Twin-Fluid Nozzle Under Controlled Condi-tions/ Proc. BCPC Conf. - Weeds, pp. 641-8, 1989.

J.H. Xing, A. Soucemarianadin and P. Attane, Experimental Study of the Breakup of ViscoeleasticFluid Jets/ Proceedings, Sixth Int. Conf. on Liquid Atomiz. & Spray Systems Paper I-9, pp. 63-70,1994.

W.E. Yates, R.E. Cowden and N.B. Akesson, Nozzle orientation, air speed and spray formulationaffects on drop size spectrums, TRANSACTION of the ASAE., pp. 1638-43, 1983.

W.E. Yates, R.E. Cowden and N.B. Akesson, Drop Size Spectra From Nozzles in High-SpeedAirstream, TRANS Amer. Soc. Agric. Eng. vol. 28(2), pp. 405-10, 1985.

86

Five Concurrent Sessions: Application Equipment & Drift

Concurrent Session #1 Aerial - Fixed Wing Application and Drift

Dennis R. GardisserUniversity of Arkansas Cooperative Extension

Little Rock, Arkansas

Agricultural aircraft play a major role in crop production for many parts of the world. Farm-ing practices have had to continually increase in efficiency as the world’s population has grown.This increase in population has also created some problems that must be addressed. Farming areasthat were typically very sparsely populated now have non-farm-oriented individuals living aroundand amongst the agricultural communities. Application accuracy is needed to provide productionefficiency and safety. Drift has surfaced as a major concern and fixed wing aircraft have had theirshare of drift related incidents.

Agricultural aircraft are constantly changing. There is a trend toward larger and faster air-craft. The total number of aircraft has been reduced in many areas, but the total production capabilityhas increased due to the size and efficiency of these newer styled aircraft. Agricultural aircraft todayare designed and built for one purpose only – to apply a precise dosage of either a pest control agent,fertilizer, or seed to large areas quickly and accurately. These aircraft are quite expensive. An aver-age sized new aircraft will sell for about $400,000 today. An equal or larger capitol outlay is neededby the operator for support equipment, insurance, and facilities. These large investments have cre-ated a real businesslike approach by most applicators. The applicators are constantly trying to imple-ment new and better technology to help safeguard this investment and their business opportunities.

Workshops are conducted all over the United States, Canada, Australia, New Zealand, Africa,and other parts of the world annually. Aircraft are flown over a variety of sample collection systemsusing both tracers and actual materials to determine deposition efficiency and drift potential. Manydifferent ideas are tested at these workshops. Some are quickly discarded, but others are fine tuned tomake the applications better.

Aircraft spray systems are not simple. The aerodynamics around the wings and fuselage maycause pattern distortions and whip the spray up in the air – increasing the drift potential. The key tomaking good applications is to use the field evaluations to determine what setup criteria may beutilized to avoid these type problems. Some the major factors are as follows:

• Droplet size – Almost every study dealing with drift and deposition ends up at the same place –droplet size. The key is to make as many of the droplets as possible close to an optimum size.Another factor, at least for drift control, is to not have many fine droplets. A lot of times thecorrect droplet size may be generated at the nozzle orifice but changed later due to air shear.

••••• Nozzle design – The best nozzle designs seem to be those that take advantage of the air flow.Spray should be emitted parallel to the dominant air flow direction to avoid aerodynamic shear.Flat fan, sheet, and straight stream type nozzles are being incorporated by many operators tomaintain good droplet size characteristics. These nozzles may also direct all the spray parallel to

87

the air stream and/or slightly down – in the direction of the crop. Aircraft speed seems to be amajor concern with many folks. As the aircraft speed increases, attention to air shear becomesmore important. New nozzles designs that allow the spray to be confined to one direction andprojected rearward so that the speed differential is less help avoid some of the speed effects ondroplet size.

• Nozzle/Boom location – There is a limited amount of space under the aircraft when it is on theground to mount nozzles. Studies have shown that nozzles mounted low, farther away from thewing and fuselage disturbances, help avoid drift problems. Nozzles should be moved away fromthe aerodynamic obstruction of other components on the aircraft such as: boom hangars, steps,plumbing fixtures, gear, pumps, and other undercarriage obstructions.

• Aerodynamics – Aircraft manufacturers and operators are continually making modifications tothe aircraft undercarriage and lower portions of the fuselage to reduce aerodynamic drag. Thiscauses the airflow around the lower areas of the aircraft to be more laminar and helps avoidvortice effects.

• Weather – weather variables do affect all spray applications. Applicators must monitor andunderstand how these variables change the fate of their spray particles.

Nozzle setup and aircraft configuration modifications are not always intuitive. Field typeworkshops have helped operators evaluate what will and will not make a difference. Half-boom shut-offs are a novel idea that dramatically helps reduce drift. These also allow the operator to make asharp edge along the field perimeter for the first pass. Field evaluations have also shown that aircraftmay be operated too low. Typically, lowering the boom height will reduce drift, but getting too lowmay increase drift due to the aerodynamic ground effect. A layer of air is compressed under thewings when heavy aircraft are very close to the ground. This pushes air outward and upward andmany times will carry spray particles with it.

The key to drift management and application efficiency is for the operator to understand andapply the best principles to the variety of conditions and products that are encountered. Those opera-tors that read, test, evaluate through field experience, or other means and incorporate the optimumcombinations of variables for the conditions that exist will be more successful. Fixed wing aircraftare a marvelous and efficient agricultural tool. If proper operating practices are used, these craft canbe used can be used efficiently and safely. As technology gets better these tools will be even moreefficient in the future.

88

(Concurrent Session #1, Part 2)

Managing Spray Drift from Aerial Fixed-Wing ApplicationsI. W. Kirk

Areawide Pest Management ResearchAgricultural Research Service

U. S. Department of AgricultureCollege Station, Texas

INTRODUCTION

Considerable research literature is available on spray drift and methods of mitigating spray drift fromaerial fixed-wing applications. In recent years the Spray Drift Task Force (SDTF) has systematicallyresearched and documented spray drift from the major methods of applying crop production andprotection materials. From the information now available, there are a number of approaches formitigating spray drift. Further research will, no doubt, bring additional and improved methods forreducing off-target spray deposits and associated environmental and property trespass. One of themajor tasks now facing the crop protection industry is widespread implementation of appropriatespray drift mitigation technology.

The Agricultural Research Service (ARS) has conducted research on aerial application technology atCollege Station, Texas for more than 30 years. More recently, some of the effort has been directedto better understanding spray drift created from applications with modern agricultural aircraft. Theobjective of this presentation is to (1) summarize fundamentals of aerial fixed-wing spray drift, (2)review results of selected studies from the College Station research program, and (3) review selectedstudies from the recently initiated ARS application technology research program at Stoneville,Mississippi.

SPRAY DRIFT

The American Society of Agricultural Engineers, through its program of voluntary, consensusstandards defines spray drift as the movement of chemicals outside the intended target area by airmass transport or diffusion. This definition is supported by definitions of: particle drift deposits –the deposition of chemical particles outside the intended target area; airbone drift – the dispersion ofchemical particles to the atmosphere outside the intended target area; and vapor drift – the dispersionof vaporized chemical to the atmosphere and areas surrounding the target area during and followingapplication (ASAE, 1997; ASAE S327.2). The American Society for Testing and Materials definesspray drift as the movement of airborne spray particles from the intended application (target) area(ASTM, 1996; ASTM E609-81). The National Coalition to Minimize Spray Drift (NCMSD) morerecently adopted a definition of drift: “Pesticide drift” means the physical movement of pesticidethrough the air at the time of pesticide application or soon thereafter from the target site to any non-or off-target site. Pesticide drift shall not include movement of pesticides to non- or off-target sitescaused by erosion, migration, volatility, or windblown soil particles that occurs after applicationunless specifically addressed on the pesticide product label with respect to drift control requirements

89

(Kindinger, 1998). The SDTF used a definition similar to that proposed by NCMSD (Johnson,1998).

The primary problems associated with drift are off-target damage and environmental impact. Publicperception of spray drift is also a problem – and is just as devastating to the industry and thoseaffected as the two primary problems. Other problems associated with drift are related to wastedmaterials and inadequate pest control. Environmental conditions and spraying practices and equip-ment are factors that influence spray drift. Environmental factors affecting drift are wind velocityand direction, air stability, and ambient air relative humidity and temperature. Aerial sprayingfactors affecting drift are spray droplet size – which is influenced by aircraft speed; nozzle type, size,angle, orientation, and spray pressure; spray release height; and smaller effects from spray boomlength and location. Crop canopy and spray mix physical properties also have small effects on spraydrift.

ARS RESEARCH, COLLEGE STATION

Pyrethroid Drift Reduction Demonstrations

In 1990, the Environmental Protection Agency (EPA), an industry group of synthetic pyrethroidinsecticide producers called the Pyrethroid Working Group (PWG), and the National AgriculturalResearch and Education Foundation contacted USDA, ARS to develop a program to increase aware-ness and reduce the hazards associated with aerial spray drift. The principals subsequently arrangedwith the Texas Agricultural Extension Service to conduct a series of aerial spray drift education anddemonstration programs across the cotton belt of the Southern United States. A standard test proto-col was developed and used with commercial applicators equipment to conduct twelve drift reduc-tion demonstrations in eleven states in the spring of 1991 (Valco, et al., 1991). Aerial equipmentwas set and operated at each of a high and a low spray-drift-potential application. Spray drift wascollected to 100 ft. downwind of the spray swath centerline on spray droplet collection cards placedon the ground at 10 ft. intervals and on four monofilament lines located 150 to 400 ft downwind ofthe swath centerline. Four monofilament lines, each 100 ft. long, were stretched between poles at 5,10, 15, and 20 ft. heights parallel to the swath centerline. Spray droplet collection cards were alsoplaced on the poles at the designated heights. Deposits on the cards were analyzed for percent areacoverage by computerized scanning and image analysis. The percent coverage measurement gave arelative measure of the swath displacement adjacent to the swath centerline. Deposits on themonofilament lines were stripped from the lines and dye rinsate from the line stripping was quanti-fied by colorimetry. The colorimetric color density measurement gave a relative measure of themovement of spray drift downwind from the spray swath. Typical results from these demonstrationsare shown in Figure1.

In each comparison it is clear that the low-drift option produced lower percentage coverage on thespray deposit cards near the swath and lower color density on the monofilament lines downwindfrom the application swath.

90

Figure 1. Selected results from drift reduction demonstrations.

Nozzle Selection for Drift Reduction with the AT-502 Air Tractor

The importance of spray droplet size as influenced by nozzle type, airspeed, and spray pressure, andthe percentage of the spray volume in the very small droplet size ranges that is more subject to spraydrift was documented by Bouse (1994) in wind tunnel studies. Based on the results of that study, afollowup research study was conducted in cooperation with Air Tractor, Inc. to determine the effectsof selected spray nozzles on spray deposit and downwind spray drift from a turbine-powered AirTractor, AT-502 (Bouse, et al., 1994). The nozzle treatments included narrow angle flat fan 4020Quick VeeJet nozzles oriented rearward and 10° down at 30 psi and whirl-type hollow cone 1/8B10-8 WhirlJet nozzles oriented rearward and 45° outward at 42 psi. Three airspeeds were used witheach nozzle treatment – 120, 135, and 150 mph. The differences in spray droplet size for the sixtreatment combinations are shown in Figure 2.

Spray output for all treatments was 70 gpm of water plus 0.1% v/v Triton X-100 and 0.5 oz/galcaracid brilliant flavine FFS fluorescent dye. Spray deposits and drift were quantifiedfluorometrically from rinsates from 4 X 4 in. mylar cards placed across the spray swath and down-wind to 450 ft. At the 450-ft. sample station, six cotton strings 100 ft. long were suspended betweenpoles at 6 ft. intervals to 30-ft. high. The amount of spray deposit was estimated by numericallyintegrating between mylar card positions and distance between cards, and integrating deposits onstrings in the vertical plane at the 450-ft. sample station. The integrated deposit at any point down-wind from the spray swath was then expressed as a cumulative percentage of the spray output at that

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

% COVERAGE COLOR DENSITY

DOWN WIND DRIFT COLLECTIONNozzle Orientation - Down vs. Back

Nozzles Down Nozzles Back

0.00

0.20

0.40

0.60

0.80

1.00

1.20


DOWN WIND DRIFT COLLECTIONSpeed

High Speed Low Speed

0.00

0.20

0.40

0.60

0.80

1.00


DOWN WIND DRIFT COLLECTIONWing Tip Vortex-Full vs. 3/4 Boom

Nozzled to End Boom Nozzled to 3/4 Boom

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40


DOWN WIND DRIFT COLLECTIONHeight of Flight - High vs. Low

High Low

91

point, with the balance being unaccounted for or still drifting at that point. The differences in sprayrecovery between the treatment extremes are shown in Figure 3. These studies show that narrowangle flat fan nozzles and lower airspeeds produce larger droplets and less spray drift than whirl-typehollow cone nozzles at higher airspeeds.

Spray Drift from Different Formulations of Roundup®

Increased usage of glyphosate in no-till crop-production systems and changes in formulations ofRoundup raised questions about increased spray drift from aerial applications of these materials. Astudy was conducted in cooperation with Monsanto Company to determine the relative drift propen-sity of four spray mixes of Roundup® (Kirk, 1997a). The spray mixes included Roundup® D-PAKplus Induce, Roundup® D-PAK plus Surf-Aid, Roundup® Ultra, and Roundup® plus Surf-Aid.These four spray mixes were applied with equal per acre rates of glyphosate in 5 gpa spray rates.Two passes were made over a 1300 ft.-long spray line at 10-12 ft boom height with an Air TractorAT-402-B at 140 mph. CP nozzles with 0.125” orifice and 30° deflector, boom length/wingspan of

050

100150200250300350400450

120 135 150Airspeed, mph

Dro

plet

Siz

e (D

V0.5),

µmNarrow Angle Flat Fan Whirl-type Hollow Cone

Figure 2. Effect ofnozzle type and airspeedon spray droplet size.

0

10

20

30

40

50

60

70

80

90

100

-100 0 100 200 300 400 500S am ple Location from F lightline, ft

Cum

ulat

ive

Rec

over

y, %

F an; 120 m ph W hirl Jet; 150 m ph

Figure 3. Cumulative spray recov-ery downwind from the centerline ofthe spray wath for narrow angle flatfan nozzles at 120 mph compared towhirl-type hollow core nozzles at150 mph. (is the center of theaircraft flightline.)

92

67%, and 50 psi were operating parameters for all applications. Treatments were applied in threereplications each at early morning, mid-day, and late afternoon to include a range of environmentalconditions. Mylar cards, 4 X 4 in., were used as sample collectors in the swath and to 1050 ft. fromthe downwind edge of the spray swath. Spray deposits on the mylar cards were quantifiedfluorometrically from card rinsates. The deposits from the cards for the four Roundup® spraymixes, averaged for all measurements are shown in Figure 4. Wind velocities averaged near 10 mphduring these spray applications. Spray deposits in the swath peaked at 10 gpa, resulting from the two5 gpa spray passes over the spray swath. There were slight differences in swath displacement for thefour spray mixes with the most displacement for Roundup® D-PAK plus Induce and the least dis-placement for Roundup® Ultra. However, these swath displacement differences correlate withdifferences in average wind velocities when the respective treatments were applied. Deposits at 525and 1050 ft., which are measures of downwind movement of driftable fine droplets, were not signifi-cantly different for the four Roundup® spray mixes.

CP Nozzle Parameters for Reduced Spray Drift

An innovation in hydraulic nozzles, the CP nozzle, has become the most widely used spray nozzleon agricultural aircraft. The CP nozzle is equipped with four orifices and three deflector plates toproduce a range of droplet sizes and spray rates. New labels for agricultural chemical sprays willlikely require that applications be made with specified droplet sizes. Consequently, a study wasconducted in cooperation with CP Products Company, Inc. to develop a relationship that aerialapplicators could use to determine droplet size and drift propensity based on CP nozzle orifice anddeflector settings along with aircraft speed and spray pressure (Kirk, 1997b). A wind tunnel, singlenozzle spraying system, and laser spectrometer were used to collect atomization data in a 27-point

0

2

4

6

8

10

12

-50 0 50 100 150 200 250 300

Distance Downwind, ft

Spra

y D

epos

it, g

al/a

cre

D-Pak Induce D-Pak Surf-Aid Ultra Roundup

Figure 4. Within-swath and near-field spray deposits on mylar cards for four Roundup® formula-tions ( 0 is aircraft swath flightline).

93

050

100

150200250300

350

400

100 110 120 130 140 150 160Airspeed, mph

Dro

plet

Siz

e (D

V0.5),

µm

0

5

10

15

20

25

30

Volu

me

less

than

100

µm

, %

DV0.5

%V<100µm

Figure 5. Predicted DV0.5 and %V<100 µm for airspeed ranging for 100 to 160 mph with CPnozzles set with 0.125-in. orifice and 30° deflector operating at 30 psi.

experimental design. This design facilitated development of response equations for DV0.5, which isthe volume median droplet size; relative span, which is a measure of the range of droplet sizes forthe mid 80 percent of the spray volume; and %V<200 µm and %V<100 µm, which are measures ofdriftable portions of the spray volume. These equations were incorporated into a spreadsheet usableon Intel and Windows computer systems. A diskette with the spreadsheet is available either fromASAE or the author. The output from a series of entries into the spreadsheet with airspeed varyingfrom 100 to 160 mph for the CP orifice size of 0.125”, 30° deflector, and 30 psi is shown in Figure5. It is apparent from Figure 5 that as airspeed increases from 100 to 160 mph that droplet size(DV0.5) is cut in half, but the percentage of spray volume in droplets smaller than 100 µm(%v<100µm) increases by 4.5 times. This could be the reason that higher speed aircraft are cited fordrift claims more often than are lower speed aircraft. If an aerial applicator with CP nozzles decidedto increase airspeed from 130 to 160 mph without changing spray nozzle setup, the highly driftablesmall droplet content of the spray would increase three times. The information available in thisspreadsheet will be useful to aerial crop protection applicators in responsible mitigation of spraydrift.

Potential for Spray Drift Mitigation Demonstrated with AgDRIFT

AgDRIFT is a Windows-based spray drift model developed by Continuum Dynamics, Inc. for theSpray Drift Task Force (SDTF) (Teske, et al., 1997; Teske and Ray, 1998; Bird, et al., 1997). Themodel was developed specifically for use by SDTF member companies and EPA in the registration/re-registration of crop protection chemicals. However, Hewitt, et al. (1997) have shown how themodel can be used in evaluating drift reduction options. We conducted a similar exercise to showhow AgDRIFT can be used to evaluate different spray application conditions and spray drift sce-narios for individual aircraft and operating conditions (Bouse, 1998). An AgDRIFT computationwith an Air Tractor AT-502 aircraft with the default values in Tier III of the model was run to showthe fraction of the application rate that could be expected to drift to different distances downwindfrom the application. A series of AgDRIFT mitigation option computations was also made with

94

default values each changed individually to show the influence of that option on predicted downwinddrift. The default and the selected drift mitigation options for the Air Tractor AT-502 are shown inTable 1.

Table 1. AgDRIFT Tier III default values for Air Tractor AT-502 with selected drift mitigationoptions.

Operating Variable Default Value Drift Mitigation Value

Airspeed 155 mph 155 mphBCPC Droplet Size Medium CoarseSpray Release Height 15 ft 8 ft.Boom Length/Wingspan 75% 60%Wind Speed 10 mph 5 mphBoom Placement Standard Lowered 9”Swath Offset ½-swath 1-swath

We have shown with the CP nozzle study reported that there is a linkage between airspeed anddroplet size if operating conditions, except airspeed, are not changed. AgDRIFT is programmedwith separate inputs for airspeed and droplet size distribution, i.e. droplet size distribution must beentered into the model for the specified airspeed. Consequently, we will not demonstrate airspeed asa drift mitigation option. And from a practical perspective, operators that invest in aircraft withhigher production capability (increased capacity and increased speed), are not inclined to reduceproductive capability by routinely decreasing airspeed. They could, however, consider decreasingairspeed to mitigate spray drift when spraying adjacent to sensitive areas. The AgDRIFT driftprediction for the default values is shown in the grey line for comparison with the drift mitigationoptions in black lines in Figure 6. In addition to the individual drift mitigation scenarios, driftcomputations were made with AgDRIFT to show the combined influence of (1) three of the driftmitigation options – BCPC coarse droplet size, 8 ft. spray release height, and 5 mph wind speed,Figure 7, and (2) all six of the drift mitigation options, Figure 8. It is readily apparent from thesecharts that several reasonable options are available to aerial applicators to significantly reduce themagnitude of spray drift from aerial applications of crop protection materials. The dramatic advan-tage of aerial applicators using the AgDRIFT model is that they can (1) select their specific aircraftfrom the catalog of aircraft imbedded in the model, (2) select the nozzle and its associated dropletsize spectrum for their specific operating conditions, either from manufacturers catalogs or otherdatabases or models, e.g. the CP nozzle model noted above or the DropKick model (Esterly, 1997),(3) select the drift mitigation options they expect to use, and (4) readily compute and display therelative drift potential for their standard and improved operations. The AgDRIFT model will be aparticularly useful tool to aerial applicators to estimate the benefit of alternative drift control prac-tices before any required investment is made to implement a selected drift mitigation option. TheAgDRIFT model is currently available on letterhead request from David M. Esterly, Chairman,Spray Drift Task Force Modeling Committee, E. I. DuPont de Nemours and Company, Wilmington,DE 19880-0402. The version 2.00 of the model will be available in late 1998 from the EPA’s Centerfor Exposure Assessment Modeling. The model can be accessed via the World Wide Web at http://WWW.EPA.GOV/CEAM/.

95

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0 500 1000 1500 2000 2500

Distance (ft)

Fra

ctio

n of

App

licat

ion

Rat

e

Default 1 Swath Offset

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0 500 1000 1500 2000 2500

Distance (ft)

Fra

ctio

n of

App

licat

ion

Rat

e

Default 5 MPH Wind

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0 500 1000 1500 2000 2500

Distance (ft)

Fra

ctio

n of

App

licat

ion

Rate

Default 60% Boom Length

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0 500 1000 1500 2000 2500

Distance (ft)

Fra

ctio

n of

App

licat

ion

Rat

e

Default 8 ft Spray Release Height

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0 500 1000 1500 2000 2500

Distance (ft)

Fra

ctio

n of

App

licat

ion

Rate

Default Coarse Droplets

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0 500 1000 1500 2000 2500

Distance (ft)

Fra

ctio

n of

App

licat

ion

Rat

e

Default 9" Drop Boom Placement

Figure 6. Downwind spray deposits or drift modelled with AgDRIFT for six spray drift mitigationoptions for an Air Tractor AT-502.

96

Potential for Spray Drift Reduction with Aerial Electrostatic Systems

Electrostatic spraying systems have been studied by several researchers for a number of years.Outbreaks of whiteflies in recent years and the possibility of electrostatic systems for improvingspray deposits on the bottom side of crop leaves where whiteflies spend much of their life cycle, hasspurred recent developments in electrostatic spray technology. Ground and greenhouse systems arecurrently being marketed, and our research on aerial electrostatic systems has led to a pending patenton an aerial electrostatic spray nozzle (Carlton, 1995). Research with this system has been concen-trated on hardware development and on improvements in efficacy on whiteflies and boll weevils.However, some observations indicate that the small spray droplets from electrostatic nozzles tend tomerge and produce larger droplets. This suggests that electrostatic charging may be efficacious inreducing spray drift; but field drift studies will be needed to confirm the impact of electrostaticcharging on spray drift mitigation.

Figure 8. Downwind spray deposits or drift modelled with AgDRIFT forsix combined drift mitigation options.

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0 500 1000 1500 2000 2500

Distance (ft)

Fra

ctio

n of

App

licat

ion

Rat

e

Default 8 ft, 5 MPH, Coarse Droplets

Figure 7. Downwind spray deposits or driftmodelled with AgDRIFT

97

ARS RESEARCH, STONEVILLE

Spray Drift from Three Spray Release Heights

Spray release height, boom height, or height-of-flight are descriptors of a factor that significantlyinfluences spray drift from aerial applications. Ground applications are similarly influenced by sprayrelease or boom height, but the range of this variable for ground applications is much smaller thanfor aerial applications. This study had several objectives; this presentation will highlight the influ-ence of spray release heights of 10, 15, and 20 ft. on spray drift from a turbine Thrush S2R T-41(Womac, et al., 1994). The aircraft was flown upwind and at an angle of 23.6° to a 2300 ft.-longsample line. Fifteen sampling stations were placed at different intervals along the sampler line in acotton field. Each sampling station consisted of a high-volume air sampler with a glassfiber filterand polyurethane foam plug supported at 6-ft. height and 8X8 in. mylar plastic sheets attached to thetop of the cotton canopy. RF 25° fan nozzles operating at 40 psi were used on the boom to spray a1.32% (v/v) cinnamyl alcohol plus 0.10% (v/v) X-77 spray solution at a spray rate of 3 gpa. Thepilot adjusted the spray release heights based on visual triangulation and a digital laser altimetryinstrument. Cinnamyl alcohol residues deposited on the samplers were removed with ethanol andquantified with gas chromotography. Drift results are expressed as means of residue concentrations(ppm) in 10 mL of solvent.. The results from this study are shown in Table 2.

Table 2. Spray drift from three different spray release heights.

Spray Release Height, Spray Drift,*Feet Ppm

10 2.2a15 9.5b20 11.4b

*Means followed by the same letter are not significantly different.

These studies show that spray drift increases as spray release height increases. However, in thesestudies, there were no significant differences in the deposits on mylar sheets within the swath for thedifferent spray release heights.

Spray Drift from Two Agricultural Aircraft

Two aircraft were available for a spray drift comparison study: a turbine-engine-powered Thrush asused in the previous study and a larger, heavier radial-piston-engine-powered M-18 Dromader(Howard, 1994). The Dromader was operated with both 50% and 70% boom-length/wingspan. TheThrush was only operated with 70% boom-length/wingspan. Each aircraft was operated at threeairspeeds as typical for the respective aircraft. The aircraft were flown upwind and at an angle of 45°to a 2200 ft.-long sample line. Fifteen sampling stations were placed at different intervals along thesampler line. Each sampling station consisted of a six-foot pole with a plywood plate mountedhorizontally 40 in. above the ground. Sheets of alpha cellulose (9 X 9 in.) were placed on the flatplywood plates and on the ground within the swath. CP nozzles were used on the boom to spray 0.1

98

lb./acre of malathion 5 EC at a spray rate of 2 gpa. The pilot operated the aircraft as close to thetarget values as his experience would allow. Malathion residues deposited on the alpha cellulosesheets were removed with ethanol and quantified with gas chromotography. Percent drift wascalculated by comparing the amount of malathion recovered from alpha cellulose sheets within theswath with that from alpha cellulose sheets along the sampler line. Results from this study areshown in Table 3.

Table 3. Spray drift from two agricultural aircraft at three airspeeds.

Aircraft Boom-Length/ Airspeed Spray Drift,*Wingspan mph Percent

Dromader 70 110 7.3 bDromader 70 120 8.1 abDromader 70 130 8.6 a

Dromader 50 110 4.2 dDromader 50 120 5.6 cDromader 50 130 6.3 c

Thrush 70 120 3.3 eThrush 70 130 3.7 deThrush 70 140 3.9 de

* Means followed by the same letter are not significantly different.

Increased drift with increased airspeed was characteristic of both aircraft. Reducing the boom-length/wingspan from 70% to 50% on the Dromader significantly reduced spray drift. However,spray drift from the Dromader with 50% boom-length/wingspan was greater than for the Thrush with70% boom-length/wingspan. The Thrush with 70% boom-length/wingspan operated at 140 mphproduced less drift than the Dromader in any configuration except with 50% boom-length/wingspanoperated at 110 mph.

SUMMARY

Aerial application technology has changed significantly in recent years with the movement to largerand more productive aircraft. Associated with that change is the transition to turbine poweredaircraft which is almost complete in the new agricultural aircraft fleet; nine of ten new agriculturalaircraft are turbine-powered compared to less than six of ten only five years ago. Spray drift fromaerial applications has emerged as the number one problem in recent years. Research has shown thatincreases in speed, which is primarily associated with the higher productivity aircraft, is largelyresponsible for increases in drift incidents and complaints. Spray drift increases with increases inaircraft speed because droplet size decreases with increased speed; and spray drift increases withdecreases in spray droplet size. There is likelihood that pilots tend to fly higher with higher aircraftspeed; and increased spray drift is associated with higher spray release heights. There are likelyother phenomena associated with contemporary large agricultural aircraft that may also contribute to

99

increased spray drift. The challenge facing the aerial application industry, and those supporting theindustry with research, is directly related to keeping the operators of highly productive aircraft inbusiness with application technology that keeps drift low and maintains the productivity associatedwith larger turbine-powered aircraft. Solution of that problem should be the primary initiative ofresearch programs supporting the agricultural aviation industry.

Acknowledgements

Appreciation is expressed to the various cooperators that facilitated the original research studiesreviewed herein and for the assistance of coworkers in assembly of this presentation.

Trade names are mentioned solely for the purpose of providing specific information. Mention of atrade name does not constitute a guarantee or warranty of the product by the U. S. Department ofAgriculture or the University of Maine and does not imply endorsement of the product over otherproducts not mentioned.

SELECTED REFERENCES

Annual Book of ASTM Standards. 1996. Volume 11.05, Section 11, ASTM, Philadelphia, PA19103-1187 USA.

ASAE Standards. 1997. ASAE, 2950 Niles Road, St. Joseph, MI 49085-9659 USA.

Bird, S. L., S. G. Perry, S. L. Ray, M. E. Teske, and P. N. Scherer. 1997. An evaluation ofAgDRIFT 1.0 for use in Aerial Applications. DRAFT REPORT. National Exposure ResearchLaboratory, Ecosystems Division, Office of Research and Development, U.S. EnvironmentalProtection Agency, Athens, GA USA.

Bouse, L. F. 1994. Effect of nozzle type and operation on spray droplet size. Transactions of theASAE 37(5):1389-1400.

Bouse, L. F., J. B. Carlton, I. W. Kirk, and T. J. Hirsch, Jr. 1994. Nozzle selection for optimizingdeposition and minimizing spray drift for the AT-502 Air Tractor. Transactions of the ASAE37(6):1725-1731.

Bouse, L. F. 1998. Personal Communication.

Carlton, J. B., I. W. Kirk, and M. A. Latheef. 1995. Cotton pesticide deposition from aerial electro-static charged sprays. ASAE Paper No. AA95-007. ASAE, 2950 Niles Road, St. Joseph, MI49085-9659 USA.

Esterly, D. M., 1997. DropKick – a new tool for estimating spray drop size. ASAE Paper No.AA97-008. ASAE, 2950 Niles Road, St. Joseph, MI 49085-9659 USA.

100

Hewitt, A. J., D. L. Valcore, C. G. Hermansky, D. M. Esterly, and M. E. Teske. 1997. Drift reduc-tion options using AgDRIFT spray deposition model. ASAE Paper No. AA97-007. ASAE,2950 Niles Road, St. Joseph, MI 49085-9659 USA.

Howard, K. D. 1994. Downwind spray drift assessment. ASAE Paper No. AA94-007. ASAE, 2950Niles Road, St. Joseph, MI 49085-9659 USA.

Johnson, D. R. 1998. Summary of Spray Drift Task Force Pesticide Registration Work. NorthAmerican Conference on Pesticide Spray Drift Management. Portland, ME USA.

Kindinger, P. 1998. Update from Spray Drift Coalition. North American Conference on PesticideSpray Drift Management. Portland, ME USA.

Kirk, I. W. 1997a. Roundup formulations drift study, fall 1996. Preliminary Data and Report,USDA-ARS Areawide Pest Management Research Unit, 2771 F&B Road, College Station,TX 77845-4966.

Kirk, I. W. 1997b. Application parameters for CP nozzles. ASAE Paper No. AA97-006. ASAE,2950 Niles Road, St. Joseph, MI 49085-9659 USA.

Teske, M. E., S. L. Bird, D. M. Esterly, S. L. Ray, and S. G. Perry. 1997. A user’s guide forAgDRIFT: A tiered approach for the assessment of spray drift of pesticides. EIGHTHDRAFT. Technical Note No. 95-10. Continuum Dynamics, Inc., Princeton, NJ USA.

Teske, M. E. and S. L. Ray. 1998. AgDRIFT: an update of the aerial spray model AGDISP. Transac-tions of the ASAE (to be submitted).

Valco, T. D., L. F. Bouse, J. B. Carlton, E. Franz, I. W. Kirk, and W. C. Hoffmann. 1991. Aerialdrift reduction demonstrations. ASAE Paper No. AA91-001. ASAE, 2950 Niles Road, St.Joseph, MI 49085-9659 USA.

Womac, A. R., J. E. Mulrooney, B.W. Young, and P. R. Alexander. 1994. Air deflector effects on aerial

101

(Concurrent Session #2)

Aerial-Rotary Application Equipment and Drift

David L. ValcoreDow AgroSciences

Indianaoplis, Indiana

Milton E. TeskeContimuim Dynamics

WHY Rotary vs. Fixed Wing- similarity - differences- helicopter wake issues

Ability to Model Drift- AgDRIFT Model

SDTF Drift data

Low Drift Helicopter Nozzles---------------------------------

Vortex Wake

Vortex Strength - a known aerodynamic fact

Helicopter lighter but slower

Roll-up or initiation point- height difference to spray boom- see new Textron Bell aerial application guide book-------------------------------

Vortex and Droplet Trajectory Helicopter Downwash and Vortex

102

Video Helicopter Wake Simulation

from Continuum Dynamics military contract indicates downwash and wake vortex roll-up behind ,slightly uneven left-right---------------------------

Helicopter vs Fixed Wing

Lower speed - lower shear- allows specialty nozzles

• Similar vortex roll up strength

• Vortex much higher than spray boom

• Downwash effect, positive

• Both can be modeled with AgDRIFT™-------------------------------

AgDRIFT Model Verified

180 treatments - 90 standard covariat, 90 variable, dropsize/spray volumeBell G47 Wasp, AT-502, height

Collected deposits on ground, (-15 to 800m)- some air dosage, a few vertical string collectors

Standard - gave wide range of weather cond.

A few treatments, tank mix properties, cotton canopy, stable air----------------------------------

SDTF Aerial Summary Charts

Major graphs on swath adjustment, dropsize effect, height,aircraft speed (type) boom length, and crosswind shown fromSDTF Aerial booklet (request via fax 660-762-4295from Stewart Agric. Res. Services)---------------------------------

The following graphs based on early AgDRIFT model used a Bell G47unless 206 is noted, data is for trends only

SDTF atomization data is draft only and nozzles types or brandsmentioned do not indicate Spray Drift Task Force endorsementor recommendation over others

103

Nozzle Type - 75 ft release ht, 7 ft canopy,4 mph wind, 20 swaths, 8gpa

Nozzle Type 75 ft release ht, 7 ft canopy,4 mile/hr wind, 8 gal-spray/ac, 3 lb-ai/ac

D8-Jet, 75 ft release ht, 7 ft canopy,8 gal-spray/acre, 3 lb-ai/acre

RD-10, 75 ft release ht, 7ft canopy,8 gal-spray/acre, 3 lb-ai/acre

104

D8-Jet, 75 ft release ht, 20 swaths,8 gal-spray/acre, 3 lb-ai/acre

TVB-030, 75 ft release ht, 7 ft canopy,8 gal-spray/acre, 3 lb-ai/acre

RD-10, 75 ft release ht, 20 swaths,8 gal-spray/acre, 3 lb-ai/acre

TVB-030, 75 ft release ht, 20 swaths,8 gal-spray/acre, 3 lb-ai/acre

105

Height 50 vs 30 vs 20 ft,Bell 206II B with D8 nozzle

Swath Width vs Boom Length TVB-030, 75 release ht, 7 ft canopy, 4 mile/hr wind

106

CP and TVB wedge nozzle

CP Nozzle Orientation

Accuflow and TVB Nozzle

107

Current Technology Status

Downwind wing boom shut-offDGPS - allow accurate buffers and offsetsElectrostatic - College St. TX -ARS- some success in cotton, alternating chargesSpecialty nozzles - TurboDrop, ML tips, Syngro, etc------------------------------

Spray Quality Standard

Allows Easy Label Use of Dropsize Specification- ASAE standard 572 approval underway- Reference nozzles from manufactures, test labs- 1998 /99 Introduction in nozzle catalogs- Global - BCPC /ISO standard--------------------------------

Nozzle Spray Quality Standard X572

ASAE standard would classify all Ag nozzles into, very fine, fine, medium, coarse, very coarse, extra coarse categories; - ease of labeling - drift mitigation options

EPA will use labeling of such spray requirementsas input into risk assessments

Nozzle manufactures will publish ratings- for aerial a dropsize/ classification booklet, (NAAREF & SDTF)------------------------------

Nozzle Spray Quality Standard X572

DropKick Atomization Model Use- will generate Aerial Dropsize booklet- phys. Prop. Defaults vs. Restrictions and Measurements

108


Air-Blast/Air-Assisted Application Equipment and Drift

Robert D. Fox, Richard C. Derksen and Ross D. BrazeeUSDA-Agricultural Research Service

Wooster, Ohio

ABSTRACT

The use of air-assisted boom sprayers and air-blast orchard sprayers is discussed. Air jetcharacteristics are important in transporting spray droplets into canopies. Travel speed, canopydensity, spray droplet size, and other factors affect spray deposition on foliage. Drift from sprayingorchards, vineyards, and nurseries is an important problem, and the results of several studies arepresented. New sprayer designs, care in sprayer operation, buffer zones, and other methods can beused to reduce exposure of sensitive areas to spray drift.

INTRODUCTION

Air-assisted spraying is important to obtaining good coverage of pest control agents on field,vineyard and orchard crops. These crops require use of pest control agents to produce abundant,healthy, pest free produce for American consumers. In this paper we will discuss several aspects ofair-assisted spraying, including sprayer air jets, factors affecting spray deposit on foliage, measure-ments of drift downwind from sprayed orchards, and methods to mitigate spray drift. Most of thesetopics will be covered by citing pertinent literature wherein scientists have conducted experimentsand theoretical studies that improve our understanding of these problems. Several relevant books onthese topics are available. Matthews and Hislop (1993) discuss all types of spraying, including spraydroplet production, drift measurement, etc. They devote one chapter to spraying trees. Lavers, et al.(1991) summarize many aspects of air-assisted spraying from physical principles to spraying infields, orchards, greenhouses and packing houses. Pompe and Holterman (1992) provide a goodreview of literature on pesticide application, including both air-assisted sleeve boom sprayers andair-blast tree and vineyard sprayers. They provide one chapter with a good discussion of spray drift.The objective of this paper is to provide an introduction to air-assisted spraying and associated driftproblems, and to provide information about current research on these topics.

AIR-ASSISTED BOOM SPRAYERS

Air-assisted boom sprayersCommercial air-assisted boom sprayers have been on the market for several years. Air-

assisted boom sprayers usually consist of a blower and air distribution system in addition to thetraditional spray boom system. One part of the air distribution system is some type of sleeve (mani-fold) that conducts the air from the blower along the spray boom. The other part of the system is aslot or series of holes along the bottom of the sleeve to provide a continuous or a series of air jetsdirected toward the ground. The nozzles are positioned in front of the jets and spray is directedtoward the jets where the droplets become entrained in the air jets and are carried toward the plantcanopy. There is often some control on the direction of the air jets and on the velocity of air fromthe jets.

109

Cooke et al. (1990) compared spray drift from hydraulic-nozzle boom sprayer with that froman air-assisted sprayer on arable crops. While the air-assisted sprayer generally produced betterdroplet distribution uniformity and equal spray deposition, it generally produced more drift than anhydraulic sprayer. Howard et al. (1994) conducted a series of studies to compare spray deposit, driftand biological effect of several air-assisted sprayers in cotton. Although there was some variationfrom year to year, some sprayers performed well under all conditions. Gaultney et al. (1996) devel-oped a protocol for measuring off-target drift from air-assisted and air-shear sprayers. In this methodtwo sprayers were operated simultaneously and active and passive collectors were used to measureairborne spray and ground deposits, respectively. In this way, two sprayers could be comparedaccurately. Hislop et al. (1993) measured spray deposits on small cereal plants treated with andwithout air-assistance. They found that the air-assisted treatments increased the amount of sprayretained by the plants compared with treatments without air-assistance. May and Stevers (1993)conducted field experiments to compare several sleeve boom sprayers with twin fluid nozzle spray-ers. They used 21 treatments of fungicide on wheat, and measured coverage and disease control.They found greater deposits with low volume sprays compared to medium volume sprays. Quanquin(1995) reported reduced drift amounts from spraying with air-assist compared with spraying withoutair-assist. He stated that drift from spraying with air-assist in 25 mile/h wind speed is similar to driftwithout air-assist in a 5 mile/h wind speed. However, there was no significant increase in yield,partly due to low disease pressure. Lavers et al. (1991) and the Second International Symposium anPesticide Application (A.N.P.P. - B.C.P.C., 1993) contain several other articles on air-assisted fieldcrop spraying.

New concepts in controlling spray droplets size and nozzle flow rates in addition to air-assistance have been developed more recently. Manor et al. (1989) used an air-sleeve field sprayerto achieve better penetration to lower levels of a cotton canopy and much more coverage on theunderside of leaves compared with a conventional boom sprayer.

AIR SPRAYER TYPES FOR TREES AND VINEYARDS

Air jet characteristicsMost tree crop and vineyard sprayers use air jets to transport spray into target canopies where

droplets are deposited. Conventional orchard sprayers have used an axial flow fan to force airthrough a narrow opening in a circular housing to form a jet. Spray nozzles are located near thecenter of the jet to provide the spray droplets transported by the air jet. The action of the air jet onspray deposit has been studied by many researchers. Fleming (1962) measured the effect of jet airvelocity/air volume relationships on the transport of 100 and 200 m DV0.5 (volume median diameter)droplets. He found that the amount of spray transported over distance was proportional to air powerof the jet. However small droplets were transported greater distances than larger droplets. The 200m droplets were transported greater distances by the high-velocity/low volume jet than by the low-velocity/high volume jet. In Great Britain, Randall (1977) conducted an extensive study of spray jetair velocity, air volume, and air power, along with sprayer travel speed and wind effects on spraydeposit in large fruit trees (canopies about 20 ft in diameter). Randall also measured air velocityprofiles across three jets at several distances from the jet outlet and found measured values agreedwell with values calculated from jet theory. For these large trees, Randall found that a minimum jetvelocity of about 20 miles/h was necessary to penetrate the canopy edge Cox apple trees. If thisminimum velocity was achieved, then sprayer jets with the largest volume, at a given air jet power,usually provided the best spray deposit. The slower the sprayer traveled, the greater the uniformityof spray deposit. Fox et al. (1982) measured air power in jets from two sprayers and comparedvolume/velocity relationships.

110

Reichard et al. (1979) measured air velocities fromthree sprayers as they travelled past a towerstanding in a mowed area and in a peach orchard.They found that measured air velocitiesdecreased as sprayer travel speed increased andthat jet velocities decreased rapidly withincreasing distance from the jet outlet. Airvelocities in jets with large air volume did notdecrease as quickly as velocities in jets with lessair volume. Brazee et al. (1981) modified theideal jet theory to account for the axial spreadingof circular, or polar jets. They measured airvelocity profiles across jets at several distancesdownstream from two commercial sprayers. The

measured air-jet velocity profiles were similar to profiles predicted by the theory for ideal jets.Maximum jet centerline velocities, both calculated radial jet model and measured for one sprayer,are shown in Figure 1. Fox et al. (1985) developed a computer model of jet deflection due to windor travel speed effects and tested the computer model results against measured air velocity values ina deflected jet produced by a scale model in a wind tunnel. Ras (1991) derived equations for airvelocity profiles from radial and axially symmetrical jets used on orchard sprayers. He includedeffects of cross flow (wind) on the jet centerline path.

Air jet/canopy interactionsThe interaction between air jets and tree canopies is a key to determining penetration and

deposition of spray transported by sprayer jets. This problem is very difficult to solve because thecanopy is difficult to describe mathematically and changes constantly. Some studies have touchedon this problem. Fox et al. (1984) measured air velocities within a semi-dwarf apple tree as an air-blast sprayer travelled pass the tree. They found measured peak velocities were about 1/2 airvelocities predicted by jet theory for stationary jets, based on distance from the jet outlet. Ras (1991)estimated the decrease in air velocity and air power of a jet penetrating a tree, based onmeasurements by Hale (1977). Walklate et al. (1996) developed equations for velocity and turbulentkinetic energy loss for an air jet as it penetrated canopies. They tested the model by using acommercial air jet and an artificial canopy made of cards arranged to produce a range of ‘foliage’densities. Experimental results verified the relationships used for the energy loss. However, theirdevelopment did not provide good correlations for some area densities.

Other sprayer jetsBecause conventional sprayers typically produce spray deposits of about five times greater

near the sprayer outlet than in the top center of the tree, sprayers with several different air jets havebeen developed to produce more uniform distributions throughout the canopy. Commercial towersprayers have been available for several years. In tower sprayers, part of the output of an axial fan isdirected to a vertical duct which transports air to outlets at several elevations. Separate air jets atthese elevations are directed horizontally at the tree which reduces the distance from spray nozzles totheir targets.

Van Ee et al. (1988,1989) discussed the development and operation of a cross-flow fansprayer. Several fans on this sprayer were arranged in a vertical plane, which reduced the distancefrom the fans (and spray nozzle) to the top sections of the tree, and provided more uniform coverage

Figure 1. Effect of distance from outlet on air jetvelocities; adapted from Brazee et al., 1981.

111

than conventional sprayers. Fox et al. (1992) measured air velocity profiles produced by cross-flowfan jets and found velocity profiles and axial centerline velocities agreed well with results from planejet theory. Svensson (1991) tested a cross-flow fan sprayer by changing the angle of the top fan toproduce a converging jet. He found this increased the air velocity and spray deposit in the densestpart of fruit trees.

Baldoin et al. (1994) developed a low volume air-assisted sprayer that used a tower system todirect air and spray toward the tree from three outlets. They compared deposit on water-sensitivepapers and scab control when using the experimental sprayer with a standard orchard sprayer. Theexperimental sprayer seemed to deposit more spray in the tree tops than the conventional sprayer butscab control was adequate for both sprayers. In tests the second year, the experimental sprayerdesign was improved and scab control was better with the experimental sprayer than with theconventional sprayer.

Doruchowski et al. (1996) used three sprayers with different air-discharge systems todetermine in-canopy and off-target deposits in semi-dwarf apple trees. Sprayers used were:conventional radial air jet; cross-flow fan jets; and a sprayer with 10 directed air jets. Air jets fromeach sprayer were operated at two or three air velocities and air volume rates. For the conventionalsprayer, greater air jet velocity improved total canopy deposit and uniformity of deposit. Air jetconditions had little effect on total or uniformity of deposit for the other two sprayers. The cross-flow and directed-jet sprayers produced better canopy penetration than the conventional sprayer.Spray loss to the soil decreased with increasing jet velocity, but airborne loss was increased. Salyaniand Hoffmann (1996) measured air velocities at 16 locations on four towers at horizontal distancesof 3.6, 6.6, 9.8, and 13.1 ft from an axial sprayer centerline. They also measured spray deposits oncitrus leaves and paper towel collectors at the 16 locations when spraying with an axial fan sprayerdelivering three spray application rates. They found that maximum air velocities were less forsprayers moving past the towers than for stationary sprayers; lower spray volumes resulted in higherdeposits on leaf collectors, probably due to runoff at higher application rates. There was little or nocorrelation between air velocity and spray deposits on leaf surfaces and paper targets collected muchmore spray than leaves, especially at locations near the sprayer.

Electrostatic spraysThere have been several studies on effects of electrostatic charging on spraying orchard

crops. Inculet et al. (1981) measured increased deposits in the tops of Macintosh apple trees usingcharged spray as compared to the same sprayer without charging. Castle and Inculet (1981)developed equations for the forces acting on droplets in spray clouds near trees. A commercialsprayer based on this research was produced for several years. Law et al. (1985) developed a sprayerwith nozzles to produce spray with an electrostatic charge. They sprayed a large grid system withcollectors using the electrostatic sprayer both with and without charging the spray droplets, and witha conventional sprayer. The charged spray had increased deposits compared with the same sprayerwith uncharged spray when applying 20-40 m droplets. However the conventional sprayer applying370 m droplets had the greatest deposit of the three treatments. Allen et al. (1991) compareddeposit and pest control when using a mist-blower sprayer in apple trees and hops. They foundincreased deposit and better pest control when the spray was charged than when the same sprayerapplied uncharged spray.

112

Figure 2. Spray deposited on dormant and full foliage bushand hedgerow apple trees by several sprayer types. Adaptedfrom Herrington et al. (1991)

DEPOSITS ON TREE AND VINEYARD CANOPIES

There have been many attempts to determine the effects of spray characteristics andoperating conditions on canopy deposition. Few of these studies were successful in producingstatistically significant results because canopy deposition varies greatly from point to point withinthe tree and even at the same point with replicated spray conditions. In this summary, we havetaken data from several papers and attempted to calculate results in a common format forpresentation in the figures. We have calculated measured deposits as a percentage of applied tracer,i.e., if the rate sprayed was 1 gm/ha, and we measured 1 g/m2 , then percent deposited was 1%.Numbers produced by this calculation method are accurate only for spray applied to the outside,downwind row. Reported values are the largest (worst case) possible. For all other rows in theorchard, much of the spray missing target trees would deposit on downwind tree rows , or on theground within the orchard.

Probably the most comprehensive studyof tree deposit was reported by Herrington etal. (1981). They measured deposit on treefoliage, shoots, branches, and trunks afterspraying bush and dwarf hedgerow apple trees.Bush trees were sprayed during late dormantand full foliage stages with a hand lance, anautomatic nozzle spray mast sprayer, aconventional air-blast sprayer at mediumvolume (MV, 120 gal/acre) and low volume(LV, 60 gal/acre) and by a hand directed ultra-low volume (ULVH) fan-assisted, spinningdisc sprayer at 0.6 gal/acre. Dwarf hedgerowapple trees were sprayed with an air-blastsprayer at LV and ULV (5 gal/acre), in both

late dormant and full foliage stages. At late dormant stage, the bush trees retained from 9 to 22% ofthe total spray by all methods except hand directed ULVH, which had 57% retained. At full foliage,retention was 22 to 37% for all sprayers. The hedgerow trees at late dormant stage retained 6% ofspray applied with LV AND 10% of ULV spray. At full foliage, retention was 25 and 63% for LVand ULV respectively. The percentage of spray Herrington et al. (1991) found on all parts of thetrees for both dormant and full canopy treatments are shown in Figure 2. They washed all surfacesof about 40 trees to obtain this data set. Note that for most air-blast sprayers (MV, LV, and ULV),spray deposited on the tree canopy (leaves, twigs and branches and trunk) averaged about 40% of theapplied spray.

Siegfried and Holliger (1996) report that about 40-50% of applied products are deposited onleaves and fruit with axial-fan or cross-flow fan sprayers while deposits on dormant trees averagedabout 24%.

Pergher and Gubiani (1995) measured the effect of spray application rate and vineyardfoliage density on spray distribution. Increasing spray application rate and air jet volume producedgreater ground deposits and less foliage deposits. Ground deposits were of about 35% of appliedspray for 33/42 gal/acre application rate and 41 to 49% for 70/78 gal/acre application rate. Off-target

113

drift ranged from 6.5 to 10.5% for low air output (15,000 ft3/min) and from 7.8 to 19.8% for high airvolume (18,000 ft3/min). Greatest deposition on foliage (about 55% of amount sprayed) was for lowspray volume and low jet air flow rate. Many studies have measured spray deposit patterns from air-blast sprayers in orchard canopies. These studies include: Hall et al. (1975), Whitney and Salyani(1991), Salyani and Whitney (1992), Salyani (1994), Derksen and Gray (1995), Hoffman andSalyani (1996), and Travis et al. (1997) and many others.

DRIFT FROM TREE AND VINEYARD SPRAYERS

Factors affecting driftMany of the same factors affect drift from spraying vineyards, orchards, and nurseries as

determine drift from other modes of spraying. Ozkan (1991) discusses factors important incontrolling drift from boom sprayers, while Elliott and Wilson (1983) describe drift problems fromthe standpoint of herbicide application. The principles they present and their discussions of allfactors important to drift are common to most spray application methods. Arvidsson (1997) testedseveral methods for measuring drift from field sprayers, evaluated the relative importance of factorsin drift, and suggested a standard method for measuring drift from boom sprayers.

One factor effecting spray drift is wind velocity and direction, although the size and densityof an orchard canopy may lessen wind effects on ground deposits close to the downwind edge.Another key factor is the release height of sprayed droplets. Air jets may transport droplets wellabove the canopy top where droplets can become entrained in air currents and dispersed higher.Spray droplet size is also an important factor in spray drift. In general, larger droplets are not carriedaround plant canopy structures but impact the plant, and if they are not deposited, they rapidly fall tothe ground. Driftable droplets (droplets less than 150 m diameter) may be carried greater distancesbefore they settle to the ground, and in suitable conditions may evaporate, leaving particles of activeingredient and formulation that can be transported long distances.

Bache and Johnstone (1992) develop relationships between droplets, their transport by aircurrents, and deposition on plant materials and other collectors. High air temperatures and lowhumidities will increase the evaporation rate and may affect drift patterns. The tree canopy densityand the match between the sprayer set-up and the tree size may be important in the amount of driftproduced. Atmospheric stability may be a factor under some conditions. Very stable conditions(with a strong temperature inversion), with low wind velocities can create conditions where a spraycloud may remain airborne and when air currents appear, spray may be deposited in larger doses atsome distance from the spray site than normally expected. These large concentrations may occur inany direction from the spray site. Sprayer operators have key roles in reducing spray drift, throughpreparing the sprayer properly and accounting for sensitive regions near the application site.

Drift measurementsMeasuring drift from spraying orchards and vineyards with air-blast sprayers is also a

difficult problem. Constantly changing winds, and canopy movement result in great variability indeposits at collection sites. Other key factors that lead to variation in results are the type of collectorused (especially for airborne spray), the tracer used, sprayer operating conditions, number of rowssprayed and crop canopy structure. In the past few years several groups have made measurements ofdrift from spraying fruit trees; some of their results are summarized here.

114

Figure 3. Airborne spray drift at 26 ft downwind as percentage ofapplied spray vs. wind speed; adapted from Gilbert & Bell, 1988

Parkin and Meritt (1988) discussed advantages and disadvantages of several methods ofcollecting drift samples. They reviewed impaction theory and the effect of droplet size, target sizeand type and wind speed on collection efficiency of the sampling methods. Finally, they discussimpaction and droplet drift models and show data to demonstrate the major points in thepresentation. Walklate (1989) discusses meteorological measurements made during a driftexperiment and presents equations to calculate relevant parameters to describe ambient conditionsthat may affect spray drift.

Gilbert and Bell (1988) describea system of collectors they havedeveloped to measure airborne sprayand ground deposits downwind of aspray site. Figure 3 is a plot ofexpected airborne spray drift forseveral spraying systems for a rangeof wind speeds. These results arebased on a series of experiments theyconducted over several years. Thisfigure provides a nice comparison ofairborne drift amounts produced byseveral boom sprayer systems and anair-blast system.

MacCollom et al. (1986) sprayedcarboryl and captan on 20 ft tallapple trees with aircraft and with twoorchard air-blast sprayers andcompared off target drift. Theyfound more drift from aircraft thanfrom air-blast sprayers and that atemperature inversion resulted in

more drift even with a 2% slope of the land. Results of measured downwind ground deposits areshown in Figure 4 along with results from several other studies. Their measured deposits were about10 times greater than ground deposits measured by other studies.

Riley and Wiesner (1990) measured off-target spray losses resulting from applying pesticideon 20 ft tall trees with an air-assisted sprayer. They measured number and size of droplets depositedon ground and airborne spray collectors. Rotorods and wires up to 36 ft elevation were used tosample airborne spray. They found that both number and size of droplets decreased rapidly withincreased distance downwind. They developed regression equations that can be used to predictworst case deposits from multiple row applications. Results of their measurements of ground depos-its are shown in Figure 4.

Fox et al.(1990, 1993a,b, 1994) assayed ground deposits and airborne spray concentrationsdownwind from air-blast spray applications to the outside row of an apple orchard. They found thatground deposits at 200 ft downwind were about 1/250 deposits near the tree row. Beyond 100 ftdownwind ground deposits were about the same when spraying without trees or through a tree row.

115

Beyond 200 ft downwind, airborne spray samples were about 10 times greater than ground depositsbased on deposit per unit area of the collector. Ground deposits from these studies have been com-bined and are shown in Figure 4.

Walklate (1992) developed a randomwalk atmospheric diffusion model to predict spraymovement from a axial flow fan orchard sprayer.Drift simulations agreed well with measured driftover stubble and orchard canopies. Ganzelmeieret al. (1992,1993,1995) developed a standardmethod for measuring drift from field and orchardsprayers. They reported 32 trials with early-season orchard spraying and 31 trials with late-season orchard spraying. The trials wereconducted by several industry, university andgovernment laboratories with different orchardsand sprayers, but with standardized procedures.They reported ground deposits up to only 100 ftdownwind. Airborne spray was collected onplastic pot scrubbers, but because of uncertaintyabout collection efficiency due to variation inwind velocity, droplet size and other factors, they

could not define what was measured, and therefore no airborne data were reported. They used a 95percentile method to represent the expected worse case of spray drift. This procedure provided aweighted maximum which may better represent the entire data set than just a few extreme valuesmeasured in one or two trials. These results are also shown in Figure 4.

May et al. (1994) measured drift downwindfrom a mature apple orchard, sprayed with foursprayers. Twelve rows (16.4 ft spacing) weresimultaneously sprayed by all sprayers. Sequentialand cumulative samplers were used to collect airbornespray at 6.6 ft elevation and ground deposits at 82 and164 m from the orchard. One conventional axial fansprayer and 3 tower sprayers were used. All threetower sprayers produced less airborne spray andground deposits that the conventional sprayer. Theseresults have been combined and are plotted in Figure 4.

The results in Figure 4 were calculated fromvalues published in the cited papers. The effect oftracer, sprayer type, spray operating conditions(sprayed droplet size, air jet characteristics, travelspeed, number of rows sprayed, etc), size of theorchard upwind from the sprayed portion, windvelocity, atmospheric stability, type of collector andother factors have been ignored. Ground deposits werecombined for all trials found for each of the treatmentsshown in the legend.

Figure 4. Ground deposits downwind from orchardspraying: a summary of several studies.

Figure 5. Airborne spray deposits downwind fromorchard spraying; a summary of several stuides.Legend symbols are F - high volume air sampler filter;S - string; Sc - nylon screen; W- wire.

116

Airborne spray deposits measured downwind from sprayed orchards are shown in Figure 5.Active collectors such as high volume air samplers usually collect more spray material than passivesamplers such as string, screen, or wire. If Figure 5 is compared to Figure 4, we see that airbornespray amounts decrease as a slower rate with increased distance than do ground deposits.

Salyani and Cromwell (1991) compared ground and airborne spray deposits resulting fromspraying an orange grove with an orchard air sprayer, a fixed wing aircraft, and a helicopter. Highand low liquid application rates were applied with the orchard air sprayer. Averaged over alldownwind locations, greatest airborne spray deposit and the least ground deposit was produced bythe orchard sprayer applying the low liquid volume, but there was not significant differencesbetween drift from aerial and ground spraying.

Xu et al. (1997) compared results predicted with a spray penetration model they developedearlier with airborne spray deposits 16.4 ft downwind from a tree row sprayed with an orchardsprayer. Measured deposit profiles agree reasonably well with predicted deposit profiles. Greatertravel speed reduced the amount of spray collected downwind from the tree row.

The Spray Drift Task Force (SDTF) (1998) conducted extensive measurements of drift fromorchard and vineyard spraying. These measurements were conducted using Good LaboratoryPractices (GLP) and are probably be the most comprehensive set of drift measurements fromorchard spray trials conducted to date. They found that only about 96% of the total spray applied tothe last six rows of an orchard stayed within the orchard area. As expected, spraying tall treesresulted in more spray deposits downwind from the orchard. They found that spray collected onvertical strings decreased greatly as spray moved from two to five rows downwind from the sprayedrow, i.e., downwind tree rows acted as a filter for spray passing through the sprayed trees.

Spraying of dormant treesMany fruit trees are sprayed when the trees are dormant. We have measured leaf area indices

(LAI) of about 3 for semi-dwarf trees with foliage and about 0.6 for dormant trees. Thus there is amuch smaller target for spray during dormant applications. This was shown by Herrington et al.(1981) and was presented in Figure 2. They found that only about 10% of applied spray wasdeposited on the tree parts during dormant application. The SDTF (1998) also found that sprayingdormant trees resulted in greatly increased downwind deposits compared to spraying trees in fullfoliage.

Steinke et al. (1992) sprayed dormant almond trees with axial flow and cross-flow sprayersand a helicopter. They measured deposit on tree twigs, downwind drift and insect control. Theyfound a strong correlation between pesticide deposit and insect activity - i.e., more deposit resultedin less insect activity. They measured increased deposit throughout the tree with the cross-flowsprayer as compared to both the axial flow sprayer and the helicopter. Downwind deposits onground collectors were less than on airborne spray collectors. The cross-flow sprayer produced thegreatest airborne spray amounts.

Spray accountabilityA obvious question at this point is: can we account for all of the spray applied to orchards?

What portion is deposited on the canopy, on the ground and remains airborne beyond a certaindistance downwind? Most of the results presented here were for full-foliage trees, so we will

117

consider the case of air-blast spraying of trees with foliage. Again, we calculated percentages on thebasis of tracer applied per unit area. Thus the results are worst case values. If more than the outsiderow were sprayed, some of the downwind spray would deposit within the sprayed area and a lowerpercentage of the total spray would be deposited downwind from the orchard. Measured deposit onfoliage by Herrington et al. (1991), shown in Figure 2, were about 40% for air-blast sprayers.Siegfried and Holliger (1996) stated that about 40-50% of spray was deposited on the leaves andfruit, about 20% on the ground and about 20% lost as drift. The total spray deposited on the groundfrom the orchard edge to 100 ft downwind was calculated and shown in Figure 6 for several driftstudies. The mean total ground deposit was about 10 to 15% of applied spray. Airborne spraydeposits at 100 ft downwind were also totaled from the ground surface to 30 ft; because data werelimited, and several assumptions were made, these results are considered to be subject to largeerrors, but airborne spray from 0 to 30 ft wasabout 12% of sprayed. Therefore the total ofdeposits on foliage, on the ground andairborne is 70%. Thus it appears that about30% or applied spray is still unaccounted for.With no justification, this missing spray islikely to be distributed as 15% additional onfoliage, 5% additional to ground deposits and10% to airborne spray. Thus the spraypartition is likely to be about 55% on thefoliage, 20% on the ground and 25% airborneas small droplets.

CONTROL OF DRIFT

Some spray drift will occur during every spray application. However there are severalmeasures that can be used to minimize the amount of spray that leaves the sprayed area and isdeposited downwind or carried long distances at very low concentrations. Generally, these practicesattempt to: 1) keep the spray as close to the ground as possible; 2) minimize the small dropletfraction; 3) match the sprayer air jet and nozzle system to the trees being sprayed; 4) use specialtechniques near sensitive areas. Most of the techniques discussed below use one or more of thetechniques mentioned above.

Overhead applicationCarpenter et al. (1985) tested a micro-irrigation system over the tree row as a possible

automatically controlled pesticide application system. They were able to design a system thatworked fairly well, but the system required a large amount of water and wind currents preventeduniform coverage under some conditions.

Tree sensingMcConnell et al. (1993) proposed a spray system that would use ultrasonic sensors to

evaluate tree volume for use in control of spray volume. Sutton and Unrath (1984) discussed usingtree volume as a basis for the volume of spray to be applied. Giles et al. (1987) used a tree sensingsystem and a spray control system to develop an air-blast orchard sprayer that sprayed only whencanopy was detected. The sprayer used sensors at three elevations to detect foliage; each sensor

Figure 6. Total ground deposits from the orchard edge to 100 ft.

118

controlled spray from the nozzles directed at the associated elevation in the tree. They tested thesprayer in a peach and an apple orchard. They found that tree-sensing/spray control saved 28 to35% of spray material in the peach orchard and 36 to 52% of spray in the apple orchard, compared tothe same sprayer without controlled spraying. Spray cards were used to evaluate spray deposit atlocations within the trees. Targets at some locations, near the leading edge of foliage near tree gapsand in the upper regions of the tree, received less spray when the tree-sensing system was used.Commercial units that use this type of system have been available for several years. In Spain, Rosellet al. (1996) developed an electronic selective spraying system which sensed tree volume as thesprayer moved down the row and adjusted sprayed volume to match measured tree volume. If notree canopy was detected, then no spray was applied. Spray trials in pear trees found that about 50%less spray was applied with the selective sprayer as compared to the same sprayer with the sensingcontroller system not used.

Tunnel sprayersHome built tunnel (over-the-row) sprayers have been used in crops such as grapes and small

fruit for some time. With increased concern for drift reduction, several researchers throughout theworld have recently designed and tested experimental tunnel sprayers. It is likely that thistechnology will be adopted for tree fruit in Europe more quickly than in the U.S. because recentplanting of apple orchards in Europe tend to be more uniform, dwarf varieties. Tunnel sprayers maynot only reduce drift and improve deposit, but allow the possibility of collecting spray that missesfoliage for reuse. A disadvantage of the tunnel sprayer is the size of trees that can be treated andproblems associated with driving such a large machine through the orchard. Morgan (1983)reported that experimental over-the-row devices had been used in spray trials on fruit crops in GreatBritain several years earlier. Tennes et al. (1976) developed an over-the-row harvester that couldstraddle trees 8.5 ft wide and 12 ft high. Reichard et al. (1982) developed an inline injection sprayerattachment for this unit. Schmidt (1990) measured ground and airborne spray while using a tunnelsprayer which collected and recycled spray that collected on the tunnel walls. The tunnel sprayerwith recycling produced about half the ground deposits as a standard axial fan sprayer.

Van de Werken (1991) described the development of a fully automatic air-assisted tunnelsprayer for use in apple orchards. This self-propelled unit also recycled spray deposited on thetunnel walls. This sprayer required a travel path at least 1.2 ft wide for travel. It could spray tree-rows up to 6.6 ft wide and 10 ft high at travel speeds up to 2.8 miles/hr. They found that 90% ormore of the spray was deposited on trees with this sprayer. Cross and Berrie (1993) compared spraydeposits and efficacy of sprays applied to apple trees with a tunnel sprayer and a conventionalsprayer. More deposits and better scab control was achieved with the tunnel sprayer applying 10.7and 21.4 gal/acre compared to conventional or tunnel sprayers applying 5.3 gal/acre. Peterson andHogmire (1994) developed and tested a self-propelled sprayer for dwarf fruit trees. The tunnel was 8X 15.4 ft, with a vertical clearance of 8 ft. Three air-delivery systems were used within the tunnelunit: 1) no air; 2) four Proptec® fans; 3) four cross-flow fans. They measured deposit within the treecanopy and drift from these sprayers and from a conventional axial-flow fan sprayer while applying20 gal/acre. Samples were taken from the outer 1.6 ft and in the center of the tree canopy, between2.3 and 5.6 ft elevation. The cross-flow fan units deposited more spray in all sections of the treesthan the Proptec equipped sprayers. Hydraulic nozzles without fans had good deposits in the upperparts of the trees. Hydraulic and spinning disk nozzles produced similar deposits in all sections ofthe tree. In a single test, low volume (20 gal/acre) produced greater deposits than high volume (100gal/acre). The best tunnel configuration produced greater deposits than the conventional sprayer.The tunnel sprayer had significantly less drift than the conventional sprayer.

119

Holownicki et al. (1996) compared two tunnel sprayers, one with cross-flow fans and theother with eight directed air-jets with a standard sprayer with 10 directed air-jets. Tree-row size was6.6 ft wide and 8.2 ft high, with a row spacing of 13 ft. There was no significant effect of travelspeed and spray volume on total deposits. Increased travel speed caused slightly reduced spraydeposits for the tunnel cross-flow sprayer. For targets along the vertical centerline-axis of the tree,significantly greater deposits were measured for the standard compared to the tunnel cross-flowsprayer. They measured the ratio of outside to inside canopy deposit. Measured ratios were:directed air-jet tunnel sprayer - 1.5 to 3, cross-flow tunnel sprayer - 7.5 to 14.6, and directed air jetsprayer - 5 to 12.7. Thus the best distribution was for the directed air jet tunnel sprayer. Wilson, etal. (1995) developed an over-the-row dust applicator for fruit trees. The tunnel was 14 ft in all threedirections. Measured deposits varied from 15 to 36 mg/cm2 on sampled leaves taken from three treesat 0.7 ft in from the canopy edge, at 3.3 and 10 ft elevations and at 4 quadrants within the tree.

When spraying dormant trees, Siegfried and Holliger (1996) reported that in small trees, atunnel sprayer achieved 60% greater deposit on branches, twigs, and scaffold compared to an axial-fan sprayer; however, deposit was not improved in older fruit trees with wide tree tops. Grounddeposits were 20-40% lower and drift was reduced by 70% with tunnel spraying compared to axial-fan spraying. At full foliage, the tunnel sprayer deposited about 20% more sprayed material onleaves than axial-fan sprayers. However, at full foliage, ground deposit with the axial-fan sprayerwas reduced to within 5% of the tunnel sprayer (28% to 23%).

Reports of several other studies on tunnel sprayers are contained in the Symposiumproceedings cited earlier (A.N.P.P.-B.C.P.C., 1993).

BarriersOrchard trees have been shown to be good collectors of spray that penetrates target trees.

Riley and Wiesner (1990) reported that most ground deposit resulted from spraying the last,downwind row. Downwind ground deposits decreased rapidly as the sprayed row was farther fromthe downwind edge of the orchard. They developed a regression equation to estimate depositproduced from spraying interior rows, based on row distance from the orchard edge. The SDTF(1998) measured large decreases in deposit away from the sprayed row in the interior of an orchard.Thus a major factor in downwind deposit near the orchard is the spraying of the last few rows.Special treatment of these rows can greatly reduce off-target drift.

Researchers in New Zealand have conducted several studies on the effect of shelter belts ondrift from orchard sprayers. Graham (1987) measured ground and airborne spray deposits downwindfrom a conventional orchard sprayer as it sprayed in the open (no shelter belt), through a natural(live) shelter, and through an artificial shelter. The natural shelter included Casurina spp andMatsudana spp which were about 25 to 33 ft high. The artificial shelter was made of mediumporosity Sarlon cloth, 20 ft high. Measured ground deposits of the fungicide Ronilan, used as thetracer, are shown in Figure 7. Ground deposits appear to be reduced by the presence of shelters; thelive shelter had a greater effect than the artificial shelter. They used both air samplers and rotatingslides to collect airborne spray. Air samplers collected more spray then either ground or rotationslides on an area basis. The live shelter also produced the greatest reduction in airborne spraycollected by both methods, but the artificial shelter also reduced deposits compared to no shelter.They suggested that the “ideal” porosity for a live shelter was such that you could see the sprayerthrough the trees, but could not see any detail, such as make, driver, etc. Artificial shelters made ofwoven cloth should have an optical porosity of 40 to 50%.

120

May et al. (1994) used a conventionalorchard sprayer for three trial sprays along a pathin a grass field, 82 ft upwind of a live shelter whichcontained poplar trees, 30 ft tall and 9 to 19 ft wide.They measured ground and airborne spraydeposits at 33 ft before and 33, 200, and 330 ftbeyond the shelter belt. The shelter was trimmedafter the second trial so a 6 ft tall fence of shadecloth was installed to reduce spray passage. Thustrial 3 had much less deposit that the first two, eventhough the wind was greater during trial 3. Thewind during the first two trials was less than 4.5mile/h. They concluded that, for the conditions oftheir study, the shelter belt was not effective inreducing downwind deposits. Mean grounddeposits for their trials are plotted in Figure 7. Ground deposits at 420 ft were noticeably greaterthan deposits at 280 ft, for all trials. It was not determined if this was a result of air flow patternsover the shelter-belt or not. Graham (1987) also measured an increase in deposits on the lastdownwind ground sampler (see Figure 7).

In another study, May (1995) measured deposits beyond a large, dense evergreen shelter-beltwhen a persimmon orchard was sprayed. They used two pesticides as tracers. Ground deposits werebelow detectable levels at 250 ft downwind. However, detectable levels of airborne spray weremeasured at 250 ft downwind. These results are also plotted in Figure 7. Combined ground depositsmeasured by Fox et al. (1991,1992,1994,1995) downwind from spraying through a single row ofsemi-dwarf apple trees are shown in Figure 7 for comparison with ground deposits shown in Figure 4.

Summary of drift mitigation practices

Drift mitigation methods can be summarized then as:

1. if there’s nothing there, don’t spray it;2. keep the spray as close to the ground as possible;3. minimize the small droplet fraction; however remember that the purpose of spraying

is to control pests. Large droplets may not provide the control desired, withoutincreasing the application rate;

4. match the sprayer air jet (volume and direction) and nozzle system to the treesbeing sprayed;

5. Be prepared to use special techniques near sensitive areas, especially for the last fewdownwind rows. These may include: a. use large droplets; b. use techniques to directspray at targets better, such as a handgun; c. spray the last few rows upwind only;d. wait and spray when the wind shifts; e. use special measures or equipment to createbarriers or direct spray at the target (tunnel sprayer, etc.).

In their discussion of reducing pesticide drift, Hall and Fox (1996) report a summary ofrecommended procedures for reducing off-target movement of pesticides. This list of actionsresulted from a Tree Crops Workshop held in 1993, and provide a good summary of approaches thatshould reduce drift from orchard spraying. An abstract of this action list is given in Table 1.

Figure 7. Ground deposits downwind from shelter-

121

Table 1. Mitigation options for Orchard Air-blast Applications*

Estimated %Action Rank drift reduction Comments

Education 1-3 20% 1. Survey current practices

2. Train individuals to critically adjust sprayer for plantinggeometry match/season and tree size

Modify edge 1-3 40-50% 1. Least costly and probably easiest practice to accomplishpractices practices

2. Spray inwards on outer 4-6 rows

3. Decrease spray volume (psi and/or liquid volume)

4. Automatic or manual shut-off (sprayer) on last 4-6 rows.

Restriction of 4 15-20% 1. Restrict by ai and time of day [not 10:00 am to 4:00 pm]ai/applications

2. Can restrict ai, e.g., safe pesticides only in high risk areas

Sensors 5 20-25% 1. This technology should be accelerated; currently not cost-effective for small growers.

Buffer zones 6 15-20% 1. Effectiveness would depend upon width of buffer, size of treeand/or block, and sprayer

Tower and/or 7 10-80% 1. No documentation of % reduction, although visual evidencesuggests tunnel sprayers an increased target placementefficiency; hence a reduced off-target movement.

2. Tunnels useful only for 8' trees/vines [ e.g. less than 5% ofapple acreage and no other tree crops]

Narrow droplet 8 10-15% 1. Possible with “dialable sprayers”. Need to change nozzles “on the go” spectrum

.Wind breaks 9 20-40% 1. Not for pecans or other high trees.

2. Practicality of strategy; will it create other problem?

Overhead or 10 20%+ 1. Use of large drops would reduce off-target movementchemigation

2. Limited to certain sites/crops, but has irrigation potential aswell.

* Adapted from Hall and Fox (1996)

122

SUMMARY

Air-assisted spraying of field crops has been developed to achieve better penetration of cropcanopies, to provide more uniform coverage of foliage, and to reduce drift. Studies show that mostof these objectives can be achieved by proper sprayer operation.

Sprayers for vineyards, orchards, and nurseries produce air jets to transport spray dropletsinto canopies and to improve the distribution of spray on all plant surfaces throughout the targetcanopy. Compared with conventional sprayers with axial air jets, tower sprayers or cross-flow fansprayers should produce more uniform distribution throughout canopies because spray is releasedfrom nozzles positioned closer to hard-to-reach regions such as the top center of trees. Such sprayersshould reduce spray lost to the atmosphere because the air jets can be aimed horizontally and lessspray should be thrown directly into the atmosphere above the orchard. However, more spray maybe deposited on the ground immediately downwind of the orchard if sprayers using these special jetsare not matched to the trees properly.

Ground deposits downwind from a sprayed trees and vineyards decrease rapidly withincreasing distance downwind. Beyond 100 ft from the edge of the sprayed area, ground deposits areusually less than 0.3% of the applied amount. Airborne spray deposits decrease less with increaseddistance downwind than ground deposits. Beyond 100 ft downwind from the edge of orchards,airborne deposits are usually less than 3% of the applied amount and airborne spray concentration isnearly uniform from the ground to about 30 ft.

Several methods can be used to reduce off-site drift. The key to any drift mitigation is thesprayer operator. The operator must configure the sprayer correctly for the crop and must be awareof sensitive sites near the vineyard, nursery, or orchard; must be aware of wind and weatherconditions and how they change; and must operate the sprayer in accordance with good driftmanagement principles. Some rules of good sprayer operation are: if there’s nothing there, don’tspray it; spray the last few downwind rows only into the wind; use the largest droplets that willproduce the desired biological efficacy; match the sprayer jet and nozzle flow rate to the trees in theorchard.

Other ways to decrease drift include: use tunnel sprayers; use windbreaks downwind of thesprayed area; provide buffer zones between the sprayed area and sensitive neighbors; and use specialspraying techniques for parts of the vineyard or orchard where sensitive areas may be subject to drift.These may include spraying some areas only when wind direction is suitable or using biologicalcontrol or low toxicity pesticides in some areas of the application site.

123

REFERENCES

Allen, J.G., A.P. Smith, D.J. Butt and T.M. Warman. 1991. Improved performance of mist-blowersprayers by electrostatic charging. In: BPCP Mono. 46, Air-Assisted Spraying in Crop Production,Levers, A, et al., Eds., 143-150.

A.N.P.P. - B.P.C.P. 1993. Second International Symposium on Pesticide Application Techniques,Vol 1, BCPC Publications Sales, Bear Farm, Binfield, Bracknell, Berkshire RG12 5QE, UK, 388pp.

Arvidsson, T. 1997. Spray drift as influenced by meteorological and technical factors - amethodological study. Acta Universitatis Agriculturae Sueciae, Agraria 71. Swedish University ofAgricultural Sciences, Uppsala, 144 pp.

Bache, D.H. and D.R. Johnstone. 1992. Microclimate and Spray Dispersion. Ellis Horwood,Chichester, England, 239 pp.

Barry, J.W., M.E. Teske, H.W. Thistle, P.J. Skyler, and A.Z. MacNichol. 1996. Spray deposition anddrift in orchards. ASAE paper AA96-006, ASAE, St. Joseph, MI. 34 pp.

Baldoin, C., D. De Zanche and C. Friso. 1994. Development of an innovatory oriented jet orchardsprayer. AGENG94, Report N. 94-D-153, 8 pp.

Brazee, R. D., R. D. Fox, D. L. Reichard, and F. R. Hall. 1981. Turbulent jet theory applied to airsprayers. Transactions of ASAE 24(2):266-272.

Carpenter, T.G., D.L. Reichard, and S.M. Wilson. 1985. Design and feasibility of a permanentpesticide application system for orchards. Transaction of ASAE 28(1):83-88.

Castle, G.S.P. and I.I. Inculet. 1981. Space charge effects in orchard spraying. IEEE pp 1155-1160.

Cooke, B.K., P.J. Herrington, K.G. Jones and N.G. Morgan. 1975. Pest and disease control onintensive apple trees by overhead mobile spraying. Pesticide Science 6:571-579.

Cooke, B.K., E.C. Hislop, P.J. Herrington, N.M. Western and F. Humpherson-Jones. 1990. Air-assisted spraying of arable crops, in relation to deposition, drift and pesticide performance. CropProtection 9:303-311.

Cross, J.V. and A.M. Berrie. 1993. Spray deposits and efficacy of a tunnel sprayer at three volumerates (50, 100, 200 L/ha) in comparison with an axial fan spray (50 L/ha) on apple. In: A.N.P.P.-B.C.P.C. - Second International Symposium on Pesticides Application Techniques Vol 1 pp 273-280. Strasbourg.

Derksen, R.C. and R.L. Gray. 1995. Deposition and air speed patterns of air-carrier apple orchardsprayers. Transactions of ASAE 38(1):5-11.

124

Doruchowski, G., R. Holownicki, and A. Godyn. 1996. Air jet setting effect on spray deposit withinapple tree canopy and loss of spray in orchard. AGENG96, Madrid, Paper 96A-139, 8 pp.

Elliott, J.G. and B.J. Wilson, Eds. 1983. The Influence of Weather on the Efficiency and Safety ofPesticide Application, The Drift of Herbicides. BCPC Occasional Publication No. 3, Croydon, UK,135 pp.

Fabado, F. A.N. Angel, B. Martin, and E. Molto. 1996. Evaluation of sprayers efficiency in pestcontrol on citrus orchards. AGENG96, Madrid, Paper 96A-143. 9 pp.

Fleming, G.A. 1962. The relationship of air volume, air velocity and droplet size to the efficiency ofspray transport in airblast spraying. PhD. Thesis, Cornell Univ. 66 pp.

Fox, R. D., R. D. Brazee, D. L. Reichard, and F. R. Hall. 1982. Power in an air sprayer jet.Transactions of ASAE 25(2): 1181-1184,1188.

Fox, R. D., D. L. Reichard, R. D. Brazee, and F. R. Hall. 1984. Penetration of an apple tree canopyby orchard-sprayer air jets. Fruit Crops 1984: A Summary of Research, OSU-OARDC ResearchCircular 283: 22-66.

Fox, R. D., R. D. Brazee, and D. L. Reichard. 1985. A model study of the effect of wind on orchardsprayer jets. Transactions of ASAE, 28(1):83-88.

Fox, R.D., R.D. Brazee, D.L. Reichard, and F.R. Hall. 1990. Downwind residue from air spraying ofa dwarf apple orchard. Transactions of the ASAE 33(4):1104-1108.

Fox, R.D., R.D. Brazee, S.A. Svensson, and D.L. Reichard. 1992. Air jet velocities from a cross-flow fan sprayer. Transactions of ASAE 35(5): 1381-1384.

Fox, R.D., D.L. Reichard, R.D. Brazee, C.R. Krause, and F.R. Hall. 1993a. Downwind residues fromspraying a semi-dwarf apple orchard. Transactions of ASAE 36(2): 333-340.

Fox, R.D., F.R. Hall, D.L. Reichard, R.D. Brazee, and H.R. Krueger. 1993b. Pesticide tracers formeasuring orchard spray drift. Applied Engineering in Agriculture 9(6): 501-506.

Fox, R.D., S.M. Hussein, D.L. Reichard, R.D. Brazee, and F.R. Hall. 1994. A Comparison of spraydrift deposited on ground and airborne spray collectors and on soybean plants. Fruit Crops 1994: ASummary of Research, OSU/OARDC Res Circular 298, 109-114.

Ganzelmeier, H., D. Rautmann, G. Backer, K.W. Eichhorn, R. Ipach, E. Kersting, H. Koch, F.-O.Ripke, and K. Schmidt. 1992. Guidelines for checking plant protection equipment. Part VII:Measuring direct drift when applying liquid plant protection products. Federal Biological ResearchCentre for Agriculture and Forestry, Braunschweig, Federal Republic of Germany.

Ganzelmeier, H. 1993. Drift of plant protection products in field crops, vineyards, orchards and hops.A.N.P.P. - B.C.P.C. Second International Symposium on Pesticides Application Techniques,Strasbourg, 125-132.

125

Ganzelmeier, H., D. Rautmann, R. Spangenberg, M. Streloke, M. Herrmann, H-J. Wenzelburger andH-F. Walter. 1995. Studies on the spray drift of plant protection products. Bibliothek derBiologischen Bundesanstalt fur Land- und Forstwirtschaft, Heft 305, Berlin (Dahlem) Germany.

Gauthier, N.L. 1966. The effects of varying air velocity and air stream of equal energy on sprayvolume transport in air blast spraying. PhD thesis, Cornell University.

Gaultney, L.D., K.D. Howard, and J.E. Mulrooney. 1996. Off-target drift with air-assistedagricultural sprayers. Pesticide Formulations and Application Systems: 16th Volume, ASTM STP1312, H.M. Collins, G. R. Goss, and M. Hopkinson, Eds., American Society for Testing andMaterials, 104-113.

Gilbert, A.J. and G.J. Bell. 1988. Evaluation of the drift hazards arising from pesticide sprayapplication. Aspects of Applied Biology 17, Environmental aspects of applied biology, 363-376.

Giles, D.K., M.J. Delwiche, and R.B. Dodd. 1987. Control of orchard spraying based on electronicsensing of target characteristics. Transactions of ASAE 30(6):1624-1630,1636.

Giles, D.K., M.J. Delwiche, and R.B. Dodd. 1988. Electronic measurement of tree canopy volume.Transactions of ASAE 31(1):264-272.

Giles, D.K., M.J. Delwiche, and R.B. Dodd. 1989a. Sprayer control by sensing orchard cropcharacteristics: orchard architecture and spray liquid savings. J. Agr. Engin. Res. 49:133-149.

Giles, D.K., M.J. Delwiche, and R.B. Dodd. 1989b. Spatial distribution of spray deposition from anair-carrier sprayer. Transaction of ASAE 32(3):807-811.

Gracia, F., M. Bosch, and S. Planas. 1996. Comparison of two measurement of the verticaldistribution of sprayers for fruit crops methods. AGENG96, Madrid, Paper 96A-148, 8 pp.

Graham, B.W.L. 1987. The effect of shelter on spray drift from orchard spraying. Report toDepartment of Health. National environmental Chemistry and Acoustics Laboratory, Auckland, NewZealand, 24 pp.

Groszkiewicz, M.L. and J.W. Hilton. 1991. Development of a small scale air-assisted Christmas treesprayer. ASAE Paper No. 91-1545. ASAE, St. Joseph, MI.

Hall, F.R., D.L. Reichard, and H.R. Krueger. 1975. Dislodgeable azinphosmethyl residues from airblast spraying of apple foliage in Ohio. Archives of Environ. Contam. 3:352-363.

Hall, F.R. and R.D. Fox. 1996. The reduction of pesticide drift. In Pesticide Formulation andAdjuvant Technology. C.L. Foy and D.W. Prichard, Eds. pp 209-239. Chemical Rubber Company,Boca Raton, Fl.

Herrington, P.J., H. R. Mapother, and A. Stringer. 1981. Spray retention and distribution on appletrees. Pesticide Science 12:515-520.

126

Hislop, E.C., N.M. Western, B.K. Cooke and R. Butler. 1993. Experimental air-assisted spraying ofyoung cereal plants under controlled conditions. Crop Protection 12:193-200.

Holownicki, R., G. Doruchowski, and W. Swiechowski. 1996. The influence of air-jet direction intunnel sprayers on spray distribution within apple tree canopy. AGENG96, Madrid, Paper 96A-140.6 pp.

Hoffmann, W.C. and M. Salyani. 1996. Spray deposition on citrus canopies under different meteoro-logical conditions. Transactions of ASAE 39(1):17-22.

Howard, K.D., J.E. Mulrooney and L.D. Gaultney. 1994. Penetration and deposition of air-assistedsprayers. ASAE Paper No. 94-1024. ASAE, St. Joseph, MI 49085.

Inculet, I.I., G.S.P. Castle, D.R. Menzies, and R. Frank. 1981. Deposition studies with a novel formof electrostatic crop sprayer. Journal of Electrostatics 10:65-72.

Law, S.E. and S.C. Cooper. 1985. Depositional characteristics of charged droplets applied by anorchard air-blast sprayer. ASAE Paper No. 85-1511. ASAE, St. Joseph, MI.

Lavers, A., P. Herrington, and E.S.E. Southcombe, Eds. 1991. Air-Assisted Spraying in Crop Protec-tion. BCPC Monograph No. 46, Farnham, UK, 308 pp.

MacCollom, G.B., W.W. Currier, and G.L. Baumann. 1986. Drift comparisons between aerial andground orchard application. J. Econ. Entomol. 79:459-464.

Manor, G, A. Hofner, R. Or, G. Phishler, Y. Epstein, J. Nakush and M. Jacobi. 1989. Stream facili-tated application of cotton foliage treatments. Transactions of ASAE 32(1): 37-40.

Matthews, G.A. and E.C. Hislop, Eds. 1993. Application Technology for Crop Protection. CABInternational, Wallingford, UK, 359 pp.

May, W.J. and D.B. Stevens. 1993. Disease control and placement of sprays in winter wheat usingsleeve boom and twin fluid nozzle sprayers. In: A.N.P.P.-B.C.P.C. - Second International Sympo-sium on Pesticides Application Techniques Vol 1 pp 373-380. Strasbourg.

May, W.A., J.F. Maber and J.P. Praat. 1994. The influences of sprayer type and live shelter on off-site spray drift. Lincoln Technology AEI Science Report 303. Hamilton, New Zealand, 56 pp.

May, W.A. 1995. Report to Waikato Outdoor Society on a specific site spray drift trial. LincolnTechnology AEI Science Report 303. Hamilton, New Zealand, 8 pp.

McConnell, R.L., K.C. Elliot, S.H. Blizzard and K.H. Kosten. 1983. Electronic measurement of tree-row volume. In: Agricultural Electronics - 1983 and beyond. Vol. 1, ASAE, St. Joseph, MI. pp. 85-90.

McCooeye, M.A., R.S. Crabbe, and R.E. Mickle. 1995. Strategies to reduce drift of aerially appliedpesticides. ASAE Paper No. 95-1307. ASAE, St. Joseph, MI.

127

Miller, D.R., W.E. Yendol, and M.L. McManus. 1992. On the field sampling of pesticide spraydistributions using teflon spheres and flat cards. J. Environ. Sci. Health B27(2):185-208.

Miralles, A. and V. Polveche. 1997. A new approach to quantifying the air and liquid streams gener-ated by air assisted sprayers. Aspects of Applied Biology 48, Optimising pesticide applications, 183-194.

Morgan, N.G. 1983. A review of orchard spraying in Great Britain. Proceedings of Conference onTree Crop Spraying with Ground Equipment, Univ. of Florida IFAS, Lake Alfred FL, pp. 34-40.

Ozkan, H.E. 1991. Reducing spray drift. Ohio Cooperative Extension Service Extension Bulletin816, Columbus, OH, 17 pp.

Parkin, C.S. and C.R. Merrit. 1988. The measurement and prediction of spray drift. Aspects ofApplied Biology, Environmental aspects of applied biology 17:351-361.

Pergher, G. and R. Gubiani. 1995. The effect of spray application rate and airflow rate on foliardeposition in a hedgerow vineyard. J. Agr. Engin. Res. 61:205-216.

Peterson, D.L. and H.W. Hogmire. 1994. Tunnel sprayer for dwarf fruit trees. Transaction of ASAE37(3):709-715.

Planas, S., F. Solanelles, A. Fillat, and C. Pifarre. 1996. A proposal of methodology for air assistedsprayers assessment in apple orchards. AGENG96, Madrid, Paper 96A-149, 8 pp.

Pompe, J.C.A.M. and H.J. Holterman. 1992. Technical aspects of pesticide application. AgriculturalEngineering and Physics, Wageningen Agricultural University, Report 92-11, The Netherlands, 84 pp.

Quanquin, B.J. 1995. Air-assist applied to field sprayers. Proceedings of National Conference onPesticide Application Technology, University of Guelph, Guelph, Ontario, Canada. pp 124-126.

Randall, J.M. 1971. The relationship between air volume and pressure on spray distribution on fruittrees. J. Agr. Engin. Res. 16(1):1-31.

Ras, M.C.D. 1991. Principles for the integration of air characteristics from mistblowers with penetra-tion into tree structures. In BPCP Mono. 46, Air-Assisted Spraying in Crop Production, Levers, A, etal., Eds., 287-295.

Reichard, D. L., R. D. Fox, R. D. Brazee, and F. R. Hall. 1979. Air velocities delivered by orchardair sprayers. Transactions of ASAE 22(1):69-74,80.

Reichard, D.L., B.R. Tennes, B.L. Burton, and G.K. Brown. 1982. Experimental orchard sprayer.Transaction of ASAE 25(1):33-37,41.

Riley, C.M. and C.J. Wiesner. 1990. Off target pesticide losses resulting from the use of an air-assisted orchard sprayer. Pesticide Formulations and Application Systems: 10th Volume, ASTMSTP1078, L.E. Bode, J.L. Hazen, and D.G. Chasin, Eds., American Society fro Testing and Materi-als, Philadelphia.

128

Rosell, J.R., A. Nogues and S. Planas. 1996. Development of an electronic selective orchard spray-ing system based on the control of applied flow rate. AGENG96 Madrid, Paper 96A-120, 10 pp.

Salyani, M. and J.D. Whitney. 1990. Effect of oscillators on deposition characteristics of an airblastsprayer. Transactions of ASAE 34(4):1618-1622.

Salyani, M. and R.P. Cromwell. 1992. Spray drift from ground and aerial applications. Transactionsof ASAE 35(4):1113-1120.

Salyani, M. 1994. Spray deposition and drift from air-carrier sprayers. AGENG94. Report N.94-D-149.

Salyani, M. and W.C. Hoffmann. 1996. Air and spray distribution from an air-carrier sprayer. Ap-plied Engr. in Agr. 12(5):539-545.

Schmidt, K. 1990. Application technology in orchards - problems and trends. Obst und Garten,May, 311-313.

SDTF. 1998. A summary of airblast application studies. Stewart Agricultural Research Services, Inc.Macon, MO 63552, 10 pp.

Siegfried, W. and E. Holliger. 1996. Application technology in fruit-growing and viticulture. FieldTrial Report, Swiss Federal Research Station, CH-8820 Wädenswil, 111 pp.

Sierra, J.G., J. Riquelme, J. Ortiz-Canavate, and A.A. Chipriana. 1996. Size and distribution ofdroplets produced by an pneumatic sprayer for high density orchards. AGENG96, Madrid, Paper96A-147, 7 pp.

Solanelles, F. A. Fillat, C. Pifarri, and S. Planas. 1996. A method of drift measurement for sprayapplications in tree crops. AGENG96, Madrid, Paper 96A-133, 8 pp.

Steinke, W.E., B.W. Wilson, J.N. Seiber, and F.G. Zalom. 1992. Drift measurements in dormantorchard spraying. ASAE Paper No. 92-1083, ASAE, St. Joseph, MI, 10 pp.

Sutton, T.B. and C.R. Unrath. 1984. Evaluation of the tree-row volume concept with density adjust-ments in relation to spray deposition in apple orchards. Plant Disease 68(6):480-484.

Svensson, S.A. 1991. Orchard spraying - deposition and air velocities as affected by air jet qualities.Swedish University of Agricultural Sciences, Report 149. Uppsala, Sweden, 79 pp.

Tennes, B.R., C.L. Burton, and J.H. Levin. 1976. Concepts for mechanizing high-density orchardfruit culture. Transaction of ASAE 19(1):35-36,40.

Travis, J.W., W.A. Skroch, and T.B. Sutton. 1987. Effects of travel speed, application volume, andnozzle arrangement on deposition and distribution of pesticides in apple trees. Plant Disease 71:606-612.

129

Van de Werken, J. 1991. The development of an unmanned air assisted tunnel sprayer for orchards.In: BPCP Mono. 46, Air-Assisted Spraying in Crop Production, Levers, A, et al., Eds., 211-217.

Van Ee, G.R., R.L. Ledebuhr, and H.S. Potter. 1985. Air curtain sprayer increases spraying effi-ciency. Agricultural Engineering 66(7):15-17.

Van Ee, G.R. and R.L. Ledebuhr. 1988. Performance evaluation of the “Air-Curtain” orchard spray-ing concept. AGENG88, Paris, Paper No. 88.043, 8 pp.

Walklate, P.J. 1989. Spray drift from orchard sprayers - AFRC Engineering contribution to 1988field experiments. Divisional Note, DN 1537 AFRC Institute of Engineering Research, Silsoe,Bedford. 26 pp.

Walklate, P.J. 1992. A simulation study of pesticide drift from an air-assisted orchard sprayer. J.Agr. Engin. Res. 51:263-283.

Walklate, P.J., K.-L. Weiner and C.S. Parkin. 1996. Analysis of and experimental measurementsmad on a moving air-assisted sprayer with two-dimensional air-jets penetrating a uniform cropcanopy. J. Agr. Engin. Res. 63:365-378.

Ware, G.W., E.J. Apple, W.P. Cahill, P.D. Gerhardt, and K.R. Frost. 1969. Pesticide drift. II. Mist-blower vs. aerial application of sprays. J. of Econ. Entomology 62(4):844846.

Watt, J. 1979. The importance of observations. Agri. Aviation 20(1):33-36.

Whitney, J.D. and M. Salyani. 1991. Deposition characteristics of two air-carrier sprayers in citrustrees. Transactions of ASAE 34(1):47-50.

Wilson, C.L., M.E. Wisniewski, and B.L. Upchurch. 1995. An over-the-row micronized-dust appli-cator for fruit trees. HortTechnology Oct./Dec. 309-313.

Womac, A.R., J.E. Mulrooney and W.P. Scott. 1992. Characteristics of air-assisted and drop-nozzlesprays in cotton. Transactions of ASAE 35(5):1369-1376.

Xu, Z.G., P.J. Walklate, and P.C.H. Miller. 1997. Evaluation of a stochastic model for spray trans-port prediction from air-assisted sprayers. Aspects of Applied Biology 48, Optimising pesticideapplications, 195-200.

130


Boom Application Equipment and Drift

Robert E. WolfUniversity of Illinois

Urbana, Illinois

Slide 1This slide set attempts to describe the various factorsthat can influence spray drift and how, as applica-tors, you can manage and minimize these factors.Almost any type of application may have drift poten-tial. Understanding the concepts included in this slideset should help reduce the potential from any typeapplication.

Slide 2Spray drift is not a new problem. However, the ap-plication of certain crop protection products has re-sulted in a heightened awareness of drift. This slideset is designed to help viewers better understand drift-causing factors and what management decisions couldbe made to help reduce the drift potential while spray-ing. The relationship of drift to spray droplet size isemphasized. As applicators develop a better under-standing of the factors that create smaller droplets andthe various weather related factors, they should bebetter able to make knowledgeable decisions aboutminimizing spray drift.

Slide 3The National Coalition on Drift Minimization has re-cently defined “pesticide drift” as the physical move-ment of pesticide through the air at the time of pesti-cide application, or soon thereafter, from the targetsite (field, crop, etc.) to any non- or off-target site.Pesticide drift shall not include movement of pesti-cides to non-or off-target sites caused by erosion,migration, volatility, or windblown soil particles thatoccurs after application unless specifically addressedon the pesticide product label with respect to driftcontrol requirements. Example: Command® herbiciderequires that the product be soil incorporated to avoidvapor drift.

131

Slide 4These two diagrams illustrate what can be consid-ered drift. In both these cases the pesticide sprayis being physically moved off-target by wind. Inone case the movement of the pesticide particlesis lateral or sideways and in the other the move-ment is upward.

Slide 5Here are two examples of what should not be con-sidered drift. Applicator error and equipment prob-lems are to blame for the misapplication in thesetwo cases. The pilot did not shut off his boom atthe end of the field and the ground rig operatorfailed to turn off nozzles that sprayed a non-targetarea.

Slide 6There are a number of reasons why we hear moreabout spray drift than we have in the past. Spraydrift can have serious consequences, such as poi-soning of farm workers, fish kills, crop damage,etc. Consequently, the public is much more awareof all types of spray applications. The public’stolerance for misapplications is very low and thevarious State Lead Agencies (SLA’s) are investi-gating hundreds of complaints every year. Ourcommunications systems are much better, so anyerrors that are newsworthy are seen by a lot ofpeople within a short period of time.

In addition, as urban areas expand into rural areassome spray applications are made closer to homesthan in the past. Off target drift in these areas isimmediately noticed and can lead to increased fric-tion between applicators and homeowners.

132

Slide 7Managing spray drift is critically important forpesticide applicators. Off-target spray drift cancause injury to humans, nearby crops, livestock,and wildlife. Spray drift also costs money. Theremust be restitution for damaged crops. If the pes-ticide application drifts off-target then there canbe a lack of control of the intended target pest.

If large numbers of drift problems continue to oc-cur you can be sure that the EPA and SLA’s willbe forced to implement additional rules and regu-lations. Companies spend relatively large sums ofmoney to train applicators and purchase expenseapplication equipment. It is in their best interest toavoid any problems.

Slide 8This chart categorizes and shows the breakdown ofthe factors related to misapplication. The source isa major agricultural insurance agency and it is basedon their investigations and payouts in 1996. Thirty-three percent of the time the misapplication was dueto drift. Another 33% of the time it was due to animproper tank mix. The application equipment wasthe source of the misapplication 24% of the time.Applications to the wrong field or site were the causeof 8% of the misapplications. Off-label applica-tions were only responsible for 2% of the misappli-cations.

Slide 9This chart shows the breakdown of factors that con-tribute to pesticide drift. Thirty-eight percent ofthe time the applicator, or the decisions made bythe applicator, is responsible for pesticide drift. Thetype of nozzle or nozzle problems are responsible26% of the time. Physical effects such as wind,inversions are responsible 23% of the time. Otherfactors that are unknown resulted in drift 13% ofthe time. Many times the source or cause of a com-plaint is hard to isolate if several applications takeplace in the nearby area.

133

Slide 10There are two basic types of drift, vapor and par-ticle drift. Vapor drift is associated with the vola-tilization of the pesticide formulation in the formof gases or fumes. Is the applicator responsiblefor vapor drift? Yes. The applicator should befamiliar enough with the product to know if thereis a potential for vapor drift. If there is a potentialfor vapor drift, steps should be taken to avoid this– such as soil incorporation.

Particle drift is probably what most people thinkof when they think of drift. Particle drift is theactual movement of spray particles, usually bywind.

Slide 12The spray equipment also affects the potential forspray drift. Nozzle type, size, orientation, pres-sure, and height of release (boom height) also af-fect droplet size and the potential for drift. Largedroplets are one of the keys to reducing spray drift.By adjusting these various nozzle factors you canincrease the number of large droplets and mini-mize the formation of small droplets. There is newnozzle and spray equipment technology that helpsapplicators keep the application on target.

Take the time to become familiar with these newadvancements and incorporate any applicable tech-nology into your spray program.

Slide 11There are many factors that affect the amount ofspray drift during an application. There are thecharacteristics of the spray itself. The chemicaland its formulation as well as any additives canaffect the droplet size and the rate of evaporation.Both of these can affect the amount of spray drift.Droplet size is the one factor that seems to havethe biggest impact on its final location after re-lease. Any property change that affects particle sizewill have a potential impact.

134

Slide 13The weather can also play a big part in the potentialfor drift. Wind speed and direction (especially if it istowards sensitive areas) are a major cause of manyspray drift problems. High temperatures and lowhumidity can increase the evaporation rate of sprayparticles which leads to smaller droplet size and moredrift potential. Temperature inversions can lead tolong distance migration of concentrated pesticide drift.The topography or “lay of the land” can also influ-ence the movement of spray particles.

Slide 14One of the most critical factors in minimizing spraydrift is reducing the number of small spray droplets.Particle drift often results from the smaller drops cre-ated during the spray process. The smaller dropletsare more easily transported by any wind that occurs.

Spray droplets are measured in microns using laserbeams. One micron equals 1/25,000 of an inch. Theaverage size of all the spray droplets for a given sprayis usually referred to as the Volume Median Diam-eter (VMD). VMD indicates that half of the volumeis in droplet sizes that size or larger and half to thespray is in droplet sizes that size or smaller.

Slide 15Large spray droplets reduce the potential for driftbecause they fall or settle more quickly, evaporatemore slowly and are less affected by wind. The keyis to set up your spray equipment to produce the larg-est droplets that will still provide adequate control ofthe target pest. There is a balancing act between thesize that is best for drift control and one that is bestfor product efficacy. In some cases, efficacy may haveto be sacrificed a little bit to avoid drift potential.

Small droplets often result from high spray pressure,small nozzle tips, and wind shear across the nozzles.Shear is especially significant for high-speed aerialapplications.

135

Slide 16The drift potential for a spray application dependsnot only on the VMD but also the total droplet spec-trum or the span of droplet sizes. A VMD of 300could mean that half the droplets were 250 micronsin diameter and half were 350 microns. Or it couldmean half the droplets were 50 microns (very sus-ceptible to drift) and half were 650 microns. Thetotal VMD plus the droplet spectrum gives a moreaccurate estimate of the droplet size relative to drift.

Generally speaking, 150-200 microns in diameter isthe lower limit for spray droplets in order to mini-mize drift.

Slide 17Here is a graphical illustration of what is meant byVMD. One-half the droplets are smaller than theVMD and ½ are larger. Set up your spray equip-ment to increase the VMD. Simply knowing theVMD alone is not significant for either efficacy ordrift potential.

Slide 18As a comparison, a pencil lead is approximately 2000microns in diameter. A paper clip is 850 microns, astaple is 420 microns, a toothbrush bristle is 300microns, a sewing thread is 150 microns, and a hu-man hair is approximately 100 microns in diameter.One hundred to one hundred fifty microns in size isvery small. A magnifier may be necessary to simplysee droplets that are this small.

136

Slide 19You may believe that small droplets coupled with highpressure will provide the best coverage. In reality, itis almost impossible to force a small droplet to movemore than a few inches. This table shows the termi-nal velocity, the final drop diameter, time of evapo-ration, and the deceleration distance (in inches) forspray droplets of various sizes.

For instance, the fastest a 20 micron droplet will fallis 4/100 of a foot per second. Due to evaporation thefinal droplet diameter will be approximately 7 mi-crons in diameter and it will fall (deceleration dis-tance) less than one inch. Therefore this droplet sizeis very susceptible to drift. In contrast, a 200 microndroplet falls at 2.4 feet per second, has a much largerfinal droplet size because it evaporates more slowly,and will fall at least 25 inches.

Slide 20The trend in spray nozzle design is emphasizing lowdrift. Most nozzle manufacturers have designednozzle types with the low drift emphasis. Furtherdesign has incorporated the use of air as a means toprovide larger droplets in the spray volume furtherattempting to minimize spray drift. New technologyshows major improvements in drift reduction poten-tial. As spray operators, become familiar with thisnew technology and adapt it where appropriate. Theimprovements in drift reduction should be noticeable

Slide 21This is a chart comparing the influence of nozzle type,size, and pressure on spray droplet size for some com-monly used nozzle types from Spraying SystemsCompany. Because of the potential for a great amountof variance in the collection of spray droplet size in-formation it is important to only compare data suchas in this chart that was collected with the same equip-ment under the same conditions. In this chart, thefirst column represents an 8002 or similar flow ratenozzle, the second column represents an 8005 or simi-lar flow rate nozzle, and the third column representsthe 8005 or similar flow rate nozzle at an increasedpressure. The influence of each change on the drop-let size is apparent and expected. The last columnreflects the most important data for today’s nozzletechnology. Note how the new technology nozzleshave greatly reduced the amount of driftable fines inthe spray volume and thus will give spray applicatorsgood options for reducing spray drift potential.

137

Slide 22These tables show the categorization of dropletsbased on their size in microns. In general, fine orvery fine droplets are most suitable for insecticideand fungicide applications where maximum cover-age is required. Herbicides and postemergent pesti-cide applications usually can be made with coarsersprays and soil applications of herbicides can be putout with very coarse sprays.

Pesticide labels are beginning to incorporate this lan-guage when discussing spray application equipmentsetup. Make sure you pay close attention to labeldirections. Spray tip catalogs are very useful in de-termining the droplet size for a given nozzle at agiven pressure.

Slide 23More efficient application of pest control productsin the future will require a better understanding ofthe proper size of droplet needed to achieve the de-sired control. This chart illustrates an effort to es-tablish a classification system to help applicatorsmake decisions regarding spray droplet parameters.This system and knowledge about the droplet spec-tra created by various nozzle types at specified pres-sures will provide applicators with improved waysto make decisions about nozzle selection and use inthe future

Slide 24This slide represents an example of the choices anapplicator would have within a single nozzle type.If the label suggested a medium sized spray dropletand the applicator wanted to use the specific nozzletype shown, then all the light blue areas in this par-ticular chart would represent a proper selection. Thiswould allow for maximum flexibility as applicationconditions changed form day to day and even dur-ing the day. As an example, as wind speed increased,or the temperature increased and humidity dropped,choosing to operate at a lower pressure making big-ger drops should minimize the drift potential.

138

Slide 25An important point to remember is that when youreduce the size of the spray droplets you greatly in-crease the number of droplets. That means there willbe more droplets likely to drift.

The diagram shows that if you cut the droplet size inhalf you produce eight times the number of droplets.You must imagine the image is in 3-D so there is anadditional droplet on the backside.

Slide 26Some strategies to reduce drift are: selecting nozzlesto increase droplet size, increase the flow rates of yourapplication (more gallons per acre), use lower pres-sures, and lower boom heights. Avoid spraying un-der adverse weather conditions and consider usingbuffer zones (check label to see if buffer zones arerequired). Consider using new available technolo-gies such as drift reduction nozzles, drift reductionadditives, spray shields, electrostatic applicators, orair-assist spray equipment.

Slide 27A buffer zone is an area where pesticide is not di-rectly applied thereby providing protection to a de-fined area. Buffer zones are usually adjacent to sen-sitive or protected (as established by local, state, orfederal regulations) areas.

An area may be designated as a buffer zone by stateregulations, pesticide product labels, the prevailingweather conditions, or nearby sensitive or protectedareas.

Check labels closely for any required buffer zones.As an applicator you are responsible for establishingbuffer zones as needed to protect sensitive or pro-tected areas.

139

Slide 28When making a pesticide application there are cer-tain factors you can control in order to minimize drift.You can control the selection of the applicator oroperator, the equipment selection and setup, the fieldconditions (wind, inversions, etc.), and the choice ofthe product.

You cannot control the weather or what is in the nextfield or areas downwind from the application area,unless you own them.

Slide 29The applicator, as we discussed earlier, can be a bigfactor in the amount of spray drift produced duringan application. Make sure your applicator is compe-tent for the application required. You may want tohire a commercial applicator for some applications.In some situations an aerial application may be moreappropriate while in others a ground application maybe better. The knowledge base and skill of the ap-plicator can increase the productivity and safety ofalmost any chemical application.

Slide 30There are various types of suitable spray equipment– make sure yours is in good operating condition andis calibrated regularly. Select your equipment to pro-duce the largest droplet size possible for drift con-trol (greater than 150 microns is best). But be awarethat some products require relatively smaller drop-lets to ensure good coverage.

140

Slide 31Consider the field conditions at the application area.What are the adjacent crops? Is the field close tohouses or a town? Are buffer zones required? Is thisa preventative treatment or have pest thresholds beenreached? Make sure you are using all the availableintegrated pest management (IPM) techniques. Largeuniform fields are good candidates for aerial applica-tions while small irregular shaped fields may be bet-ter suited for ground applications.

Slide 32When choosing a pesticide there are a number of fac-tors to keep in mind to help minimize drift. Of courseyou must control your target pest. If you have theoption, choose a product that is safer for your appli-cation conditions. Understand the product chemistrysuch as the need for surfactants, drift control agents,temperature or wind restrictions. Consider workerexposure and safety and any label restrictions. Con-sider the effect this product may have on homes andgardens near the application site. Also make sure youconsider environmental and wildlife safety.

Slide 33When making spray applications you cannot controlthe weather. Wind, temperature, and the humiditycan all affect the spray application and increase thepotential for drift.

You also cannot control the presence of susceptiblecrops or other non-target areas of concern near yourapplication site.

Make sure you have the proper application conditionsbefore making a spray application to ensure your spraystays on-target.

141

Slide 34Common sense tells you the drift potential increaseswith increasing wind speed. However, many factorscan influence drift such as droplet size and boomheight. The effects of wind are reduced if small drop-lets are minimized and the application is made at theproper height.

Wind gauges are a very valuable and economical wayto determine wind speed. A compass is good to pre-cisely determine the wind direction. Wind speeds,magnetic directions, and a time stamp should be in-cluded in the spray record often enough to reflect anychanges that occur during the application.

Remember: If you end up in court because of a pos-sible pesticide misapplication, the better your sprayrecords are the better your defense will be.

Slide 35The wind direction during a spray application is veryimportant. Make sure you know the location of sen-sitive areas. Wait until the wind is blowing awayfrom these areas or establish safe buffer zones. Donot spray at any wind speed if it is blowing towardssensitive areas – ALL NOZZLES HAVE THE PO-TENTIAL TO DRIFT. Spray when the breeze isgentle, steady, and blowing away from sensitive ar-eas. Dead calm conditions are never recommendedbecause of the likelihood of temperature inversions.

Slide 36Be aware that drift potential may be high at low windspeeds. This is because light winds (0-3 mph) tendto be unpredictable and variable in direction. Calmor low wind conditions may indicate the presence ofa temperature inversion.

Drift potential is lowest at wind speeds between 3and 10 mph (gentle but steady breeze) blowing in asafe direction away from sensitive areas.

142

Slide 37This graph illustrates normal air conditions when tem-perature decreases as you move upward. Under theseconditions air tends to rise and mix with the air above.Small spray particles will move upward and disperseor dilute out in the atmosphere and usually not causeproblems.

Slide 38Under temperature inversion conditions the tempera-ture increases as you move upward. This prevents airfrom mixing with the air above it. This causes small-suspended droplets to form a concentrated cloud thatcan move in unpredictable directions for long dis-tances. If large numbers of small droplets are cap-tured in this warm or inversion layer, the depositioncontrol is lost. Records indicate that movement ofthese inversion layers may transport chemicals forseveral miles.

Slide 39The most common cause of temperature inversionsclose to ground level is radiant cooling of the ground– the ground cools off quicker than the air above it.Clear skies favor radiant cooling and therefore favorthe formation of surface inversions. Early morningand late afternoon are the times when surface inver-sions are most likely to occur.

Low heavy cloud cover, strong to moderate winds(greater than 5-6 mph), a temperature rise of 5 de-grees, and bright sunshine are all conditions that donot favor inversions.

143

Slide 40It is important to be able to recognize when in-versions are present. Bodies of water or well-ir-rigated fields both favor the formation of inver-sions. Under clear to partly cloudy skies and lightwinds, a surface inversion can form as the sunsets. Under these conditions a surface inversionwill continue into the morning until the sun be-gins to heat the ground. Usually, if you will waitfor a 5-degree increase in temperature after sunup the chances for an inversion decreases greatly.

Slide 41Inversions only affect the small droplets from an ap-plication that don’t settle quickly. There is a higherpotential drift and therefore off-target effects if theapplication is made during a surface inversion. Thesmall droplets can remain in a concentrated cloud untilthe inversion dissipates or until the cloud moves outof the area where the inversion conditions exist.

Minimizing the production of small droplets willminimize the potential or drift under inversion con-ditions.

Slide 42You should take precautions for inversions becausesurface inversions are common at certain times ofthe year. Be especially careful near sunset and anhour or so after sunrise unless there is low heavy cloudcover, the wind speed is greater than 5-6 mph atground level, and there is a 5-degree temperature riseafter sun-up.

It may be illegal to start a fire to determine the pres-ence of an inversion or wind direction. But there aresmoke bombs or smoke generators that are legal touse and their use is recommended to identify inver-sion conditions.

144

Slide 43Temperature and humidity are two other weather re-lated factors that can affect the amount of spray drift.The temperature affects the speed at which spray drop-lets evaporate (the faster they evaporate the morelikely they are to reach a driftable size before reach-ing the target). The temperature also affects the windsat the application site and the ability to get the prod-uct down into a dark canopy.

Humidity also affects the speed of evaporation of spraydroplets. The higher the humidity, the slower theevaporation and the less chance for drift.

Slide 44This illustration shows the relationship between hu-midity, droplet size, and drift. The lower the humid-ity, the faster the droplets evaporate. As they evapo-rate they become smaller and more likely to drift.Evaporation is not as much of a problem for largedroplets. So minimize the number of small dropletsto combat spray drift.

Slide 45There are some other things you need to keep in mindwhen planning a spray application. Make sure youallow enough time for scheduling and planning theapplication, obtaining the pesticide products, and set-ting up the application date. Have contingency plansfor weather delays or maintenance problems, if nec-essary. Remember that applicator decisions are oneof the most important factors in minimizing spray drift.

By planning ahead you can avoid the trap of declar-ing “I need to spray RIGHT NOW”. Forcing a sprayapplication under poor conditions almost always leadsto drift or other errors.

145

Slide 46If you decide to use a commercial applicator, makesure you find a reputable professional one. Contractthe job with commercial applicator as early as pos-sible. Discuss the specifics of the application andany precautions about the application site. Give thecommercial applicator the freedom to apply theirexperience and training.

A reputable, conscientious commercial applicatorshould provide you with a quality job.

Slide 47In conclusion, remember that minimizing spray driftis in the best interests of everyone. Do your part tokeep agrichemical applications on target.

This slide set was based partially on a set obtained from the Western Crop Protection Association with additions andrevisions provided by Dr. Dennis Gardisser, Extension Agricultural Engineer University of Arkansas, Dr. Robert Wolf,Extension Specialist Pesticide Applicator Training, University of Illinois, and Ples Spradley, Extension PesticideAssessment Specialist, University of Arkansas.

146


High Volume Sprayers for Treating Trees:Managing Drift and Exposure

Managing Pesticide Spray DriftHandheld Power Equipment

Bruce R. FraedrichBartlett Tree Research Laboratories

Charlotte, North Carolina

Pesticides are used in landscapes to help manage a variety of pests on turf, herbaceous orna-mentals, woody ornamentals, and on rights-of-way to manage vegetation. Handheld poweredsprayers are often used for these pesticide applications although other options are available.Because these sprayers are used in urban and suburban landscapes, managing drift must be amajor objective especially when treating tall vegetation such as trees and shrubs. This presen-tation describes handheld power equipment that is commonly used to treat plants and providescalibration and application techniques to manage spray drift. Emphasis is placed on sprayingtall vegetation, especially trees and shrubs where the potential for drift can be significant.Alternative techniques to spraying for pest management will be presented where appropriate.

Hand-Held Power Sprayers:Trees and ShrubsEquipment-Hydraulic Sprayers: Most pesticide applications to trees and shrubs are performedwith hydraulic sprayers with pump capacities ranging from 10 to 60 gallons per minute (gpm).Trees and shrubs under 25 feet in height can be treated with 10 gpm sprayers; taller treesusually require 25 to 60 gpm sprayers depending on height.

Pumps must be capable of generating pressures of 500-1000 psi depending on required heightof the spray column and the length and diameter of the spray hose. Sprayers may be equippedwith single or multiple tanks capable of storing and applying different treatments. With theadvent of landscape IPM programs, many sprayers now have a large fresh water tank andsmaller mix tanks. Products are custom mixed on site depending on the specific plant and pestand on customer preference.

Treatments are applied to trees and shrubs with handheld spray guns that have variable-sizednozzle discs. Large nozzle discs provide the necessary flow volume that affords treatment oftaller plants. Smaller nozzle discs provide less flow volume and are adequate for treatingshorter plants . Table 1 provides recommended nozzle disc sizes for the FMC 785 spray gunthat is commonly used for treating trees and shrubs. Spray hose used for treating trees andshrubs usually varies from 1/2” to 1” in diameter and must be capable of withstanding pres-sures of 1000 psi. Large diameter hose is required to minimize pressure loss from friction thatoccurs due to the high flow rates required to attain height.

147

Table 1: Disc sizes and corresponding output capacities at specific pressures necessary toattain a specified height with minimum drift using an FMC 785 Spray Gun.

HEIGHT DISC SIZE* CAPACITY (GPM) PRESSURE @ GUN (PSI)

<10’ 6 2-3 200-25010-20’ 8 5 30020-30’ 10 8 30035-50’ 12 14 40045-70’ 14 21 40065-80’ 16 27 400>75’ 18 34 400>90’ 22 53 400

*Disc size represents hole diameter in increments of 1/64”

Calibration-Hydraulic Sprayers: Managing spray drift begins with calibration of the hydraulicsprayer. Calibration is required to ensure that adequate height of the spray column is attainedusing the largest spray droplet size to decrease the likelihood of off-site movement.

The first step is estimating the height of the plant to be treated. This dictates the required flowcapacity to attain height which is controlled by the spray gun nozzle disc and pressure. Table 1lists the recommended nozzle disc size and corresponding flow capacity to attain variousheights using the FMC 785 Spray Gun. Once the disc size is selected, pump pressure is set toprovide 200-to-400 psi at the spray gun. The required pressure depends on the height of thetarget plant (Table 1). Pump pressure usually must be higher than the pressure at the gun tocompensate for pressure loss from friction that occurs as the spray fluid moves through thehose. The amount of pressure loss is influenced by flow rate, hose length and diameter andhose material (Figure 1). Each hose coupling causes an additional pressure loss of up to 4 psiand hose reels and meters cause losses up to 10 psi each.

Proper calibration of hydraulic sprayers is a critical step in managing pesticide spray driftespecially when treating tall vegetation. Excessive pressure for a chosen flow capacity (nozzledisc) will result in fracturing the spray column producing small droplets that are more subjectto drift. In other words, the release point, (the height at which the spray droplets are no longerinfluenced by the spray equipment or the applicator), of the spray will be too low to the groundwhich increases the likelihood of off-site movement.

When treating tall trees when wind is a factor, larger nozzle discs can be used to increasevolume while maintaining the same pressure at the gun. This will maintain the spray columnfor a greater height and produces larger spray droplets in the upper crown that are less subjectto drift. In other words, the release point of the spray will occur at a greater height. Whentreating short plants when light wind is present, larger nozzle discs and lower pressures willprovide larger droplets that are less subject to drift.

148

Application Technique To Manage Drift: Hydraulic Sprayers: Drift is minimized by sprayingunder calm conditions and using proper application technique. Applicators should always bepositioned close to the target plant with any wind at his/her back or side. This will providethorough coverage and ensure that the spray release point is close to the target plant, which willminimize off-site movement . For tall trees, the applicator usually is positioned just outside thecrown. For very broad-crown trees, the applicator can begin spraying beneath the canopythereby using the trunk and branches as protection from any wind.

Using a properly calibrated sprayer, the applicator uses a straight stream to build a column ofspray. This is done by holding the gun perfectly steady and allowing the column of spray tobuild immediately above the applicator (Figure 2). If slight wind exists, the gun may actuallybe pointed slightly back over the shoulder of the applicator thereby allowing the wind to carrythe column into the crown. The surges created by the pump and updraft created by the columncarry the spray into the top of the tree.

149

Once the column reaches the top, the gun isslowly moved from side-to-side and down-ward. Sudden movements of the gun mustbe avoided because this breaks the spray col-umn resulting in poor coverage and exces-sive drift. After the top of the plant is cov-ered, the applicator fans-out the spray col-umn to reduce flow volume and cover themiddle and lower portions of the tree. Theapplicator then shuts off the gun, repositionsto another area of the crown and repeats thesame procedure until the necessary level ofcoverage is obtained. The applicator neverwalks and sprays simultaneously even whentreating small trees and shrubs

When spraying near sensitive areas such asproperty lines or near ponds and streams, theapplicator should be positioned between thesensitive area and target plant to reduce thepotential for drift to the sensitive area. Ap-plicators commonly sacrifice thorough cov-erage to prevent drift to sensitive areas. Ontall trees, only the lower portion may betreated if off-site movement of spray can notbe tolerated.

On small trees and shrubs, applicators should be positioned close to the target plant and use afan spray pattern. If necessary the applicator should kneel down to spray lower portions of theplant. The spray gun can be inserted inside the canopy of dense shrubs to obtain coverage.Pressure and volume should be not exceed the specifications in Table 1. The potential for drift,“over-spray” and phytotoxicity increases when applicators spray from a distance using astraight stream at high pressure.

The impact of drift can be avoided on urban and suburban landscapes by taking some sensibleprecautions. Select products carefully to avoid pesticides that have the greatest health andenvironmental risks. If there is potential for drift onto neighboring properties, notify propertyowners and ask permission to spray. Turn-off air conditioners, close windows and get peopleand pets away from the treatment area. Overturn birdbaths, remove sensitive items such asbird feeders, pet dishes and any outdoor laundry from the treatment area. If items such aspicnic tables, swings, lawn furniture or cars can not be moved from treatment areas, theyshould be washed down with fresh water before and after spraying.

Miscellaneous Handheld Sprayers for Pest Management

Backpack Units: Motorized, low volume (1-2 gpm) sprayers that are available as “backpack”or cart units are occasionally used to spray vegetation under 15 feet in height. These sprayershave minimum capacity to adjust pressure and volume output. Drift is minimized by using the

150

lowest pressure and lowest engine speed necessary to provide height and the applicator ispositioned as close as possible to the target plant.

Mistblowers: Truck mounted or backpack mistblowers were once widely used for pest man-agement on landscape trees and shrubs. Today, few products are registered (labeled) formistblower applications (product labels seldom list mixing rates for a mistblower, which aregenerally ten times greater than hydraulic mixing rates). Of the 28 pesticide products approvedfor use by the Bartlett Company, only 3 products provide mistblower rates.

Mistblowers have the highest capacity for drift because air rather than water is used as thepesticide “carrier” which produces a very small spray droplet relative to hydraulic applications.Due to limited availability of products for mist application and the high potential for drift,mistblowers are seldom used for treating landscape trees and shrubs or for treatment of right-of-way vegetation.

ALTERNATIVE TREATMENT TECHNIQUES

Landscape Tree & Shrub Pests: Numerous tree injection products are now available that can bedirectly injected or implanted into the trunk or root flare of trees to provide pest management.These products consist of systemic pesticides that are inserted or implanted into the sap-streamand are subsequently translocated throughout the crown. Trunk wounding and the potential forwood decay are the primary disadvantages of tree injection. Many tree injection products arebeing sold without adequate efficacy testing. Subsequently some of the products are ineffec-tive for their intended purpose.

Recently, a category 3 (Caution label signal word) systemic insecticide (imidacloprid) has beenregistered for soil injection and drenching for insect pest management. The product need onlybe applied to the soil area immediately adjacent to the tree trunk or beneath the crown of theshrub. Roots absorb the insecticide which is then translocated throughout the crown. A growthregulator for trees is highly effective when applied in a similar manner. There is great potentialfor pest management products that can be applied as a soil injection or a soil drench as analternative to spray treatments.

Right-Of-Way Vegetation Management: The trend in vegetation management on utility rights-of-way is away from high volume treatments with hydraulic equipment and toward selectivelow volume application, basal stem and cut stump treatments. These latter techniques usecompressed air (backpack) sprayers which apply low volumes of spray. Treatments are di-rected only to selected plants that may eventually grow into conductors. Plants that mature tolow heights are often left untreated to form stable plant communities in the rights-of-way.

Drift is minimized with low volume techniques by selecting the proper nozzle type, using lowpressure to ensure large droplets and using proper application technique . For low growingbrush (< 6 feet) a 40 degree flat fan nozzle is generally recommended; for medium brush (6-12feet), a 15 degree flat fan nozzle and for tall or hard to reach brush, a straight stream nozzle isrecommended. Straight stream nozzles also are used for basal stem treatments and cut stumptreatments. With most herbicide treatments for brush management, 50-70% foliage or stemcoverage is all that is needed to obtain control. Spraying to runoff is not needed or recom-

151

mended. Applicators should always be positioned as close to the target plant as possible toreduce risk of drift.

Hand-Held Sprayers:Turf Treatments

Equipment: Handheld power sprayers for turf generally consist of low volume,(5-to-10 gpm)hydraulic units that operate under low pressures (usually in the range of 100 psi). Sprayersmay be equipped with multiple tanks that are capable of applying different treatments. Somesprayers now have product injection capabilities at the pump or at the spray gun which allowsgreater versatility in customizing treatments to meet plant requirements and consumer prefer-ences. Most turf applications on residential and commercial properties are made with hand-held spray guns with flooding nozzles that provide 2-to-6 gpm. Spray boom attachments thatare manually operated also are available. Spray hose that connects the pump to the spray gun ormanual boom is narrow diameter (3/8”-1/2”). Very little pressure loss occurs between thepump and gun due to the low volume application.

Calibration: Calibrating sprayers to minimize drift primarily involves setting pressure as lowas possible to deliver the required flow that is dictated by the specific flooding nozzle on thespray gun. Using higher than needed pressures could produce small droplets that are moreprone to drift.

Application Techniques: As with all spraying, drift can be minimized when applications aremade under calm conditions. Spray guns should be kept relatively low to the ground to reduceeffects of any wind. Applicators should position themselves between sensitive areas and thetreatment area and direct the spray inward. Untreated buffer zones can be left adjacent tosensitive areas if drift is possible to these areas. Spot treatments as opposed to broadcastapplication can be used for post emergence herbicide treatments when weed density is sparse.This will minimize pesticide usage and reduce risk of drift.

Alternative Treatments for Turf: Granular applications can be used for most pesticide applica-tions on turf. Drop spreaders leave little potential for off site movement of the product.

MINIMIZING THE IMPACT OF DRIFT THROUGH PRODUCT AND PROGRAMSELECTION-LANDSCAPE PEST MANAGEMENT

Many low toxicity products are now available that offer effective management of landscapepests. Products such as insecticidal soaps, horticultural oils, pyrthrum and biological insecti-cides such as Bacillus thuringiensis are widely used for pest management in urban areas.Biologically derived products such as the recent introduction of Spinosad provide low toxicityalternatives for effective pest management. Many synthetic pesticides such as pyrethroids andsterol inhibiting fungicides offer low mammalian toxicity combined with extremely low mix-ing rates to obtain effective pest management.

Integrated pest management programs are now offered by many commercial landscape man-agement companies. IPM programs provide a Monitor technician who inspects properties atperiodic intervals for pest infestations and plant health problems. The number of inspectionsprovided depends on the plant species diversity, previous history of pest infestations, client

152

expectations and budget. Chemical, cultural and/or biological treatments are applied beforepests reach damaging levels.

Equipment has been developed that allows custom mixing and application of products on eachproperty according to the specific need. Landscape IPM programs have reduced pesticide useby as much as 90% while providing improved management of plant health compared to tradi-tional programs using planned targeted treatments (Holmes et al.).

REFERENCES

Holmes, John J. and J.A. Davidson. 1984. Integrated Pest Management for Arborists: Imple-mentation of a Pilot Program. J. Arboric. 10:65-70.

Anonymous. Owner’s Manual Service Parts List FMC 785 Spray Gun Manual No. 5261245.FMC Corporation Agricultural Machinery Division. Jonesboro, AR 10pp.

Anonymous. 1987 On Target Part II Hydraulic Sprayer Calibration (Video Publication).National Arborist Association, Amherst NH.

Anonymous. 1987 On Target Part III Proper Pesticide Application for Urban Trees (VideoPublication) National Arborist Association, Amherst NH.

153

Drift Happens: A National Public Interest Perspective

Norma GrierNorthwest Coalition for Alternatives to Pesticides

Eugene, Oregon

Drift is a regular occurrence.

Last fall, a woman contacted our office looking for information about the health andenvironmental effects of two herbicides. She told us her story over the phone. Her ruralnorthwest Oregon property included some pasture in addition to her cottage. The adjacent propertywas owned by a private timber company. The forest had been clear-cut several years earlier andthe woman had previously communicated her dislike for herbicide sprays to the timber company.

One morning while sitting at her table near the window, this woman noticed the timbercompany's pick-up truck parked on the dirt road near the corner of her pasture. The truck withpeople inside was there for over half an hour. The next morning, the woman heard a deafeningroar over her home. She opened her front door to be greeted by a fine mist that covered herclothing, face and head — spray drift. After washing herself and changing her clothes, she calledthe timber company and found out what herbicides they had sprayed. When she asked them whythey hadn't bothered to notify her about their spray plans, they claimed they were unable to findher at home.

I got a phone call from one of our members who told me another story. Her parking spotat the school where she works is next to a five foot high hedge that divides the school from thehouse next door. As she pulled into her spot one morning, a shower of sticky stuff came over thehedge onto her car's hood, windshield and roof. A gardener in a uniform was shooting out of ahose into the tops of trees, sending a fountain of spray over the hedge onto the cars of the teachersand staff arriving at the school next door. Before calling us, this woman learned from the gardenerthat he was making prophylactic treatments with the organochlorine insecticide Kelthane to preventtree pests.

Our organization hears from lots of people who experience drift — a woman who said shewas sprayed walking past the groundskeeper at the local post office in an Oregon town while hewas making a lawn application with a backpack sprayer during business hours; a mother who cameout of a supermarket in southeast Washington to witness the drift from a cropduster moving off theadjacent field onto her parked car and the cars around hers. I've watched a plane aerially applypesticides to an agricultural field adjacent to a rest stop along Interstate 5 in Oregon, while childrentumbled out of cars to make a B-line for the restrooms and elderly people exercised their pets in thedesignated area along the back fence.

Drift incidents happen many times a day, everyday, across the United States. Most ofthese incidents never get reported or recorded with a state or federal agency. For most of them, noresidue samples are taken. No physician examines these people to learn if there are symptoms ofexposure and to test for residues. No one checks to see what environmental damage has beendone, both in the short- and the long-term. No one thinks about whether there is a label violation.Rarely is someone fined or even sent a warning letter. Most of these incidents never end up in

154

court. No one gets a settlement check from these incidents. These drift incidents slip through thecracks of our regulatory, public health, environmental protection, and legal systems.

Citizens make a difference.

There are some instances where drift incidents get the attention they deserve. One examplecomes from south central Washington state near the Tri-Cities and the Hanford NuclearReservation. The uproar over drift, started in the 1980s by a groups of active citizens, hasn'tcompletely settled down a decade later. In 1988, Margaret Hue noticed that the leaves on the plantsin her yard around her farmhouse had a mottled pattern of spots. For some time, Margaret hadsuspected that the sprays used by area farmers were drifting off site, leaving unwanted residues onher farm's crops. So Margaret starting comparing notes with her friends and neighbors, and itsoon became clear that the spots on the plants on Margaret's farm were the same pattern found onplants a mile or more away. These residents were convinced there was drift, so the foliage wastested and sure enough, at the center of each splotch on the leaf was a trace of paraquat. Wordabout paraquat drift started spreading. Soon a community meeting was called. After the issue wasin the local paper, Margaret got a call from a retired engineer who indicated his interest in the topic.When Margaret visited him several miles away, she spotted the now familiar pattern on theshrubbery outside his home. Laboratory tests confirmed paraquat on his plants. All in all,Washington state agriculture officials received 141 complaints and documented 100 square miles ofparaquat drift.

The paraquat applications were being made on upland wheat fields, drifting down throughsteep canyons, and spreading out on the irrigated orchards and fields and the towns below. Atfirst, the wheat farmers claimed it was impossible for their paraquat to drift in a northerly direction.After all, they had tested the ground wind direction prior to spraying and the breezes were comingfrom the northeast. However, the winds several hundred feet above the surface were flowingstronger and from the southwest. As droplets of paraquat moved up into these winds aloft, theywere transported north and east, eventually mixing and dropping into the air that worked its waydown Badger Canyon and across the Tri-Cities. The paraquat had drifted against the wind,causing spotting on vegetation up to 15 miles away. (Glantz, 1989)

This story is amazing because of the far-reaching effect these residents had on (a)documenting the problem, (b) involving regulators in taking action, (c) educating elected officialsand the public, and (d) forcing new research on drift. The story doesn't stop with paraquatthough. Heightened local concern soon brought needed scientific, regulatory and media attentionto problems caused by the sulfonylureas that were also being used on the upland grain fields.These incidents would never have gotten the attention they deserve without the years of tireless,volunteer contribution the local residents made to remedy these drift problems. We are all indebtedto these community activists for their efforts in the public interest.

How big of a problem is drift?

Drift is "that portion of the spray cloud that leaves the target area." (Barry and Ciesla,1961) Drift is a major problem for the pesticide industry because it is unavoidable. In 1993, theNational Research Council of the National Academy of Sciences characterized drift as"considerable" because it ranges from about 5 percent under optimal, low-wind conditions to 60

155

percent under more typical conditions. (National Research Council, 1993) The CongressionalOffice of Technology Assessment estimates that about 40 percent of an aerial insecticide applicationleaves the "target area" and that less than one percent actually reaches the target pest. (USCongress, 1990) Two years ago, our staff reviewed 16 studies about aerial drift (virtually all thestudies available to us) and found that in each study there were pesticides detected as far away fromthe application as samples were taken. (Cox, 1995) The drift in these studies ranged from 100 to1600 meters.

The amount and distance drift travels are not the only concerns, however. What applicatorsor researchers think are the optimal conditions for spraying pesticides are not always accurate. Onespring morning, two Oregon women started out on their regular exercise walk for several milesalong the road near their town in the mountains of the Oregon Coast Range. The weather on thevalley floor was foggy. These two friends talked and visited while they walked, all the whilehearing the sound of a helicopter in the distance. As long-time residents of their community, theywere familiar with these sounds. Besides, the husband of one of the women was a logger and hadworked on helicopter logging operations. By the time they were ending their walk, a lingeringsmell in the air matched a very unpleasant taste in their mouths. They both realized that thehelicopter sound was probably not a logging operation but perhaps a spray operation. Concernedabout her health, one of the women contacted forestry officials to find out if she might have beenexposed. The forestry agents would only conclude that there were no violations of forest practiceact regulations.

The weather pattern is not an unusual one for spring in the Coast Range mountains. Whilethe valley floors with their roads and houses stay blanketed in fog, the forested hillsides above arebathed in sunshine with clear visibility. Above the fog, the humidity, wind direction and speed,and air temperature are all within desired ranges — a perfect day to spray. The fog in the valleyfloors may pose a special health concern, however. Research from the 1980s has documented thatpesticide residues in fog can concentrate up to thousands of times higher that concentrations thathad been reported in rain and would be predicted from physical laws. (Glotfelty, 1987; Glotfelty,1990) The strong taste in the two women's mouths at the end of their walk contradicts theconventional wisdom about what conditions are perfect for spray applications.

We do not know enough about how pesticide drift happens and why it happens toadequately protect the environment or human health. I'm interested in pointing out some of themajor pitfalls in how we regulate pesticides and pesticide drift to make my point.

Is pesticide drift regulation working?

Many people are convinced that the problem of drift can be fixed with technology. Thesepeople argue that if farmers used better nozzles and kept them calibrated or did more precisionapplications with GIS mapping and satellite communications, we would not have drift problems.Overall, technological advances are not going to fix drift because much of the problem isinformational, institutional and cultural.

Let me start with the issue of the identities of the inert ingredients in pesticide products.Pesticide users and regulators of drift have a serious information gap when it comes to pesticideinerts. Pesticides contain active ingredients that are listed by name on product labels. Pesticide

156

products also have one or more of over 2,500 inert ingredients that the US EnvironmentalProtection Agency thinks are added as "inert" ingredients. (EPA, 1995) These ingredients aredivided up into five lists by EPA. (EPA, 1989) List 1 are the inerts of toxicological concern andEPA requires these eight "inerts" to be listed by name on product labels. Another 101 inerts areon List 2, the potentially toxic inerts. I'm going to skip over List 3 for a moment. List 4A are theinerts that are of minimal concern because they are "generally regarded as safe." There are 119ingredients on List 4A. List 4B has 309 ingredients and they are the inerts for which EPA hassufficient information to reasonably conclude that the current use patterns will not adversely affectpublic health and the environment. By far, the largest list with 1,981 or 78% of the ingredients isList 3, the inerts of "unknown toxicity."

This is a bit shocking, because through research using EPA information conducted by agraduate intern at our organization, we found that over 400 ingredients on EPA's list of inerts ofunknown toxicity are regulated as hazardous under other federal or state statutes or by anotherfederal or international health agency. (Knight, 1998) It doesn't make sense that the EPA canclaim they know nothing about the toxicity of a substance when the same chemical is regulated ashazardous under the Clean Air Act or Superfund Law or one of several other environmental lawsadministered by EPA.

Some "inert" ingredients are actually currently or formerly registered "active" ingredients.On EPA's list of inerts of unknown toxicity are chemicals such as the restricted use fungicidechlorothalonil, or the toxic fumigant, chlorpicrin. These are pesticide active ingredients that posesuch a great toxic concern that a person cannot purchase them or use them without special trainingand a license. Yet, they can be found in pesticides as inerts and no one even knows that they are inthe product and they are not listed on the label. It's disturbing that EPA allows these substances inpesticide products as "inert" ingredients, but it's appalling that EPA claims to know nothing abouttheir toxicity.

There are solvents and other chemicals in pesticides that are used as inerts that can seriouslyaffect the potential for drift. Yet, users and regulators of pesticides are generally limited toknowing the active ingredient in a pesticide product. Yes, it's possible to find out some of theinerts by reviewing the scientific literature or checking on MSDSs or sending a sample to alaboratory to be reverse engineered like our organization did. A farmer could submit a Freedom ofInformation Act request to EPA and after at least a few months and sometimes a few years, thatfarmer might find out the ingredients in a specific product. As a society, we should not beaddressing a problem as serious as drift without having publicly available the basic informationabout all the product ingredients. EPA should require product labels to list all ingredients.Pesticide manufacturers should make public the information about all the ingredients in theirproducts. There's no excuse to keep it secret.

From what I can tell, product labels are written to protect pesticide manufacturers, not toprotect the environment or human health. The common phrase for drift on a product label usuallyreads like this: "Do not apply in a manner likely to drift." The pesticide manufacturers claim thatthey want to leave the specifics of the site conditions up to the professional judgment of theapplicators, because they are the ones who know their equipment and they have the experience. Ithink it's a rotten deal for the applicator who now has assumed all of the liability. When drifthappens, it's the applicator who applied the product in a manner likely to drift. It's surprising that

157

applicators haven't insisted that manufacturers provide them with explicit directions for how toapply a product so it cannot drift.

More and more, states are offering pesticide applicator certification tests in Spanish or othernon-English languages. More than not, these licenses are for farm workers or their foremen. Oneconcern our organization has is for the responsibility that accompanies these licenses. If a farmworker now is liable for pesticide "drift" because of the label language, it's a shameful way topractice agriculture.

Pesticide drift violations happen in a regulatory culture that does not hold much promise forimproving the situation. Some of this stems from the background of the investigators involved.About five years ago, a fixed wing aircraft made an application of the fungicide Bravo on a 50 acregrass seed field located within the city limits of Eugene, Oregon. The field was ringed with ahousing development to the north, a row of houses to the east, and a shopping center, two schoolsand more houses to the south and major highway to the west. A resident of one of the houses tothe east of the field was not pleased about the application. First, he was woken up just after 5 amby a cropduster, and second he watched a mist of drift land on his backyard. At 5 am, he was notsure whom he could contact to find out what was being sprayed and who was spraying it. But, heknew something about flying. He called the airport less than three miles away and was able to talkto the air traffic controllers. Low flying aircraft within a five mile radius were supposed to be incontact with the airport, but this aircraft was not and attempts by the control tower to contact thepilot were not successful. By mid-afternoon, all concerned parties, including the school nurse,finally had information about what had been sprayed. The pilot was eventually fined for driftingon the resident who complained. (Oregon Department of Agriculture, 1992)

The resident filed a number of complaints over this incident. One complaint was to theFederal Aviation Administration. When it comes to aerial applications, the FAA can play a keyinvestigatory role, but in the Pacific Northwest we've seen less than an impressive showing. Theagency has a regulation that if aerial applications are conducted in a congested area, then there mustbe notification of persons who might be affected prior to spraying and a permit must be secured(14 CFR 127.51). The FAA inspector who looked into the situation determined that the locationdid not qualify as a congested area, despite that the field was inside city limits, ringed withdevelopment, and entered by school children walking to school before the pesticide had anopportunity to dry.

When I saw the FAA's determination, I was incredulous, and immediately called the FAAoffice over 100 miles away. In the course of my conversation, the FAA official assured me thatthe inspectors have a good understanding of the conditions that aerial applicators face because theyare all former aerial applicators. I know that it was meant to reassure me, but it had the oppositeeffect. It's like telling someone that they can feel safe in their community because all the policewho are responsible for upholding the laws have lots of experience serving time. This is a culturalissue. Most people who apply pesticides do not understand how it feels being at the other end ofthe spray nozzle when you don't want to be there.

Another problem is getting the medical community to take seriously your concerns aboutbeing exposed to drift. Take for example the eight women who complained of weakness,dizziness, abdominal cramps, nausea, diarrhea, and irritability over a month-long period. (Ratner,

158

1986) These women lived within 150 yards of a cotton field that had been sprayed 17 times with12 different insecticides during a growing season of less than 100 days. The women stayed athome, while other family members left for work or school. The women experienced more acutesymptoms than other family members. The local physician who first saw them believed he wasdealing with "group hysteria." A visit to two other physicians resulted in blood tests for theactivity level of acetylcholinesterase, and the test results showed a reduction of 45 percent. Thesewomen had signs of acute poisoning, but their local physician did not take them seriously.Unfortunately, it's not an uncommon experience, and it's one of a number of reasons why thehuman health damage caused by pesticide drift is not adequately documented.

Extension agents also lack enthusiasm for making pesticide users face the realities of theirpractices. One Oregon extension bulletin says this about drift concerns: "One of my least favoritejobs is to refer irate individuals, who claim to have their property or person hit by spray from anorchard operation, to the Oregon Department of Agriculture Investigators. Drift is against the law,even though it is virtually impossible to keep drift from occurring under the best of sprayconditions." (Mid-Columbia Hort News, 1998) One practice that the extension agent noted is thatgrowers try to minimize the visibility of their spray operations to the public. I guess the thinking isthat what you don't see can't hurt you.

Drift is a tricky thing to define legally. The EPA doesn't have a definition for drift that canbe used universally. In Oregon, any movement of a pesticide off site is drift. In other states, onlythe movement of a sufficient quantity of a pesticide to cause harm is considered drift. Formembers of the public who experience drift, your state of residence or the state in which you hadyour drift experience can make it a lot easier or a lot harder to bring needed legal attention to yourproblem.

Our organization is sometimes asked to take a position categorically in opposition to aerialspraying. It's a position we've resisted. One reason is that taking such a position will not solvethe drift problem. The biggest concern we have is for the increased human exposure to workerswho would then have to apply pesticides from ground rigs that have leaky cabs, improper filters orother faulty equipment. Or, workers would apply pesticides with backpack sprayers and otherhand-held equipment. Wishing the cropdusters out of the air to put more pesticides on the backsand in the lungs of farm workers is hardly a just position to take.

Recommendations for change.

Drift happens whenever pesticides are sprayed. The US EPA estimates that about three-fourths of the one billion pounds of conventional pesticide active ingredients used in 1995 wereapplied on America's food crops. (Aspelin, 1997) That is a lot of pesticide. Drift problems willstop only when we stop spraying pesticides, not when we spray better.

One problem is that we have not held pesticide manufacturers accountable for the productsthey have created. The public subsidizes too much of the costs of pesticide use. Just like the stateattorneys general who no longer want to have their state responsible for the health cost of smoking,we need to start assessing the cost of pesticide use to public health, to contaminated drinkingwater, to soil health, to air quality, and to wildlife and fish, and these costs need to be owned bythose who make these products. Having pesticide manufacturers accountable for their productswould go a long ways to protecting the environment and human health.

159

It's time that we set specific goals for eliminating pesticide use. Using currently availablebiological, cultural and environmental pest management information, researchers have estimatedthat we could eliminate 50% of our current pesticide use nationwide without reductions inagricultural yields. (Pimentel, 1991) Then, I believe by putting our resources into finding andimplementing alternatives, we could eliminate the next 30-40% of pesticide use. The last 10-20%elimination will be the most difficult. Our environment and our health have much more to benefitfrom measuring reductions in pesticide use instead of measuring drift.

Our society's best interests are not met by spraying better but by farming better. Ourextension agents, university researchers and farm advisors need to focus on helping ouragricultural systems get off the pesticide treadmill. We need to build more ecological diversityback into our farms. We need more profit going into farmer's pockets. We need to better supportfarming communities and help farmers share information and experiences about successes ineliminating pesticide use. It's our best hope for the future.

References:

Aspelin, A. L., Senior Economist. 1997. Pesticide Industry Sales and Usage: 1994 and 1995Market Estimates. Biological and Economic Analysis Division. Office of Pesticide Programs. USEnvironmental Protection Agency. Washington, D.C. (August)

Barry, J.W. and W.M. Ciesla. 1961. Managing drift in forest spray operations. Aerial Applicator(November/December):8-12, 17.

Cox, C. 1995. Indiscriminately from the skies. Journal of Pesticide Reform 15(1):2-6.

EPA, Office of Pesticide Programs. 1989. Inert ingredients in pesticide products; Policy statement;Revision and modification of lists. Fed.Reg. 54(224):48314-48316 (Nov. 22)

EPA, Office of Pesticide Programs. 1995. List of pesticide product inert ingredients. May 17.Unpublished.

Glantz, CS, MN Schwartz, P.J. Perrault, et.al. 1989. An assessment of the meteorologicalconditions associated with herbicide drift in the Horse Heaven Hills/Badger Canyon/Tri-Cities areaduring the period from August 6 through 11, 1988. Prepared for WSDA by Batelle PacificNorthwest Laboratories. Olympia, WA. Contract 15721. (July.)

Glotfelty, D.E., J.N. Seiber, and L.A. Liljedahl. 1987. Pesticides in fog. Nature. 325:602-605.(February 12.)

Glotfelty, D.E., M.S. Majewski, and J.N. Seiber. 1990. Distribution of severalorganophosphorus insecticides and their oxygen analogues in a foggy atmosphere. Environ. Sci.Technol. 24, 353-357.

160

Knight, H and C Cox. 1998. Worst kept secrets: Toxic inert ingredients in pesticides. NorthwestCoalition for Alternatives to Pesticides. Eugene, Oregon.

Mid-Columbia Hort News. 1998. Hood River County Experiment Station. Oregon StateUniversity Extension Service. (March)

National Research Council. Board on Agriculture. Committee on Long-Range Soil and WaterConservation. 1993. Soil and Water Quality: An Agenda for Agriculture. Washington, DC:National Academy Press, pp. 323-324.

Oregon Department of Agriculture Information Office. 1992. Director upholds civil penalties forpesticide misuse in Lane County. News from Agriculture. Salem, Oregon. (August 10)

Pimentel, D. et.al. 1991. Environmental and economic impacts of reducing U.S. agriculturalpesticide use. In Pimentel, D. and A.A. Hanson (eds.) CRC handbook of pest management inagriculture, 2nd edition, volume 1. Boca Raton, FL: CRC Press, Inc.

Ratner, D. and E. Eschel. 1986. Aerial pesticide spraying: An environmental hazard. JAMA256(18):2516-1517.

US Congress, Office of Technology Assessment. 1990. Beneath the bottom line: Agriculturalapproaches to reduce agrichemical contamination of groundwater. Report number OTA-4-418.Washington, DC: US Government Printing Office. (May.)

161

Risk Perception and Communication

Vincent T. CovelloCenter for Risk Communication

New York, New York

Risk Perception, Risk Communication, Pesticides, and Pesticide Drift:Tools and Techniques for Communicating Risk Information

I. Introduction

Risk communication is a systematic, structured, scientifically based method for communicatingeffectively in high concern, high stress environments. These environments include, but are notlimited to, any situation where individuals or groups perceive a threat to their health, safety, orenvironment. Risk communication involves the exchange of information among interested partiesabout the nature, magnitude, significance, or control of a risk. Interested parties include governmentagencies, corporations or industry groups, unions, the media, scientists, professional organizations,special interest groups, communities, and individual citizens.

Information about risks is communicated through a variety of channels. These range from mediareports and warning labels or signs to public meetings, open houses, or hearings involving represen-tatives from government agencies, industry, the media, and the general public. These communica-tion efforts can be difficult for both risk communicators and for the intended audiences. Governmentofficials, industry representatives, and scientists, for example, often argue that non-experts and laypeople do not perceive and evaluate risk information accurately.

Representatives of citizen groups, worker groups, and individual citizens, in turn, often argue thatgovernment officials, industry representatives, and scientists are uninterested in their concerns orunwilling to take actions to solve seemingly straightforward problems. In this context, the mediaoften serve as transmitters and translators of risk information. But the media, too, have been criti-cized for exaggerating risks and for emphasizing drama over scientific facts.

In response to this situation, the literature on risk communication has grown rapidly. Hundreds ofarticles and books, for example, have been published on the topic. Most of these works focus ofproblems and difficulties in communicating information during crisis and non-crisis situations aboutrisks of exposures to environmental risk agents—particularly chemicals, heavy metals, and radiationin the air, water, land, and food. Pesticides, including pesticide drift, are among these risk agents.

Why the interest in risk communication? One explanation is the increased number of hazard commu-nication and environmental right-to-know laws relating to exposures to environmental risk agents.Another is that the public’s concern about exposures to environmental risk agents from past, present,and future industrial activities has led to an increased demand for risk information. A third explana-tion is the expanded media coverage of environmental issues, which in turn reflects greater publicinterest in environmental issues. But a fourth explanation underlies the first three — the loss of faithand trust in government and industry officials as competent risk managers and credible sources ofrisk information.

162

In this context, more than three decades of research indicates that the major challenges to effectiverisk communication include:

· Lack of trust and credibility of information sources· Overly complex scientific and policy messages· Distortions by the media and other stakeholders· Public perceptions and misperceptions

Given these challenges, the purposes of this paper are to provide those with risk communicationresponsibilities related to pesticides and pesticide drift the theoretical foundations and practical toolsneeded to establish effective risk communication programs.

II. The Risk Communication Literature: An Overview of Research Findings

A significant part of the risk communication literature focuses on difficulties in communicating riskinformation effectively. These challenges are directly related to issues of science and perception andcan be organized into four categories:

(1) Characteristics and limitations of scientific data about risks;(2) Characteristics and limitations of spokespersons in communicating information about risks;(3) Characteristics and limitations of the media in reporting information about risks;(4) Characteristics and limitations of the public in evaluating and interpreting risk information.

(1) Characteristics and Limitations of Scientific Data on Health, Safety, and EnvironmentalRisks

One source of difficulty in communicating information about risks is the uncertainty and complexityof data on health, safety, and environmental risks. Risk assessments, despite their strengths, seldomprovide exact answers. This is especially the case for pesticides and pesticide drift. Due to limita-tions in scientific understanding, data, models, and methods, the results of most risk assessments areat best approximations, leaving uncertainties about the real extent of risk. Moreover, the resourcesneeded to resolve these uncertainties are seldom adequate to the task.

Such uncertainties invariably affect communications with the public in the hostile climate thatsurrounds many health, safety, and environmental issues. For example, uncertainties in risk assess-ments often lead to radically different estimates of risk. Underlying many debates about risks are theconflicting assessments produced by government agencies, industry, and special interest groups.Given these uncertainties, one goal of risk communication is to provide detailed information on theassumptions underlying the risk calculation. Since many disagreements stem from underlying as-sumptions (such assumptions about doses and exposures), candid disclosures are critical to publicconfidence and understanding.

(2) Characteristics and Limitations of Spokespersons in Communicating Risk Information

The Loss of the Public’s Confidence and Trust

A central question addressed by the literature on risk communication is why some individuals andorganizations are trusted as sources of risk information and others are not. This question takes on

163

special importance given that two of the most prominent sources of risk information—industry andgovernment—often fail to elicit trust and credibility. In most developed countries, for example,overall public confidence in government and industry as trusted sources of information has declinedprecipitously over the past two decades. In the U.S., for example, most Americans view industry andgovernment as among the least credible sources of information about the risks of exposures to riskagents. Yet at the same time, industry and government are believed to be among the most knowl-edgeable sources of information about such risks.

Public distrust of government and industry is grounded in the beliefs that they have been:

· Insensitive to public concerns and fears about health, safety, and environmental risks,· Unwilling to acknowledge problems,· Unwilling to share information,· Unwilling to allow meaningful public participation,· Negligent in fulfilling their health, safety, and environmental responsibilities.

Compounding the problem are commonly held beliefs that health, safety, and environmental laws aretoo weak, that the environment is worse today than it was in the past, and that government andindustry have done a poor or inadequate job protecting the public health, safety, and the environ-ment.

Several factors have played a role in creating these perceptions and problems. Five in particular arelisted below.

1. Debates and Disagreements. Many officials have engaged in highly visible debates and dis-agreements about the reliability, validity, and meaning of the results of health, safety, and environ-mental risk assessments. In many cases, for example, equally prominent experts have taken diametri-cally opposed positions on the risks of pesticides. While such debates may be constructive for thedevelopment of scientific knowledge, they often undermine public trust and confidence in industryand government.

2. Insufficient Resources. Resources for risk assessment and management are rarely sufficient tomeet demands by citizens and public interest groups for definitive findings and quick action. Expla-nations by officials that generating reliable data is expensive and time consuming, or that risk assess-ment and management activities are constrained by resource, technical, legal, or other limitations,are seldom perceived to be satisfactory. When individuals face what they believe is a new andsignificant risk, they are especially reluctant to accept such claims.

3. Lack of coordination. Coordination among pubic or private organizations with risk managementresponsibilities is seldom adequate. In many debates about risks, for example, lack of coordinationamong responsible organizations has severely undermined public faith and confidence. Compound-ing these problems are the inconsistent approaches to risk assessment and management by organiza-tions at the local, regional, national, and international levels. For example, few requirements exist forregulatory authorities or industries to develop coherent, coordinated, consistent, and interrelatedplans, programs, and guidelines for managing risks. As a result, risk management and control sys-tems tend to be highly fragmented. For government, this fragmentation often leads to jurisdictionalconflicts about which agency or level of government has the responsibility for assessing and manag-ing a particular risk. Lack of coordination, different mandates, and confusion about responsibility

164

and authority also lead, in many cases, to the production of multiple and competing estimates of risk.A commonly observed result of such confusion is the erosion of public trust, confidence, and accep-tance.

4. Inadequate training. Many officials in government and industry lack adequate training incommunications and in the specific requirements of risk communication. For example, many offi-cials display poor non-verbal skills. In addition, they often use complex and difficult technicallanguage and jargon in communicating information about risks and benefits to the media and thepublic. The use of this language is not only difficult to comprehend, but it creates a perception thatthe expert is being unresponsive, dishonest, or evasive.

5. Insensitivity. Government and industry officials have often been insensitive to the informationneeds of the public and the differences between expert and lay perceptions of risk. Officials oftenassume that they and their audience share a common framework for evaluating and interpreting riskinformation. However, this is rarely the case. One of the most important findings to emerge from riskperception and communication studies is that non-experts often consider a much more complex arrayof qualitative and quantitative factors than experts in defining, evaluating, and acting on risk infor-mation.

Strategies for Regaining Public Trust

One of the costs of this heritage of mistrust is the public’s reluctance to believe information fromgovernment and industry about the risks of exposure to a wide variety of risk agents, includingpesticides. When trust and credibility are missing or weak, the primary goal of risk communication isto build them up.

Research indicates that programs for overcoming distrust require improvements first and foremost inrisk assessment and risk management. Improvements in risk assessment and risk management must,however, be accompanied by improvements in the way information is communicated. Better com-munications, in turn, requires improvements in the:(1) Communication skills of individual spokespeople,(2) Credibility of organizations with risk assessment and management responsibilities,

Improved communication skills requires that those who interact with the public on risk issues de-velop better verbal and non-verbal risk communication skills. For some audiences, such as themedia, this requires highly refined skills and continuous practice.

Skills are not enough, however. As communication skills increase, so should ethical accountabilityand moral responsibility. In some cases this may require changes in actions and performance. Peoplejudge others more on their actions than on their words; when actions fail, words are no longertrusted. Because spokespersons represent their institutions, their credibility depends on, and will beenhanced by improvements in the actions of those institutions. Finally, improved credibility forspokespersons involves thinking broadly about risk communication and attending to the importanceof developing ongoing partnerships with all stakeholders. Health, safety, and environmental riskproblems are generally long-term, complex problems that require continuing investigation, active

165

listening and two-way communication. Improved credibility for organizations can be achievedthrough a variety of means, including:

(1) Improvements in health, safety, and environmental performance;(2) Communication and outreach efforts based on a credo of ethical and responsible care(3) Linkages with other credible organizations;(4) Respect for the differing values and world-views that come into play when people evaluate risk

information.

Respect for differing values is based on the understanding that public evaluations of risk are oftenbroader than expert evaluations of risk. In addition to information about risks, costs, and benefits,people take into account a wide range of considerations in making risk decisions, including informa-tion about trust, fairness, control, voluntariness, alternatives, catastrophic potential, familiarity, anddue process.

(3) Characteristics and Limitations of the Media in Reporting Information About Risks

Surveys and case studies indicate that the mass media are critical to the delivery of risk information.Given this importance, researchers have focused their attention on the role, the characteristics, andthe limitations of the media that contribute to problems in risk communication.

A major conclusion emerging from risk communication research is that the media tend to be biasedtoward stories that contain drama, conflict, expert disagreements, and uncertainties. The media isespecially biased toward stories containing dramatic or sensational material, such as pesticide inci-dents involving children. . Much less attention is given to daily occurrences that kill or injure farmore people each year. In reporting about risks, journalists often focus on the same concerns as thepublic, e.g., potentially catastrophic effects, lack of familiarity and understanding, involuntariness,scientific uncertainty, risks to future generations, unclear benefits, inequitable distribution of risksand benefits, and potentially irreversible effects.

Media coverage of risks is frequently deficient since the stories presented are often oversimplified,distorted, and inaccurate —with substantial omissions. For example, media reports on cancer risks—one of the health concerns associated with pesticides—contain numerous omissions. For example,they frequently:

· Fail to provide adequate statistics on general cancer rates for purposes of comparison;· Provide little information on common forms of cancer;· Fail to address issues of public ignorance about cancer;· Minimize information about detection, treatments, and other protective measures.

Many of these problems stem from characteristics of the media and its constraints, such as tightdeadlines limiting research and the pursuit of information; and lack of time or space to deal with thecomplexities and uncertainties surrounding many risk issues. Many of these problems also stemfrom how journalists do their job. For example, journalists achieve objectivity in a story by present-ing opposing views. Truth in journalism is different from truth in science. In journalism, there areonly different or conflicting views and claims, to be covered as equally as possible. Journalists are

166

often forced to rely heavily on sources that are easily accessible and willing to speak out; others tendto be ignored. Finally, few reporters have the scientific background or expertise needed to evaluatecomplex data and disagreements that surround many debates about risks. Given these limitations,effectiveness in communicating with the media about risks depends in part on understanding theconstraints and needs of the media, and adapting one’s behavior and information to meet theseneeds.

(4) Characteristics and Limitations of the Public in Evaluating and Interpreting RiskInformation.

Much of the risk communication literature focuses on characteristics and limitations of the public inevaluating and interpreting risk information. These include: (1) inaccurate estimations of risk levels,(2) difficulties in understanding probabilistic information related to unfamiliar activities or technolo-gies, (3) strong emotional responses to risk information, (4) desires and demands for scientificcertainty, (5) strong beliefs and opinions that are resistant to change, (6) weak beliefs and opinionsthat are easily manipulated by the way information is presented, (7) ignoring or dismissing riskinformation because of its perceived lack of personal relevance, (8) perceiving accidents and mis-haps as signals, and (9) using health, safety, and environmental risks as proxies or surrogates forother concerns or agendas.

1. Inaccurate estimates of levels of risk. People typically overestimate some risks and underesti-mate others. For example, people tend to overestimate the risks of dramatic or sensational causes ofdeath such as cancer and underestimate the risks of less dramatic diseases such as diabetes andasthma. This bias is caused in part by the tendency for risk judgments to be influenced by the memo-rability of past events and by the imaginability of future events. A recent disaster, intense mediacoverage, or a vivid film can heighten the perceived degree of risk. Conversely, risks that notmemorable, obvious, palpable, tangible, or immediate tend to be underestimated.

2. Difficulties in understanding probabilistic information related to unfamiliar activities ortechnologies. Cognitive biases and related factors hamper people’s ability to understand probabilis-tic information, particularly when such information relates to unfamiliar activities or technologies.These difficulties, in turn, complicate discussions of risk probabilities between experts and non-experts. For example, risk experts are often confused by the public’s unwillingness to accept anycancer risk from a new activity, such as a new power line, even when the risk is as low as one in amillion. To an expert, a one in a millions risk is minuscule, especially when compared to the back-ground chance of cancer for the population as a whole (approximately one in four in the UnitedStates). This problem is exacerbated by the fact that people have difficulty understanding and inter-preting small probabilities—such as the difference between one chance in one hundred thousand andone chance in a million.

In rejecting probabilistic arguments (e.g., that an activity or exposure will increase the risk of cancerby only one in a million), people often raise concerns about:

· Their Personal Risk (For example: What if the one in million turns out to be me or a loved one?).· Cumulative Risks (For example: Why should I accept more risks — I am already exposed to

enough risks in life?)· Trust (For example: Why should I believe your calculations?).

167

· Voluntariness (For example: Why should I accept a risk that is imposed upon me or that I did notchoose voluntarily?

· Benefits (For example: Why should I accept a risk that provides little to no benefit?· Equity and Fairness (For example: Why should I accept a risk that provides most of the benefits

to others?)· Ethics and Morality (For example: Who gave you—e.g., government or industry—the right to

play god and determine that one person in a million will develop or die of cancer? Would you bewilling to volunteer your own family?)

These same problems hamper discussions between experts and non-experts on low probability/highconsequence events and other “worst case scenarios.” Information that helps people imagine theworst case is often counter-productive and leads to confusion about what is remotely possible andwhat is possible or probable.

Given these difficulties, many organizations focus on qualitative risk messages, particularly when littletime is available for discussion. Among the three most effective of these are messages that describe:

· The degree to which public health, safety, or environmental standards have been, are, or will bemet;

· Monitoring or testing activities designed to assure compliance with standards;· Review, audit, or oversight activities by trusted and credible authorities;· Co-operation with trusted and credible authorities.

Other effective messages include:

· Risk reduction measures;· Comparisons of the risks, costs and benefits of decision options;· Statements indicating that applicable standards are based on worst case, unrealistic, or pessimis-

tic assumptions designed to be protective of public health and safety.

3. Strong emotional responses to risk information. Emotional arousal tend to be most intensewhen people perceive the risk in question to be involuntary, unfair, not under their personal control,and low in benefits. Because of the anger and feelings they can generate, these characteristics areoften referred to in the risk communication literature as “outrage” factors. Emotional arousal reac-tions also typically occur when the risk is believed to affect children in some special way (e.g.,miscarriages or birth defects among children exposed to pesticides or pesticide drift), or when theadverse consequences are particularly dreaded. (e.g., cancer from exposure to pesticides). Strongemotional feelings often make it difficult to engage in rational discourse about risk in public settings.

4. Desires and demands for scientific certainty. People are adverse to uncertainty and use avariety of coping mechanisms to reduce the anxiety it causes. This aversion often translates into amarked preference for statements of fact over the statements of probability which are typically thelanguage of risk assessment. The public often wants to know exactly what will happen, not whatmight happen.

5. Strong beliefs and opinions that are resistant to change. People tend to ignore evidence thatcontradicts their current beliefs. Strong beliefs about risks, once formed, change very slowly and areextraordinarily persistent in the face of contrary evidence. Initial beliefs about risks influence how

168

subsequent evidence is interpreted. New evidence, such as data provided by a government or indus-try official, appears reliable and informative only if it is consistent with the initial belief; contraryevidence is dismissed as unreliable, erroneous, irrelevant, or non-representative.

6. Weak beliefs and opinions that are easily manipulated by the way information is presented.When people lack strong prior beliefs or opinions, subtle changes in the way that risks are expressedcan have a major impact. A variety of studies have demonstrated the powerful influence of suchpresentation or “framing effects. They suggest that risk communicators can, under some circum-stances, easily manipulate risk perceptions. One study tested this hypothesis by asking two groups ofphysicians to choose between two types of therapy: surgery or radiation. Each group received thesame information but with one major difference—probabilities were expressed either in terms ofdying or in terms of surviving. Even though these two numbers are the same, the difference resultedin dramatic differences in the choice of therapy. Virtually the same results have been observed forother test populations.

7. Ignoring or dismissing risk information because of its perceived lack of personal relevance.Most risk data relate to society as a whole. These data are usually of little interest or concern toindividuals, who are more likely to be concerned about risks to themselves than about risks to society.

8. Perceiving accidents and mishaps as signals. The significance of an accident is determinedonly in part by its health, safety, or environmental consequences (e.g., the number of deaths orinjuries that occur). Of equal if not greater importance is what the accident or mishap signifies orportends. A major accident with many deaths and injuries, for example, may have only minor publicsignificance if it occurs as part of a familiar and well understood system (e.g., a train wreck). How-ever, a minor accident in an unfamiliar or poorly understood system—such as a leak at a radioactivewaste disposal site—can have major social significance as a harbinger of future, possibly cata-strophic events.

9. Using health and environmental risks as proxies or surrogates for other concerns or agen-das. The risks people focus on reflect their beliefs about values, social institutions, nature, andmoral behavior. Risks are exaggerated or minimized accordingly. Therefore, debates about risks areoften a proxy or surrogate for other, more general social, economic, political, or cultural concerns.Many debates about pesticides, for example, has often been interpreted as less a debate about thespecific health risks of exposure to pesticides than about:· Noise· Property values· Privacy· Political and Economic Power· Due Process

III. Theoretical Foundations of Risk Communication

The risk communication literature draws from a number of theoretical models that describe how riskinformation is processed, how risk perceptions form, and how risk decisions are made. Since eachtheoretical model views these processes from a different perspective, they should be viewed ascomplimentary. Described below are several of the most important theoretical models and theirimplications for risk communication theory and practice.

169

1. Risk Perception (RP) Theory

Beginning with the pioneering work in the 1960’s of Chauncey Starr and of the Decision ResearchGroup based in Eugene, Oregon, a large research literature has accumulated on the influence ofperceptual factors on judgements of risk acceptability. What this research has discovered is thateven though the level of risk is related to risk acceptability, it is far from a perfect correlation. Manyfactors affect the way people assess risk and evaluate acceptability. These include:

1) Familiarity. Unfamiliar risks (such as exposure to drift from pesticide applications) are morethreatening than familiar risks (such as household accidents).

2) Understanding. People are more concerned about activities characterized by poorly understoodexposure mechanisms or processes (such as long term exposure to low doses of pesticides) thanthose that are well understood or self explanatory , (e.g., such as pedestrian accidents or slippingon ice).

3) Uncertainty. Risks that are scientifically unknown or uncertain (e.g., risks from a radioactivewaste facility designed to last 20,000 years) create more concern than risks that are relativelyknown to science (e.g., actuarial data on automobile accidents).

4) Controllability. Risks perceive to be out of a person’s control (e.g., accidental releases of toxicchemicals) are more worrisome than risks within one’s control (e.g., driving an automobile orriding a bicycle).

5) Voluntariness. People are more concerned about risks that they perceive to be involuntary (e.g.,exposure to pesticide drift) than about risks perceived to be voluntary (e.g. smoking, sunbathing,or mountain climbing).

6) Effects on children. Activities that put children specifically at risk (e.g., pregnant womenexposed to pesticides) generate more concern than activities that do not put children specificallyor directly at risk (e.g., workplace accidents).

7) Effects manifestation. The public’s concern about risks with delayed effects (e.g., the develop-ment of cancer after exposure to pesticides) is greater than that of risks with immediate effects(e.g., poisonings).

8) Effects on future generations. Activities that pose risks to future generations (e.g., geneticeffects due to exposure to pesticides) are more provocative than those posing no future threat(e.g., skiing accidents).

9) Catastrophic potential. Fatalities and injuries that are grouped in time and space (e.g., thoseresulting from a major explosion or accidental release of toxic chemicals) are more important topeople than fatalities and injuries that are scattered or random in time and space (e.g., automobileaccidents).

10)Victim identity. Risks to identifiable victims (e.g., a worker exposed to high levels of pesticides)have greater impact than risks to statistical victims (e.g., statistical profiles of automobile acci-dent victims).

11) Dread. People are more concerned about risks that evoke fear, terror, or anxiety (e.g., exposureto cancer causing agents) than to risks that do not cause these feelings (e.g., common colds andhousehold accidents).

12) Trust in institutions. Lack of trust and credibility in a risk management institution (e.g., certaingovernment agencies for their perceived close ties to industry) create more concern than atrustworthy and credible institution (e.g., the management of biotechnology, genetic engineer-ing, and recombinant DNA risks by universities).

170

13) Media attention. Risks that receive considerable media attention (e.g., cancer clusters amongmigrant workers) are more provocative than risks that receive little media coverage (e.g., on-the-job accidents).

14) Accident history. Activities that have a history of major and sometimes minor accidents (e.g.,leaks at waste disposal facilities) are more threatening than activities with little or no such history(e.g., recombinant DNA experimentation).

15) Equity and fairness. People are more concerned about activities that carry a perceived inequi-table or unfair distribution of risks and benefits (e.g. inequities related to the siting of powerlines or cellular telephone towers) than about activities characterized by a perceived equitable orfair distribution of risks and benefits (e.g., vaccination).

16) Benefits. Hazardous activities perceived to have unclear, questionable, or diffused benefits (e.g.,pesticide applications by airplane) create more concern than hazardous activities perceived tohave clear benefits (automobile driving).

17) Reversibility. Activities with potentially irreversible adverse effects (e.g., cancer from exposureto pesticides) are more provocative than activities with reversible adverse effects (e.g., injuriesfrom sports or household accidents).

18) Personal stake. People are more concerned about activities that they believe place them (or theirfamilies) personally and directly at risk (e.g., being exposed to pesticide drift) than activities thathave less personal risk (e.g., disposal of hazardous waste in remote sites or in other nations).

19) Nature of evidence. Risks based on evidence from human studies (e.g., risk assessments basedon adequate epidemiological data) prove more significant than risks based on animal studies(e.g., laboratory studies of the adverse effects of pesticides using rats or mice).

20) Human vs. natural origin. Risks caused by human actions and failures (e.g., accidents atindustrial facilities caused by negligence, inadequate safeguards, or operator error) cause moreconcern than risks caused by nature or “Acts of God” (e.g., exposure to geological radon orcosmic rays).

Recent research using electronic message testing and scenario evaluation indicate that people notonly use these factors in their decision making but also assign different weights to each factor.Research indicates, for example, that the risk of an activity with few perceived benefits may beperceived one thousand times greater than the risk of an activity with high perceived benefits. Simi-larly, the risk of an activity over which there is little perceived control (such as through participation,knowledge, or choice) may be perceived one thousand times greater than the risk of an activity overwhich there is high perceived control. Most importantly, the risks of an activity for which thereperceived little trust in responsible authorities may be perceived two thousand times greater than therisk of an activity for which there is high perceived control.

These factors largely explain why certain population segments are adverse to activities and technolo-gies such as aerial applications of pesticides. They also help to explain phenomena such as the “notin my back yard” (NIMBY) response to such activities. For example, surveys indicate that manyresidents in communities where pesticide drift is a problem believe that government and industryofficials: (1) have excluded them from meaningful participation in the decision making process; (2)have denied them the resources needed to evaluate or monitor independently the associated health,safety, or environmental risks; (3) have denied them the opportunity to give their “informed consent”to management decisions that affect their lives and property; (4) have imposed or want to imposeupon them technologies that provide few local economic benefits; (5) have imposed or want toimpose upon them technologies that entail high costs to the community (e.g., adverse impacts on

171

health, safety, wildlife, recreation, tourism, property values, traffic, noise, visual aesthetics, commu-nity image, and quality of life); (6) have imposed or want to impose on them activities that providemost of the benefits to other parties or to society as a whole; and (7) have dismissed their opinions,fears, and concerns as irrational and irrelevant.

The recognition that a fairly distributed risk is more acceptable than an unfairly distributed one iscritical to resolving NIMBY and related controversies. A risk involving significant benefits to theparties at risk is more acceptable than a risk with no such benefits. A risk for which there are noalternatives is more acceptable than a risk that could be eliminated by alternative technology. A riskthat the parties affected can control is more acceptable than a risk that is beyond their control. A riskthat the affected parties can assess and decide voluntarily to accept is more palatable than an im-posed risk. These statements are true in the same way that a small risk is more acceptable than alarge risk. Risk is multidimensional; but size is only one of the dimensions.

If the validity of these points is accepted, then a whole range of risk communication and manage-ment options become available. Because factors such as fairness, familiarity, and voluntariness areas relevant as size in judging the acceptability of a risk, efforts to make a risk fairer, more familiar,and more voluntary are as significant as efforts to make the risk smaller. Similarly, because per-sonal control is important, efforts to share power, such as establishing and assisting communityadvisory committees or supporting third party research, audits, inspections, and monitoring, can beeffective in making a risk more acceptable.

People vary in how they assess risk acceptability based on their values and well as their perceptions.They weigh factors according to their own values, sense of risk, and stake in the outcome. Becauseacceptability is a matter of values and opinions, and because values and opinions differ, debatesabout risk are often debates about values, accountability, and control.

2. Mental Noise (MN) Theory.

Mental noise theory focuses primarily on how people process information under stress. Researchindicates that when people are in a state of high concern, their ability to process information effec-tively and efficiently can be severely impacted. When people feel that that which they value is beingthreatened, they experience a wide range of emotions. These range from anxiety to anger. Theemotional arousal and/or mental agitation generated by strong feelings of anxiety, worry, fear,hostility, anger, panic, and outrage creates a phenomena known as mental noise. Much like atmo-spheric static and its effect on radio communications, mental noise can reduce the ability of theindividual to process information efficiently and effectively by as much as 80%. Research based onelectronic message testing indicates that exposure to unwanted, involuntary, uncertain, and dreadedrisks is almost always accompanied by severe mental noise. Severe mental noise, in turn, ofteninterferes with the ability of individuals to engage in rational discourse about health, safety, andenvironmental risks.

Several communication tools can be used to overcome the effects of mental noise. These toolsincrease the efficiency and effectiveness of communications in high concern, high stress environ-ments. The most important of these are tools that maximize two valued communication attributes:clarity and brevity.

172

Clear messages are those that are easily processed by the receiver and easily understood. Importanttools and techniques for enhancing message clarity are:

1) Message repetition, e.g., messages that are repeated exactly the same way two to four timeswithin the same presentation;

2) Message visualization, e.g., messages enhanced by the use of audio-visual material (graphs,charts, photographs, or video) or by the use of word pictures (analogies or story telling).

3) Structured messages, e.g., messages presented using the triple T, or “tell me what you are goingto tell me, tell me, tell me again” model;

4) Message readability/comprehension, e.g., messages geared to the knowledge/comprehensionlevel of the target audience (articles in most national newspapers, for example, are written at the7th-9th grade comprehension level.).

Characteristics of concise messages include:

1) A limited number of key messages, e.g., no more than three key messages in any communica-tion;

2) A limited number of words for each message, e.g., no more than 12-15 words per key message;3) A limited number of supporting facts for each message, e.g., no more than 2-3 supporting facts,

reasons, or examples for each message.4) A limited amount of time for the presentation of messages, e.g., no more than 15-20 minutes for

a briefing in a high concern situation and no more than 2 minutes for answering a question.

3. Trust Determination (TD) Theory

A common thread in all communication strategies is the need to be proactive in establishing trust.Only when trust has been established can other goals, such as education and the sharing of informa-tion, follow.

Research indicates that trust cannot be built quickly. Instead, it is the result of ongoing partnerships,actions, performance, and skill in communications. More specifically, trust is determined by fourfactors:

· Perceived caring/empathy;· Perceived competence/expertise;· Perceived honesty/openness;· Perceived dedication/commitment.

In high concern, low trust situations, caring/empathy is the most important. People want to know thatyou care before they care what you know. More specifically, people want to know that the communi-cating organization:

(1) Cares about the same things they care about — be it a health, safety, environmental, economic,aesthetic, fairness, or process concern;

(2) Empathizes with their concerns and is capable of seeing the situation from a variety of perspec-tives;

(3) Is listening carefully to what is being said.

173

Perceptions of competence/expertise are influenced by several factors. These include:· Information relating to the organization’s health, safety, and environmental track record;· Information relating to the credentials, education, experience, knowledge, and presentation skills

of the organizational spokesperson;· Information relating to organizational affiliations and associations.

Perceptions of honesty/openness derive from actions, words, and non-verbal cues that convey truth-fulness, candidness, and accessibility. In high concern, low trust situations, non-verbal cues tend todominate. Research indicates, for example, that 50-75% of information about honesty/openness isderived from non-verbal cues.

Perceptions of dedication/commitment are influenced largely by the actions, words, and non-verbalcues that communicate diligence and hard work in the pursuit of health, safety, and environmentalgoals. It is influenced by beliefs that the communicator is committed, willing to work overtime, andenthusiastic.

In decisions regarding trust, gender plays a significant role. For example, women in general receivesubstantially higher initial ratings than men on three of the four trust factors – caring/empathy,honestly/openness, and dedication/commitment to others. However, women receive lower initialratings than men on competence and expertise. Given the importance attached to caring and empathyin high concern situations, and given that this personality attribute is assigned more readily towomen than to men, a woman perceived as competent and expert can outrank most men in ratings oftrust.

For both industry and government, prospects for establishing high levels of public trust are modest atbest — at least in the short run. They do, however, appear to be better at local levels than nationallyor globally. For example, judgments of the credibility of local spokesperson or organization canoverride judgments of the credibility of the industry as a whole. One result of this finding is that thefocus of many risk communication programs and activities sponsored by industry and government isto develop, at the local level, a track record of dealing openly, fairly, safely, and responsibly with thepublic.

Key to the success of many of these programs is the principle of credibility transference. Credibil-ity transference states that a lower credibility sources takes on the credibility of the highest crediblesource that agrees with its position on an issue. Surveys indicate that organizations and individualsperceived to have relatively high to medium credibility on health, safety and environmental riskissues include:

· Health professionals (e.g., physicians, nurses, dentists, and pharmacists),· Safety professionals (e.g., fire chiefs),· Educators,· Professional scientific and engineering organizations,· The media,· Non-management employees,· Non-profit voluntary health organizations,· Environmental/citizen activist groups,· Local citizens who are respected, neutral, and informed.

174

Coordination, collaboration, and dialogue with such groups can substantially enhance credibility. Italso limits the effectiveness of challenges, since a lower credibility source that attacks a highercredibility source generally loses further credibility.

4. Negative Dominance (ND) Theory

Negative dominance theory describes the asymmetrical processing of negative and positive informa-tion by people, particularly in high concern situations. Two aspects of this asymmetrical processingof information are particularly relevant for risk communication purposes.

1. Negative information has substantially greater psychological impact than positive information inhigh concern situations. For example, sentences that contain negatives – negative grammaticalconstructions (no, not, never, nothing, none constructions) or words with negative connotations –receive closer attention and are remembered longer.

2. Non-verbal cues are typically interpreted negatively.

Several practical recommendations follow from these principles. First, avoid non-verbal cues havethe ability to communicate strong negative messages, such as poor eye contact and poor posture.Second, provide messages that indicate solutions or commitment to solutions.

IV. Principles of Risk Communication Practice

Effective risk communication is a complex skill requiring knowledge, preparation, practice and execu-tion. Only by mastering risk communication skills can individuals and organizations achieve the pri-mary goals of risk communication:

• Achieve mutual understanding.• Establish and maintain trust and credibility.• Establish a dialogue about risk, benefits; and process.• Produce an informed public that is involved, interested, reasonable, thoughtful, solution-

oriented, and collaborative.

These goals, in turn, need to be turned into clear, explicit objectives—such as providing informationto the public, motivating individuals to act, or contributing to conflict or dispute resolution.

Given these goals and objectives, and considering the challenges presented by limitations and char-acteristics of data, spokespeople, the public, and the media, a set of principles have been identified asa guideline for effective risk communication. Those principles follow.

Principle 1. Accept and involve the public as a legitimate partner.

Two basic tenets of risk communication in a democracy are generally understood and accepted.First, people and communities have a right to participate in decisions that affect their lives, theirproperty, and the things they value. Second, the goal of risk communication should not be to diffusepublic concerns or avoid action. The goal, as noted above, should be to produce an informed publicthat is involved, interested, reasonable, thoughtful, solution-oriented, and collaborative.

175

Guidelines:

♦ Demonstrate respect for the public by involving the community early, before importantdecisions are made.

♦ Clarify that decisions about risks will be based not only on the magnitude of the risk but onfactors of concern to the public.

♦ Involve all parties that have an interest or a stake in the particular risk in question.

Principle 2. Listen to the audience.

People in the community are often more concerned about issues such as trust, credibility, control,competence, voluntariness, fairness, empathy, caring, and compassion than about mortality statis-tics and the details of quantitative risk assessment. If people feel or perceive that they are not beingheard, they cannot be expected to listen. Effective risk communication is a two- way activity.

More generally, this principle is based on the observation that what is perceived as real is real in itsconsequences. Risk communication activities must therefore be grounded in knowledge and under-standing of the target audience’s perceptions rather than in the factual reality. Perception is fragileand can be influenced by dozens of factors. A key conclusion of the perception research literature isthat perceptions and opinions form quickly; beliefs form slowly.

Guidelines:♦ Do not make assumptions about what people know, think or want done about risks.♦ Take the time to find out what people are thinking: use techniques such as interviews,

facilitated discussion groups, and surveys.♦ Let all parties that have an interest or a stake in the issue be heard.♦ Recognize people’s emotions.♦ Let people know that what they said has been understood, address their concerns.♦ Recognize the “hidden agendas”, symbolic meanings, and broader economic or

political considerations that often underlie and complicate the task of risk communication.

Principle 3. Be honest, frank, and open.

Before any message or messenger can be accepted, they must be perceived as trustworthy andcredible. Therefore, the primary goal of any risk communication effort must first be the establish-ment of trust and credibility. Trust and credibility judgments are resistant to change once made.Short-term judgments of trust and credibility are based largely on verbal and non-verbal communica-tions. Long term judgments of trust and credibility are based largely on actions and performance.

In communicating risk information, trust and credibility are a spokesperson’s most precious assets.Trust and credibility are difficult to obtain. Once lost they are almost impossible to regain.

Guidelines:♦ State credentials; but do not ask or expect to be trusted by the public.♦ If an answer is unknown or uncertain, express willingness to get back to the

questioner with answers.♦ Make corrections.

176

♦ Disclose risk information as soon as possible (emphasizing any appropriatereservations about reliability).

♦ Do not minimize or exaggerate the level of risk.♦ Speculate only with great caution.♦ If in doubt, lean toward sharing more information, not less—or people may think

something significant is being hidden.♦ Discuss data uncertainties, strengths and weaknesses—including the ones identified by other

credible sources. Identify worst-case estimates as such, and cite ranges of risk estimateswhen appropriate.

Principle 4. Coordinate and collaborate with other credible sources

Allies can be effective in helping communicate risk information. Few things make risk communi-cation more difficult than conflicts or public disagreements with other credible sources.

Guidelines:♦ Take time to coordinate all inter-organizational and intra-organizational communications.♦ Devote effort and resources to the slow, hard work of building bridges, partnerships, and

alliances with other organizations.♦ Use credible and authoritative intermediaries.♦ Consult with others to determine who is best able to answer questions about risk.♦ Try to issue communications jointly with other trustworthy sources such as credible university

scientists, physicians, citizen advisory groups, trusted local officials, and national or localopinion leaders.

Principle 5. Meet the needs of the media.

The media are a prime transmitter of information on risks. They play a critical role in setting agen-das and in determining outcomes. The media are generally more interested in politics than in risk;more interested in simplicity than in complexity; and more interested in wrongdoing, blame anddanger than in safety.

Guidelines:♦ Be open with and accessible to reporters.♦ Respect their deadlines.♦ Provide information tailored to the needs of each type of media, such as sound bites, graphics

and other visual aids for television.♦ Prepare in advance and provide background material on complex risk issues.♦ Follow up on stories with praise or criticism, as warranted.♦ Try to establish long-term relationships of trust with specific editors and reporters.

Principle 6. Speak clearly and with compassion.

Technical language and jargon are useful as professional shorthand. But they are barriers to success-ful communication with the public. In low trust, high concern situations, empathy and caring cancarry more weight than facts.

177

Guidelines:♦ Use clear, non-technical language.♦ Be sensitive to local norms, such as speech and dress.♦ Strive for brevity, but respect people’s information needs.♦ Use vivid, concrete images that communicate on a personal level.♦ Use stories, examples and anecdotes that make technical data come alive.♦ Avoid distant, abstract, unfeeling language about deaths, injuries and illnesses.♦ Acknowledge and respond (both in words and with actions) to emotions that

people express—anxiety, fear, anger, outrage, helplessness.♦ Acknowledge and respond to the distinctions that the public views as important in

evaluating risks.♦ Use risk comparisons to help put risks in perspective; but avoid comparisons that

ignore distinctions that people consider important.♦ Always try to include a discussion of actions that are under way or can be taken.♦ Promise only what can be delivered, and follow through.♦ Acknowledge, and say, that any illness, injury or death is a tragedy.

Principle 7. Plan carefully and evaluate performance.

Different goals, audiences, and media require different risk communication strategies. Risk com-munication will be successful only if carefully planned.

Guidelines:♦ Begin with clear, explicit objectives—such as providing information to the public,motivating

individuals to act, stimulating emergency response, or contributing to conflict or disputeresolution.

♦ Evaluate the information about risks and know its strengths and weaknesses.Classify the different subgroups among your audience.

♦ Aim communications at specific subgroups in the audience.♦ Recruit spokespersons who are effective with presentation and interaction.♦ Train staff—including technical staff—in communication skills and reward outstanding

performance.♦ Whenever possible, pretest messages.♦ Carefully evaluate efforts and learn from mistakes.

Analyses of case studies suggest that these principles and guidelines form the basic building blocksfor effective risk communication and public dialogue. Each principle recognizes, in a different way, that:

1) that effective risk communication is an interactive process based on mutual trust, cooperation,and respect among all parties;

2) that effective risk communication is a complex art and skill that requires substantial knowledge,training, and practice;

3) that there are no easy prescriptions for effective risk communication;4) that there are limits on what can be accomplished through risk communication alone — no

matter how skilled, committed, and sincere an organization or person is;5) that the single, most important goal of the risk communicator is to establish and maintain trust

and credibility.

These principles and guidelines are the foundations for all risk communication activities and providethe basis for the creation of a successful pesticide and pesticide drift risk communication program.

178

GENERAL RISK COMMUNICATION RESOURCES

Arkin, E. B. 1989. “Translation of Risk Information for the Public: Message Development.” Effec-tive Risk Communication: The Role and Responsibility of Government and Nongovernment Organi-zations, editors V. T. Covello, D. B. McCalum, and M. T. Pavlova, pages 127-135. Plenum Press,New York.

Chess, C., B. J. Hance, and P. M. Sandman. 1989. Planning Dialogue with Communities: A RiskCommunication Workbook. Rutgers University, Cook College, Environmental CommunicationResearch Program, New Brunswick, New Jersey.

Covello, V. T., P. M. Sandman, and P. Slovic. 1988. Risk Communication, Risk Statistics, and RiskComparisons: A Manual for Plant Managers. Chemical Manufacturers Association, Washington,D.C.

Covello, V. T., D. B. McCallum, and M. T. Pavlova. 1989. “Principles and Guidelines for Improv-ing Risk Communication.” Effective Risk Communication: The Role and Responsibility of Govern-ment and Nongovernment Organizations, editors V. T. Covello, D. B. McCalum, and M. T. Pavlova,pages 3-16. Plenum Press, New York.

Davies, J. C., V. T. Covello, and F. W. Allen, editors. 1987. Risk communication: Proceedings ofthe National Conference on Risk Communication held in Washington, D.C., January 1986. Conser-vation Foundation, Washington, D.C.

EPA (U.S. Environmental Protection Agency). 1987. Risk Assessment, Management, and Commu-nication: A Guide to Selected Sources. EPA 1MSD/87-002, U.S. Environmental ProtectionAgency, Office of Information Resources Management and Office of Toxic Substances, Washington,D.C.

Hance, B. J., C. Chess, and P. M. Sandman. 1988. Improving Dialogue with Communities: A RiskCommunication Manual for Government. New Jersey Department of Environmental Protection,Division of Science and Research, Trenton, New Jersey.

Hance, B. J. C. Chess, and P. M. Sandman. 1990. Industry Risk Communication Manual. CRCPress/Lewis Publishers, Boca Raton, Florida.

International Research Group on Risk Communication, R. E. Kasperson, Chair, CENTED, ClarkUniversity, Worchester, Massachusetts 01610, (617) 793-7665.

NRC (National Research Council). 1989. Improving Risk Communication. National AcademyPress, Washington, D.C.

Environmental Risk Communication Resources

EPA (U.S. Environmental Protection Agency). 1988. Community Relations in Superfund: A Hand-book. EPA/540/G-88/002, U.S. Environmental Protection Agency, Office of Emergency and Reme-dial Response, Washington, D.C.

179


Hance, B. J., C. Chess, and P. M. Sandman. 1990. Industry Risk Communication Manual. CRCPress/Lewis Publishers, Boca Raton, Florida.

Krimsky, S., and A. Plough. 1988. Environmental Hazards: Communicating Risks as a SocialProcess. Auburn House, Dover, Massachusetts.

Sachsman, D. B. 1991. “Environmental Risk Communication and the Mass Media.” Paper pre-sented at the 41st Annual Conference of the International Communication Association, Chicago.School of Communications, California State University, Fullerton, California.

Sachsman, D. B., M. R. Greenberg, and P. M. Sandman, editors. 1988. Environmental Reporter’sHandbook. Rutgers University, Cook College, Environmental Communication Research Program,New Jersey Agricultural Experiment Station, New Brunswick, New Jersey.

Sandman, P. M., D. B. Sachsman, and M. R. Greenburg. 1988. The Environmental News Source:Providing Environmental Risk Information to the Media. New Jersey Institute of Technology,Hazardous Substance Management Research h Center, Risk Communication Project, Newark, NewJersey.

Health Risk Communication Resources

Baram, M. S., and P. Kenyon. 1986. “Risk Communication and the Law for Chronic Health andEnvironmental Hazards.” Environmental Professional 8(2):165-179.

Cohen, A., M. J. Colligan, and P. Berger. 1985. “Psychology in Health Risk Messages for Work-ers.” Journal of Occupational Medicine 27(8):543-551.

Fischhoff, B. 1989. “Helping the Public Make Health Risk Decisions.” In Effective Risk Communi-cation: The Role and Responsibility of Government and Nongovernment Organizations, editors V.T. Covello, D. B. McCalum, and M. T. Pavlova, pages 111-116. Plenum Press, New York.

Negotiation Communication Resources

Chess, C., B. J. Hance, and P. M. Sandman. 1989. Planning Dialogue with Communities: A RiskCommunication Workbook. Rutgers University, Cook College, Environmental CommunicationResearch Program, New Brunswick, New Jersey.


180

Renn, Ortwin. 1992. “Risk Communication: Toward a Rational Discourse with the Public.” Jour-nal of Hazardous Materials 20:465-519.

Wilson, T. 1989. “Interactions between Community/Local Government and Federal Programs.”Effective Risk Communication: The Role and Responsibility of Government and NongovernmentOrganizations, editors V. T. Covello, D. B. McCallum, and M. T. Pavlova, pages 77-81. PlenumPress, New York.

Crisis Communication Resources

Caernarven-Smith, P. 1993. “Managing a Disaster.” Technical Communication 40(1):170-172.

Carney, B. 1993. “Communicating Risk.” IABC Communication World May:13-15.

International Association of Business Communicators (IABC). 1993. Crisis Communication Hand-book. International Association of Business Communicators, Washington, D.C.

Lave, T.R., and L. B. Lave. 1991. “Public Perception of the Risks of Floods: Implications forCommunication.” Risk Analysis 11(2):255-267

Approaches to Communicating Risk

Weinstein, N.D., and P. M. Sandman. 1993. “Some Criteria for Evaluating Risk Messages.” RiskAnalysis 13(1):103-114.

Kasperson, R. E. 1986. “Hazardous Waste Facility Siting: Community, Firm, and GovernmentalPerspectives.” Hazards: Technology and Fairness, pages 118-144. National Academy of Engineer-ing/National Academy Press, Washington, D.C.

Johnson, B. B. 1993. “‘The Mental Model’ Meets ‘The Planning Process’” Wrestling with RiskCommunication Research and Practice.” Risk Analysis 13(1):5-8.

Morgan, G., B. Fischhoff, A. Bostrom, L. Lave, and C. J. Atman. 1992. “Communicating Risk tothe Public.” Environ. Sci. Technl. 26(11): 2048-2056.

NRC (National Research Council). 1989. Improving Risk Communication. National AcademyPress, Washington, D.C.

Risk=Hazard + Outrage ... A Formula for Effective Risk Communication.” Videotape course pre-sented by Peter M. Sandman. Available from the American Industrial Hygienists Association,Washington, D.C.

Rogers, E. M., and D. L. Kincaid. 1981. Communications Networks: Toward a New Paradigm forResearch. The Free Press, a division of Macmillan Publishing Company, Inc., New York.

Rowan, K. W. 1991. “Goals, Obstacles, and Strategies in Risk Communication: A problem-SolvingApproach to Improving Communication about Risks.” Journal of Applied Communication ResearchNovember: 300-329.

181

Sandman, P. m. 1989. “Hazard versus Outrage in the Public Perception of Risk.” Effective RiskCommunication: The Role and Responsibility of Government and Nongovernment Organizations,editors V. T. Covello, D. B. McCallum, and M. T. Pavlova, pages 45-49. Plenum Press, New York.

Barriers to Effective Risk Communication

Chess C., P. M. Sandman, and M. R. Greenburg. 1990. Empowering Agencies to Communicateabout Environmental Risk: Suggestions for Overcoming Organizational Barriers. Rutgers Univer-sity, Cook College, Environmental Communication Research Program, New Brunswick, NewJersey.

Hadden, S. G. 1990. “Institutional Barriers to Risk Communication.” Risk Analysis 9:301-308.


Sanderson, W., and K. Niles. 1992. “Effective Outreach is Good Public Policy.” ER ’91: Proceed-ings of the Environmental Restoration Conference for the U.S. Department of Energy. U.S. Depart-ment of Energy, Washington, D.C.

Sandman, P. M. 1989. “Hazard Versus Outrage in the Public Perception of Risk.” Effective RiskCommunication. The Role and Responsibility of Government and Nongovernment Organizations,editors V. T. Covello, D. B. McCallum, and M. T. Pavlova, pages 45-49. Plenum Press. New York.

Trust and Credibility Issues

Covello, V. T. (1992), Trust and credibility in risk communication, Health & Environment Digest6(1):1-3

Harris, L. and Associates (1980), Erosion of public confidence in business and other major socialinstitutions, Public Opinion 3:26

Kasperson, R. E., Golding, D., and Tuler, S. (1992), Social distrust as a factor in siting hazardousfacilities and communicating risks, Journal of Social Issues 48(4): 161-187

Lipset SM and Schneider W (1983), The Confidence Gap: Business, Labor, and Government in thePublic Mind, New York, NY: Macmillan.

Renn O and Levine D (1991), Credibility and trust in risk communication, in Kasperson and Stallen(eds.) Communicating Risks to the Public, Dordrecht, the Netherlands: Kluwer Academic Publishers.

Ruckelshaus WD (1984), Risk in a free society, Risk Analysis 4:157-162.

182

Sternthal B, Phillips LW and Dholakia R (1978), The persuasive effect of source credibility: Asituational analysis, Public Opinion Quarterly 42:285-314.

US EPA (1990), Public Knowledge and Perceptions of Chemical Risks in Six Communities: Analy-sis of a Baseline Survey, Washington, D.C.: USGPO.

Non-Verbal Communication

Brehm SS and Brehm J. Psychological Reactance. NY: Academic Press, 1981.

Brownlow S, Zebrowitz LA. Facial appearance, gender, and credibility in television commercials. Jof Nonverbal Behavior, 14(1):51-60, Spr 1990.

Burgoon JK, Birk T and Pfau M. Nonverbal behaviors, persuasion and credibility. Human Commu-nication Research, 17(1):140-169, Fall 1990.

DePaulo PJ. Research on deception in marketing communications: Its relevance to the study ofnonverbal behavior. J of Nonverbal Behavior, 12(4, Pt 2):253-273, Winter 1988.

Ekman P. Telling Lies. NY: WW Norton, 1985.

Hamilton MA, Hunter JE and Burgoon M. An empirical test of an aciomatic model of the relation-ship between language intensity and persuasion. J Language and Social Psych. 9(4):235-255, 1990.

Kotler P. Social Marketing: Strategies for Changing Public Behavior. NY: Macmillan, 1989.

Mehrabian A. Silent Messages. Belmont, CA: Wadsworth, 1971.

Ethical Issues

Bullard, R. D. 1990. Dumping in Dixie: Race, Class, and Environmental Quality. Westview Press,Boulder, Colorado.

Bullard, R. D. 1992. “In Our Backyards: Minority Communities Get Most of the Dumps.” EPAJournal 18(1):12.

Chess, C., P. M. Sandman, and M. R. Greenberg. 1990. Empowering Agencies to Communicateabout Environmental Risk: Suggestions for Overcoming Organizational Barriers. Rutgers Univer-sity, Cook College, Environmental Communication Research Program, New Brunswick, NewJersey.

Covello, V. T., D. B. McCallum, and M. T. Pavlova. 1989. “Principles and Guidelines for Improv-ing Risk Communication.” Effective Risk Communication: The Role and Responsibility of Govern-ment and Nongovernment Organizations, editors V. T. Covello, D. B. McCallum, and M. T.Pavlova, pages 3-16. Plenum Press, New York.

183

Gelobter, M. 1992. “Expanding the Dialogue: Have Minorities Benefited ...? A Forum.” EPAJournal 18(1):32.

Kasperson, R. E. 1986. “Hazardous Waste Facility Siting: Community, Firm, and GovernmentalPerspectives.” Hazards: Technology and Fairness, pages 118-144. National Academy of Engineer-ing/National Academy Press, Washington, D.C.

Kasperson, R. E. 1986. “Six Propositions on Public Participation and Their Relevance for RiskCommunication.” Risk Analysis 6:275-281.

Morgan, M. G., and L. B. Lave. 1990. “Ethical Considerations in Risk Communication Practice andResearch.” Risk Analysis 10(3):355-358.

STC (Society for Technical Communication). 1992. “Code for Communicators.” Technical Com-munication 39(3-A):viii.

Principles of Risk Communication

Arkin, E. B. 1989. “Translation of Risk Information for the Public: Message Development.” Effec-tive Risk Communication: The Role and Responsibility of Government and Nongovernment Organi-zations, editors V. T. Covello, D. B. McCallum, and M. T. Pavlova, pages 127-135. Plenum Press,New York.

Callaghan, J. D. 1989. “Reaching Target Audiences with Risk Information.” Effective Risk Commu-nication: The Role and Responsibility of Government and Nongovernment Organizations, editors V.T. Covello, D. B. McCallum, and M. T. Pavlova, pages 137-142. Plenum Press, New York.

Covello, V. T., and F. W. Allen 1988. Seven Cardinal Rules of Risk Communication. OPAL-87-020, U.S. Environmental Protection Agency, Washington, D.C.

Covello, V. T., P. M. Sandman, and P. Slovic. 1988. Risk Communication, Risk Statistics, and RiskComparisons: A Manual for Plant Managers. Chemical Manufacturers Association, Washington,D.C.

Covello, V. T., D. B. McCallum, and M. T. Pavlova. 1989. “Principles and Guidelines for Improv-ing Risk Communication.” Effective Risk Communication. The Role and Responsibility of Govern-ment and Nongovernment Organizations, editors V. T. Covello, D. B. McCallum, and M. T.Pavlova, pages 3-16. Plenum Press, New York.

Hance, B. J. C. Chess, and P. M. Sandman. 1988. Improving Dialogue with Communities: A RiskCommunication Manual for Government. New Jersey Department of Environmental Protection,Division of Science and Research, Trenton, New Jersey.

Hance, B. J. C. Chess, and P. M. Sandman. 1990. Industry Risk Communication Manual. CRCPress/Lewis Publishers, Boca Raton, Florida.

184

NRC (National Research Council). 1989. Improving Risk Communication National Academy Press.Washington, D.C.

Morgan, G. B. Fischhoff. A. Bostrom, L. Lave, and C. J. Atman. 1992. “Communicating Risk tothe Public.” Environ. Sci. Technol. 26(11):2048-2056.

Roth, E., M. G. Morgan, B. Fischhoff, L. B., Lave, and A. Bostrom. 1990. “What Do We KnowAbout Making Risk Comparisons?” Risk Analysis 10(3):375-392.

Determining Objectives

Kasperson, R. E., and I. Palmlund. 1989. “Evaluating Risk Communications.” Effective Risk Com-munications.” Effective Risk Communication: The Role and Responsibility of Government andNongovernment Organizations, editors V. T. Covello, D. B. McCallum, and M. T. Pavlova, pages143-158. Plenum Press, New York.

Rowan, K. E. 1991. “Goals, Obstacles, and Strategies in Risk Communication: A Problem-SolvingApproach to Improving Communication about Risks.” Journal of Applied Communication ResearchNovember:300-329.

Santos, S. L. 1990. “Developing a Risk Communication Strategy.” Management and OperationsNovember:45-49.

Audience Analysis

Arkin, E. B. 1989. “Translation of Risk Information for the Public: Message Development.” Effec-tive Risk Communication: The Role and Responsibility of Government and Non-government Orga-nizations, editors V. T. Covello, D. B. McCallum, and M. T. Pavlova, pages 127-135. Plenum Press,New York.

Babbie, E. 1973. Survey Research Methods. Wadsworth Publishing Company, Belmont, California.

Callaghan, J. D. 1989. Reaching Target Audiences with Risk Information.” Effective Risk Commu-nication: The Role and Responsibility of Government and Nongovernment Organizations, editors V.T. Covello, D. B. McCallum, and M. T. Pavlova pages 137-142. Plenum Press, New York.

Hodges, M. 1992. “How Scientists See Risk.” Research Horizons, Summer 1992, page 22-24.Georgia Institute of Technology, Atlanta, Georgia.

McDonough, M. H. 1984. “Audience Analysis Techniques.” Supplements to a Guide to Culturaland Environmental Interpretation. U.S. Army Corps of Engineers, Waterways Experiment Station,Vicksburg, Massachusetts.

Pearsall, T. E. 1969. Audience Analysis for Technical Writing. Glencoe Press, Beverly Hills, Cali-fornia.


185

Warren, T. L. 1993. “Three Approaches to Reader Analysis.” Technical Communication 40(1):81-88.

Weinstein, N. D., and P. M. Sandman. 1993. “Some Criteria for Evaluating Risk Messages.” RiskAnalysis 13(1):103-114.

Risk Communication Strategy


Sandman, P. M., D. B. Sachsman, and M. R. Greenberg. 1988. The Environmental News Source:Providing Environmental Risk Information to the Media. New Jersey Institute of Technology,Hazardous Substance Management Research Center, Risk Communication Project, Newark, NewJersey.


Developing a Risk Communication Plan

EPA (U.S. Environmental Protection Agency). 1988. Community Relations in Superfund: A Hand-book. EPA/540/G-88/002, U.S. Environmental Protection Agency, Office of Emergency and Reme-dial Response, Washington, D.C.

Shyette Barnett, B., and S. Pastor. 1989. “Community Assessment: A Planned Approach to Ad-dressing Health and Environmental Concerns.” Superfund ’89: Proceedings of the 10th NationalConference, pages 635-641. Hazardous Materials Control Research Institute, Washington, D.C.

Written Messages

Golding, D., S. Krimsky, and A. Plough. 1992. “The Narrative versus Technical Style in RiskCommunication.” Risk Analysis, 12(2).

Kolin, J. L., and P.C. Kolin. 1985. “Instructions.” Models for Technical Writing. St. Martins Press,New York.

Oral Messages

Nelkin, D. 1987. Selling Science: How the Press Covers Science and Technology. W. H. Freemanand Company, New York.

Kolin, J. L., and P. C. Kolin. 1985. “News Releases.” Models for Technical Writing. St. MartinsPress, New York.


186

Sandman, P. M., D. B. Sachsman, and M. R. Greenberg. 1988. The Environmental News Source:Providing Environmental Risk Information to the Media. New Jersey Institute of Technology,Hazardous Substance Management Research Center, Risk Communication Project, Newark, NewJersey.

Visual Messages

Tufte, E. R. 1983. The Visual Display of Quantitative Information. Graphics Press, Cheshire,Connecticut.

Evaluating Risk Communication Efforts

Desvousges, W. H. 1991. “Integrating Evaluation: A Seven-Step Process.” Evaluation and Effec-tive Risk Communications Workshop Proceedings, editors A. Fisher, M. Pavlova, and V. Covello,pages 119-123. EPA/600/9-90/054, U.S. Environmental Protection Agency, Washington, D.C.

Kasperson, R. E., and I. Palmlund. 1989. “Evaluating Risk Communication.” Effective Risk Com-munication: The Role and Responsibility of Government and Nongovernment Organizations, editorsV. T. Covelo, D. B. McCallum, and M. T. Pavlova, pages 143-158. Plenum Press, New York.

Kline, M., C. Chess, and P. Sandman. 1989. Evaluating Risk Communication Programs: A Cata-log of “Quick and Easy” Feedback Methods. Rutgers University, Cook College, EnvironmentalCommunication Research Program, New Brunswick, New Jersey.


Smith, V. K., W. H. Desvousges. A. Fisher, and F. R. Johnson. 1987. Communicating Radon RiskEffectively: A Mid-Course Evaluation. U.S. Environmental Protection Agency, Office of PolicyAnalysis, Washington, D.C.

Weinstein, N. D., and P. M. Sandman. 1993. “Some Criteria for Evaluating Risk Messages.” RiskAnalysis 13(1):103-114.

187

TUESDAY, MARCH 31 1998

Chemistry and Drift Management: A Biologist’s Perspective

Roger A. Downer & Franklin R. HallThe Ohio State University

Wooster, Ohio

The use of chemistry of one sort or another to protect crops from damage, disease, andcompetition from weeds has been with us for centuries. Records of the use of olive oil extracts forblight control by the Greek philosopher Democrates date from 470 B.C. Vine pests were controlledwith sulfur fumes by Cato in Italy in 200 B.C. The ancient Chinese used biological control in theform of ants to protect trees from insect pests. In this century, pesticide use was not common beforethe 1940’s. However, following the discovery of DDT (dichlorodiphenyltrichloroethane) in 1939,market growth was rapid for the succeeding 20 years but has seen something of a decline since the1970’s. For example, the worldwide crop protection market rose from $580 million in 1960 toapproximately US$ 26400 million in 1990, (Goosey, 1992). Market growth has since declined from10% in the ‘60’s, to 6.7% in the 70’s and 2.7% in the 80’s with a prediction for the’90’s of only 2.3%. Pesticide use in the US currently stands at 1.25 billion lb. active ingredient (AI)/yr. (AENEWSJan. 1997).

Use of pesticides is a proven method of enhancing agricultural production and crop quality.Without pesticides it is estimated that as much as 45 percent of the worlds food supply is lost topests: 30 percent to weeds, pests and diseases before harvest and another 15% between harvest anduse. It is also estimated that losses would increase a further 10% if no pesticides were used at all:specific crop losses would range from zero to 100% (Pimentel et al 1992). A perhaps more severeestimate puts potential crop losses at 70%, reducing global food supply by nearly 50% (Oerke et al1994). World population figures are predicted to increase by 2.8 billion by the year 2025, 95% ofthem in developing countries (FAO, 1995). Can we achieve and sustain our goal of global foodsecurity and improved living standards? If so, what may be the costs?

To many, there is no such thing as a “good chemical pesticide.” However, it should beremembered that the pesticide industry predominately markets thoroughly researched and low-riskchemical technologies that meet governments legal requirements and integrate well with many cropproduction systems (Perrin, 1997). Unfortunately, as a result of unbalanced media reporting and anapparent inability or unwillingness of the industry to defend itself, there is increasing apprehensionon the part of the public with regard to technology advances in agriculture. Examples include theuse of genetically engineered crops leading to general and perhaps overuse use of pesticides resultingin the possibility of food safety issues and run-off from herbicide use in no-till situations. Thesefactors all combine to put pressure on the Ag Chem Industry to review current pesticide use.

Today’s pesticide molecules are becoming increasingly active, complex, and often targetspecific while at the same time being environmentally friendly. Use rates have declined steadilyfrom around 1.5 kg/ha in 1940 to less than 0.5 kg/ha in 1980 (Hall 1991). Use of broad-spectrumproducts is now almost universally discouraged. Increased regulatory demands for more productinformation before registration and subsequent re-registration schemes is helping to remove the oldermore environmentally unacceptable compounds from the market place. Improvements in syntheticdesign and novel formulation also help to decrease the environmental burden and reduce the risk tothe user. With specific reference to formulation technology we also find that certain solvents that arecurrently used in the formulation of pesticides are of great concern for both their toxicity and their

188

safety relative to such factors as low flash points and high vapor pressures. Consequently, legisla-tion is forcing formulation changes by prohibiting the use of solvents with high toxicity (Environ-mental Protection Agency Lists 1 and 2, 40 CFR 154.7), (Narayanan and Chaudhuri 1992). As aresult of this need to improve the safety of pesticides, the discovery, development, and registration ofa new pesticide now requires that a manufacturer screen up to 30,000 new molecules and spendUS$40-$80 million before a new chemical reaches the market (Goosey 1992). To offset these costs,manufacturers, researchers, and end-users are looking toward improvements in existing formulationand adjuvant technology as well as improved strategies for pest management.

Presentation Objectives1. Review the often-conflicting goals of maximum efficacy and environmental safety driving

formulation research and adjuvant use.2. Demonstrate the impact that formulation and adjuvant technology have on pesticide dose transfer

and the efficiency of use of pesticides,

Formulation DesignThe concept of designing agrochemical formulations for optimal biological activity is rela-

tively new (Stock, 1996) and is a direct result of the pressures mentioned above. In order to designformulations for optimal expression of biological activity, certain criteria must be met and the designprocess should be an integrated research process involving several other disciplines including appli-cation specialists, chemists, engineers, and biologists. There are two main factors that must beaddressed during formulation design. The first of these relates to pesticide mode of action. Thesecond relates to the physico-chemical properties of the AI. Knowledge of these two factors iscritical and will direct the design of the system used for the field-ready formulation. Whatever theoutcome of the formulators efforts, it is likely that the end product will have an impact on drift sinceit is likely that the mere inclusion of the formulation in the spray tank will affect perhaps the mostcritical aspect of dose transfer i.e., atomization. That is not to say that this impact will be negative.Indeed it is well documented that particulates will “control” the atomization process, as will manyother chemical groups (e.g., Butler Ellis et al, 1997). That being so, formulating drift managementinto a field-ready product is obviously possible although in this authors experience, that seems to berarely done in the US. It is more common to add tank mixed drift management adjuvants, as weshall demonstrate later. Formulation technology is more often directed at optimizing pesticideperformance once in contact with the target plant and rightly so. Drift management typically reliesupon reducing the quantity of small drift-prone droplets within the spray cloud. This is usuallyaccomplished by using polymeric spray thickeners to increase the visco-elasticity of the mixture andthereby control the production of fine droplets in the spray cloud. This process certainly reduces thedrift potential but ultimately results in reduced droplet density and a spray cloud prone to reflectionfrom hard to wet surfaces. For some crop protection materials this results in poor coverage andconsequently poor pest or weed control. The formulators aim, however is to provide better sprayqualities with better adhesion, better spreading on and wetting of surfaces and better delivery to thetarget. Already we find we have a conflict of interest between the goals of maximizing efficacy vsthat of minimizing environmental contamination.

Use of AdjuvantsThere are many factors that can be modified by formulation to manipulate biological re-

sponse or environmental impact. The significance of these factors and freedom to vary them dependupon the properties of the pesticide and its intended site of action. These manipulations can befurther enhanced by use of tank-mixed adjuvants. The decision to go with a complete formulation or

189

with one to which tank-mixed adjuvants may be beneficially added depends in part on the marketinto which it is introduced. This in turn may be determined by the regulatory requirements for thatmarket. For example, use of tank-mix adjuvants in the USA is much higher compared to Europe. In1992 adjuvant use in the USA amounted to 149,000 tonnes as compared to 20,300 tonnes in WesternEurope (Uttley, 1995). There are other practical constraints to building a one-pack optimized formu-lation such as, compatibility and the space available within the formulation for incorporation of anadjuvant. Whatever the decision, as we shall see, it is the properties of the final tank-mix that willgovern the efficiency with which the formulation is delivered to the target area. Judicious andthoughtful use of adjuvants make them a powerful and essential management tool for pesticideapplicators. The key to successful adjuvant use is in making the correct choice for the job in hand,do not use an adjuvant if the product label says do not and use the right one if the label says to useone. The literature abounds with reports of how well this adjuvant works with this or that herbicidebut it is rare to find an integrated study on adjuvant use where all aspects of performance are consid-ered. An adjuvant such as an organosilicone may work well as a spreader but is unlikely to workwell as a drift management adjuvant since it is designed to lower surface tension a property whichwill tend to result in more fine droplets in the spray cloud.

The number of adjuvants available for herbicide applicators alone has increased dramaticallyover the last few years. In 1992 there were 76 available from 22 companies, two years later therewere 163 available from 27 companies and by 1996 there were 330 available from 33 companies.These adjuvants can be classified by several methods, but probably the most common classificationis as Wetters, Spreaders, Stickers/Extenders, drift management adjuvants, Oils, and Penetrants. Allthese adjuvant types will affect pesticide behavior to some degree or other but for the purposes ofthis document the main adjuvant class of interest is, of course, the drift management adjuvant.

Drift management adjuvants are principally polyvinyl polymers of the polyacrylamide type,polyacrylamide/polysaccharide mixtures, polyethylene oxides, invert emulsions and invert suspen-sions and some polymeric starches. Most function as spray thickeners by raising the viscosity of thespray mixture in which they are present. A few others have a mode of action that is not well under-stood but may be associated with reduced evaporation or an internal association with the formulationwhich generates charged AI containing particles which are large enough not to drift.

We must remember, however, that the ultimate goal of pesticide use in food and fiber cropsis to maximize yield by control or management of weeds, pests, or diseases. But good crop protec-tion is dependent upon optimal delivery of a biologically effective dose to a target with maximumsafety and economy (Hislop, 1987). As we hope to show this is not an easy task.

Pesticide Application Dynamics.The pesticide delivery process, hereinafter referred to as pesticide dose transfer, is generally

regarded as highly inefficient. For insecticides typically < 1% reaches the target organism (Graham-Bryce, 1983), and uptake efficiency of most pesticides is considered to be around 20%. Much of thewasted material contributes to environmental and/or operator contamination and also represents asignificant material loss to the end user.

Pesticide dose transfer, whether from the ground or from the air, involves a series of inter-linked events including atomization, transport, impaction and deposit formation, acquisition by thetarget and consequent biological effect Figure 1. These events take the active ingredient from thebulk spray tank to the site of action, which is often within the target organism. There are also eventsrelevant to pesticide formulation chemistry and adjuvant use that have an impact on delivery prior tothe spray nozzle, but for now let us assume that complete mixing of the formulation and any addedadjuvants with the bulk carrier liquid (water) has occurred.

190

Size Class (µm)

Perc

ent b

y vo

lum

e

0

5

10

15

20

25

30

35

40

< 100< 150

100-200200-300

300-400400-500

500-600600-700

>700

WATERNALCOTROLFREEWAYROUNDUP

Figure 2: Droplet frequency distributions (percent by volume) fowater, two adjuvants, and Roundup®

AtomizationThe processes associated with the application of a pesticide to foliar targets have been di-

vided into a number of distinct phases (Figure 1). The first of these is atomization, which may beregarded as the most important of all the phases since the resultant drop size and velocity distribu-tions have a significant impact on all the following stages. For example, drift management adjuvantsthat are targeted at the atomization process are typically polymers and work by virtue of their viscos-ity-modifying behavior. Increases in viscosity of the spray mixture as well as elastic propertiesgenerated by the polymers have the effect of producing spray clouds with larger droplets and re-duced numbers and volume of fine droplets (Figure 2).

Atomization

Transportto Target

Impaction

DepositFormation

Movementin/on Plant

BiologicalEffect

driftlosses

evaporation

reflection

retentionspreading

drying

losses

losses

redistribution,weathering

uptake,activity

physical properties,operatingconditions

atmosphericand operatingconditions

spray andsurfaceproperties

atmosphericconditions

depositand surfaceproperties

atmosphericconditions

Figure 1: Dynamics of the Dose transfer Process

191

However, these sprays also tend to be poorly distributed across the swath with excessiveoverdosing in some areas and underdosing in others (Downer et al 1994) (Figure 3). This is gener-ally undesirable, although when using recommended label rates for herbicides, the rate is highenough to deliver an adequate dose and thus overcome these problems. At reduced rates, under “asneeded” tactics, reduced risk policies, or IPM strategies however, it is likely that greater variability

in biological results will be observed.Other materials such as theorganosilicones, for example, are used aspenetrants, spreaders, and wetters. In thiscapacity they typically cause a significantreduction in surface tension of the spraymixture which is, at least partly, respon-sible for drop size distributions which havegreater volume of the spray in small(<200µm) droplets (Figure 2). Thesesmall drop sizes are, of course, more driftprone and thus greater attention must bepaid to application parameters such ashardware and operating conditions whenusing these adjuvant types.

Transport to the target.

There are many factors which affect thetransport of a pesticide spray cloud fromnozzle to target foliage, including formu-lation components, atomization specifics,and environmental factors. In recent years,use of drift reducing agents and anti-evaporants has received increasing atten-tion, particularly with regard to aerial,controlled droplet application, and airblastspraying. Figure 4 shows the change inrate of static evaporation between water

The reasons for this attention are related to perceived benefits in terms of better targeting and subse-quent improved environmental stewardship. However, the effects of using an anti-evaporant maybe both negative and positive. Recent work has shown that the incorporation of an anti-evaporantinto a formulation of permethrin not only reduced in-flight evaporation but also decreased dropletretention and increased the bioavailability of the A.I. (Thacker and Hall 1992). Other test resultsillustrate that the presence of certain formulation components, for example an anti-evaporant, masksirritant effects that can occur with some formulations containing permethrin (Hall and Thacker1993). This will allow the pests, in this case spider mites, to come into contact with a toxin that mayotherwise be avoided.

Figure 3: Swath distribution patterns for a herbicide with and withoutpolymeric adjuvants (DR = AgRHÔ DR-2000, N = Nalcotrol).

Distance from center nozzle (cm)

Spr

ay o

utpu

t (L/

ha)

0

50

100

150

200

250

300

350

-50 -25 0 25 50 -50 -25 0 25 50 -50 -25 0 25 50

Herbicide aloneCV = 8%

Herb. + DRCV = 36%

Herb. + NCV = 42%

Figure 4: Evaporation rate over time for water and a drift manage-ment adjuvant and water containing 38-F, a polymeric adjuvant.

192

2

3

4

5

6

7

8

0.5 1.5 2.5 3.5 4.5

Log dose (ng a.i. dish-1)

Prob

it

D325TF2465AmbushPounce

Figure 5: Comparison of permethrin formulations showingdifferences in efficacy due to changes in formulation. After

Impaction and Deposit Formation

Adjuvants, particularly surfactants that reduce surface tension, also give rise to spray cloudswith small droplets. Reduced droplet reflection from leaf surfaces is well correlated with smalldroplets and low dynamic surface tension. This is because, liquid physico-chemical properties,droplet momentum and trajectory, and leaf surface structure affect impaction, retention, and subse-quent deposit formation. However, it is not always true to say that a reduction in surface tension of aformulation will invariably enhance retention and herbicidal activity (Hull et al 1982). Indeed, insome cases an increase in retention will not result in increased biological activity of any pesticide.The problem may arise that while a change in physico-chemical properties of a tank mix may resultin increased retention for one species it may result in reduced retention for another and thus alter theselectivity of the herbicide (Jansen et al 1961).

Many adjuvants are considered to improve pest control because they increase droplet spread,and this is certainly true for protectant fungicides. However, this might not always be the case:Increased spread will also lead to a decrease in the dose of A.I. per unit area and, in the case ofinsecticides, the proportion transferred to an insect per encounter with a deposit may actually de-crease (Ford et al 1987). As we have already mentioned, increased spread may lead to increasedevaporation and also increased run-off potential. On the other hand, spreaders used with herbicidescan be extremely beneficial as a result of stomatal infiltration although this is only thought to occurat surface tensions of < 20 dynes/cm, also the benefit of stomatal infiltration per se has not yet beendocumented. However, the real advantages of these materials are their ability to give superiorwetting, greater penetration for systemic materials, combined with the potential for increased raintenacity and reduced photodegradation. There are, of course, other problems associated with spread-ers other than organosilicones. For instance, an increase in spread exposes a greater surface areafrom which evaporation can take place, this is particularly important if applications are made underconditions with low relative humidity.

Dose Acquisition and Biological Response.

The acquisition of A.I. by a tar-get from a spray deposit is a complexprocess. The mere act of causing someportion of the spray cloud to deposit ona plant, insect or fungus is rarely theend of the story. Many pesticides andherbicides require movement of thetoxin into the target organism. The ex-act manner in which a spray deposit ad-heres to and penetrates a leaf surfaceor transfers to and penetrates an insectpest is a function of both the chemicaland physical nature of the spray itself.This complex relationship can be mark-edly altered by addition of adjuvantsto either the formulation applied or thetank mixture.

193

In tests with a permethrin formulation containing an anti-evaporant, two of four formulationstested gave rise to deposits that demonstrated increased spread. However, the two formulations thatspread the least were up to 15 times more effective than the others, due to the increased probabilityof transferring a lethal dose to the insects upon contact with the deposit (Thacker et al 1992) (Figure 5).

Surface deposits of glyphosate have been shown to vary with the formulation used. Theenhancement of the herbicidal effects, brought about by use of surfactants, is reported to extendbeyond that attributable to increased contact area between deposit and plant surface (MacIsaac et al1991). To facilitate uptake, herbicides need to remain in solution and it is thought that the hygro-scopic properties of some surfactants (including drift management adjuvants may reduce crystalformation and thus maintain some of the active ingredient in solution longer. This effect may beobserved with organosilicone surfactants where rapid stomatal infiltration allows some of the activeingredient to remain in solution in the humid conditions within the substomatal cavity, facilitatingabsorption and translocation (Smith 1993).

While use of adjuvants with herbicides can clearly be demonstrated to be beneficial, in manycases care must be taken not to over-use surfactants with the intention of increasing speed of action.Too high a concentration of surfactant may cause localized damage to the plant tissue that willreduce uptake and translocation. Some adjuvants can elicit strong responses in the target plantwithout the inclusion of a herbicide. This is due to the adjuvant’s ability to dissolve the lipid compo-nent of the cell membrane, which alters both permeability and integrity.

Summary and Conclusions

The beneficial effects of adjuvants, whether formulated or tank mixed, can easily be demon-strated. Use of adjuvants can sometimes allow spray operations to take place in conditions that areperhaps not ideal for application. For instance, use of drift control agents, while they should not beregarded as the first line of defense against off target movement of pesticide, can widen the windowof opportunity for application and allow spraying operations to be carried out in less favorable windconditions. Oils can reduce evaporation and improve transfer and distribution of insecticide to insectpests. Many penetrants have been shown to increase rain tenacity, reduce evaporation, reducephotodegradation and in some cases increase the speed of action of pesticides. Spreaders and wettersreduce the surface tension of the tank mix facilitating coverage of waxy surfaces and improvingpenetration of certain weed species via stomatal infiltration. Stickers and extenders can increasepersistence of certain pesticides and reduce wash-off caused by rain or irrigation water.The effect of adjuvants upon the dose transfer process is complex, and involves many factors andtheir interactions. For example, the addition of a drift control agent will reduce the uniformity of thespray distribution, causing localized over- and underdosing. Adjuvants that demonstrate excellentspreading characteristics may also evaporate too quickly, or they may increase drift potential bymaking the spray finer. Many of these effects are unpredictable, and clearly some of them arecounterproductive to the goals of sound pesticide application. Adjuvants must therefore be carefullychosen with full regard for implications at all phases of the dose transfer process. Stricter registra-tion guidelines that require data on these phenomena would benefit producers by allowing moreinformed adjuvant choice decisions, a worthy goal if continued regulatory pressures are placed onthe pesticide user to reduce risks – to mammalian and environmental systems..

194

References

Butler Ellis,MC; Tuck,CR; Miller,PCH (1997): The effect of some adjuvants on sprays produced byagricultural flat fan nozzles. Crop Protection 16(1), 41-50.

Downer,RA; Wolf,TM; Chapple,AC; Hall,FR; Hazen,JL (1995): Characterizing the Impact of DriftManagement Adjuvants on the Dose Transfer Process. Paper presented at the Fourth InternationalSymposium on Adjuvants for Agrochemicals, Melbourne, Australia, 3-6 October 1995, pp. 138-143.

Ford,MG; Salt,DW (1987): Behaviour of Insecticide Deposits and their Transfer from Plant to InsectSurfaces. In: Pesticides on Plant Surfaces. (Ed: Cottrell,HJ) John Wiley & Sons, New York, 26-81.

Goosey,MW (1992): Towards the Rational Design of Crop Protection Agents. Pestic. Sci. 34, 313-320.

Graham-Bryce, I. J., In: Pesticide Chemistry: Human Welfare and the Environment, Vol 1, ed. J.Miyamoto and P. C. Kearney. Pergamon Press, Oxford , UK., 1983

Hall,FR; Thacker,JRM (1993): Laboratory Studies on Effects of Three Permethrin Formulations onMortality, Fecundity, Feeding, and Repellency of the Two-spotted Spider Mite (Acari:Tetranychidae). Journal of Economic Entomology 86, 537-543.

Hislop,EC (1987): Can we define and achieve optimum pesticide deposits? Aspects of AppliedBiology 14, 153-172.

Hull, H. M., Davis, D. G., and Stolzenberg, G. E., (1982) In: Adjuvants for Herbicides WSSAMonograph, WSSA Champaign IL 61820

Jansen, L. L., Gentner, W. A., and Shaw, W. C., 1961. Weeds 9: 381-405.

MacIsaac,SA; Paul,RN; Devine,MD (1991): A Scanning Electron Microscope Study of GlyphosateDeposits in Relation to Foliar Uptake. Pestic. Sci. 31, 53-64.

Narayanan,KS; Chaudhuri,RK (1992): N-alkyl Pyrrolidone Requirement for Stable Water-basedMicroemulsions. In: Pesticide Formulations and Application Systems: 12th Volume, ASTM STP1146. (Eds: Devisetty,BN; Chasin,DG; Berger,PD) American Society for Testing and Materials,Philadelphia, 85-104.

Oerke, E.-C., Dehne, H.-W., Schonbeck, F. and Weber, A. (1994) Crop Production and Crop Protec-tion – Estimated losses in Major Food and Cash Crops. Elsevier, Amsterdam.

Perrin,RM (1997): Crop protection: taking stock for the new millennium. Crop Protection 16(5),449-456.

Pimentel,D; Acquay,H; Biltonen,M; Rice,P; Silva,M; Nelson,J; Lipner,V; Giordano,S; Horowitz,A;D’Amore,M (1992): Environmental and Economic Costs of Pesticide Use. BioScience 42(10), 750-760.

195

Smith, A., In Adjuvants in Crop Protection, AGROW Report # (DS 86) 1993.

Stock,D (1996): Achieving Optimal Biological Activity from Crop Protection Formulations: Designor Chance? Brighton Crop Protection Conference - Pests and Diseases 2, 791-806.

Thacker,JRM; Hall,FR (1992): The Benefits of an Anti-evaporant in Pesticide Applications. In:Pesticide Formulations and Application Systems: 12th Volume, ASTM STP 1146. (Eds:Devisetty,BN; Chasin,DG; Berger,PD) American Society for Testing and Materials, Philadelphia,303-318.

Thacker,JRM; Hall,FR; Downer,RA (1992): The Interactions between Routes of Exposure andPhysicochemical Properties of Four Water-Dilutable Permethrin Formulations in Relation to TheirActivities against Trichoplusia ni (Hubner). Pestic. Sci. 36(3), 239-246.

Uttley,MJ (1995): Adjuvant use in the USA and Western Europe. Proceedings of the Fourth Interna-tional Symposium on Adjuvants for Agrochemicals. Ed Gaskin R.E. NZ FRI Bulletin No. 193, 356-361.

196

Changing Pilot Behavior

Niels C. AndrewsHelicopter Ag, Inc.Salinas, California

I would like to thank the Organizing Committee for the opportunity to be involved with this impor-tant conference.

My primary business is Helicopter aerial application in the Salinas Valley of California, the “Na-tions Salad Bowl”. In the Salinas Valley we raise 84 different fresh vegetable crops with 2.2 billiondollars in annual sales, our average field size is only 12 acres. The Salinas Valley averages about tenmiles wide and 80 miles long. Within that area reside over 200,000 people. Pesticide drift has hadmajor attention in our area for some time.

When I was first asked to speak on “Changing Pilot Behavior”, my thoughts were, do they mean,how Pilot Behavior is changing, or how do we change Pilot Behavior? I concluded that there was aneed to discuss both aspects of Pilot Behavior.

I am here to say that there are a growing number Professional Aerial Application Pilots, who areenvironmentally conscious, aware of the issues, and want to do the job right. This I would say is theattitude of an increasing majority of Ag pilots. There also exist pilots and operators who are in needof education in drift management.

Ag Pilots of today are a diverse group, their backgrounds can range from being a military trainedpilot, to as the majority, learning to fly at the local airport. Their education can range from highschool to advanced college degrees. The average age of Ag Pilots is just over fifty. Most are inde-pendent small businessmen, who own, operate and fly their own aircraft. They are superb pilots whoare very adept at instantaneous decision making.

The Mission of aerial application remains today as it has been since the beginning. It is a tool for usein the production of food and fiber. One of the principle attributes of Ag aircraft, is the ability toapply crop protection products, fertilizer and seed, to large or inaccessible areas in a short amount oftime. This is vital in the utilization of an Integrated Pest Management Strategy.

To feed, cloth and house an increasing World population, producers need the services of aerialapplication. This tool must be properly managed and operated within prescribed parameters. Allmethods of application should be considered and the proper method selected. You don’t use a rollerwhen painting by the numbers.

Aerial Spray Drift Management is not a technology issue. We have the technology to properly applyAg products. Every spray drift incident can be traced back to the wrong decision being made. Notjust by the Pilot or Operator, it often times involves the grower, the advisor, or maybe even theregulator.

Several years ago the National Agricultural Aviation Research and Education Foundation(NAAREF) began to examine Ag aircraft accidents, and determined that when problems occur, an

197

aircraft accident or a drift incident, the cause was rarely a hardware or mechanical issue. Mostproblems could be traced to Human Performance Error or HPE.

Most prior safety and training programs have been based on technology. Never before had a programbeen developed based on decision making and the avoidance of human performance error. Thequestion arose, can decision making be taught? Can human behavior be changed? We soon found theanswer to both questions was yes.

A discipline referred to as Aeronautical Decision Making or ADM has been taught to MilitaryAviators as well as Airline Pilots for the last twenty years. All of you who were a passenger on anairliner to get here, were the benefactor of ADM training. The study of Human Performance Errorhas led to exciting programs for many disciplines where decision making is critical.

In all situations where Human Performance Error has been addressed and a program implemented,there have been significant reductions in accidents and incidents. Every discipline.

So how can this be implemented with Ag Aviators? If you analyze an Ag aircraft accident or driftincident, you see distinct similarities in the events that conclude in an accident or incident occurring.Does anyone believe that a pilot wakes up and says “Boy it looks like a great day to drift, or a goodday to wreck a plane!

The analyses of these actions, the pressures, the attitudes, the personality traits of an individual, areall considered in the study of Human Performance Error. The end result is creating first an aware-ness, and then the tools to recognize and work through a decision making process, to insure a posi-tive outcome.

This video you are about to see is the first in the series of Aeronautical Decision for Ag Pilots as partof the PAASS program. Here we are creating an awareness of the drift situation, and developing thedesire to change.

The Professional Aerial Applicators Support System is being developed by a Coalition of Applica-tors, Regulators, Manufacturers, Producers, everyone involved in the Aerial Application process. Allof you who are involved with spray drift management have a role to play in the further developmentand implementation of the PAASS program.

VIDEO (22 minutes) “Drifting to Extinction, Or?”

Now you have seen the first work in the process of changing pilot behavior. This is only the begin-ning. By the time we have full implementation of this program, the PAASS trained pilot will be oneof the most skilled, trained, and committed professional pesticide applicators in the world.

True Drift Management requires more than proper action by a pilot. Drift Management takes theinvolvement of the producers, regulators, applicators and the Public at large. Everyone involved inthe application process.

The theme of this Conference Building Better Applicators … One Neighbor at a Time, defines theevolution of applicators in the Salinas Valley, as well as the future for aerial application.

198

Just over fifteen years ago we began an evolution in the Salinas Valley, and not by choice. I believethere are lessons to be learned from what happened in this area.

The Salinas Valley as well as being the major vegetable producing area in the United States, hasbecome a bedroom community for Silicon Valley. Crop values of fifteen to twenty-five thousanddollars per acre are not uncommon. Farm ground rarely changes ownership, some that recently didsell, went for one hundred thousand dollars per acre.

The nature of vegetable farming is such that it requires intensive hand labor and time sensitivecultural practices. This involves large crews to have one hundred people in a 12 acre field is notuncommon. Drift is not only a concern from a worker safety aspect, which cannot be overstated.When 100 farmworkers go to the hospital it will cost one thousand dollars per worker to find outthey were not exposed. One hundred thousand dollars, not including attorney fees.

Unwanted and illegal residue from spray drift is also a major concern. Almost all fields are sampledand tested for residue prior to harvest. If a crop were to reach say the east coast with an illegalpesticide residue, it would be dumped. At that point you not only have the loss of the produce, butshipping and damage to the reputation of a label.

Aside from the intensity of production agriculture in the Salinas Valley, many of the fields we sprayare surrounded by highways, houses , and schools. Not only are we working in close proximity to anurban environment, we have walkers joggers, and bike riders as well as curious on lookers andchildren to be concerned with.

With all these challenges, we have very few problems. This is related directly to Pilot Behavior. Notall the Pilots who were flying in Salinas fifteen years ago, are flying there today. Only those of uswho are left were willing to change.

Many of the problems that have been experienced in the Salinas Valley are just reaching the rest ofCalifornia and the Nation. We can learn from the Salinas experience and facilitate a more timelychange in operating practices in other areas.

It is my belief that drift management begins before the crop is planted. Crops that by their naturerequire high utilization of aerial application should not be planted in a sensitive area. Crops that havepesticide conflicts should not be planted adjacent to one another. Concern and awareness of driftissues must to go beyond just the pilot.

The key elements in changing pilot behavior are education and communication. We must be proac-tive to properly manage spray drift. Growers, applicators, regulators, all involved with applicationeither air or ground need to be made aware and educated about spray drift management.

Communication must extend beyond the grower and the applicator. Regulators, applicators, andgrowers should establish the parameters under which applications will be made in sensitive areas.These parameters might include time of day, wind conditions, or using less odiferous or less toxiccompounds, or buffer zones. It may be prudent to have an individual on the ground with radiocontact with the pilot, or a in problem areas have a regulator present. And some times it will beprudent not to do the job by air, or even ground.

199

Communication should then continue with anyone concerned in the local community. I have learnedby experience that many people who are concerned about an application, appreciate the fact that weacknowledge their concerns. Many times this alone will diffuse an issue. We call quite a few peopleprior to an application being made and many of our growers do the same. It works.

If I were a regulator, anytime a incident occurred, no matter how benign, I would summon allparties, grower, advisor, and applicator, etc.. I would sit them down at a table and say “How will weprevent this from occurring again.”

I have tried to share how we have approached the changes required for production in a highly inten-sive food growing area, that has a large, well educated population, and has extremely sensitiveenvironmental considerations. A change in attitudes and practices has made it possible.

In summary, the key to changing Pilot Behavior, is quite simple. Awareness, Education, and Com-munication. We, the PAASS Coalition, have started this endeavor. We need each and everyone ofyou involved. The World population is increasing, as arable land is decreasing. Producers of Foodand Fiber will need every tool possible to meet this demand. Let us all work together to make surethat proper drift management is a cornerstone of any application made. Let us pursue a path ofeducation, not regulation.

Society ask us in the application business, but one thing. That when we do our jobs, we do it right.Should we expect anything less of the total community.

200

Summary of Research in Ohio including the Laboratory forPest Control Application Technology (LPCAT)

REVIEW OF PESTICIDE APPLICATION RESEARCH IN OHIO

Robert D. Fox, USDA- Agricultural Research Service (ARS), Wooster, Ohio, Frank R. Hall, OhioAgricultural Research and Development Center/The Ohio State University (OARDC/OSU),Wooster, Ohio; H. Erdal Ozkan, The Ohio State University, Roger A. Downer, Richard C. Derksen,Charles R. Krause, Michael G. Klein, and Ross D. Brazee, USDA-ARS, ATRU, Wooster, Ohio.

ABSTRACT

The major effort on application technology research in Ohio is conducted in three research units.All authors are associated with the Laboratory for Pest Control Application Technology (LPCAT) withat least adjunct appointments, and work cooperatively on many projects. For discussion purposes,projects will be divided into three groups, based on the major source of funding. The groups are:LPCAT, FABE Department, and USDA-ARS, ATRU. Research projects now active and/or active inthe recent past are discussed. Approximately 30 research projects are summarized and publishedreferences listed.

INTRODUCTION

The most important element in any research program is the people involved. Therefore we beginby listing scientists associated with each major research team.

Laboratory for Pest Control Application Technology (LPCAT)Frank R. Hall, Head of LPCAT and Professor, Roger A. Downer, Research Associate, Timothy A. Ebert,Research Associate, and Venkat Pedibhotla, Research Associate, Dept. of Entomology, OARDC/OSU,Wooster, OH

Food, Agricultural, and Biological Engineering (FABE), The Ohio State University, Columbus,OHH. Erdal Ozkan, Professor and Tim Stombaugh, Assistant Professor.

USDA-ARS Application Technology Research Unit (ATRU), located at OARDC, Wooster, OH.Ross D. Brazee, Research Leader, Robert D. Fox, Agricultural Engineer, Richard C. Derksen,Agricultural Engineer, Charles A. Krause, Plant Pathologist, and Michael Klein, Entomologist.

The Laboratory for Pest Control Application Technology is an interdisciplinary researchprogram established in 1981 by OSU/OARDC. LPCAT has 18 faculty members representing fivedisciplines, agronomy (including weed science), agricultural engineering, entomology, horticulture andplant pathology. LPCAT is a unique program that integrates and links biologists and engineers in aneffort designed to advance the application process for delivery of pest control agents.

An active collaboration exists between LPCAT and ATRU, which is also located at the WoosterCampus. The LPCAT program includes sharing of techniques and equipment among cooperators and

201

active communication with research partners in industry, academic, and government research institutesin problem solving, development engineering, and advanced computer modeling of spray particledelivery - all within the diverse area of application technology. Of special interest is the optimizationof the newer “biological” pesticides in both formulation and delivery to insure an efficient exposure anddose-transfer to pest organisms. LPCAT currently has research links with the US Forest Service, theUSDA-Natural Resources Conservation Service, and the US Environmental Protection Agency.

Current LPCAT research efforts include improving bioavailability for improved toxin effect,effect of adjuvants and formulations on droplet size spectra of spray delivery pattern, retention, andherbicide efficacy, other factors effecting retention of sprays on plants, safety issues of agriculturalspraying, modelling of factors effecting pesticide efficacy, and development of bioassays measuringeffects of deposit quality.

The FABE research program has included studies of shield effects on improved deposition andreduced drift from boom spraying, mixing of dry material in sprayer tanks, effect of worn nozzles ondroplet size spectra and spray pattern, in-line injection of pesticides into sprayer booms, and with theaddition of a new faculty member, a beginning project on precision application of sprays. This programhas also included many research projects that were conducted in close cooperation with the ATRU.

The ATRU has a long history of research on application problems, beginning with the corn borerproblems in the 1930’s. Recent research has included studies of air-assisted spraying of orchard andnursery crops, including drift studies, on droplet impaction/reflection from plant surfaces, applicationto vegetable crops, spray dispersion in turbulent flow, methods of measuring spray deposition anddistribution on plants, and improved application systems and methods.

SUMMARY OF RESEARCH PROJECTS

LPCAT PROJECTS

BioavailabilityThe research focus is on the interaction of application and biological effect. This includes the

process whereby an applied toxin in encountered by the target organism, transferred to the target, arrivesat the active sight, and produces a biological result. Some parts of this process are unique to individualcrop protection agents (e.g. herbicides, insecticides) while other aspects are more universal. Forpesticides which are sprayed, the spray must impact and be retained by the target surface (plant or soil).The retained pesticide must be encountered by the target organism. Contact is through movement andfeeding for insects. For soil applied herbicides contact is through plant growth. Uptake of pesticide isthrough a series of events which are affected by plant and insect cuticular microstructure, pesticideformulation and adjuvants, target metabolism, application method, and behavior. Reliable informationon the effects of these variables does not exist, and there is no general body of theory to aid in predictingtheir effects. As a result many of the questions asked in scientific articles 50 years ago are the same onesbeing asked today. Advances in other fields (mathematics, computer science, chemistry, etc.) continueto provide solutions to intractable problems in understanding this complex process which isfundamental to understanding and manipulating bioavailability. LPCAT as a multidisciplinary team hasplayed a key role in applying these innovations to understanding this process. This work has recentlybeen facilitated through a three year EPA grant for examining the dose transfer process in biopesticides.References: Hall (1991c), Hall et al. (1996a,b) Hall (1997a), Hall (1997), Wolf et al. (1997)

202

Deposit structure and efficacyThis project has developed the use of mixture models for examining the relationship between

deposit structure (deposit size, deposit number and a.i. per deposit) and biological effect. These effortshave included the development of bioassays (cabbage looper on insecticide treated cabbage, andglyphosate treated velvetleaf), and the development of a computer simulation. The computer modelallows rapid evaluation of a large number of “experiments” while the bioassays provide a biologicalfoundation. The Pesticide Dose Simulator (PDS) model can be used to explore the effects of depositstructure on efficacy. Mixture design models have led to several non-intuitive insights into the dosetransfer process which clear up several inconsistencies in the literature - such as smaller dropletsproviding better efficacy in the lab, but CDA sprayers (which produce smaller droplets) requiringsimilar application rates in the field. Basically: 1) the chance of an insect dying from a pesticideapplication is never less than the probability of contacting the toxin; 2) uniform deposit structures resultin lower insecticide efficacy for mobile chewing insects because they do not acquire a large enough doserapidly enough for the toxin to overcome insect growth. The former has promoted the notion thatuniform applications are “good” while the latter has forced increased application rates to overcome thedisadvantage of a uniform application. References: Adams and Hall (1990), Royalty et al. (1990),Adams et al. (1990b,1992), Thacker and Hall (1991), Thacker et al. (1992), Cooper and Hall (1993),Hall et al. (1993b), Head et al. (1995), Downer et al. (1997), Hoy et al. (1998)

Spray Atomization and PatternationThe Aerometrics Phase Doppler Particle Analyzer is being used to obtain droplet size spectra

data of pesticide and additives. An Image Analyzer (IA) is used to size pesticide deposits on targetsurfaces, e.g. water sensitive paper. Water sensitive spray cards which capture droplets and allow forsize measurements by the IA are extensively used in the field. A unique spray simulation lab is used tomonitor spray patterns and >capture efficiencies of various plant canopies. In the past four years,atomization studies have included: effect of drift retardants on droplet spectra; effect of shearingpolymers on spectra; effect of surfactants on spectra using several nozzle types; effect of adjuvants onspectra of commercial pesticide formulations in combination with several adjuvants; factors affectingspectra when spraying Bt; effect of Bivert on spectra; effect of temperature on spectra for formulations,spectra of rainfall simulator, etc. References: Chapple et al. (1992,1993,1995), Downer et al.(1993,1995)

Drift and TargetingPesticide drift studies have traditionally used a variety of collectors. Associated protocols on

drift and eco-toxicological effects are being developed in conjunction with orchard drift experimentswith collaborators in USDA. A wind tunnel capture efficiency model is being used to develop dropletcapture efficiency data on target (plant) and non-target species (windbreaks). References: Downer et al.(1996) ,Hall and Fox (1996), Reed et al. (1993)

Worker Exposure StudiesHealth risks to pesticide applicators are being scrutinized more closely than ever before.

Although the available data from epidemiological studies concerning pesticide use and certainassociated disorders are practically non-existent, federal and state agencies are mandating this researchbe initiated Current worker exposure studies revolve around (1) a US-EPA grant to LPCAT onvalidating passive dosimeters, and (2) a NIOSH grant on “Risks to Farm Families” to OSU’sDepartment of Preventive Medicine, with LPCAT as principle collaborator on the chemical exposurerisk phase. Numerous grant inquiries are underway involving neuro-behavioral responses of workers,neural network modelling of toxins and the PI’s involvement in developing an American Chemical

203

Society symposium on pesticide safety (in ’97). Pesticide risk mitigation related to mixtures ofpesticides. Insecticides, herbicides, fungicides, adjuvants, and fertilizers may be combined in a singlespray application. Testing individual pesticides is not relevant to human health risk assessment becausepesticides are not encountered as isolated compounds. References: Reed et al. (1990b), Kirchner et al.(1996a,b), Wolf et al. (1997)

Pesticide Risk Benefit AnalysesA pesticide cost-benefit assessment model was delivered to all US State Pesticide Coordinators

in 1995. Analyzing risks and benefits in a useful assessment/prediction scheme will require additionalinformation on actual environmental hazards which remains a major effort at LPCAT. Pesticide policyissues (PI focus) are critical if pest control agents are to continue as effective tools of world agriculture.References: Hall and Lemon (1990), Lemon et al. (1992), Hall (1996)

ModellingThe LPCAT pesticide dose simulator (PDS) model was developed to simulate diamond back

moth larvae feeding on Bt (Bacillus thuringiensis) treated cabbage leaves. It provides a fundamentalcapability for examining the effects of deposit structure on efficacy. Further development has increasedthe generality of the model for examining different formulations and AIs. The LPCAT evaporationmodel combined with other physic-chemical measurements allows a greater level of inquiry intopesticide characteristics, and optimizing toxin presentation to target pests. References: Hall et al. (1995)

FABE RESEARCH PROJECTS

Effect of drift retardant chemicals on spray drift, droplet size and spray patternSpecific objectives of this study were to determine the effects of various drift retardant chemicals

(Direct®, Driftgard®, Formula 358®, Nalco-trol®, and Target®) on droplet size, spray pattern, andspray drift reduction. The results of this study indicated that, at recommended rates, Nalco-trol providedthe largest increase in volume median diameters of the sprays followed by Direct, Target, Driftgard, andFormula 358. In general all drift retardants created patterns with greater volume toward the center thanthat of water only. Cumulative deposits beyond 1.6 ft downwind increased for all drift retardants whenthe wind velocity was increased from 4.5 to 9 mile/h. In general, the effectiveness of drift retardantmixtures for minimizing spray deposit distances was closely related to droplet size increase.References: Ozkan et al. (1993a,b, 1994)

Effect of nozzle wear on spray pattern and droplet sizeThe effects of nozzle wear on spray patterns delivered by fan pattern nozzles made from different

materials were investigated. An automated computerized weighing system was used to rapidly evaluatethe spray deposit distribution. The results indicate that there was some difference between the spraydeposit distributions of new and worn fan nozzles. The width of the spray pattern remained nearlyconstant but the worn nozzles delivered greater volumes of liquid in the centers of the patterns. Theeffects of nozzle wear on droplet size spectrums delivered by fan pattern nozzles made from differentmaterials were investigated. Flow rates of the nozzles tested were 0.2, 0.4, 0.6 and 0.8 gal/min, and thematerials were brass, nylon, plastic, stainless steel and hardened stainless steel. Although the wornnozzles produced slightly larger DV0.5 values, generally there was little difference in droplet sizedistributions between new and worn nozzles with flow rates smaller than 0.6 gal/min. The difference,however, was greater for the nozzles with flow rates of 0.6 and 0.8 gal/min. A standard procedure formeasuring nozzle wear was develop and approved by ASAE as Standard S471. References: Ozkan etal. (1991, 1992a,b), Ozkan and Reichard (1991,1993), Reichard (1991a,b), Reichard et al. (1991), Zhuet al. (1995a,b)

204

A survey on attitudes of applicators toward pesticide waste reductionAs part of the ongoing pesticide education programs in Ohio, a survey was conducted in eighteen

counties to learn more about current pesticide application and disposal practices. The survey alsoprovided information related to applicators’ attitudes toward reducing pesticide waste. Survey resultsbased on 1380 responses indicate over two-thirds of the respondents calibrate their sprayers at least oncea year. Approximately 10% never calibrate. Over 90% of the respondents always rinsed empty pesticidecontainers. However, only 71% followed acceptable rinsing procedures. About 3% indicated they do notrinse containers at all. Burning was the number one method of pesticide container disposal used byapplicators. Although over two-thirds of the applicators feel well-informed about pesticide containerdisposal practices, the number of improper disposal methods identified by the respondents indicate thateducational programs are needed to help applicators choose the most environmentally sound disposalpractice. In general, the pesticide applicators expressed a positive attitude toward reducing pesticidewaste. References: Ozkan (1992b)

Subsurface injection of turfgrass insecticidesSurface application of insecticides on turfgrass for control of many subsurface grubs is not very

efficient. It can be potentially hazardous to people, pets and other animals exposed to the insecticides.To reduce this danger, three injection systems were developed to place insecticides below the turfsurface and into the main grub activity zone. Results indicate that insecticides can be successfullyinjected with little damage to the turf. Analyses of surface residues after injection of two commonturfgrass insecticides showed significant reductions ranging from 38 percent to 95 percent over theamount remaining from spraying on the surface. Grub control using two of the three injection methodswas equal to or better than that achieved with the conventional surface application method. A thirdinjection method using a rolling point applicator was not evaluated for grub control because thepreliminary data showed little dispersion of insecticide from the point of injection and a low probabilityof achieving effective control. References: Ozkan et al. (1990a,b)

Deposition efficiency of air-assisted, charged sprays in a wind tunnel Small spray droplets which rely primarily on electrostatic and gravitational forces for

transportation and deposition are highly susceptible to drift. Also, spray penetration into dense plantcanopies is often inadequate. Spray deposits of air assisted charged sprays, with volume mediandiameter of 92 m, were collected in a wind tunnel with wind velocities up to 11 mile/h. The resultsindicated that an air jet with 24.6 mile/h downward air velocity at the point spray was entrained, greatlyincreased the amount of spray deposited in the target area and also improved penetration of the spraydownward into the canopy and reduced drift. References:Almekinders et al. (1992,1993a,b), Khdair etal. (1994)Computer simulation of spray drift from field sprayers

A computer program was used to determine the effects of several variables on drift distances ofindividual spray droplets. Variables were initial droplet size, velocity and height of discharge, windvelocity and turbulence intensity, relative humidity, and volatility of the liquid. Drift distances of waterdroplets as large as 200 m diameter were influenced by initial droplet velocity and height of discharge.Experimental data from tests in a wind tunnel verified the accuracy of the computer program inpredicting drift distances of water droplets. A computer program was developed to calculate mean driftdistance for individual spray droplets. This program accepts input parameters, then interpolates amonga data base of results from flow simulation trials to obtain drift distancd for the input conditions.References: Reichard (1992a,b), Reichard et al. (1994), Reichard and Zhu (1995), Zhu et al. (1994,1995c)

205

An automated computerized spray pattern analysis systemMost of the patternators used currently to investigate nozzle spray pattern characteristics are of

the manual type using collection cylinders. These patternators are susceptible to human error duringrecording and analyzing data. This process is also labor intensive and time consuming. Results of asurvey conducted indicate that with manual patternators it takes an average of 35 minutes to collect andanalyze pattern data for one nozzle. The automated single collection unit system described in this articleprovides a more efficient means of data collection and analysis. On an equivalent per cylinder basis, thetime for data collection takes about 0.5 seconds. It also takes only about a minute to complete a test withthis system. The automated system was found to be relatively accurate compared to manual systems.References: Ozkan and Ackerman (1992)

Use of shields to reduce driftThe effects of partially covering spray booms with six different mechanical shields on

deposition distances of spray droplets were simulated by using a computational fluid dynamic software,Fluent®. The same shields were mounted in a wind tunnel and drift distances of uniform-sized dropletsin a 13.4 mile/hr air stream were measured. Use of solid bluff-plate shields inevitably resulted in a lowvelocity zone immediately behind the shield or within the shielded area. As compared withconventional straight-down spraying, all shields simulated, except ones, reduced drift potential. Thedouble foil shield was confirmed to be the best design for mechanical shields in this study. The optimaloperating parameters of pneumatic shielded spraying, obtained by a multifactor analysis of variance,were jet velocity of 90 mile/h, jet flow rate of 3600 ft3/min, and jet angle of 15 degrees. Mean depositiondistances from simulation and experimental distances to centers of masses agreed well for only 2 of 6mechanical shield designs tested. Effect of shield-induced vibration and improper size ratio of shieldsto the wind tunnel may be reasons for this inconsistency. References: Ozkan et al. (1997a,b), Tsay(1997)

Measuring mixing in an agrochemical sprayer tankEffectiveness of hydraulic jet agitation systems of agricultural chemical sprayers were

investigated by measuring the concentration of a kaolin clay/water mixture in the line to the boom. Asurface scatter type turbidimeter was employed to evaluate the concentration of simulated wettablepowder pesticides during an application. An agitation index, called “AGEF”, was defined to helpevaluate the effectiveness of each agitation system separately regardless of tank size and shape. AGEFwas based on three measured mixing criteria: particle deposit remaining on bottom of tank followingapplication, the coefficient of variation of mixture concentration in the line to the boom, and ratio ofmaximum deviation of mixture concentration at the tank outlet to the mean concentration measuredduring the application. Experiments were conducted on several sprayer tanks of different capacities andagitator type. The results showed AGEF was sensitive enough to enable reasonable comparisons andthis method can be used to standardize minimum requirements of a hydraulic jet agitation system.System pressure was the most important factor affecting agitation effectiveness through its directinfluence on jet velocity. Single-phase solutions to Fluent computer models agreed well with theseresults. However, solving three dimensional, turbulent, multiphase flows (Eulerian granular model)was not feasible using personal computers because computation times would be several months.References: Ackerman et al. (1993), Ucar (1997).

Lag times and uniformity of inline injection of spray materialsInjection sprayers can eliminate some problems associated with conventional sprayers,

however, injection sprayers have inherent problems of lag time and mixture uniformity at nozzles. A

206

turntable sampling system was designed to measure uniformity of the mixture in the spray boom and thelag time required for the desired mixture concentration to be sprayed from nozzles at a range of boomlengths. A computer controlled system allowed the operator to collect samples easily at any nozzlewhile the simulated sprayer underwent accelerations or decelerations. Three water-soluble and one non-water-soluble liquids (water, Prime Oil, Prime Oil II and Silicon Oil) with viscosities that ranged from0.9 to 97.7 centipoise were used as the simulated pesticides. Uniformity of the mixtures with thesimulated pesticides in two boom sizes (3/8 and 3/4 in. diameters) and uniformity across the spraypatterns of nozzles at different positions on the boom were investigated. Lag times to the expected ratesof application were also measured. Viscosity of water-soluble or non-water-soluble liquid slightlyinfluenced the mean flow rate from the metering pump, but did not influence the lag time. Simulatedpesticides with the highest viscosities were very difficult to mix with water, and it was necessary to usea spiral mixer. Increasing the number of active nozzles on the spray boom reduced the variation of themixture uniformity in the spray boom. Lag time to the desired rate of application at the nozzle at the endof the boom was greatly reduced by reducing the boom diameter, but this lag time was not reducedsubstantially by reducing the number of active nozzles on the boom. References: Zhu, et al. (1998a,b,c)

USDA-ARS ATRU RESEARCH PROJECTS

Orchard air jet velocity profiles and modelThe mathematical model for ideal, plane jets was modified to include the effect of radial

expansion as the air jet moved away from a circular jet outlet. This model was found to have animproved fit to the maximum velocity across a jet as distance from the jet increased, as compared to theplane jet model previously used. Jet profiles were measured for two axial fan sprayers and agreed wellwith model predictions using the radial jet model. Centerline velocities in an air jet produced by a cross-flow fan sprayer were measured and agreed well with predicted values computed using a plane jetmodel. For jets that have equal air power at the jet outlet, models for ideal jets predict that axial jetvelocities from jets with greater air volume and lower maximum air velocities will decrease much lessas distance from the outlet increases, compared to jets with high velocity and lower air volume.Measured air velocities for sprayers passing an array of hot-film anemometers on towers in the open andin apple trees found that maximum jet velocities produced by moving sprayers was much less thanvelocities measured for the same jets when stationary. A model of the deflection of an air jet by travelspeed or cross wind was developed. Jet deflection and velocity profiles predicted by for the deflectedjet were similar to velocities measured for a model jet operated in a wind tunnel. References: Brazee etal. (1981), Fox et al. (1985, 1992b)

Drift from orchard sprayersGround-level and airborne spray samples were collected downwind of apple orchard in a series

of drift experiments over the past 8 years. Convention axial fan and air-curtain/cross-flow fan sprayerswere used to successively spray the downwind, edge row of trees each year. With an available crew ofabout 12 people, about 5 replications could be conducted in one day. Due to row planting directions,measurement of drift is only possible when the wind is approximately perpendicular to the rowdirection. In our experience, only about 1 to 2 days per month had a suitable wind direction for driftexperiments. We usually set up the major collection and meteorological towers for about 2 months peryear, set up temporary collectors and prepared for drift trials about 4 to 5 times per year, and actuallysprayed about 2 days per year. Fluorescent tracers were used. Rigid plastic sheets and, later, plastic tapewas used to collect ground deposits. Airborne spray was collected on passive collectors such as string,

207

plastic tape and, recently on nylon screen. High volume air samplers were also as an active collector ofairborne spray. Different fluorescent tracers were used in each sprayer and collectors were changed afterboth sprayer completed each pass. A total of about 50 spray passes have been made during the 7 yearswhen drift experiments were conducted, thus a range of wind conditions have been encountered. Threeorchard sites have been used to provide a range of canopy sizes and shapes. References: Fox et al.(1990a,b, 1991b, 1993a,b,c, 1994b, 1997), Fox (1993), Reichard et al. (1992a,b, 1994), Derksen andBreth (1994), Reichard and Zhu (1995,1996), Derksen and Gray (1995), Perez et al. (1995), Coffmanand Derksen (1997)

Greenhouse sprayingElectron beam analysis (EBA) was used to measure chlorothalonil smoke particles on artificial

target surfaces in greenhouses. Particles averaging less than 3.0 µm in diameter and as small as 0.4 µmwere found to vary significantly in number with location within a poinsettia canopy and with distancefrom the source of the smoke. Particles did not vary significantly in size either within the canopy or withdistance from the source. No measurable residue was found when the greenhouse was not tightly sealed.EBA proved to be a viable method of investigating fungicide smoke deposition and can provide preciseinformation about the environmental fate of pesticides related to application technology. References:Tappan et al. (1995), Derksen and Sanderson (1995), Obendorf et al. (1995)

Spraying of nursery cropsSpray penetration and off-target spray drift from a conventional, air-assist, axial fan sprayer and

a high-clearance, boom-type sprayer were investigated in honey locust or canadian hemlock located intwo different production nurseries. Another study in a production nursery compared spray coverage onsheared red maple from an axial fan sprayer with a cross-flow fan sprayer. Aqueous tracer solutions ofeither Ca(NO3)2 foliar fertilizer, Cu(OH)2 fungicide, or food coloring were used in the experiments.Spray distribution and drift were assessed via residues collected on foliage, electron microscope stubs,vertical and ground-level profile tapes, clamped leaves, and high-volume air samplers. Electron beamanalysis (EBA) was used to assay residues on stubs, leaves and needles placed and/or collected at severallocations and elevations in the canopy. Profile-tape samples were evaluated with a laboratory spraydeposit analyzer using a conductivity detector. Spray coverage for the hemlock and locust treatmentswas incomplete throughout either canopy as assessed by either method. Experimental results indicatedthat ground-level spray deposits and airborne drift varied with the spray method used. Spray depositson red maples (about 3.5 m tall) were measured using blue food coloring and Cu(OH)2 fungicide.Colorimetry and EBA were used to measure deposits on leaves clamped at 12 locations (3 elevations,4 quadrants) in each of three trees. The cross-flow fan sprayer produced more uniform distributionsthroughout the tree, but the axial-fan sprayer produced greater deposits at almost all locations than thecross-flow fan sprayer. References: Krause et al. (1997), Zhu et al. (1997b)

Effectiveness of low turbo teejet and TurboDrop nozzles in drift reductionSmall-to-medium size droplets are desirable when applying insecticides and fungicides because theyprovide better penetration into the canopy and better coverage. However, small droplets can drift longdistances. Almost all major agricultural nozzle manufacturers have recently introduced “low-drift”nozzles which claim to be effective in reducing spray drift. The objective of this study was to determineeffectiveness of two “low-drift” nozzles (Turbo TeeJet® and TurboDrop®) in reducing drift. This wasaccomplished by measuring droplet sizes, and deposition distances of droplets in a wind tunnel (11 mile/h) using the low-drift nozzles and comparing the data from these measurements with those obtainedfrom a standard flat-fan nozzle. The low-drift nozzles produced fewer drift prone droplets and less

208

downwind deposits than the standard flat-fan nozzle (XR). Droplet size measurements taken along thelong axis of the spray patterns showed less variation in droplet size for the XR® and Turbo TeeJet (TT)nozzles than for the TurboDrop (TD) nozzles. The TD nozzles produced lower downwind deposits thanTT nozzles operated at similar pressures (40 psi); however, a larger orifice TT nozzle operated at a lowerpressure (25 psi) performed similar to the TD nozzle operated at 40 psi. Plugging the air intake hole onthe TurboDrop nozzle increased nozzle output, decreased VMD, and slightly increased the percent ofspray volume in drift prone droplets and downwind deposits. References: Derksen et al. (1997)

Shear effects on drift retardantsSome research has indicated that certain drift retardants may degrade due to the shearing action ofrecirculation through a agricultural sprayer pump. A laboratory system was developed to simulate shearon spray mixtures of water and drift retardants due to recirculation of mixtures in sprayer tanks. Threedrift retardants were evaluated in both a Myers A36 orchard, airblast sprayer and the laboratory system.Droplet size distributions of sprayed samples from the sprayer and the laboratory system were measuredwith an Aerometric Phase/Doppler Particle Analyzer. Droplet size distributions of sprayed sampleswith drift retardants sheared with the laboratory system had similar trends to those of samples shearedwith the airblast sprayer as the number of recirculations increased. In a further study, ten polymerswhich are primary active ingredients in commercial drift retardants were tested. Samples of thesolutions were taken after 0, 1.0, 2.3, 3.9, 6.4, and 11.4 passes through a centrifugal pump system.Apparent extensional viscosity (AEV) and screen factor (SF) were measured for all samples. Afterbeing sheared by more than 4 passes through the pump, both non-ionic and anionic polymer-solutionsat 100 ppm did not increase DV.5 much over values for water alone. Both apparent extensional viscosity(R2 = 0.8) and screen factor (R2 = 0.7) were well correlated with spray DV.5. . These results show thatsome drift retardants may fail to maintain their ability to increase spray drop sizes after they havebypassed several times in an agricultural sprayer. References: Fox et al. (1996), Reichard and Zhu(1996), Reichard et al. (1996), Zhu et al. (1997a)

High speed image captureHigh speed movies (6000 frames/s) were made of droplets impacting on leaf surfaces. Many plantleaves have a surface wax structure that reflects spray droplets on initial impact. The movies enabledobserving the number of droplets that were reflected and the height of rebound, but measurements ofrebound characteristics were not easy to make. A high speed video system was developed to captureseveral video frames in succession. The video speed was only from 15 to 150 fields/s, however, by usinghigh speed strobe lighting as a shutter, interesting images of droplet rebound paths could be obtained.The video system, used in conjunction with two different mono-disperse droplet generators, quantifieddroplet impaction and any consequent reflection. Three techniques were used for assessing thedeformation at impaction of a single droplet on an artificial surface, and reflection of both single dropletsand droplets in a spray cloud, from a variety of plant surfaces. Determination of droplet in-flightdiameter, dimensions of impacting droplets, droplet velocity prior to and immediately after impaction,and reflection height and number were all possible depending upon the technique selected. References:Reichard et al. (1986), Fox et al. (1992a)

Droplet impaction and reflectionDroplet reflection depends, to some extent, on the speed of the impacting droplet and droplet size, butthe main factor in determining reflection is the micro-structure of the leaf surface. Some plants, such ascabbage, wheat, and rice reflect nearly all spray droplets that impact on the surface. Large droplets (500m diameter) tend to be reflected more than small droplets (100 m diameter), but we have recorded water

209

droplets less than 70 m that reflect from cabbage leaves. Typical droplets impacting on reflective leavesremain on the leaf surface less than 1 ms. While the droplet is on the leaf, it greatly increases its surfacearea by distorting into a pseudo-torus shape, then reduces surface area by drawing back into a sphericalshape before springing from the leaf surface. Some adjuvants, such as surfactants tend to reducereflection. In fact, if high concentration of some surfactants are used, refection can be eliminated. Mostsurfactants must move to the liquid interface to become active. With the large changes in droplet surfacearea during the impaction process, the diffusion rate of typical surfactants is too slow to reduce surfacetension in the one millisecond available. References: Bukovac and Reichard (1990), Reichard (1990),Bukovac et al. (1993,1995), Brazee et al. (1994,1997), Reichard et al. (1998)

Dynamic surface tensionSeveral physical properties of the droplet liquid, such as surface tension and extensional viscosity, mayaffect reflective potential of spray droplet from plant leaves. Equilibrium surface tension, a commonlymeasured liquid property, is not a reliable indicator of reflection tendency. However, dynamic surfacetension has been found to be strongly related to droplet reflection. An oscillating jet method wasdeveloped enabling measurement of dynamic surface tension at a range of short surface ages, even asshort as 1 ms. Bohr’s equation and Bechtel’s inverse method were used to calculate surface tension frommeasurements of the jet waveforms. Some surfactants are unable to reduce surface tension rapidly atshort air-liquid interface ages typical of droplet impaction processes. Hence, they may be unable toeffectively limit reflection and improve retention. A thin-film diffusion model was developed whichcan be used to calculate dynamic surface tension at a range of surface ages, given liquid properties,surfactant diffusivity, apparent interfacial film thickness, and surfactant concentration. Correlatingmeasured dynamic surface tension data with the diffusion model provides estimates of apparent filmthickness and diffusion of surfactant/water mixtures. These activity properties are useful inunderstanding surfactant effects on high shear rate physical processes such as droplet atomization andleaf-surface impact, where short surface ages are critical. Most agricultural sprays are mixtures ofmaterials, not true solutions, and as such their surface tensions change with surface age. Measuringsurface tensions at short surface times may also be valuable in predicting droplet size spectra fromatomization processes, because these processes are usually completed in less than 3 ms. Brazee et al.(1991), Bechtel et al. (1995), Reichard et al. (1997)

Image analysisComputer imaging equipment and image processing software has been used by ATRU staff to

measure quality aspects of spray applications. Measurements of feature density, size, and targetcoverage have been used to compare the performance of different application techniques. Evaluationshave been made using artificial targets such as oil and water sensitive paper and natural targets such asplant leaves. Different image processing algorithms have been used to evaluate images depending onthe target, tracer, and droplet size characteristics. Morphological image processing techniques provedmost useful when evaluating parameters of features produced by water-soluble tracers. Recentacquisition of an epi-fluorescence microscope with a high intensity, UV light source will improve ourability to evaluate coverage produced by different application methodologies through use of fluorescenttracers and other materials that naturally fluoresce. This equipment will also permit study of theinteraction between the spray quality and pest damage on leave surfaces as well as the effect of sprayformulations on plant material. Natural fluorescence of plant pathogens and leaf structures will also bestudied to determine if these may aid in evaluating the application process, pest management, or cropproduction. References: Salyani and Fox (1994,1997), Derksen and Jiang (1995), Jiang and Derksen(1995)

210

Japanese beetleAdult and immature Japanese beetles (JB) are serious pests of turfgrass, flowers, fruit crops and

ornamentals. The larvae, white grubs, develop in the soil in the grass root zone. Control of these grubsis difficult because a significant portion of pesticides applied to the turf can become bound by organicmatter in the thatch and never reach the feeding sites. Several entomopathogenic bacteria, fungi, andnematodes have been tested for grub control. Although several commercial biological products areavailable, results of their use has been inconsistent. A survey of northern Ohio golf course turf foundabout 20% of the sites had detectable entomopathogenic nematode (EN) populations. However, onlyabout 15% of these EN provided more than 75% control of grubs in laboratory tests. Selected isolatesof Ohio EN performed as well in field tests as did commercially available nematodes. Improvedapplication methods may enhance EN control of JB larvae. In addition, EN performance may beincreased when used with other control agents. An insecticide, imidacloprid, was shown not only to benon-toxic to EN, but to have a synergistic effect against masked chafer and JB larvae when both controlagents were used simultaneously. In a new approach to pathogen application, autodissemination,beetles are lured to a trap where they become coated with a fungal pathogen and subsequently transferthe fungus to larval feeding sites. References: Mannion et al. (1996), Grundler and Klein (1997), Kleinand Moyseenko (1997)

LPCAT PUBLICATIONS

Adams, A.J. and F.R. Hall. 1990. Microdroplet application for determination of comparative topical andresidual efficacy of formulated permethrin to two populations of Diamondback moth (Plutellaxylostella L.). Pesticide Science 28:337-343.

Adams, A.J., F.R. Hall, R.K. Lindquist, I.A. Rolph and I.H.H. Adams. 1990a. Video-taping the responseof the melon aphid (Homoptera: Aphididae) to bifenthrin spray deposits on chrysanthemums. Journalof Economic Entomology 83(3):955-960.

Adams, A.J., F.R. Hall and C.W. Hoy. 1990b. Evaluating resistance to permethrin in Plutella xylostella(Lepidoptera: Plutellidae) populations using uniformly sized droplets. J. Econ. Entomol. 83(4):1211-1215.

Adams, A.J., C.W. Hoy, F.R. Hall and S.Y. Nettleton. 1992. Larval Feeding and Movement in TwoPlutella xylostella (Lepidoptera: Plutellidae) Populations Exposed to Discrete Deposits of Permethrin.Pestic. Sci. 35:243-247.

Chapple, A., R.A. Downer and F.R. Hall. 1992. Effects of Pump System on Atomization of SprayFormulations. Pesticide Formulations and Application Systems. 11th Volume. ASTM, Philadelphia,PA. ASTM STP 1112:193-205.

Chapple, A. C., R. A. Downer and F. R. Hall. 1993. Effects of Spray Adjuvants on Swath Patterns andDrop Spectra for a Flat-Fan Nozzle. Crop Protection 12(8):579-590.

Chapple, A. C., R. A. J. Taylor and F. R. Hall. 1995. Spatial Temporal Transformations and theirRelevance to Drop-sizing Agricultural Sprays. J. Agric. Eng. Res. 60:49-56.

Chapple, A.C., T.M. Wolf, R.A. Downer, R.A.J. Taylor and F.R. Hall. 1996a. Use of Nozzle-InducedAir-Entrainment to Reduce Active Ingredient Requirements for Pest Control. Crop Protection.16(4):323-330.

211

Chapple, A.C., R.A. Downer, T.M. Wolf, R.A.J. Taylor and F.R. Hall. 1996b. The Application ofBiological Pesticides: Limitations and a Practical Solution. Entomophaga. 41(3/4):465-474.

Cooper, J. A. and F. R. Hall. 1993. Effect of Surface Tension on the Retention of Various Pesticides byApple Leaves. J. Environ. Sci. Health B28(5):487-503.

Downer, R. A., E. C. Escallon and F. R. Hall. 1993. The Effect of Diluent Oils on the ElectrostaticAtomization of Some Insecticides. ASTM STP 1183:203-204.

Downer, R.A. and F.R. Hall. 1995. Droplet Analysis in Agricultural Applications. Journal of theFlorida Mosquito Control Association, vol. 65: 54-58.

Downer, R. A., J. A. Cooper, A. C. Chapple, F. R. Hall, D. L. Reichard and H. Zhu. 1995. The Effectof Dynamic Surface Tension and High Shear Viscosity on Droplet Size Distributions Produced by a FlatFan Nozzle. Pesticide Formulations and Application Systems: 14th Volume, 1234, Franklin R. Hall,Paul D. Berger and Herbert M. Collins Eds., American Society for Testing and Materials, Philadelphia,1994, ASTM STP 1234:63-70.

Downer, R.A., L.M. Kirchner, B.A. Lucius and F.R. Hall. 1996. The Relationship Between SprayAtomization and Drift of Fluorescent Tracers Using a Wind Tunnel. Pesticide Science.

Downer, R.A.; Ebert, T.A.; Thompson, R.S.; Hall, F.R. 1997. Herbicide Spray Distribution, Qualityand Efficacy Interactions: Conflicts in Requirements. Aspects of Applied Biology. 48:79-89.

Hall, F.R. 1990a. An Integrated Approach for Improvements in Application Technology. E. Hodgsonand R. Kuhr, ed in Safer Insecticides: Development and Use, Dekker Publications, NY, pp 453-508.

Hall, F.R. 1990b. “Controlled delivery and foliar spraying.” Controlled Delivery of Crop ProtectionAgents. Taylor and Francis, Ltd., U.K., pp. 3-21.

Hall, F.R. and J.R. Lemon. 1990. The CASH System of On-Farm Decision Tools for HorticulturalEnterprises. Acta Horticulture 276:323-346.

Hall, F.R., R.A. Downer and A. Chapple. 1990. Evaluation of the CARBO-FLO Pesticide WasteManagement System. 11th Volume. ASTM, Philadelphia, PA. ASTM STP 1112:24-32.

Hall, F.R. 1991a. Pesticide Application Technology and IPM. In Handbook on Pest Management inAgriculture. ed. D. Pimental, CRC Press. Boca Raton, FL. Vol. II:135-167.Hall, F.R. 1991b. Influence of Canopy Geometry in Spray Deposition and IPM. Proceedings of 1990Colloquium on “Canopy Development in Model Systems: Measurement, Modification, Modeling.” InHort. Sci. Vol. 26(8):1012-1017.

Hall, F.R. 1991c. Pesticide Targeting: Improving the Dose Transfer Process. Proceedings US-JapanPesticide Seminar: Pesticides and the Future: Toxicological Studies of Risks and Benefits, ed. E.Hodgson, M. Roe, and N. Motoyama, Rockville, MD., N.C. State Press, Reviews in PesticideToxicology 1:305-315.

212

Hall, F.R., L.M. Kirchner and R.N. Downer. 1992. Some Practical Limitations of Fluorescent TracersUsed to Measure Off-Target Pesticide Deposition. Pesticide Formulations and Application Systems:12th Volume. Bala N. Devisetty, David G. Chasin and Paul D. Berger, eds., American Society forTesting and Materials, Philadelphia. ASTM STP 1146:247-256.

Hall, F.R., A.C. Chapple, R.A. Downer, L.M. Kirchner and J.R.M. Thacker. 1993a. PesticideApplication as Affected by Spray Modifiers. Pestic. Sci. 38:123-133.

Hall, F.R., J.R.M. Thacker and R.A. Downer. 1993b. Laboratory Studies Upon the Effects of ThreePermethrin Formulations on the Mortality, Fecundity, Feeding and Repellency of the Two spottedSpider Mite. J. Econ. Entomol. 86(2):537-543.

Hall, F.R., T.R. Thacker and R.A. Downer. 1993c. Movement of the Physic-Chemical Properties, InFlight Evaporation and Spread of Spray Droplets Containing Pesticide Adjuvants. ASTM 1183:191-202.

Hall, F.R. and L.M. Kirchner. 1994. Measurement of Evaporation from Adjuvant Solutions Using aVolumetric Method. Pesticide Science 40:17-24.

Hall, F.R. 1995a. Pesticide Delivery. In Proceedings of 4th Int. Adjuvants Symposium, 3-6Oct.,Melbourne, Australia, FRI Bulletin No. 193:85-93.

Hall, F.R. 1995b. Critical Factors Affecting Pesticide Delivery. In Proceedings, National Conferenceon Pesticide Application Technology, Aug. 1995, Guelph, Ont., CAN., 5-10.

Hall, F.R. and J. Barry. 1995. An Overview of Biorationals - Formulation and Delivery. In BiorationalPest Control Agents: Formulation and Delivery. Eds. F. Hall and J. Barry. ACS Books SymposiumSeries 595.

Hall, F., A. C. Chapple, R. A. J. Taylor and R. A. Downer. 1995. Modeling the Dose Acquisition Processof Bt: The Influence of Feeding Pattern on Survival. In Biorational Pest Control Agents: Formulationand Delivery. Eds. F. Hall and J. Barry. ACS Books Symposium Series 595.

Hall, F.R. 1996. Coupling Cost/Benefit/Environmental Risk Assessment Models for Decision Makers:An Overview of the Opportunities. ASAE Paper No. 961034, Phoenix, AZ, 20 p

Hall, F.R. and R.D. Fox. 1996. The reduction of pesticide drift. In Pesticide Formulation and AdjuvantTechnology. C.L.Foy and D.W. Prichard, Eds. pp 209-239. Chemical Rubber Company, Boca Raton, Fl.

Hall, F.R., J.A. Cooper, L.M. Kirchner, R.A. Downer, and J.R.M. Thacker. 1996a. Assessment of Off-target Movement of Orchard Pesticides: Capture Efficiencies of Synthetic and Biological Biomarkers.Journal of Environmental Science and Health, B31(4), 815-830.

Hall, F.R., R.A. Downer, T. M. Wolf and A.C. Chapple. 1996b. The “Double Nozzle” - A New Wayof Reducing Drift and Improving Dose Transfer?” In: Pesticide Formulations and Application Systems:16th Volume, ASTM STP 1312. (Eds: Hopkinson, M.J., Collins, H.M., Goss, R.G.) American Societyfor Testing and Materials, Philadelphia, 1996. (In press).

213

Hall, F. 1997a. Spray Deposits: Opportunities for Improved Efficiency of Utilization via Quality,Quantity, and Formulation. Phytoparasitica Special Supplement 255:395-525.

Hall, F. 1997b. Integrating the New Technologies into Pets Management Strategies for HorticulturalCrops. New Developments in Entomology 1:149-159.

Hall, F.R., R.A. Downer, J.A. Cooper, T.A. Ebert and D.C. Ferree. 1997. Changes in Liquid Retentionon Apple Leaves During a Growing Season. HortScience. 32(5):858-860.

Head, G., C.W. Hoy and F.R. Hall. 1995. Direct and indirect selection on behavioral response topermethrin on Larval Diamondback Moths. J. Econ. Ento. 88(3):461-469.

Hoy, C.W., G. Head and F.R. Hall. 1995. Monogenic Models in a Heterogenous Environment.Resistant Pest Mgt. Newsletter 7(2):6-9.

Hoy, C.W., G.P. Head and F.R. Hall. 1998. Spatial Heterogeneity and Insect Adaptation to Toxins.Annu. Rev. Entomol. 43:571-594.

Kirchner, L.M., R.A.J. Taylor, R.A. Downer and F.R. Hall. 1996a . Calibrating the Pesticide CaptureEfficiency of Passive Dosimeters. Pesticide Science, 46:61-69.

Kirchner, L.M., R.A.J. Taylor, R.A.J.; Downer, R.A.; Hall, F.R. 1996b. Comparison of the PesticideCapture Efficiency of Potential Passive Dosimeter Materials. Bulletin of Environmental Contaminationand Toxicology. 57:938-945.

Lehtinen, J.R., H. Simmons, R. Lindquist, A.J. Adams and F.R. Hall, 1989. Use of Air-AssistedElectrostatic Sprayer to Increase Pesticide Efficiency in Greenhouses. ASTM STP: 1036: 165-178.

Lemon, J.R., W.T. Rhodus and F.R. Hall. 1992. Neural Networks and their Application. In: ProceedingsAdvanced Computer Applications in Animal Agriculture, Dallas, TX. Feb. 1992.

Reed, J.P., F.R. Hall, D.L. Reichard. 1990a. Influence of atomizers upon efficacy of tridiphane plusatrazine applied postemergence. Weed Technology 4:92-96.

Reed, J.P., F.R. Hall, and H.R. Krueger. 1990b. Measurement of ATV Applicator Exposure to AtrazineUsing an ELISA Method. Bull. Environ. Contam. Toxicol. 44:8-12.

Reed, J., F. R. Hall and R. Riedel. 1993. Biological Implications of Drift from Sprayer in TomatoFungicide Field Trials. Plant Disease Vol. 77(2):186-189.

Royalty, R.N., F.R. Hall and R.A.J. Taylor. 1990. Effects of Thuringiensin on Tetranychus urticae(Acari: Tetranychidae) Mortality, Fecundity and Feeding. J. Econ. Entomol. 83(3):792-798.

Thacker, J.R.M. and F.R. Hall. 1991. The Effects of Drop Size and Formulation Upon the Spread ofPesticide Droplets Impacting on Water-sensitive Papers. J. Environ. Sci. & Health, Part B,26(5&6):631-651.

214

Thacker, J. R. M. and F. R. Hall. 1992. The Benefits of an Anti-Evaporant in Pesticide Applications.Pesticide Formulations and Application Systems: 12th Volume. Bala N. Devisetty, David G. Chasin andPaul D. Berger, eds., American Society for Testing Materials, Philadelphia. ASTM STP 1146:303-310.

Thacker, J.R.M., F.R. Hall and R.A. Downer. 1992. The Interactions Between Routes of Exposure andPhysic-chemical Properties of Four Water-dilutable Permethrin Formulations in Relation to TheirActivities Against Trichoplusia ni. Pestic. Sci. 36:239-246.

Thacker, J.R.M., R. Young, S. MaCaskill, A. Dixon, F.R. Hall and R.A. Downer. 1997. Using SprayAdjuvants to Enhance Arthropod Pest Control. New Developments in Entomology 1:187-202.

Wolf, T.M., R.A. Downer, F.R. Hall, O.B. Wagner and P. Kuhn. 1996. The Effect of ElectrostaticCharging on the Dose Transfer of Water-Based Pesticide Mixtures. In: Pesticide Formulations andApplication Systems: 15th Volume, ASTM STP 1268. (Eds: Collins, H.M.; Hall, F.R.; Hopkinson, M.)American Society for Testing and Materials, Philadelphia. 3-14.

Wolf, T.M., K.S. Gallander, R.A. Downer, F.R. Hall, R.W. Fraley and L.D. Vargyas. 1997. AerosolGeneration During Mixing and Loading - Source Identification and Contribution to Operator Exposure.In: Pesticide Formulations and Application Systems: 17th Volume, ASTM STP 1328. (Eds: Goss, G.R.;Hopkinson, M.; Collins, H.M.) American Society for Testing and Materials, Philadelphia. 115-128.

FABE DEPARTMENT PUBLICATIONS

Ackerman, K.D., H.E. Ozkan, D.L. Reichard, and T.G. Carpenter. 1993. Technique for measurement ofmixture variability in sprayer tanks. ASAE Paper No. 931114.

Almekinders, H., H.E. Ozkan, D.L. Reichard, T.G. Carpenter, and R.D. Brazee. 1992. Spray depositpatterns of an electrostatic sprayer. Transactions of the ASAE 35(5):1361-1367.

Almekinders, H., H.E. Ozkan, D.L. Reichard, T.G. Carpenter, and R.D. Brazee. 1993a. Depositionefficiency of air-assisted charged sprays in a wind tunnel. Transactions of the ASAE 36:321-325.

Almekinders, H., H.E. Ozkan, D.L. Reichard. 1993b. Design of air assist system for an electrostaticsprayer. ANPP-BCPC 2nd Int Symp on Pest Appl Tech., pp. 93-100.

Khdair A.I., T.C. Carpenter, and D.L. Reichard. 1994. Effects of air jets on deposition of charged sprayin plant canopies. Transactions of the ASAE. 37(5):1423-1429.

Ozkan, H.E., D.L. Reichard, H.D. Niemczyk, M.G. Klein, and H.R. Krueger. 1990a. A subsurface pointinjector applicator for turfgrass insecticides. Applied Engineering in Agriculture 6(1):5-8.

Ozkan, H.E., D.L. Reichard, H.D. Niemczyk, M.G. Klein, H.R. Krueger. 1990b. Subsurface injectionof turfgrass insecticides. pp. 236-247. IN: Pesticide Formulations and Application Systems, 10th Vol.,ASTM STP 1078, ASTM, Philadelphia PA. 257 p.

215

Ozkan, H.E., D.L. Reichard, K.D. Ackerman, and J.S. Sweeney. 1991. Effect of wear on spraycharacteristics of a fan pattern nozzles made from different materials. IN: Pesticide Formulations andApplication Systems: 11th Vol., ASTM STP 1112, American Society for Testing and Materials,Philadelphia. PP. 206-217.

Ozkan, H.E. 1992a. Reducing spray drift. Ohio Cooperative Extension Service, Extension Bulletin 816.Ohio State University, Columbus, OH. 17 pp.

Ozkan, H.E. 1992b. A survey on attitudes of applicators toward pesticide waste reduction. AppliedEngineering in Agriculture 8(6):771-776.

Ozkan, H.E., and D.L. Reichard. 1992. Effect of orifice wear on flow rate, spray pattern and droplet sizedistributions of fan-pattern nozzles. Proceedings of 1992 ILASS-Americas 92, 5th Annual Conferenceof Atomization and Spray Systems. pp. 162-166.

Ozkan, H.E. and K.D. Ackerman. 1992. An automated computerized spray pattern analysis system.Applied Engineering in Agriculture 8(3):325-331.

Ozkan, H.E., D.L. Reichard, and K.D. Ackerman. 1992a. Effect of orifice wear on spray patterns fromfan nozzles. Transactions of the ASAE 35(4):1091-21096.

Ozkan, H.E., D.L. Reichard, and J.S. Sweeney. 1992b. Droplet size distributions across the fan patternsof new and worn nozzles. Transactions of the ASAE 35(4):1097-1102.

Ozkan, H.E., and D.L. Reichard. 1993. Effect of orifice wear on flow rate, spray pattern and droplet sizedistributions of fan-pattern nozzles. ANPP-BCPC 2nd Int Symp PesticideApplication Techniques, pp159-166.

Ozkan, H.E., D.L. Reichard, H. Zhu and A.S. Babeir. 1993a. Drift retardant chemical effects on spraydroplet size, pattern and drift. ANPP-BCPC 2nd Int Symp Pesticide Application Techniques, pp 149-156.

Ozkan, H.E., D.L. Reichard, H. Zhu, and K.D. Ackerman. 1993b. Effect of drift retardant chemicals onspray drift, droplet size and spray pattern. pp. 173.190. IN: P.D. Berger, B.N. Devisety, and F.R. Hall(eds.) Pesticide Formulations and Application Systems: 13th Volume, ASTM STP1183. Amer. Soc. forTesting and Materials, Philadelphia, PA.

Ozkan, H.E., D.L. Reichard, and H. Zhu. 1994. Influence of Drift retardant chemicals on spray dropletsize, pattern and drift. Proc. Symp. Engr. as a Tool to Reduce Pest. Consump. and Oper. Hazards inHort.., Acta Horticulture No. 372:25-32.

Ozkan, H.E., A. Miralles, C. Sinfort, H. Zhu and R.D. Fox. 1997a. Shields to reduce spray drift. J.Agricultural Engineering Research 67:311-322.

216

Ozkan,H.E., A. Miralles, C. Sinfort, H. Zhu, D.L. Reichard and R.D. Fox. 1997b. Effect of shieldingspray boom on spray deposition. Pesticide Formulations and Application Systems: 17th Volume, ASTMSTP 1328, G. Robert Goss, Michael Hopkinson, and Herbert M. Collins, Eds., American Society forTesting and Materials, Philadelphia, PA. pp129-142.

Tsay, J.-R. 1997. Effect of pneumatic and mechanical shields on spray deposition and drift. PhD Thesis,The Ohio State University, Columbus, OH, 289 pp.

Reichard, D.L. 1991a. ASAE Standard S471: Procedure for measuring sprayer nozzle wear rates. ASAEStandards, ASAE, St. Joseph MI 49085.

Reichard, D.L. 1991b. Wear rates of flat spray tips. Proc. Pesticide Application & Waste ManagementTechnology Workshop, Ohio Coop. Ext. Svc./ Ohio State Univ. p. 1-11.

Reichard, D.L., H.E. Ozkan and R.D. Fox. 1991. Nozzle wear rates and test procedure. Transactions ofthe ASAE 34(6): 2309-2316.

Reichard, D.L., H. Zhu, R.D. Fox and R.D. Brazee. 1992a. Computer simulation of variables thatinfluence spray drift. Transactions of ASAE 35(5): 1401-1407.

Reichard, D.L., H. Zhu, R.D. Fox and R.D. Brazee. 1992b. Wind tunnel evaluation of a computerprogram to model spray drift. Transactions of ASAE 35(3): 755-758.

Reichard, D.L., H. Zhu, and H.E. Ozkan. 1994. Computer simulations of spray drift from field sprayers.pp. 836-842. IN: A.J. Yule and C. Dumouchel (eds.) Proc. 6th Inter. Conf. Liquid Atomization andSpray Systems. Begell House, Inc., New York, NY.

Reichard, D.L. and H. Zhu. 1995. Computer model of factors influencing spray drift. Proc. Nat. Conf.Pesticide Application Technology. PP 52-61.

Ucar, T. 1997. Simulation and experimental study of jet agitation effects on agrochemical mixing insprayer tanks. PhD Thesis, The Ohio State University, Columbus, OH, 260 pp.

Zhu, H., D.L. Reichard, R.D. Fox, R.D. Brazee and H.E. Ozkan. 1994. Simulation of drift of discretesizes of water droplets from field sprayers. Transaction of ASAE. 37(5):1401-1407.

Zhu, H., R.D. Brazee, D.L. Reichard, R.D. Fox, A.C. Chapple and C.R. Krause. 1995a. Fluid velocityand shear in elliptic-orifice spray nozzles. Atomization and Sprays. 5:343-356.

Zhu, H., D.L. Reichard, H.E. Ozkan, R.D. Brazee and R.D. Fox. 1995b. A mathematical model topredict the wear rate of nozzles with elliptical orifices. Transactions of ASAE. 38(5):1297-1303.

Zhu, H., D.L. Reichard, R.D. Fox, H.E. Ozkan and R.D. Brazee. 1995c. Driftsim, a program to estimatedrift distances of spray droplets from field sprayers. Applied Engineering in Agriculture. 11(3):365-369.

Zhu, H., R.D. Fox, H.E. Ozkan, R.D. Brazee and R.C. Derksen. 1998a. A system to determine lag timeand mixture uniformity for inline injection sprayers. Applied Engineering in Agriculture. 14(2):

217

Zhu, H., H.E. Ozkan, R.D. Fox, R.D. Brazee and R.C. Derksen. 1998b. Mixture uniformity in supplylines and spray patterns of a laboratory injection sprayer. Applied Engineering in Agriculture. 14(3):

Zhu, H., R.D. Fox, H.E. Ozkan, R.D. Brazee and R.C. Derksen. 1998c. Reducing time delay forinjection sprayers. Transaction of ASAE 41(3):

PUBLICATIONS OF USDA-ARS, APPLICATION TECHNOLOGY RESEARCH UNIT

Bechtel, S.E., J.A. Cooper, M.G. Forest, N.A. Petersson, D.L. Reichard, A. Saleh and V.Venkataramanan. 1995. A new model to determine dynamic surface tension and elongational viscosityusing oscillating jet measurements. J. Fluid Mech. 293:379-403.

Brazee, R. D., R. D. Fox, D. L. Reichard and F. R. Hall. 1981.Turbulent jet theory applied to air sprayers.Transactions of ASAE. 24(2):266-272.

Brazee, R.D., D.L. Reichard, M.J. Bukovac and R.D. Fox. 1991. A partitioned energy transfer model forspray impaction on plants. J. Agric. Engng. Res. 50:11-24.

Brazee, R.D., M.J. Bukovac, J.A. Cooper, D.L. Reichard and R.D. Fox. 1994. Surfactant diffusion anddynamic surface tension in spray solutions. Transactions of ASAE. 37(1):51-58.

Brazee, R.D., R.D. Fox, J.A. Cooper, D.L. Reichard and M.J. Bukovac. 1997. Dynamic surface tensionin relation to droplet impaction interactions with leaf surfaces. Proceedings of Symposium on Growthand Development of Fruit Crops, June 19-21, 1997, East Lansing, MI. Acta Horticulturae

Bukovac, M.J., and D.L. Reichard. 1990. Spray droplet/chemical deposit interaction with leaf surfaces.HortScience 25:1146.

Bukovac, M.J., R.E. Whitmoyer, R.D. Brazee, and D.L. Reichard. 1993. Low volume application ofethephon: surfactant effects of spray droplet/deposit interaction with leaf surfaces. HortScience 29:125.

Bukovac, M.J., J.M. Leon, J.A. Cooper, R.E. Whitmoyer, D.L. Reichard, and R.D. Brazee. 1995. Spraydroplet: plant surface interaction and deposit formation as related to surfactants and spray volume. Proc.4th Inter. Symposium on Adjuvants for Agrochemicals, FRI Bulletin 193:177-185.

Coffman, C.W. and R.C. Derksen. 1997. Pesticide Deposition of Coveralls During VineyardApplications, Symposium Proceedings, The Third International Symposium on ConsumerEnvironmental Issues: Safety, Health, Chemicals and Textiles in the Near Environment, Ed. B.M.Gatewood, pp 156-165. St. Petersburg, FL, May 7-9.

Derksen, R.C. and D.I. Breth. 1994. Orchard air-carrier sprayer application accuracy and spraycoverage evaluation. Applied Engineering In Agriculture 10(4):463-470.

Derksen, R.C. and R.L. Gray. 1995. Deposition and air speed patterns of air-carrier apple orchardsprayers. Transactions of the ASAE 38(1):5-11.

Derksen, R.C. and C. Jiang. 1995. Automated detection of fluorescent spray deposits with a computervision system. Transactions of the ASAE 38(6):1647-1653.

218

Derksen, R.C. and J.P. Sanderson. 1995. Volume, speed, and distribution technique effects on poinsettia foliar deposits. Transactions of the ASAE 39(1):5-9.

Derksen, R.C., H.E. Ozkan, R.D. Brazee, H. Zhu and R.D. Fox. 1997. Effectiveness of TurboDropnozzle in drift reduction. ASAE Paper No. 971070.

Fox, R. D., R. D. Brazee, and D. L. Reichard. 1985. A model study of the effect of wind on orchardsprayer jets. Trans. of ASAE 28(1):83-88.

Fox, R.D., D.L. Reichard and R.D. Brazee. 1990a. Orchard sprayers: How much spray moves out of theorchard? Fruit Crops 1990: A Summary of Research, OSU/OARDC Res Circular 297:9-15.

Fox, R.D., R.D. Brazee, D.L. Reichard and F.R. Hall. 1990b. Downwind residue from air spraying ofa dwarf apple orchard. Transactions of the ASAE 33(4):1104-1108.

Fox, R.D., R.D. Brazee and A.W. Swank. 1991a. A tower mounted calibrator for hot-film anemometers.Transactions of the ASAE 34(6):2579-2583.

Fox, R.D., D.L. Reichard and R.D. Brazee. 1991b. Drift from an orchard air sprayer. Proceedings ofPesticide Application and Waste Management Technology Workshop, Sep 11-12, 1991, Ohio StateUniversity. 7 pp.

Fox, R.D., D.L. Reichard and R.D. Brazee. 1992a. A video analysis system for measuring dropletmotion. Applied Engineering in Agric. 8(2):153-157.

Fox, R.D., R.D. Brazee, S.A. Svensson and D.L. Reichard. 1992b. Air jet velocities from a cross-flowfan sprayer. Transactions of ASAE 35(5): 1381-1384.

Fox, R.D. Spray drift research review. 1993. Proceedings of Workshop on Pesticide Application andWaste Management Technology. OSU, 12pp.

Fox, R.D., D.L. Reichard, R.D. Brazee, C.R. Krause and F.R. Hall. 1993a. Downwind residues fromspraying a semi-dwarf apple orchard. Transactions of ASAE 36(2): 333-340.

Fox, R.D., F.R. Hall, D.L. Reichard, R.D. Brazee and H.R. Krueger. 1993b. Pesticide tracers formeasuring orchard spray drift. Applied Engineering in Agriculture. 9(6): 501-506.

Fox, R.D., D.L. Reichard, S.A. Svensson, C.R. Krause, R.D. Brazee and F.R. Hall. 1993c. Effect ofsprayer type on downwind deposits from spraying orchards. ASAE Paper No. 93-1078.

Fox, R.D., R.D. Brazee, S.A. Svensson and D.L. Reichard. 1994a. Experimental vs. computer-predicted air velocities for a cross-flow sprayer. Fruit Crops 1994: A Summary of Research, OSU/OARDC Res Circular 298, 115-119.

Fox, R.D., S.M. Hussein, D.L. Reichard, R.D. Brazee and F.R. Hall. 1994b. A Comparison of spray driftdeposited on ground and airborne spray collectors and on soybean plants. Fruit Crops 1994: A Summaryof Research, OSU/OARDC Res Circular 298, 109-114.

219

Fox, R.D. 1996. How drift is measured: test procedures/standards. Proceedings of AgrichemicalApplication Technology Update Inservice. OSU, March 1996. 10 pp.

Fox, R.D., R.W. Dexter, H. Zhu, D.L. Reichard and R.D. Brazee. 1996. Spray droplet size andextensional viscosity of sheared polymer solutions. ILASS Americas 9th Annual Conference on LiquidAtomization and Spray Systems. May, 1996, San Francisco, CA. 215-219

Fox, R.D., R.D. Brazee, C.R. Krause, R.C. Derksen, S.A. Svensson and H.E. Ozkan. 1997. Effect ofwind velocity on downwind deposits from spraying orchards. Proceedings of 5th InternationalWorkshop on Spraying Techniques in Fruit Growing. June 16-19, 1997, Radziejowice, Poland. ActaHorticulturae

Grundler, J. A. and M. G. Klein. 1997. Autodissemination of entomopathogenic fungi into a populationof Japanese beetles, Merimec State Park, Sullivan, Missouri, 1996. Proc. 1997 Regulatory Review -Japanese Beetle/Pine Shoot Beetle. pp. 55-62.

Jiang, C. and R.C. Derksen. 1995. Morphological image processing for spray deposit analysis.Transactions of the ASAE 38(5):1581-1591.

Klein, M. G. and J. J. Moyseenko. 1997. Isolation and infectivity of entomopathogenic nematodes fromOhio. J. Nematol. 29:590.

Krause, C.R., R.D. Brazee, R.C. Derksen, H. Zhu and R.D. Fox. 1997. Penetration of copper hydroxideinto hemlock canopies. Phytopathology 87(6): S54-S55.

Mannion, C. M., D. G. Nielsen, M. G. Klein, and W. McLane. 1996. Impact of root ball dips on whitegrub survival. Proc. SNA Research Conference 41:165-167.

Obendorf, S.K., J.F. Stone, R.C. Derksen, V. Ravichandran, C.W. Coffman, Y. Koh, J.P. Sanderson,and H.M. Stahr. 1995. Clothing contamination resulting from greenhouse spraying of pesticides.Performance of Protective Clothing: Fifth Volume, ASTM STP 1237. J.S. Johnson and S.Z. Mansdorf,Eds., American Society for Testing and Materials, Philadelphia, 1995.

Perez, C.J., A.M. Shelton, and R.C. Derksen. 1995. Effect of Application Technology and Bacillusthuringiensis Subspecies on Management of B. Thuringiensis subsp. kurstaki-resistant DiamondbackMoth (Lepidoptera: Plutellidae). J. of Economic Entomology 85: 1113-1119.

Reichard, D. L., R. D. Brazee, M. J. Bukovac, and R. D. Fox. 1986. A system for photographicallystudying droplet impaction on leaf surfaces. Trans. ASAE 29(3): 707-713.

Reichard, D.L. 1990. A system for producing various sizes, numbers and frequencies of uniform-sizedrops. Transactions of the ASAE 33(6): 1767-1770.

Reichard, D.L. and H. Zhu. 1996. A system to measure viscosities of spray mixtures at high shear rates.Pesticide Science, 47:137-143.

220

Reichard, D.L., H. Zhu, R.A. Downer, R.D. Fox, R.D. Brazee, H.E. Ozkan and F.R. Hall. 1996. Alaboratory system to evaluate effects of shear on spray drift retardants. Transactions of ASAE. 39(6):1993-1999.

Reichard, D.L., J.A. Cooper, S.E. Bechtel and R.D. Fox. 1997. A system for determining dynamicsurface tension, using the oscillating jet technique. Atomization and Sprays 7(2):219-233.

Reichard, D.L., J.A. Cooper, M.J. Bukovac and R.D. Fox. 1998. Effect of various parameters onrebound, and the techniques used to measure those parameters. Pesticide Science.

Salyani, M. and R.D. Fox. 1994. Performance of image analysis for assessment of simulated spraydroplet distribution. Transactions of ASAE. 37(4):1083-1089.

Salyani, M. and R.D. Fox. 1997. Measuring deposit from orchard sprayers with oil and water sensitivepaper. ASAE Paper No. 971049.

Tappan, C., C.R. Krause, and C.C. Powell. 1997. The use of electron beam analysis to determine thedeposition of chlorothalonil smoke particles in greenhouses. J. Environ. Hort 15(1):19-22.

Womac, A.R., J.R. Williford, B.J. Weber, K.T. Pearce, and D.L. Reichard. 1992. Influence of pulsesignal spike and liquid characteristics on performance of uniform-droplet generator. Transactions of theASAE 35(1):71-79.

Yang, X., L.V. Madden, D.L. Reichard, R.D. Fox and M.A. Ellis. 1990. Motion analysis of dropimpaction on a strawberry surface. Agricultural and Forest Meteorology 56:57-92.

Yang, X., L.V. Madden, and R.D. Brazee. 1991. Application of the diffusion equation for modellingsplash dispersal of point-source pathogens. New Phytol. 118:295-301.

Yang, X., L.V. Madden, D.L. Reichard, L.L. Wilson, and M.A. Ellis. 1992. Splash dispersal ofColletotrichem acutatum and Phytophthora cactorum from strawberry fruit by single drop impactions.Phytopathology 82(3):332-340.

Zhu, H., D.L. Reichard, R.D. Fox, R.D. Brazee and H.E. Ozkan. 1996. Collection efficiency of spraydroplets on vertical targets. Transactions of ASAE. 39(2):415-422.

Zhu, H., R.W. Dexter, R.D. Fox, D.L. Reichard, R.D. Brazee and H.E. Ozkan. 1997a. Effects of polymercomposition and viscosity on droplet size of recirculated spray solutions. J. Agricultural EngineeringResearch 67:35-45.

Zhu, H., C.R. Krause, R.D. Brazee, R.D. Fox and R.C. Derksen. 1997b. Assessment of spray coverage,canopy penetration and drift deposition in nurseries. ASAE paper No. 975006.

221

Reducing Drift from Air Assisted Sprayers Using TimingTargeting and Towers

Gary R. Van EeMichigan State UniversityEast Lansing, Michigan

Visual spray drift is an obvious problem associated with conventional air-carrier, orchard sprayers.The objective of our MSU research team is to improve application technology. That means concur-rently to reduce drift, maintain fruit quality and tree vigor, reduce quantity of needed pesticides, in-crease deposition efficiency and uniformity on the target, and maintain economic viability for thegrower. Air carrier sprayers use water and air to carry agricultural chemicals to the target canopy. Inan effort to reduce operating cost and loading time many growers have reduced the volume of water inthe spray solution. This trend towards “low volume” spraying has tempted growers to purchase spray-ers with too small an air delivery system. The result is inadequate spray coverage, increased pesticideuse, loss of fruit quality, and/or higher operating cost. The three primary factors to improve applica-tion technology are: Timing, Targeting and Towers.

Timing consists of two components: First, full implementation of Integrated Pest Management(IPM) strategies assure that pesticides are applied only “as needed”. It is no longer efficient to applyprotectant sprays following the traditional “Spray Calendar”. Second, availability of high capacitysprayers to cover the critical production area within a narrow window of concurrent “as needed” and“acceptable weather” conditions (typically 24 to 48 hours). Less pesticides are required to providecontrol if they are effectively applied at the optimum time.

Targeting consists of three operations: First, manually close all the nozzles that directed sprayeither above or below the target canopy. Second, adjust the application rate of each nozzle to match thedensity of the canopy it targets. Third, install an automated canopy sensing system, “electric eyes,”that turns a nozzle or group of nozzles “on” when it senses a target canopy.

Towers sprayers have a radically different air distribution system that produces three signifi-cant benefits. First, a conventional air-carrier orchard sprayer directs the air radially out from onecentral source. Many small droplets are carried through the canopy and released as “drift” in theatmosphere above the trees. An ideal tower sprayer is taller than the target canopy and produces acontinuous curtain of “straight stream”, uniformly spray laden air. The top of the tower focuses the airslightly downward toward the center of the canopy as well as providing a boundary of clean air abovethe canopy. This boundary of clean air traps the spray laden air into the target canopy, thus minimizingdrift. Second, a tower sprayer moves the spray laden air horizontally, parallel to the ground. Thehorizontal air movement provides each spray droplet the maximum opportunity to deposit on a targetsurface before it evaporates or lands on the soil.

Third, a tower sprayer typically produces smaller size spray droplets. Because of the greatlyexpanded length of the air outlet on a tower sprayer, the manufacturer needs to install many more,smaller nozzles to atomize the spray. Smaller nozzles produce smaller drops which result in improveddeposition uniformity. Pest problems start in the areas where it is the most difficult to deposit spraydroplets (ie. back side of leaves and fruit). Careful observation of the target canopy will reveal that bigdrops tend to deposit on the front side of the first layer of leaves and only small drops land in the hardto reach areas. Spraying smaller drops decrease deposition on the outside edge of the tree where thereis excess and increases deposition in the hard to reach areas of the fruit canopy. Some tower sprayersuse mechanical rotary atomizers with individual peristaltic metering pumps to minimize nozzle plug-ging, maximize the number and uniformity of small spray drops, and provide a wide range of continu-ously variable application rates.

222

Compact canopies like grapes, blueberries, and dwarf apples enable a grower to use a “tunnel”or “covered” sprayer. Conceptually this is the same as putting two tower sprayers into a portable,three-sided enclosure. The tunnel sprayers tend to be expensive, bulky, and awkward to maneuver inthe field. Some units show promise by providing good spray coverage and reducing spray drift. Theyare particularly effective in minimizing the effect of ambient wind. Catching and recycling the excessspray that drips from the canopy has presented significant problems. Spraying at ultra-low volume andrecycling the spray within an air vortex inside the tunnel looks promising.

In conclusion, many growers are spending far too much money on pesticides because they arenot investing enough money in a quality sprayer. Improved chemical application equipment whenproperly integrated with an IPM program produces high quality fruit, reduces pesticide use, reducesspray drift, lowers maximum fruit residues, and returns cash dividends. ______________________________________________________________________________________________*30 minute narrated visual presentation of sixty 35mm slides and 12 min. VHS video.

Air Carrier Fruit SprayersTargeting, Towers, and Tunnels

1998 - Video (VHS)

Introduction and BackgroundMin:Sec Scene0:00 Ag Tec PC400 in semi-dwarf apples0:30 Ag Tec PC400 in semi-dwarf apples - Night Time / Light Show1:00 Curtec 4-Fan spraying small cherries1:12 Curtec 8-Fan Diesel in young apples1:29 Curtec 8-Fan Diesel in semi-dwarf apples1:50 Curtec 8-Fan Diesel in semi-dwarf apples - Night Time / Light Show

Targeting the Canopy of Dwarf ApplesMin:Sec: Scene2:15 Conventional FMC - all nozzles spraying2:30 Ag Tec PC400 - targetted at dwarf apples2:50 FMC / CropCare - operating with sonic “eyes”3:10 Ag Tec PC400 / Tree Sense - operating with laser “eyes”

Tower Style Units Spraying Dwarf ApplesMin:Sec: Scene3:40 Ag Tec Tower - targetted at dwarf apples4:05 Durand Wayland Tower - all nozzles spraying4:20 Durand Wayland Tower / Tree See - operating with sonic “eyes”4:40 MSU Prototype Grape Sprayer with air seal on top of PropTec atomizers5:00 MSU Prototype Blueberry Sprayer with four PropTec atomizers5:20 Curtec C2000 with top atomizer not spraying5:40 Durand Wayland Streamliner - Conventional unit with all nozzles spraying

223

Night Time / Halogen Light Show in Dwarf ApplesMin:Sec: Scene6:00 Durand Wayland Streamliner - Conventional unit with all nozzles spraying6:10 MSU Prototype Grape Sprayer with air seal on top of PropTec atomizers6:25 Ag Tec PC400 / Tree Sense - operating with laser “eyes”6:45 Durand Wayland Tower - targetted at dwarf apple/ top nozzels off7:00 Durand Wayland Tower / Tree See - operating with sonic “eyes”7:15 MSU Prototype Blueberry Sprayer with eight PropTec atomizers7:30 Curtec C2000 with top atomizer not spraying

Curtec C2000 Demonstration in Semidwarf ApplesMin:Sec: Scene7:45 Curtec C2000 with top fans tilted 10o down & top atomizers off - Day Light8:55 Curtec C2000 with top fans tilted 10o down & top atomizers off - Light Show9:15 Curtec C2000 with top fans tilted 10o down & all atomizers on - Light Show9:30 Curtec C2000 with right top fan tilted 10o up & all atomizers on - Light Show9:45 Comparison Scene - Ag Tec PC400 in semi-dwarf apples - Light Show10:00 Curtec C2000 with top fans tilted 10o down & top atomizers off - Light Show

Tunnel Sprayer & Other UnitsMin:Sec: Scene10:10 MSU Prototype Peach Sprayer with six PropTec atomizers10:40 MSU Prototype Tunnel Sprayer with six PropTec atomizers - dwarf apples11:15 MSU Tunnel Sprayer (no sides) with six PropTec atomizers - wine grapes11:45 Durand Wayland Pecan Sprayer - 65' trees12:10 MSU Prototype Pecan Sprayer (Curtec) - 65' trees12:35 Complete

Gary R. Van Ee ([email protected])Richard Ledebuhr [email protected])Agricultural Engineering /Michigan State Univ.

224

Insurance Issues

Mike KellyFarmland InsuranceDes Moines, Iowa

Misapplication Categories

- Equipment Problem/Rinse Tank

- Overspray/Drift

- Rate/Patter/Wrong Product

- Wrong Field

Summary of Misapplication Losses

1996 1997

% of % of % of % ofLoss Claim $ Loss Claim$

Rinse 24% 26% 28% 33%Drift 31% 24% 20% 11%Wrong Product/Rate 39% 45% 42% 48%Wrong Field 6% 5% 10% 8%

Summary of Misapplication Losses

# of Loss CostOccurences Difference(97 v. 96) (97 v. 96)

Rinse 16% Fewer 23% LessDrift 52% Fewer 11% LessWrong Product/Rate 21% Fewer 48% LessWrong Field 12% More 7% More

There were 27 ½% fewer claims occurrences in 1997 vs. 1996 There was areduction of 37 ½% in number of claim dollars in 1997 vs. 1996. There wasabout $4.8 million in misapplication claims, which equates to a reduction ofabout $2.9 million in 1997 vs. 1996.

226

Safety Performance

1. Losses Far More Costly Then We Realized…

Ave. loss costs 4 times more then insurance claim.

Upset or lost customersLost future business & other businessRespraying time and productInvestigation & paperwork timeDeductible, increased ins. CostsStress

2. It’s A Management Concern

90%+ of mishaps are due to a faulty “process” (method of doing the task.)

inadequate traininglack of sleep & too rushedunsure of companies valuesincomplete instructionsimproper tools

3. Action Steps

Take time to train new workers

Share values (production & quality)Critical risks, repair procedures…

Reward production & quality equallyEmpower workers to do it……right

4. More Action Steps

Investigate mishaps yourselfRe-design the “process”Supervisors write up investigationPart of their performance

227

Guidelines for Fact Gathering of Spray Claims

What is the underlying issue?1. Weed problem?2. Chemical damage?3. Insect infestation?4. Weather related (cold, wet, dry, etc.)?5. Type of tillage (e.g., no till; chemical control won’t be 100% effective.

What is the general appearance of the problem?1. Cupped leaves?2. Dead plants?3. Spotted leaves?4. Hail damage?

What does the spray pattern look like?1. Skips?2. Nozzle plugged?3. Overlap?4. Uneven?

Information/Fact Items:1. Obtain a copy of spray report.2. Take several color pictures.3. Documentation of environmental conditions.4. Field history (fertilizer management practices or carryover concerns.)5. Statements from claimant.6. Agronomy Department Management insight/opinion.

Predicting yield loss due to drift is difficult because there is no way of determining how muchchemical came in contact with the plant. Usually crops can recover from drift concerns if it occurredearly enough in the growing season. However, with additional environmental stress the crop doesn’tresume normal growth quickly and yields will probably be affected.

Steps to Take:

1. Document unaffected areas.2. Document affected areas.3. Take color pictures of both.4. Obtain planting dates and field history.*5. Yield check in the fall.

Collecting complete documentation of producer’s management practices is essential now morethan ever.

* e.g., If a producer uses Counter insecticide when he plants his corn and has grass escapes thathe applies Accent to (post applied), there is a good chance of major yield loss. This is not amisapplication claim but a mismanagement claim.

229

The Measurement and Prediction of Spray Drift -Work at the Silsoe Research Institute

Paul S. MillerSilsoe Research Institute

Wrest Park, Silsoe, BEDFORD

1.0 Introduction

Silsoe Research Institute is an engineering research institute that has a long history of being involvedwith studies aimed at improving the application of agricultural pesticides. Work since the mid 1980’shas particularly examined methods by which spray drift can be measured, predicted and minimised.This has been conducted against a background of increasing environmental and human safety concernsrelating to the use of pesticides in the UK and throughout Europe such that there is now strong pressureto ensure that applications are confined to the target area. There are now legislative tools and codes ofpractice in a number of European countries that provide a framework for ensuring that spray drift iscontrolled while in some other countries there are financial incentives to encourage the use of applica-tion systems that limit the risk of spray drift. There is particular concern regarding the contamination ofsurface waters and buffer (or no-spray) zones are now used as part of the approvals procedure both inthe UK and in other European countries (Tooby, 1997) to minimise the risk of contaminating water inrivers, streams and ditches. This means that for chemicals with a toxicological profile that attracts abuffer zone, an area 6 m wide must be left unsprayed when using a boom sprayer and a variabledistance, commonly 18 m wide, left unsprayed when using an air-assisted machine to treat bush andtree crops. The distance in the case of a boom sprayer is fixed, but consideration is now being given tomaking the distance variable and dependent upon a localised risk assessment procedure.

In the UK, most pesticides are applied to arable crops using boom sprayers and a large proportion of thecomplaints relating to pesticide use investigated by the Health and Safety Executive involve spray drift(Anon, 1997). An important factor influencing the efficacy of applied pesticides is timeliness and thisis directly related to work rate for a given spraying configuration. For a boom sprayer, work rate can beincreased by using:

· higher forward speeds,· reduced liquid volume rates (smaller nozzles/finer sprays),· wider booms (but a tendency for greater boom heights),

but all of these factors can lead to an increased risk of spray drift. The need to control drift is thereforean important factor relating to the use of boom sprayers in arable farming situations. It is now widelyrecognised that the use of air-assisted sprayers to treat bush and tree crops can pose an increased risk ofdrift (Ganzelmeier et al 1995), the importance of which can be further emphasised because of therelatively high frequency of treatment of this type of crop.

This paper reviews some of the recent work that has been concerned with the measurement and predic-tion of spray drift conducted at Silsoe Research Institute. Much of this work has been funded by theMinistry of Agriculture, Fisheries and Food in the UK in support of pesticide registration proceduresbut with some measurements funded by commercial companies and Levy boards.

230

2.0 Field Measurement of Drift

2.1 From Boom Sprayers

Most field measurements of drift from boom sprayers have been made with the system operating overa short cut grass surface. Typically, multiple passes are made along a spray track between 60 and 120m long aligned at right angles to the mean wind direction (Miller, 1993). Measurements of the mete-orological conditions at the time of spraying have been made with a 10 m mast positioned upwind ofthe spray track and fitted with cup anemometers at five heights, temperature difference sensors at twoheights, a wind direction indicator and wet and dry bulb temperature probes. During a spray run, theoutputs from these sensors are recorded on a computer driven data logger at a frequency of typically 1hz. Weather conditions between recorded runs are monitored at a much lower frequency so as to tracktrends and weather changes during an experimental day. Ultra-sonic anemometers are used to recordturbulent air movements where such information is required particularly in conjunction with computermodelling studies – see section 4 of this paper. The recorded meteorological data is analysed to give amean wind speed at a reference height, commonly 2.0 m for boom spraying studies, from the recordedwind speed profile and a measure of atmospheric stability.

Measurements of airborne spray volumes downwind of the spray track are commonly made usingcylindrical passive collective polythene lines having a diameter of 1.98 mm (Gilbert and Bell, 1988),supported vertically to a height of 10.0 m on pneumatic masts. At least two lines are used at eachsampling distance. A spray liquid of water, non-ionic surfactant and coloured tracer dye is used suchthat drift deposits recovered from the sampling lines can be quantified by spectrophotometry or fluor-imetry, calibrated against samples of spray liquid taken directly from the spray nozzles during theexperiment. Sampling distances in the range 5.0 to 50.0 m from the edge of the spray swath arenormally used.

Accurate calibration and operation of the spraying system is an important part of any spray drift meas-urement. Detail measurements of the spraying speed and boom height are made during the experimentand measurements of nozzle flow rates made prior to each set of experimental runs. Measurements tocharacterise nozzles in terms of droplet size and velocity distributions are also made to provide addi-tional information to aid the interpretation of results.

Field experiments measuring the drift from boom sprayers can be either comparative or aimed at estab-lishing a reliable estimate of pesticide being carried downwind of the treatment area. In comparativetests, arrangements are made to support two different spraying systems, one on either side of the boomand each supplied with a different tracer dye that can be recovered separately from the drift samplingarray. Multiple passes in front of the target array gives captured airborne spray volumes that can bedirectly related to the output from each system and compared directly. For systems where it is notpossible to mount the application methods to be compared on the same boom structure (e.g. when usingair-assistance), then two complete machines have been used to make alternative passes of the spraytrack again using different tracers. The spraying between the systems travelling down the track is suchas to ensure no air disturbance from one machine to another and the tractor/sprayer combination sup-porting the systems to be compared are as similar as possible. Where best estimates of “absolute” driftlevels are required, care is taken to accurately monitor conditions so that an interpolative analysis candetermine best estimates of drift levels.

231

Results of measured drift volumes are normally expressed as a percentage of sprayer output that isairborne at a defined distance downwind of a single pass of the sprayer (Miller, 1993). Experience hasshown that when plotted against wind speed this commonly gives an approximately straight-line rela-tionship between wind speed and drift that is useful for an interpolative analysis, see Figure 1. It isrecognized that this linear relationship with an intercept on the x-axis of about 1.0 m s-1 arises because:

(a) at low wind speeds collector efficiency becomes low and wind speed and direction variablesuch that reliable estimates of airborne drift are difficult to obtain (NB we do not make meas-urements in wind speeds of <1.0 m s-1 measured at 2.0 m for this reason);

(b) in normal field conditions, forward and wind speed conditions are such that relatively smallpercentages of the total spray output are detrained and become airborne drift: most of the sprayis directed on to the target area and operations are a long way from a theoretical maximum of100% drift.

Figure 1. Measured drift from a boom sprayer operating over a short crop with two sizes of nozzles.

Results can also be expressed as a percentage of liquid volume leaving a treated area froma defined number of successive upwind passes of the sprayer in a field (Gilbert and Bell, 1988). Itshould be noted that numerical values are dependent upon the method of calculation with much lowerfigures relating to a treated area.

The results in Figure 1 also provide some indication of the level of variability that is commonlyassociated with the field measurement of spray drift. There is often a need to give relative measures ofdrift for a defined typical condition and this has been done for the results presented in Figure 1 inFigure 2 by using the fitted regression lines to give mean drift values at each wind speed. This showsthat the risk of drift from an application using flat fan nozzles to apply 120 l ha-1 as a fine quality sprayis approximately twice that of a similar arrangement applying 240 l ha-1 as a medium quality spray.

232

Figure 3. Field measurements of drift at different forward speeds.

Our work to examine the effects of sprayer forward speed on the risk of drift (Miller and Smith 1997)is an example of one of our field studies. Measurements were made in a range of wind speeds over ashort crop (approximately 10 cm tall) with a 12 m boom sprayer travelling at speeds of 4.0, 8.0, 12.0and 16.0 km h-1. Drift was measured 5.0 m downwind of the spray track using vertical sampling lines(see section 2.4) and the results are summarised in Figure 3. There was considerable variability in themeasured values but with an identifiable trend to suggest that increasing speed increased the potentialrisk of drift from boom sprayers particularly in low wind speed conditions. The effect of forward speedon the risk of drift from boom sprayers has also been studied in wind tunnel experiments –see section3 of this paper.

Figure 2. Spray drift as a function of wind speed for two sizes of conventional flat fan nozzlemounted on a boom sprayer.

233

2.2 From air-assisted sprayers operating in bush and tree crops.

The same basic protocols as used in arable crop situations have also been used to measure the spraydrift from air-assisted sprayers in bush and tree crops. Sampling lines are commonly positioned withinthe cropped area downwind of a defined spray track within the tree or bush rows. The presence of therow structure reduces the ability to respond to changes in wind direction during a trial (see section 2.3)and imposes some constraints on the positioning of collector masts at different downwind distances.The need to sample above relatively tall tree structures also means that sampling lines must be sup-ported to heights up to 15 m.

Spray deposits on collecting lines used in both arable and orchard experiments can be recovered fromsectioned lines to give airborne profiles of spray drift. Typical airborne profiles measured downwindof an air-assisted orchard sprayer operating at two different forward speeds are shown in Figure 4 andcompared with model predictions as discussed in section 4 of this paper (Xu, et al., 1997).

Results from this work have suggested that, for a given sprayer setting, spray drift tends to be reducedby operation at higher forward speeds although the extent to which this can be used as a practical driftcontrol strategy requires further study.

2.3 The development of a standardised protocol for the field measurement of drift

No field experiment measuring spray drift can be exactly repeated since a number of factors, andparticularly those relating to the weather, are variable. Interpolative analyses as referred to above aretherefore often used to compare results from experiments that have used comparable sampling strate-gies. Experience has shown that it is much more difficult to compare results from experiments thathave used very different sampling protocols. For this reason the International Standards CommitteeISO/TC 23/SC6 has been involved with a programme of work aimed at defining a standardised ap-proach to the field measurement of spray drift, and Silsoe Research Institute has made an input to thiswork. The standard aims to facilitate some flexibility in the measurement of drift while imposing someconstraints that enable the results from different trials to be compared.

Figure 4. Drift profiles measured from an orchard sprayer operating at two different forward speeds:left – low speed; right – higher speed.

234

The main features of the draft standard protocol are:

· the use of defined sampling distances of 5.0 and 10.0 m downwind of the sprayed swath or 5.0 mwith horizontal collectors to 50.0 m;

· a wind speed reference at a height of 2.0 m and a minimum wind speed for measurements of 1.0 ms-1;

· the use of a reference cylindrical passive collector which has a high collection efficiency and aknown sampling area;

· the use of reference spraying conditions for both arable crop (boom) sprayers using reference noz-zles (defined within the International BCPC scheme) and air-assisted orchard sprayers using areference machine;

· a defined wind direction of 90o to the spray track with a maximum tolerance of +/- 30o;

· a requirement to fully report the conditions under which the measurements are made.

The standard is currently in draft form with a timetable that will provide a version for circulation bymid-1998. An important implication of the spray drift standard relates to the classification of nozzleperformance and particularly the use of reference nozzles to define the boundaries between spray quali-ties and drift risk classes. Work is now in progress to define agreed protocols for determining sprayquality from measurements of droplet size distributions and a direct measure of drift risk from windtunnel test (Southcombe et al., 1997) – see section 3.1 of this paper.

2.4 The performance of drift sampling systems

The performance requirements for a reliable spray drift sampling strategy include the use of collectorshaving:

· a high and definable collection efficiency;· a high collection capacity such that losses from the collector due to run-off are minimised;· a good recovery such that the quantity of airborne spray can be accurately determined;· a definable collection area particularly if estimates of “absolute” drift are required.

An initial study (Miller et al., 1989) compared the sampling performance of different passive samplingsurfaces with a Rotorod and a laser-based imaging/shadowing instrument (PMS). Results showedwide variations in performance depending upon the airborne concentration distribution being sampled,the sampling method and the methods of calculating the results.

235

A more recent experimental investigation was conducted to determine the airborne sampling character-istics of cylindrical targets with diameters in the range 0.61 to 7.80 mm. Assessments were made of thetotal collection capacity and the apparent collection efficiency by sampling the airborne spray from anagricultural spray nozzle operating in a wind tunnel. As expected, the smaller diameter sampling lineshad a higher collection efficiency and a greater specific collection capacity – see Figures 5 and 6. Therelationships between cylinder diameter and collection efficiency did not follow characteristics definedby authors such as May and Clifford (1967) and the differences were related to the droplet size distri-butions in the drifting spray cloud. Some differences in collection efficiency were also identified forsampling lines formed from different plastic materials (Miller and Rubbis, in preparation).

Figure 6. The total collection capacity of different size sampling lines operating in the same driftconditions in a wind tunnel.

Figure 5. Collection efficiencies for polythene and PVC collection lines of different diameter comparedwith predictions using May & Clifford (1967) and measured droplet size distributions;EV = volume median diameter, EN = number median diameter.

236

Results of studies using absorbent collection surfaces such as woollen lines or pipe-cleaners haveshown that these systems have a very high collection capacity in comparison with passive collectorswith a non-absorbent surface, but that the effective collection area can be more difficult to define.

3.0 The Use of Wind Tunnels

The relatively well controlled conditions in a wind tunnel provide a suitable environment for studyingthe drift from agricultural spraying systems. At Silsoe Research Institute we have been using an openEffiel type tunnel design with a working section 2.0 m wide, 1.5 m high and approximately 5.0 m longin which to make measurements of airborne spray downwind of both single nozzles and small boomarrangements. Similar approaches to those used under field conditions have been used in the tunnel.Typically, a matrix of horizontal sampling lines is supported across the tunnel 2.0 m downwind of a testnozzle and with a vertical spacing between lines of 100 mm. As in field tests, tracer dye techniques areused to quantify airborne spray profiles downwind of a spraying system.

3.1 Single Nozzle studies

Much of our initial work in wind tunnels has involved studies with single nozzles mounted statically inthe tunnel. A study to characterise the potential drift reduction from a number of nozzle systems aimedat giving drift control has been conducted. The results from the work confirmed that the use of a pre-orifice in a flat fan nozzle design and the use of twin-fluid nozzle systems could give improved driftcontrol when compared with conventional designs (Walklate, et al., 1994). Results from this and otherstudies showed that drift was a function of droplet velocity and spray structure as well as droplet sizedistribution and that the percentage of spray volume in small droplet sizes was not always a reliableindicator of the potential for drift. More recently, nozzles using a Venturi type principle to mix air andspray liquid in the nozzle body have also been shown to have the potential to reduce drift. The resultsin Figure7 show measured airborne spray profiles for conventional, pre-orifice and Venturi types ofnozzle operating at the same liquid output and demonstrate the potential for drift control by appropriatenozzle design.

Figure 7. Measured airborne profiles in tests with three different flat fan nozzle designs.

237

The work with single nozzles in a wind tunnel has also aimed at providing a basis for the classificationof nozzle performance in relation to the risk of drift when operating on boom sprayers. An initial studyinvolving a number of laboratories in the UK (Miller, et al., 1993) showed that, by using a definedprotocol, good agreement could be obtained between results for total downwind airborne spray volumein a range of tunnel conditions and using different sampling systems. It is now proposed to extend theexisting British Crop Protection Council classification of nozzle systems to include a drift risk factorthat will be determined from the results of airborne spray measured in wind tunnel conditions(Southcombe et al., 1997). The drift factor will use an analysis that will account for both the totalvolume of spray measured downwind of a nozzle operating in defined airflow conditions and the ver-tical (or horizontal) profile of the airborne drift. This will then account for material that is detrainedfrom a spray structure at greater heights above the ground that will be more prone to drift. Discussionsare still taking place to completely define the protocols for wind tunnel measurement and to agree theterminology that will be used in conjunction with the drift factor descriptor.

Wind tunnel studies have also been used to show that the detrainment of spray from a flat fan nozzle isa function of the angle that the airflow direction makes with the spray fan (Smith and Miller, 1994).With the spray fan aligned with the airflow, the airborne spray has been found to be only 10 to 15% ofthat measured with the spray fan arranged at right angles to the airflow. This result suggests that theforward speed component of a moving sprayer is an important parameter influencing drift perform-ance. This has been studied directly in a series of studies in which a nozzle was moved across theairflow in the tunnel and in which the simulated speed of both the airflow and the nozzle could bevaried independently. Results from this study showed that the forward speed did influence the risk ofdrift from flat fan nozzles operating on a boom sprayer particularly at relatively low wind speeds(Miller and Smith, 1997) – see Figure 8.

Figure 8. Measure airborne spray downwind of a moving nozzle in a wind tunnel.

238

The results of this work are in relatively good agreement with those found in field tests with compara-ble systems (Figure 3) and demonstrate the advantages of operating in a wind tunnel where closecontrol over operating conditions can be maintained.

Wind tunnel testing also enabled the effects of pressure and forward speed to be studied separately.Interactions between speed and pressure are important since many boom sprayers used in Europe em-ploy a control system that adjusts pressure in response to measured forward speed so as to keep appli-cation rates constant. The results from experiments with a moving nozzle at different pressures areplotted in Figure 9.

Figure 9. The interactions between forward speed and operating pressure for two sizes of flat fan nozzle:left – a small output nozzle creating a fine spray; right – a medium output nozzle creating amedium quality spray.

For the medium nozzle, the results show some effect of pressure on the measured drift although differ-ences in drift at pressures of 3.0 and 4.0 bar are small. In the case of the small output nozzle, there waslittle difference in drift at pressures of 2.0, 3.0 and 4.0 bar. Increasing pressure decreases droplet sizebut also increases the velocity of droplets leaving the nozzle and these two factors have opposite effectson spray drift. The results suggest that the increases in drift due to forward speed that are recognisedwith full-scale boom sprayers in European conditions arise mainly due to the interactions of an airflowwith the spray structure. This is consistent with the formation of vortices that have been observed as airflows past flat fan nozzles both in wind tunnel and field experiments (Young, 1991).

3.2 Studies with boom sections and multiple nozzles

The airflow around a spray nozzle has been identified as an important mechanism in the detrainment ofdroplets from a spray cloud (Young, 1991; Miller, 1993). It is likely that one of the reasons why driftreductions are achieved with sprays produced by twin-fluid and Venturi type nozzles relates to therelatively porous structure of the sprays produced by these nozzles.

Practical boom spraying systems use nozzles mounted in a linear array along the boom structure. Someexperiments were therefore conducted to examine the interactions of nozzles on a boom and this workis continuing via a studentship project being conducted jointly with Cranfield University (Silsoe Col-lege). Results from a study in which the airborne spray profiles downwind from single nozzles operat-

239

ing alone and as part of a boom system are summarised in Figure 10. When operating as part of a boomarrangement, the test nozzle was supplied with a tracer dye solution in the same way as for singlenozzle tests and the nozzles on either side of the test unit sprayed only water but using the sameoperating conditions. In this way measured results from the two experimental runs were directly com-parable.

The airborne spray profiles showed higher levels of drift from the multiple nozzle arrangement. Thetotal quantity of airborne spray, expressed as a percentage of nozzle output, was 18% higher than for asingle nozzle for a low output nozzle creating a fine spray and, 86% higher in the case of the mediumspray nozzle (Miller et al., 1995). Figure 10 also shows that the airborne spray cloud from the multiplenozzle arrangement is less spread in the transverse direction but extends to a greater height. This resultis consistent with the hypothesis that air tends to flow round the spray structure. In the case of themultiple nozzle system, air accelerates in the region between nozzles and this accelerating airflowcauses some small droplets to be detrained from the spray fan.

3.3 Future trends for wind tunnel work and the further development of test protocols.

The proposals to extend the existing British Crop Protection Council nozzle classification system toinclude a drift risk factor based on the results from wind tunnel tests has been discussed in section 3.1above. There is a need within this scheme to identify ways of classifying nozzle systems that producesprays having “air-included” droplets such as the twin-fluid and Venturi nozzle systems so that the driftreducing capabilities of these designs can be fully exploited.

Recent work has also shown that the physical properties of a formulation can have substantial effectson spray formation with flat fan nozzles operating on boom sprayers (Butler Ellis et al., 1997), and thatthis is likely to have important implications relating to the risk of drift. At Silsoe Research Institute wehave therefore recognised the importance of being able to make measurements in controlled condi-

Figure 10. Measured airborne spray profiles from singe and multiple nozzle arrangements creating amedium quality spray; top – for a single nozzle; bottom – for a multiple nozzle configuration.

240

tions, at a realistic scale and using real pesticide formulations. We have built a new re-circulating windtunnel with a working section 3.0 m wide, 2.0 m high and 7.0 m long and a maximum wind speedcapability of up to 12.0 m s-1. Figure 11 shows the arrangement of this new wind tunnel facility.

4.0 Computer Simulation Models

Modelling approaches have been developed to predict the downwind airborne spray fluxes from bothboom sprayers operating over arable crops and for air-assisted machines operating in bush and treecrops. We have used both random-walk type approaches to describe the trajectories of droplets down-wind of a spray and plume dispersion models to predict the behaviour of a drifting spray cloud. Modelshave been verified by comparison with field measurements made in well monitored conditions andhave been used to extend predictions of drift risk to a wide range of conditions (Hobson et al., 1993).

4.1 Modelling the drift from boom sprayers operating over arable crops.

We have developed models for simulating droplet trajectories from hydraulic flat fan pressure nozzlesby considering droplet motion in two phases, namely:

· close to the nozzle where trajectories are dominated by the conditions associated with droplet for-mation; and

· a second phase that tracks movement of detrained droplets as they are dispersed by atmosphericturbulence.

Our initial approaches used a simplified description of trajectories close to the nozzle which used aninitial velocity equal to that of the liquid sheet (Miller, 1993) and a uniform entrained air velocityprofile based on the structural geometry of the spray fan (Miller and Hadfield, 1989). The descriptionof this simplified entrained air flow field has been modified in more recent work to give values of thelocal air speed that more closely matched measurements of small droplet velocities within the spray

Figure 11. Wind tunnel arrangement for spray drift studies at Silsoe Research Institute.

241

cloud (Smith and Miller, 1994; Miller et al., 1996). Figure 12 plots the entrained air velocities atdifferent positions in the spray cloud from a flat fan nozzle estimated by measuring the velocities ofdroplets <50 mm diameter and shows the agreement with model predictions to be encouraging (Milleret al., 1996).

The interaction of cross flows with the entrained airflow in the spray has been studied analytically inconjunction with Cambridge University. The results of this work show that the tendency for the crossflow to penetrate the spray structure can be related to the ratio between the entrained air and crossflows. When the cross flow is substantially stronger than the entrained air flow then the spray structureis penetrated and droplet trajectories directly influenced by the action of the cross flow. The work alsoidentified that the turbulence structure in the entrained air jet of a spray had a much smaller scale thanthat of an equivalent free air jet and that this has implications for modelling spray droplet behaviourclose to the nozzle.

An important use of simulation modelling approaches has been to examine the relative effect of thedifferent factors influencing drift (Hobson, et al., 1993) and to assess the sensitivity to variables thatcan be changed by application techniques. As an example, results from this type of modelling studysuggested that operating an 800 nozzle at a height of 0.5 m would give more drift than an equivalent1100 nozzle at a height of 0.35 m even though the droplet size from the 800 nozzle was coarser.

4.2 Modelling spray drift from air-assisted orchard sprayers.

We have developed models that use a random-walk approach to predicting droplet trajectories awayfrom orchard sprayers (Walklate, 1992). In this model the spray source is represented as an extendedsource close to the sprayer but remote from the mean forced airflow field generated by the machine.Results from this model were shown to be in reasonable agreement with those from field tests andenabled factors such as the efficiency of drift collector lines in experiments to be quantified.

Figure 12. Measured and predicted entrained air velocities within the spray from an agricultural flat fan nozzle.

242

Recent work (Xu et al., 1996; Xu and Walklate, 1996) has developed a numerical model to study thecomplex flow structure close to an air-assisted orchard sprayer by solving the time- and spatial- aver-aged mass and momentum conservation equations. When applied to a machine operating in an artifi-cial crop, the velocity profiles predicted were in good agreement with measurements. For spray trans-port, the liquid phase has been treated separately and trajectories of droplets calculated using randomsampling to estimate turbulence levels in the air flow. Mean dispersion properties were obtained byaveraging over a statistically significant number of droplets and model predictions have been shown toagree well with field measurements (see Figure 4).

We have found the use of a computer simulation model to be very useful in estimating the likelymaximum airborne concentrations at large distances downwind of chemicals applied to orchard cropswith air-assisted sprayers. Practical measurements of drift at distances of 200 m and more from theedge of a treated crop are difficult to make with a defined level of accuracy. We have therefore used anapproach of making measurements relatively close to the sprayer (10 m downwind) and using modelpredictions to make estimates of the likely behaviour and concentrations at much larger downwinddistances.

5.0 Conclusions

Engineering research work at Silsoe Research Institute relating to the measurement and prediction ofspray drift has provided a sound basis for estimating downwind deposition and airborne concentrationsof chemical formulations applied to crops as sprays. This work is being further developed and used bycommercial organisations and regulatory bodies to estimate the effects of drift and identify methods bywhich it can be minimised.

Acknowledgement

The author wishes to express his thanks to all members of Chemical Application Group who havecontributed directly or indirectly to this paper and to the organisers of the conference for the invitationto present the work and the hospitality while at the conference.

References

Anon (1997) Pesticide Incidents Report 1996/97. Field Operations Directorate Report. The Healthand Safety Executive.

Butler Ellis, M. C.; Tuck, C. R.; Miller, P. C. H. (1997) The effect of some adjuvants on spraysproduced by agricultural flat fan nozzles. Crop Protection, 16, 41 – 50.

Ganzelmeier, H.; Rantmann, D.; Spangenberg, R.; Stieloke, M.; Herrman, M.; Wenzelburger, H. J.;Walter, H. F. (1995). Studies on the spray drift of plant protection products. Blackwell Wissenschafts-Verlag GmbH Berlin/Wien.

Gilbert, A. J.; Bell, G. J. (1988). Evaluation of drift hazards arising from pesticide spray application.Aspects of Applied Biology, 17, 363 – 375.

Hobson, P. A.; Miller, P. C. H.; Walklate, P. J.; Tuck, C. R.; Western, N. M. (1993) Spray drift fromhydraulic spray nozzles: the use of a computer simulation model to examine factors influencing drift.Journal of Agricultural Engineering Research, 54, 293 – 305.

243

May, K. R.; Clifford, R. (1967). The impaction of aerosol particles on cylinders, spheres, ribbons, anddiscs. Annals of Occupational Hygiene, 10, 83 – 95.

Miller, P. C. H. (1993). Spray drift and its measurement. In “Application Technology for Crop Protction”(Eds. G. A. Matthews and E. C. Hislop), 101 – 122.

Miller, P. C. H.; Butler Ellis, M. C.; Tuck, C. R. (1996) Entrained air and droplet velocities producedby agricultural flat fan nozzles. Atomization and Sprays, 6, 693 – 707.

Miller, P. C. H.; Hadfield, D. J. (1989) A simulation model of the spray drift from hydraulic nozzles.Journal of Agricultural Engineering Research, 42, 135 – 147.

Miller, P. C. H.; Hislop, E. C.; Parkin, C. S.; Matthews, G. A.; Gilbert, A. J. (1993) The classificationof spray generator performance based on wind tunnel assessments of spray drift. Proceedings, ANPP-BCPC Second International Symposium on Pesticide Application Techniques, Strasbourg, 1, 109 – 116.

Miller, P. C. H.; Rubbis, M. (in preparation) The collection efficiency of cylindrical targets for spraydrift measurement. (for submission to Crop Protection).

Miller, P. C. H.; Smith, R. W. (1997) The effect of forward speed on the drift from boom sprayers.Proceedings, Brighton Crop Protection Conference – Weeds, 399 – 408.

Miller, P. C. H.; Smith, R. W.; Tuck, C. R.; Walklate, P. J. (1995) The classification of agriculturalsprays based on droplet size distributions and the results from wind tunnel tests. Proceedings, BrightonCrop Protection Conference – Weeds, 1125 – 1134.

Miller, P. C. H.; Walklate, P. J.; Mawer, C. J. (1989) A comparison of spray drift collection techniques.Proceedings, British Crop Protection Council Conference – Weeds, 669 – 676.

Smith, R. W.; Miller, P. C. H. (1994) Drift prediction in the near nozzle region of a flat fan spray.Journal of Agricultural Engineering Research. 59, 111 –120.

Southcombe, E. S. E.; Miller, P. C. H.; Ganzelmeier, H.; van de Zande, J. C.; Miralles, A.; Hewitt, A.J. (1997) The International (BCPC) Spray Classification System including a drift potential factor. Pro-ceedings, Brighton Crop Protection Conference – Weeds, 371 – 380.

Tooby, T. E. (1997) Buffer zones: Their role in managing environmental risk. Proceedings, BrightonCrop Protection Conference – Weeds, 435 – 442.

Walklate, P. J. (1992) A simulation study of pesticide drift from an air-assisted orchard sprayer. Jour-nal of Agricultural Engineering Research, 51, 263 – 283.

Walklate, P. J.; Miller, P. C. H.; Rubbis, M.; Tuck, C., R. (1994) Agricultural nozzle design for spraydrift reduction. Proceedings ICLASS-94 conference, Rouen, France, 851 – 858.

Xu, Z. G.; Walklate, P. J. (1996) 3-D flow structure and transport from a moving orchard sprayer.Proceedings of 3rd ECCOMAS CFD Conference, 547 – 552.

244

Xu, Z. G.; Walklate, P. J.; Miller, P. C. H. (1997) Evaluation of a stochastic model for spray transportprediction from air-assisted sprayers. Aspects of Applied Biology, Optimising Pesticide Applications,48, 195 – 200.

Young, B. W. (1991) A method for assessing the drift potential of hydraulic nozzle spray clouds, andthe effect of air-assistance. British Crop Protection Council Monograph No. 46. Air-assisted Sprayingin Crop Protection, 77 – 86.

245

Small Group Concurrent Sessions: Developing DriftManagement Practices (Summary)

Concurrent Session #1 Aerial-Fixed Wing

Dennis Gardisser, Technical ExpertUniversity of Arkansas Cooperative Extension

Little Rock, Arkansas

Tammy Gould, FacilitatorMaine Board of Pesticides Control

Augusta, Maine

Clay Kirby, ScribeUniversity of Maine Cooperative Extension

Orono, Maine

The Tuesday afternoon fixed-wing application equipment session began with three shorttechnical presentations.

(1) Dr. Ernest J. Hewett, III, Extension Associate, North Carolina State University, Departmentof Biological and Agricultural Engineering

This presentation will outline the North Carolina Department of Agriculture Pesticide DriftReduction Project. Dr. Ernest J. Hewett III is the project leader of a two-year, $200,000 projectfunded by the North Carolina Pesticide Environmental Trust Fund. The objective of the project is toreduce off-target drift from both aerial and airblast sprayers used in fruit and Christmas tree produc-tion. The objective will be accomplished by providing swath and droplet analysis training utilizingswath and droplet analysis equipment developed by WRK Inc. Currently North Carolina is one ofthe states to adopt “restricted areas” where pesticides can not be deposited by aerial application. Theimplementation of these “restricted areas” have further motivated aerial applicator professionals toimprove their spray pattern, to reduce off-target drift and provide better service to their clients. Theproject is working with the state and National Agricultural Aviation Association by incorporating theNAAA Operation SAFE and PAASS programs. Participation in the Drift Reduction Project isvoluntary, but viewed as a good faith effort and a professional commitment by North Carolina’sapplicators to reduce or eliminate off-target drift.

(2) Nicholas Woods, Director, The Centre for Pesticide Application and Safety (C-PAS),University of Queensland, Australia

Fixed Wing BMPs - Discussion and examples of management practices being developed in Austra-lia.

246

(3) Buddy Kirk, USDA-ARS, College Station, Texas

Demonstration of the AgDrift computer model.

****************************************************************************Following the presentations, the group briefly discussed and selected the following statement

as their goal for the afternoon:

GOAL: The development of application-specific best management practices (BMPs) to managepesticide drift problems and concerns.

The group then brainstormed ideas about managing pesticide drift. These ideas were thenseparated into one or more of five categories:

A. Material/Chemistry - Roy Macki, Monsanto-CanadaB. Machine/Equipment - Buddy Kirk, USDA-ARSC. Environment/Conditions - Harold Thistle, USDA Forest ServiceD. Decision Makers - Jack Peterson, Arizona Dept. of AgricultureE. Other - Adolfo Marvin-Gallo, California Dept. of Pesticide Regulation

As indicated, a leader was assigned to each category and the group broke up into smaller units todiscuss those ideas related to their category. After 40 minutes, each sub-group summarized theirwork and presented it to the entire breakout session. Sub-group notes are included here.

A. Material/Chemistry - Roy Macki, Monsanto-Canada

Active Ingredient Additives Characteristics

Formulations Drift agents Least toxicRate (application) Formulations Residue levelsDry formulations pH buffers, additives Tank mixesNon-volatile Efficacy

Droplet sizeDepositionAgitation

Precision application of pesticides can be undertaken using aircraft by:

establishing pre-application communication between all partiesselecting wind vectors away from susceptible areasselecting appropriate meteorological conditions (e.g., neutral stability)choosing large droplets and correctly calibrating aircraft for DGPScontrolled placement applicationusing downwind in crop buffer distancesmaking use of vegetative buffers where appropriate.

247

BMPs1. Drift agent present and understand impact2. Low toxic chemistry to non target3. Low residue on crop4. High efficacy formulation5. Ions residual kill (minimize degradation in tank)6. Low rate of application but still get efficacy7. Droplet size - balances drift and deposition and efficacy8. Require low agitation9. Low volatility

R&D/Quantifications1. The interaction of all the chemical components is not well understood.2. [It is] difficult to measure drift in the field vs. lab.3. What is the interaction with equipment?4. Modeling - Pull it all together5. Education and implementation

B. Machine/Equipment - Buddy Kirk, USDA-ARS

BMP’S

Spray Nozzles: Minimum number of nozzles

Specifications Place nozzles on boom to give uniform deposition in swath.Orientation (No wider nozzle placement than 2/3 wingspan.)Placement Nozzles, pressure, orientation, etc. adjusted to give largest

droplet size consistent with maintenance of deposition and efficacy.

248

Boom Position Placement/Length:

• Boom length and placement such that wing tip vortex influence is minimizedand nozzles are releasing spray in direction of air flow off the wing.

• Spray release height 8 - 10 ft ? above target.• Use half boom shut off for spraying edges of fields and adjacent to sensitive

areas to minimize off-target deposits.• Use flow control to maintain consistent application rate.• Maintain optimum mix tank/aircraft hopper agitation for uniform AI rate.

Aircraft:

• Air speed consistent with aircraft operating specifications and consistentwith maintenance of droplet size for reduced drift.

• Use GPS for position/swath location to eliminate flaggers and maintainuniform deposit/dosage on target areas.

• Maintain aircraft & nozzles for proper operation.• Attend fly-in’s to fine-tune operations at least every 3 years.

C. Environment/Conditions - Harold Thistle. USDA Forest Service

Conditions were broken down into three subcategories:Meteorological = MPest Conditions = PSite Conditions = S

Type ofItem Conditions Effect on Application

Timing PM Efficacy/Pest Activity Obstacle Contribution S Influence Wind and Release Height Ground & Surface Water S Off-Target Impact, Legal &

Regulatory, Mosquito, Larvaciding Noise & Odor Trespass S Nuisance Buffer Zones S Protect Sensitive Non-Targets Resistance to Pesticides P Choice of Product Pest Type P Choice of Method, Product etc. Crop Canopy S Micromet, Spray Capture, Target Pest Pressure P Timing and Economics, Threshold Drop Size PM Optimize for Efficacy and Drift Mgmt. Release Height SM Drift Management Sensitive Areas/Restricted Areas S Off Target Impacts, Regulatory

249

Type ofItem Conditions Effect on Application

Inversion M Drift Management, Efficacy Deposition M Optimize for Target Temperature & Relative M Drop Size Evaporation, Humidity, Climate Stability, Pest Activity Forestry and Vector Control MPS Specific Activity for Met, Pest & Site Wind Speed/Direction M Deposition, Efficacy, Drift Mgmt.,

Stability, Activity Crop Proximity/Selection S Target Consideration Endangered Species S Off Target Impact, Regulatory Population Exposure S Health Effects Night Technique MPS Control Strategies, Public

D. Decision Makers - Jack Peterson, Arizona Dept. of Agriculture

1) Education/Communication

Information Consolidation/Current Information SimplificationUnderstanding of Issues - Stewardship, responsibility, behaviorOutreach - to all partiesPlanning - Models

2) Operational Practice

These are field practices/activities controlled by the operator that must be considered before makingan application to minimize drift.

Air Speed Notification/PostingAlternate Application Methods Optimization StrategyDrift Extension/Agent Proper RinsingGIS/GPS Release HeightNo/Yes Swath Adjustment

Vector Spraying

E. Other - Adolfo Marvin-Gallo, California Dept. of Pesticide Regulation

♦ Communication by Applicator/Grower of Application Specific Data to CommunityBefore Application: (Community Training): Conferences, Training, Outreach Materials

♦ Check With/Know Laws and Regulations (Federal, State & Local)

250


Concurrent Session #2 Aerial-Rotary Application Equipment & Drift

David L. Valcore Dow AgroSciencesand Milton E. Teske, Continuum Dynamics, Technical Experts

Maxwell L. McCormack, Jr., FacilitatorMonsanto

Deer Isle, Maine

Henry Jennings, ScribeBoard of Pesticides Control

Augusta, Maine

This draft was hastily crafted during a short time period with limited preparation for the participants.Thus, among the participants, it was considered to be a valuable learning experience. The group prima-rily was composed of operational forestry interests. Therefore, it had a biased focus on herbicideprograms of industrial forest management in Maine and New Hampshire.

The content of an “Aerial Drift Reduction Advisory” by the National Coalition for Drift Minimizationserved as an outline and a dominant focus for the discussions; these conclusions should be consideredin concert with this document. During the discussions there was a persistent concern over the role ofthe US EPA and the relative importance of local administration of drift management programs.

1. General considerations of drift should be differentiated from off-target deposition ofconsequence.

2. BMP’s should be organized according to:

(1) Boom-nozzle configuration groups (e.g. conventional, Microfoil, TVB, etc.),(2) Use categories (e.g. forestry, ROW, vector control, general agricultural, etc.),(3) Target pest categories (e.g. insects, weeds, pathogens, etc.)

3. All factors which determine droplet size should be reviewed in order to achieve the largestdroplets consistent with efficacy objectives. Efficacy of treatments is an essential qualifierin defining large-size droplets.

Focus on minimizing fine droplets which could result in unacceptable drift. Narrow dropletspectra are desirable. Spraying system pressure should be consistent with nozzle type andorientation so as to avoid formation of fines.

251

4. Spray boom length should be less than rotor length and be consistent with the boom-nozzlesystem and desired spray pattern. The basis for determining best boom lengths requiresadditional research and elaboration.

5. Application height should be at the lowest level possible as recommended by respectivemanufacturers while providing for maximum safety during application.

6. Applicators should adjust the path of the aircraft in order to compensate for displacementof spray patterns in cross winds. This adjustment should be proportional to the existingdrift potential.

Half boom shut-offs may be used to help reduce downwind swath displacement near treatmentarea edges.

7. Applications should not be made when wind speed exceeds 10 mph. Be cautious when applyingin wind speeds less than 2 mph because temperature inversions may be present and winddirections may vary.

Applicators should consider established local wind patterns. Wind conditions should be moni-tored at treatment sites during application.

8. Applicators should give special attention to exercising care near identified sensitive areas andwhen such areas are downwind, buffer zones should be considered. Monitoring of sensitiveareas with spray cards can be considered.

9. Applicators should compensate for extremes of temperature and humidity.

10. Temperature inversions should be recognized and care taken to release spray patterns belowboundary layers, or narrow spray droplet spectra with coarse droplet sizes should be used.

11. Landowners with large area spray programs should have specific operational manuals, BMP’s,and drift management plans.

12. Training should be conducted on a regular basis for all spray program participants.

13. Special precautions should be taken to eliminate leaks and other off-target release (e.g.modifying Micronair nozzles for positive shut-off.)

14. GIS/GPS technology should be used for navigation, assurance of spraying the correct site,and for maintenance of complete, accurate records.

252


Concurrent Session #3Airblast/Air-Assisted Application Equipment & Drift

Robert D. Fox, Technical ExpertUSDA-ARS

Wooster, Ohio

Bill Seekins, FacilitatorMaine Board of Pesticides Control

Augusta, Maine

Don Barry, ScribeUniversity of Maine Cooperative Extension

Orono, Maine

Best Management Practices

♦ Manage the outside/inside, upwind/downwind areas appropriately

♦ IPM/ICM

♦ Tree row volume

♦ Use the wind as a tool when possible

♦ Adjust equipment for the crop and conditions

♦ Identify sensitive areas and buffer zones

♦ Maintain communication with operators, spotters, etc.

♦ Never spray when conditions are inappropriate

♦ Select products for near neighbors and sensitive areas

253

Long Range Goals

♦ Better control of spray deposition

♦ Equipment controls

♦ Incentive programs

♦ Identify research needs

♦ Certification of sprayers

♦ Develop crop specific spray guidelines

♦ Retrofit sprayers with towers

♦ Materials with low odor

♦ Economic analysis of new technologies

♦ Funding for equipment and application research from growers

♦ EPA and government funding for equipment research

Training and Education

♦ Better training for newer, more complicated spray technology

♦ Better operating manuals written in native language

♦ Training for supervisory level applicators

♦ Certification for applicators on specific equipment

♦ Emphasize and create internet sites that deal with spray drift

♦ Training for applicators in cultural controls that reduce drift

254


Concurrent Session #4Boom Application Equipment and Drift

Robert E. Wolf, Technical ExpertUniversity of IllinoisChampagne, Illinois

Terry Bourgoin, FacilitatorMaine Department of Agriculture

Augusta, Maine

Scribe, James DwyerUniversity of Maine Cooperative Extension

Presque Isle, Maine

BMPs:- There is material already in print that could be used for BMPs including professional

applicator books and industry publications.

Training:- Hands on interactive training such as using a drift table.- Standardize the message from extension, regulators and others.- Train the trainer: Tailor this for the audience, eg. professional applicators or growers.- Tighten certification and recertification standards (5 yrs).- All applicators should be certified.- Coordinate training between industry, government and universities.- Promote peer recognition and use this in training.- Standardize drift management sections in PAT manuals and certification requirements.

Encourage a change in attitude by:- Recognition of early adopters.- Peer pressure.- Enforcement incentive.

Public awareness:- Promote public awareness about the use of products and a general public knowledge of drift.

255

Funding:- Increase PAT funding.- User fees.- Industry support.

Research:- Improved timing of applications.- Construction of wind breaks.- Factors affecting maximum wind speeds.

Sprayers:- Need to have better boom designs. They need to be more stable and self leveling.- Manufacturers need to be involved in drift management.- Hands on assistance and inspection should be available.

Professionalism of Applicators:- Code of conduct.- Record keeping.- Integrate IPM and drift control.

256


Concurrent Session #5High Volume Sprayers for Treating Trees:

Managing Drift and Exposure

Bruce R. Fraedrich, Technical ExpertBartlett Tree Research Laboratories

Charolette, North Carolina

Gary Fish, FacilitatorMaine Board of Pesticides Control

Augusta, Maine

Paul Gregory, ScribeMaine Board of Pesticides Control

Augusta, Maine

Best Management Practices

• High Volume Application• Low Volume Application• Group recommends use of low volume application whenever possible.

Equipment

• Select Equipment Properly• Calibrate

Must understand the relationship between volume and pressure toachieve height while minimizing drift.

Application Techniques

• High volume application techniques-Build column and use wind – avoid sudden movements

• Position close to the target• Use lowest pressure and adequate volume• Seek permission if drift is possible• Spray only that portion of the plant which can be done without drift• Apply between target and sensitive area• Management drift effects

-Notify neighbors-Remove toys, bird feeders, pets and people-Close windows, shut down air conditioners

257

Low Volume Application

• Use alternative application techniques-Tree injection-Soil treatments & systemics-Low volume foliar techniques

• Must use IPM in urban areas-Dealing with a very valuable crop

• Must use cultural and biological treatments whenever possiblePlant pest resistant plants

Where do we go now?

• Research• Education, Training and Public Info• Equipment• Regulatory issues

Research

• Equipment & Application Techniques• Formulations and adjuvants

Equipment & Application Technique Research

• Low Volume• Closer to targetFormulation & Adjuvant Research

• Need formulations and adjuvants that facilitate low volume application efficacy

Education & Training

• Train-the-trainer• Train all applicators

-Certification & Licensing-Involve manufacturers-Remedial training-Sell results not spray

• Education Customers-lower the bar on perfection/expectations

• Educate at-home applicators

258

Public Information

• What are pesticides?• Reward industry for public education• Promote value of hiring certified/licensed applicators

Equipment

• Low volume techniques• Have all the tools available for site specific needs

-cut surface – brush saw-tree and soil injection-backpack sprayers-wick applicators-shielded nozzles-ball valve before spray gun

Regulatory Issues

• Enforce existing regulations• Need more specific performance based standards e.g., - Wind Speed• Use drift case investigation results to promote future drift prevention

on an industry wide basis –-Learn from other’s mistakes

• Regulate adjuvants to establish standards of efficacy

259

WEDNESDAY, April 1 1998

Summary of Spray Drift Task Force Pesticide RegistrationWork

4 Brochures are included with this proceedings

David JohnsonStewart Ag Research Services, Inc.

Macon, Missouri

Aerial Application Studies

Airblast Application Studies

Chemigation Application Studies

Ground Application Studies

260

A Summary of Spray Drift Research in Canada

Christopher M. RileyNew Brunswick Research & Productivity Council

Fredericton, New Brunswick, CANADA

In Canada, as in most other countries, pesticides are essential tools in crop protection andpest management. Herbicides account for over 70% of annual retail pesticide sales and these areused predominantly in the production of cereal and oil seed crops which are grown on more than 23million hectares is the Provinces of Alberta, Manitoba and Saskatchewan. It is not surprising there-fore that there have been extensive studies to evaluate both droplet, and vapour drift from ground aswell as aerially applied herbicide sprays eg. Grover et al. (1985); Maybank et al. (1978 a, b).

In recent years the agricultural industry has seen a shift from pre-emergence to post-emer-gence herbicides, the introduction of higher potency products with lower margins of tolerance thatare used at lower dosage rates and which therefore demand better application management, a reduc-tion in total spray volumes and the development of larger and more efficient spray equipment.Researchers such as Maybank et al. (1990), Panneton et al. (1998), Storozynsky (1998), and Wolfand Grover (1992) have been heavily involved with the development of improved application tech-nology including shrouded sprayers, shielded atomizers, air- assisted sprayers and low pressurenozzles that reduce spray drift and permit pesticide application at higher wind speeds.

Tree fruits and horticultural crops are grown intensively in many parts of Canada and withincreasing urban encroachment upon agricultural lands, the issue of bystander exposure to spray drifthas been an important concern of pesticide regulators. This has led to several studies such as thoseby Crabbe and McCooeye (1985) and Riley and Wiesner (1990 a).

It is said that the forestry industry is worth more to the Canadian economy than the combinedtotal of agriculture, fisheries and mining and as such Canadian forests are a very valuable economicresource. From time to time the health of the forests and the future timber supply is threatened byinsect pests such as the spruce budworm and the hemlock looper. High populations of these defoliat-ing insects can completely destroy healthy forests in a period of three or four years and consequentlycrop protection programs must be implemented. At the height of the last cyclical outbreak of thespruce budworm in eastern Canada which began in the 1970’s and ended in the early 1990’s, up tothree million hectares of forest lands were being treated on an annual basis within a period of ap-proximately three weeks.

Although forest insect spray operations generally use much less than 1% of the total amountof pesticides used in Canada, these aerial spray programs are a subject of great concern to the publicand come under intense scrutiny and restriction by regulatory agencies. The reasons why the use ofpesticides in forestry receives a vastly disproportionate amount of attention compared to agriculturalpesticide use are manyfold. The large areas of private and public lands that are treated encompassmany environmentally sensitive areas that must be protected, and the highly organized aerial sprayoperations, often with large numbers of spray aircraft, are much more obvious to the general publicthan ground based agricultural-type spray operations. In response to the concerns raised by suchpractices, Federal and Provincial pesticide regulatory agencies and the forest industry have actively

261

supported several multi-year research projects to investigate the deposition and drift of aeriallyapplied sprays in the silvicultural environment.

One of the first major issues to be investigated by the New Brunswick Spray Efficacy Re-search Group (NBSERG), a collaborative, multi-disciplinary multi-agency research group formed inthe early 1980’s, was the transport and drift of silvicultural insecticide sprays. This work extendedover several years and included several studies of long and short range drift (eg. Crabbe et al. (1980a,b), Crabbe and McCooeye (1988, 1989) and Riley et al. (1989) and three large field studies. Thesefield studies employed a range of spray drift and deposit collection devices including foliage simula-tors, high volume air samplers, and rotorods suspended to a height of 600 m from tethered balloonsto investigate the effects of a range of application systems and meteorological parameters (Picot etal., 1993). Additional studies by Environment Canada pioneered the use of LIDAR for the real-timetracking of spray drift (Hoff et al., 1989; Mickle, 1990) and led to two studies to evaluate the differ-ential behaviour and drift of material emitted into upwind and downwind aircraft vortices (Riley1991, and McCooeye et al., 1993).

Following the conclusion of these studies, the expertise of the, now renamed, Spray EfficacyResearch Group (SERG), was concentrated on the aerial application of silvicultural herbicides thatare used in conifer release programs to suppress competing vegetation and promote the growth ofplanted or naturally regenerated forest lands (Riley and Wiesner, 1989, 1990b, and Riley 1992).Additional studies were also carried out e.g. Dostie (1991), Dostie and Lécuyer (1991); Payne et al.(1990), Riley et al. (1989) and Shewchuck et al. (1991).

Spray drift and the potential for negative environmental impact thereof have historically beenmanaged through the use of no-spray buffer zones, or set backs from environmentally sensitiveareas, which are stipulated in the required application permits. In many cases, buffer zones havebeen established on an arbitrary basis with little or no consistency from one Province to another. Itwas recognized by pesticide regulators that there was a need for the accurate assessment of pesticidedrift and deposit and that the mathematical models being developed at the time could be used todevelop a generic predictive approach which would reduce the need for empirical data and possiblyproduce a more effective efficient, science-based risk assessment method for the calculation andestablishment of buffer zones.

In 1989 the Canadian Interdepartmental Task Force on Pesticide Drift (ITFPD) was formedto develop new science-based regulatory guidelines for the management of pesticide drift. The TaskForce consisted of representatives from each of the Federal agencies responsible for the registrationand/or regulation of pesticides i.e. Agriculture and Agri-Food Canada, the Department of Fisheriesand Oceans, Environment Canada, Health Canada and Natural Resources Canada. The activities ofthe ITFPD included the development and compilation of a computer database on spray drift, areview of international data requirements for the establishment of buffer zones and a sensitivityanalysis and verification of the AGDISP 6.1, FSCBG 4.3 and PKBW2 drift and deposit modelsusing some of the approximate 200 data sets generated by SERG.

In 1990 the US Spray Drift Task Force (SDTF) began its activities as described elsewhere inthese Proceedings. It soon became apparent that the goals and objectives of the ITFPD, the USEnvironmental Protection Agency and the SDTF were very similar and that much of the informationgenerated was complementary. In both countries, work was underway to develop and validate

262

models and databases to predict off-target drift and deposit that could be used to assess the expectedenvironmental pesticide concentration which, in association with toxicity data, could be used todetermine the environmental significance of the predicted drift and, if necessary, to estimate bufferzones as a mitigative measure. The Canadian database was strong in forestry application scenariosand the SDTF database was strong in agricultural application scenarios.

In 1996 an agreement was signed between Canada and the United States as a part of theNAFTA Technical Working Group on Pesticides for the exchange of information and the collabora-tion of all parties. At this time both Canadian and US pesticide manufacturers support the use of theAgDrift model and there is general stakeholder agreement that this model is an acceptable tool forestimating spray drift and deposit. The agency responsible for the registration of pesticides inCanada, the Pest Management Regulatory Agency (PMRA), has adopted the model as a means ofestimating spray drift and deposit for the aerial application of pesticides in agricultural andsilvicultural scenarios. In addition the Agency is working on the means by which appropriate infor-mation will be communicated to the users.

There are three principal means by which information on the reduction and avoidance ofspray drift can be delivered to the pesticide applicator i.e. as part of the formal training received forthe certification of professional applicators as required by Provincial regulatory agencies; throughtraining sessions and extension materials provided by professional associations, pesticide manufac-turers or extension specialists; or via the pesticide label. The current challenge for federal regulatorsis to determine the best way to deliver the various types of information that can be used to reduce orprevent drift and particularly the scientifically valid information which can be produced by spraydrift models.

Three options are currently being considered for use of the AgDrift model. The first is as atool with which Provincial regulators could develop buffer zones for those applications whichcurrently require site-specific permits. In these cases, model parameters would be based on knownvalues for controllable application parameters (e.g. droplet size and aircraft height) and realisticworst case default values for meteorological conditions. In certain circumstances, depending uponthe meteorological conditions at the time of application, the use of the model in this way couldproduce buffer zone requirements that are overly restrictive.

The second option, as a tool to be used on-site by pesticide applicators using the actualmeteorological conditions and application parameters, would provide the best opportunity to reducebuffer zones to the minimum. However, it is unrealistic to expect all applications around environ-mentally sensitive areas to be made with reference to the spray drift model.

The third option is to use the model as a tool to develop buffer zones that would be specifiedon the pesticide label. The advantage of this would be that the information would always be avail-able with the product and that, because the label is a legal document, the buffer zones would beenforceable. The disadvantage of this approach is that a single buffer zone specified on the labelwould likely be based on realistic worst-case application and meterological conditions and aretherefore most likely to be the most stringent and demanding on the applicator. The problem couldbe addressed by providing a number of buffer zones on the label and giving users the responsibilityof deciding which one to use. Assistance in this regard could be provided by specifying the paramet-ric values used in the calculation of the various buffer zones e.g. droplet size, release height andwind speed.

263

The interim approach adopted by the PMRA for aerially applied pesticides is to use themodel to determine buffer zones, assuming that application conditions are within an acceptablerange, and provide on the label the information on the conditions used to arrive at the specifiedbuffer zone (in the future it is possible that there will be separate tables for aerial and ground appli-cation which will specify the droplet size range and other key model parameters).

Many pesticide products which are currently approved for aerial application do not havespecific label wording to that effect. However, by the end of year 2000, all products for aerialapplication must be so labelled and registered. This will trigger a labelling review and an opportu-nity to revise labels with buffer zone information. Furthermore, within the next 6 years the registra-tions of all active ingredients are to be reevaluated and this will provide an even greater opportunityfor all pesticide labels to be improved with respect to spray drift management.

Labelling information and options are being developed by the PMRA with input from thescientific community, provincial pesticide regulators, registrants and pesticide applicators in terms ofhow the model can be used to develop practical buffer zones, reasonable worst-case parameters,appropriate biological indicators and end points, information and wording to be included on the labeland the information that must be covered by professional training activities. Other questions whichwill need to be answered include what proportion of the crop can be left as an untreated buffer zoneand still provide acceptable control of the target pest and how biological efficacy is affected by thedroplet size in attempting to address drift issues. This latter issue has started to be addressed by theExpert Committee on Weeds, Application Technology Working Group (Tom Wolf, pers. com.).

References:

Crabbe, R.; Elias, L.; Krzymien, M. and Davie, S. New Brunswick forestry spray operations: Fieldstudy of the effect of atmospheric stability as long range pesticide drift. National Research CouncilLaboratory Technical Report LTR-UA-52. Ottawa, Ontario, 1980.

Crabbe, R.; Krzymien, M.; Elias, L. and Davie, S. New Brunswick spray operations: measurementof atmospheric fenitrothion concentrations near the spray area. National Aeronautical Establish-ment. National Research Council of Canada. Laboratory Technical Report LTR-UA-56. Ottawa,1980.

Crabbe, R. S. and McCooeye, M. 1989. Kapuskasing field study relating atmospheric stability towind drift from aerial forest spray operations. National Research Council Report No. LTR-UA-99,Ottawa, Ontario.

Crabbe, R. S. and McCooeye, M. 1988. The Dunphy field study relating atmospheric stability towind drift from aerial forest spraying. National Research Council Report No. LTR-UA-98. Ottawa,Ontario.

Dostie, R. Dépôt du glyphosate à l’extérieur des aires traitées par voie terrestre en 1989,Gouvernement du Québec, Ministére des Forêts, Direction de l’environment, Service du suivienvironnemental, Charlesbourg, Québec, 15 p., 1991.

264

Dostie, R. et Lécuyer, H.. Dépôt du glyphosate à l’intérieur et à l’extérieur des aires traitées par voieaérienne en 1988, Gouvernement du Québec, Direction de l’environnment, Ministére des Forêts. 29p., 1991.

Grover, R. Shewchuck, S. R.; Cessna, A. J.; Smith, A. E. and Hunter J. H. 1985. Fate of 2, 4-D Iso-octyl ester after application to a wheat field. J. Env. Qual. 14: 203-210.

Hoff, R. M.; Mickle R. E. and Fropude, F. A. 1989. A rapid acquisition lidar for aerial spray diag-nostics. Trans A. S. A. E. 32: 1523-1528.

Maybank J. , Shewchuk S. R., and Wallace K. 1990. The use of shielded nozzles to reduce off-targetherbicide spray drift. Canadian Agricultural Engineering 32: 231-235.

Maybank, J.; Yoshida, K. and Grover R. 1978. Spray drift from agricultural pesticide applications.J. Air Pollution control Assoc. 28: 1009-1014.

Maybank, J., Yoshida, K., Shewchuk, S. R. and Grover, R. 1978. Spray drift behaviour of aerially-applied pesticide: report of the 1977 field trials. Saskatchewan Research Council Report No. P. 78-2. Saskatoon, Saskatchewan.

McCooeye, M. A.; Crabbe, R. S.; Mickle, R. E.; Robinson, A.; Stimsen, E. B.; Arnold, J. A. andAlword. D. G. 1993. Strategy for reducing drift of aerially applied pesticides. National ResearchCouncil Report. Ottawa, Ontario.

Mickle, R. E., 1990. Canadian laser mapping technique for aerial spraying. A.S.A.E. Paper No.AA90-004. Reno, Nevada, 1990.

Panneton, B., Piché, M. and Theriault, R., 1998. Poster presentation “Spray drift from a high vol-ume air-assisted sprayer”. North American Conference on Pesticide Spray Drift Management.Portland, Maine.

Payne, N. J., Feng, J. C. and Reynolds, P. E. 1990. Off target deposits and buffer zones requiredaround water for aerial glyphosate applications. Pestic. Sci. 30: 183-198.

Picot, J. J. C., Kristmanson, D. D. Mickle, R. E., Dickison, R. B. B., Riley, C. M. and Wiesner, C. J.1993. Measurements of foliar and ground deposits in forestry aerial spraying. Transactions of theA.S.A. E. 36: 1013-1024.

Riley, C. M. 1992. Continuation of studies to examine the effects of aircraft application parameterson deposit and drift of forestry herbicides. RPC Report No. C/92/443 (a). Fredericton, NewBrunswick.

Riley, C. M., Wiesner, C. J. and Sexsmith, W. A. 1991. Estimating off-target spray deposition onthe ground following the aerial application of glyphosate for conifer release in New Brunswick. J.Env. Sci. and Health. B26 (2): 185-208.

265

Riley, C. M. 1991. The effects of Aircraft vortices on spray deposition and drift. RPC Report No.C/89/632. Fredericton, New Brunswick.

Riley, C.M. and Wiesner, C.J. 1990a. “Off-Target pesticide losses resulting from the use of an air-assisted orchard sprayer”, Pesticide Formulations and Application Systems: 10th Volume, ASTMSTP 1078, L.E. Bode, J.L. Hazen, and D.G. Chasin, Eds., American Society for Testing and Materi-als, Philadelphia.

Riley, C. M. and Wiesner, C. J., 1990b. Examination of the influence of aircraft application param-eters on deposit and drift of forestry herbicides. RPC Report No. C/90/1401, Fredericton, NewBrunswick.

Riley, C. M., and Wiesner, C. J., 1989. Examination of the influence of aircraft operating param-eters on herbicide deposition and drift. RPC Report No. C/89/077. Fredericton, New Brunswick.

Riley, C. M., Wiesner, C. J. and Ecobichon D. J. 1989. Measurement of aminocarb in long distancedrift following aerial application to forests. Bull. Environ. Contam. Toxicol. 42: 891 - 898.

Shewchuk, S. R., Wallace, K. and Maybank, J. 1991. Spray drift and deposit pattern from a forestherbicide application. Saskatchewan Research Council Report No. E-2310-4-E-90. Saskatoon,Saskatchewan.

Storozynsky, B., 1998. Poster presentation “1994-1996 Airborne spray drift results”. North Ameri-can Conference on Pesticide Spray Drift Management. Portland, Maine.

Wolf T. M. and Grover R. 1992. The role of application factors in the effectiveness and drift ofherbicides. Agriculture Canada Research Station, Regina, Saskatchewan.

266

Update from Spray Drift Coalition

Paul KindingerAgricultural Retailers Association

St. Louis, Missouri

Goal: Reduce Drift.

Purposes of the Coalition

Develop a national educational program that will bring about the desired behavior fromapplicators and other decision makers and thus, manage and minimize off-target drift offertilizer and chemicals.

Achieve improved coordination and communication between the federal, state and localregulatory community and the educational and technological providers.

Make it possible for applicators to utilize the latest technologies available that will help themminimize drift with the least possible impact on efficacy.

Composition of the Coalition

Federal government agenciesEPAOPPUSDACREES, FS, ARSState government (AAPCO)University PAT coordinatorsCompaniesAssociationsRepresentatives of the insurance industryRepresentatives of the government of Ontario, CanadaPublic Interest Groups

Organization

Co-chaired byMr. Jim BoillotDr. Paul Kindinger

Responsibilities divided into three major areas:

Education: Taskforce Chair- Dr. Bob Wolf, University of Illinois.Regulatory: Taskforce Chair- Mr. Paul Liemandt, AAPCO.Technology: Taskforce Chair- Dr. Dennis Gardisser, University of Arkansas.

267

Major Accomplishments to Date, March 1998

Pulled stakeholders together and formed coalition.Reviewed findings of Spray Drift Task Force.AAPCO regulatory survey.Coalition educational survey.Developed vision of ‘ideal’ behavioral goals.Developed definitions for drift and buffer zone.Developed suggested national curriculum for spray drift component in all educationalprograms.Developed a video presentation to acquaint applicators (private and commercial) with driftfundamentals.

Additional Actions Under Consideration

Develop materials for site-specific applicator technology.Develop guidelines, booklets, carry-home materials.Development of ‘smart systems’ computer model.

Additional Future

Actions taken at meeting March 28-29, 1998.

*Finalize Video for Module I.

*Mary Grodner - Pre-proposal draft Module II(applicator decision making & regulatory)

*Dennis Gardisser - Pre-proposal draft Module III(technology)

*Paul Liemandt (Regulatory Task Force) work in conjunction withEducation and Technical Task Force to develop a white paper addressingpesticide label issues.

Including issues such as:

Technology AdoptionResearch NeedsBMP’sEnforcement

Next Meeting: July 21-22, 1998- Kansas City

268

List of Attendees*

*disclaimer : Addresses were taken from hand-written registrations.

Roy Aber, Sr. John W. AckleyAgway Agricultural Products Mead Publishing Paper19 East Mountain Road P.O. Box 702Allentown, PA 18103 Bingham, ME 04920USA USA

Jerry Alldredge Niels AndrewsColorado Ag Aviation Association Helicair Ag Inc.425 N. 15th Avenue 37 Mortensen AvenueGreeley, CO 80631 Salinas, CA 93905USA USA

Darlene Back William E. BagleyUnion Carbide Corporation Wilbur-Ellis CompanyP.O. Box 670 6307 Ridge Pass141 Baekeland Avenue San Antonio, TX 78233Round Brook, NJ 08805 USAUSA

Bruce Ballard Tom BalsBallard’s Custom Spraying Micron Sprayers Limited517 Palmyra Road Three MillsSt. Albans, ME 04971 BromyardUSA Herefordshire, HR7 4HU

UK

Don Barry Robert I. BatteeseUniversity of Maine Cooperative Extension Maine Board of Pesticides Control491 College Avenue 28 State House StationOrono, ME 04473-1295 Augusta, ME 04333-0028USA USA

Dolly Batteese Roger BeaulieuMaine Board of Pesticides Control Maine Board of Pesticides Control28 State House Station 28 State House StationAugusta, ME 04333-0028 Augusta, ME 04333-0028USA USA

Lloyd Belbin David BellDept. of Forest Resouces & Agrifoods Maine Wild Blueberry CommissionFortis Towers 5715 Coburn HallP.O. Box 2006 University of MaineCorner Park, New Foundland A2H 6J8 Orono, ME 04469-5715CANADA USA

Robert G. Bellinger Linda BergeyClemson University Bishop Equipment Manufacturing, Inc.Dept. of Entomology 755 Forty Foot Road107 Long Hall, Box 340365 Lansdale, PA 19446Clemson, SC 29634-0365 USAUSA

269

Donald Bernier Andrew BerryBernier Egg Farms, Inc. Maine Board of Pesticides ControlRFD #2, Box 1386 28 State House StationNew Dam Road Augusta, ME 04333-0028Sanford, ME 04073 USAUSA

Jack A. Best Tom BeyerBASF Tuckahoe Turf Farms26 Davis Drive 305 Hubbard RoadRTP, NC 27709 Berwick, ME 03901USA USA

Sandra L. Bird Mark BloethU.S. EPA Environmental Protection Agency960 College Station Road 61 Forsythe StreetAthens, GA 30605 Pesticides Section - 12th FloorUSA Atlanta, GA 30303

USA

James B. Boillot Malcolm BoltonNational Agricultural Aviation Assn. Rt. 2, Box 1321005 E Street, SE Clitherall, MN 56524Washington, DC 20003 USAUSA

Renaud Bordage June BostonJ.D. Irving, Ltd. Boston Co. Golf & Athletic Fields300 Union Street P.O. Box 94Saint John, New Brunswick E2L 4M3 South Berwick, ME 03908-0094CANADA USA

Rick Boston Terry L. BourgoinBoston Co. Golf & Athletic Fields Maine Department of AgricultureP.O. Box 94 28 State House StationSouth Berwick, ME 03908-0094 Augusta, ME 04333-0028USA USA

A. Temple Bowen, Jr. Dick BradburyThermo Trilogy Corporation Maine Forest ServiceP.O. Box 669 State House Station #22Antrim, NH 03440 Augusta, ME 04333-0022USA USA

Frank Bradford Barry M. BrennanColorado Dept. of Agriculture USDA/CSREESDivision of Plant Industry 901 D Street, S.W.700 Kipling Street, Suite 4000 Washington, DC 20250-2220Lakewood, CO 80215 USAUSA

James R. Brown Jonathan E. Bryant, Ph.D.Navy Disease Vector Ecology & Control Center BASF CorporationP.O. Box 43 P.O. Box 13527Naval Air Station RTP, NC 27713Jacksonville, FL 32212-0043 USAUSA

270

Donna Buckley William H. BuzzardUniversity of Maine Cooperative Extension Penn Dept. of Con. & Nat. Res.491 College Avenue Forest Pest ManagementOrono, ME 04473-1295 34 Airport DriveUSA Middletown, PA 17057

USA

Marcus Campbell Matthew G. CarmichaelS.D. Warren - NE Timberlands M.G. Carmichael Air ApplicatorP.O. Box 400, Mountain Avenue 378 Park Hurst Sid. Rd.Fairfield, ME 04937-0400 Presque Isle, ME 04769USA USA

Jeffrey L. Case Affonso Celso Ribeiro FilhoNovartis Crop Protection, Inc. Maquinas Agricolas Jacto S.A.P.O. Box 18300 RUA Dr. Luiz Miranda, 1650-Greensboro, NC 27419 Pompeia - SP, Brazil 17580-000USA BRAZIL

Wendy Chapley Wayne ClarkNew Hampshire Dept. of Agriculture Maine Helicopters, Inc.Division of Pesticide Control P.O. Box 110P.O. Box 2042 Whitefield, ME 04353Concord, NH 03302-2042 USAUSA

Jeremy Compton Raymond ConnorsRutgers- The State Univ. of NJ Maine Board of Pesticides ControlSnyder Research & Extension Farm 28 State House Station140 Locust Grove Road Augusta, ME 04333-0028Pittstown, NJ 08867 USAUSA

Pete Coody Alex M. CorderoBayer Corporation Florida Dept. Environ. Protection17745 South Metcalf 3900 Commonwealth Blvd.Stilwell, KS 66085 M.S. 240USA Tallahassee, FL 32399-3000

USA

Michael P. Corey Vincent CovelloMaine Potato Board Center for Risk Communication744 Main Street, Room 1 39 Claremont Avenue., Suite 71Presque Isle, ME 04769 New York, NY 10027USA USA

Jerre Creighton Greg CremersChampion International Minnesota Dept. of AgricultureP.O. Box 87 4318 Plaza LaneCantonment, FL 32533 St. Cloud, MN 56303USA USA

Jim T. Criswell Edward A. CrowOklahoma State University Maryland Dept. of Agriculture127 NRC 50 Harry S. Truman ParkwayStillwater, OK 74078 Annapolis, MD 21401USA USA

271

Michael C. Crutchley Mary-Lynn CummingsUniversity of Guelph Cornell UniversityRidgetown College 5138 Comstock HallMain Stree East Ithaca, NY 14853Ridgetown, ON NOP 2CO USACANADA

Edward A. Cunningham Michael CunninghamAgRotors, Inc. Monsanto Canada, Inc.P.O. Box 1537 P.O. Box 3142, Stn. BGettysburg, PA 17325 Frederickton, NBUSA CANADA

Paul Dailey David C. DaviesNorthport Golf Club Forest Protection LimitedP.O. Box 187 Fredericton AirportBelfast, ME 04915 2502 Route 102USA Lincoln, NB E3B 7E6

CANADA

Glenn J. Davis Thomas W. DeanAg Aviation University of FloridaP.O. Box 986 UF Campus Bldg. #842Creedmoor, NC 27522 Gainesville, FL 32611USA USA

Storer E. DeMerchant, Jr. Richard DerksenMaine Potato Growers, Inc. USDA-ARSP.O. Box 271 Agricultural Engineering Bldg.56 Partons Street 1680 Madison AvenuePresque Isle, ME 04769-0271 Wooster, OH 44691USA USA

Jim Dill Richard J. DionneUniversity of Maine Cooperative Extension University of Maine491 College Avenue Cooperative Forestry Research UnitOrono, ME 04473-1295 Room 130, Nutting HallUSA Orono, ME 04469-5755

USA

Don Dodson Roger A. DownerLoveland Industries, Inc. LPCAT at OARDC/OSUP.O. Box 818 1680 Madison AvenueBrownstown, PA 17508-0818 Wooster, OH 44691USA USA

Travis Drake Francis A. DrummondJasper Wyman & Son University of MaineRt. 193, Box 20D Dept. of Biological SciencesDeblois, ME 04622 305 Deering HallUSA Orono, ME 04469

USA

Jacques Dugal Alan DunhamSOPFIM Simulation Technologies, Inc.1780 rue Semple 1700 N. Moore StreetQuebec, QB G1W 4B8 Suite 1650CANADA Arlington, VA 22209

USA

272

James D. Dwyer Carol EckertUniversity of Maine Cooperative Extension Maine Board of Pesticides ControlP.O. Box 727, Houlton Road RR 1, Box 410Presque Isle, ME 04769-0727 Windsor, ME 04363USA USA

Jay Ellenberger David M. EsterlyEPA, Field & External Affairs Division (7506C) Dupont Agricultural Products401 M Street SW P.O. Box 30Washington, DC 20460 Barley Mill Plaza P15USA Wilmington, DE 19880-0015

USA

Gregory Eurich Theodore A. FeitshanUniversity of Vermont NCSU - Dept. of Agr. & Res. Econ.Plant & Soil Dept. P.O. Box 8109Hills Building Raleigh, NC 27695-8109Burlington, VT 05405 USAUSA

Anthony Filauro John H. FilhiolBOWATER, Great Northern Paper Northeast Louisiana University1024 Central Street Dept. of AviationMillinocket, ME 04462 NLUUSA Monroe, LA 71209-0590

USA

Gary Fish David T. FoggMaine Board of Pesticides Control Cherryfield Foods, Inc.28 State House Station P.O. Box 189Augusta, ME 04333-0028 Gray, ME 04039USA USA

Robert D. Fox Bruce FraedrichUSDA-ARS Bartlett Tree Research LaboratoriesOhio Research & Development Center 13768 Hamilton RoadWooster, OH 44691 Charlotte, NC 28278USA USA

Derek Francois Dennis R. GardisserPest Management Regulatory Agency University of ArkansasHealth Canada Cooperative ExtensionSir Charles Tupper Bldg., 2250 Riverside Drive 2301 South University AvenueRoom E768, Address Locator 6607E1 Room 305Ottawa, Ontario K1A 0K9 Little Rock, AK 72203CANADA USA

Ronald D. Gardner Jeff GillisCornell University F.A. Bartlett Tree Expert Co.Pesticide Management Education Program P.O. Box 68285123 Comstock Hall Scarboro, ME 04070-6828Ithaca, NY 14853-0901 USAUSA

273

Anthony Glencross Robert L. Goglia, Jr.P.E.I. Dept. of Agriculture & Forestry MonsantoP.O. Box 1600 20-B Sycamore LaneCharlottetown, P.E.I. C1A 7N3 Manchester, CT 06040CANADA USA

Greg Goodband Paul GoodwinPlymouth County Mosquito Control Project Ontario Ministry of Agriculture201 East Street Food & Rural AffairsSharon, MA 02067 P.O. Box 587USA Simcoe, ONT N3Y4N5

CANADA

Tammy L. Gould John GrandeMaine Board of Pesticides Control Rutgers- The State Univ. of NJ28 State House Station Snyder Research & Extension FarmAugusta, ME 04333-0028 140 Locust Grove RoadUSA Pittstown, NJ 08867

USA

Bob Graney Paul GregoryBayer Corporation Maine Board of Pesticides Control17745 S. Metcalf 28 State House StationStilwell, KS 66085 Augusta, ME 04333-0028USA USA

Norma Grier Mary L. GrodnerNorthwest Coalition for Alternatives to Pesticides Louisiana State Univ. Agric. Ctr.P.O. Box 1393 Cooperative ExtensionEugene, OR 97440-1393 P.O. Box 25100USA Baton Rouge, LA 70894-5100

USA

William R. Guptill, Sr. Carl L. HaagGuptill Farms, Inc. S.D. Warren Co.P.O. Box 188 49 Mountain AvenueMachias, ME 04654 P.O. Box 400USA Fairfield, ME 04937

USA

David T. Handley Keith HansenUniversity of Maine Cooperative Extension For Ever Green Forestry ServicesHighmoor Farm P.O. Box 277P.O. Box 179 Jackman, ME 04945Monmouth, ME 04259-0179 USAUSA

Thomas A. Harnett Susan HawkinsMaine Attorney General’s Office Champion Valley Crop Mgmt. Assn.6 State House Station RD 2, Box 4690Augusta, ME 04345 Bristol, VT 05443USA USA

Karen Heisler Ernest J. Hewett, IIIU.S. EPA Region 9 North Carolina State University75 Hawthorne St. (CMD-4-3) Biol. & Agric. EngineeringSan Francisco, CA 94105 201-A Weaver Labs, Box 7625USA Raleigh, NC 27695

USA

274

Andrew Hewitt Marty HeyenStewart Ag Research Services, Inc. Spraying Systems Co.P.O. Box 509 P.O. Box 7900Macon, MO 63552 Wheaton, IL 60189USA USA

Lebelle Hicks Greg HinerMaine Board of Pesticides Control Rhodia, Inc.28 State House Station CN 7500Augusta, ME 04333-0028 Cranbury, NJ 08512-7500USA USA

P. Lloyd Hipkins Patricia A. HipkinsVirginia Tech Virginia Tech - Pesticide ProgramsDept. Plant Pathology, Physiology & Weed Science 139 Smyth HallGlade Road Research Center Blacksburg, VA 24061Blacksburg, VA 24061-0330 USAUSA

Winand K. Hock William HoffmanPennsylvania State University The Pennsylvania State University113 Buckhout Laboratory 116 Buckhout LaboratoryUniversity Park, PA 16802-4506 University Park, PA 16802-4506USA USA

Kerry Hoffman Vernon HofmanThe Pennsylvania State University North Dakota State University114 Buckhout Laboratory Ag. & Biosystems EngineeringUniversity Park, PA 16802-4506 Box 5626USA Fargo, ND 58105

USA

L.J. Hollingworth Dan M. HopperPesticide Applications Professional Association FMC CorporationP.O. Box 30095 10150 North Executive Hills Blvd.Salinas, CA 03912-0095 Suite 520USA Kansas City, MO 64153

USA

Mike Howard Dennis F. HowardKalo, Inc. Florida Dept. of Agriculture42 NW 247 Road 3125 Conner Blvd.Clinton, MO 64735 Building 6USA Tallahassee, FL 32399-1650

USA

John E. Hunter, III Steve HuntleyNorth Carolina Dept. of Agriculture 237 State Street., No. 1BConsumer Services, Pesticide Section Portland, ME 04101P.O. Box 27647 USARaleigh, NC 27611USA

275

Peter Hurd Dottie HutchinsSimulation Technologies, Inc. M.S. Lavoie Air Applicator1700 N. Moore Street P.O. Box 829Suite 1650 Presque Isle, ME 04769Arlington, VA 22209 USAUSA

John W. Impson Henry S. JenningsUSDA/CSREES/PAS Maine Board of Pesticides Control901 D Street, SW 28 State House StationAerospace Bldg., Rm. 834, 8th Floor Augusta, ME 04333-0028Washington, DC 20250 USAUSA

David R. Johnson Monte P. JohnsonSpray Drift Task Force University of KentuckyStewart Ag. Res. Services, Inc. S-225 Agriculture Science Center NorthP.O. Box 509 Dept. of EntomologyMacon, MO 63552 Lexington, KY 40546-0091USA USA

Roy R. Johnson Lee JohnsonWaldrum Specialties, Inc. Central Maine Power Company4050-A Skyron Drive 83 Edison DriveDoylestown, PA 18901 Augusta, ME 04336USA USA

Robert J. Jordan Pollyanne KapalaGreat Northern Paper, Inc. Michigan Dept. of AgricultureP.O. Box 200 Pesticide & Plant Pest ManagementPortage, ME 04768 P.O. Box 30017USA Lansing, MI 48909

USA

Kevin Keaney Larry KeiperU.S. EPA - Pesticide Programs S.D. Warren - NE Timberlands401 M Street S.W. P.O. Box 400Washington, DC 20460 Mountain AvenueUSA Fairfield, ME 04937-0400

USA

Michael Kelly John KenneyFarmland Insurance Massachusetts Pesticide Bureau1963 Bell Avenue 100 Cambridge StreetDes Moines, IA 50315 Boston, MA 02202USA USA

Steven E. Kenyon Mohamed S. KhanMassachusetts Dept. of Food & Agriculture Cooperative Extension - UDCLeverett Saltonstall Building 4200 Connecticut Avenue100 Cambridge Street N.W. Bldg. 38Boston, MA 02202 Washington, DC 20008-1122USA USA

276

Nancy Kierstead Paul KindingerCountry Folks Magazine Agricultural Retailers Assn.Palatine Bridge, NY 11701 Borman Dr., Suite 110USA St. Louis, MO 63146

USA

Clay Kirby Ivan KirkUniversity of Maine Cooperative Extension USDA-ARS491 College Avenue 2771 F&B RoadOrono, ME 04473-1295 College Station, TX 77845USA USA

Richard Kochendoerfer, Jr. Robert KoetheGuptill Farms, Inc. US EPA - Region IP.O. Box 188 Pesticides Program (CPT)Machias, ME 04654 JFK Federal BuildingUSA Boston, MA 02203-0001

USA

Robert Krantz Jan LangenauensChampion International Corp. Inspection Services of Sprayers, BelgiumP.O. Box 527 B. Van Gansberghelaan 115Machias, ME 04654 9820 MerelbekeUSA Burg. Van Gansberghelaan, Merelbeke

BELGIUM

Fred Langley Mike LavoieConsultant M.S. Lavoie Air Applicator17 Tidewater Farm Road P.O. Box 829Greeland, NH 03840 Presque Isle, ME 04769USA USA

Lee Lawrence Robert LazzaraNevada Division of Agriculture New York State Dept. of Env. Con.350 Capitol Hill Avenue 50 Wolf RoadReno, NV 89502 Albany, NY 12233USA USA

Mark Ledson Ronald C. Lemin, Jr.Zeneca Ag. Products Timberland Enterprises, Inc.Western Research Center 231-A Bomarc Road1200 5th 47th Street Bangor, ME 04401Richmond, CA 94804 USAUSA

Gene F. Lemire Joseph H. LeslieCollier Mosquito Control District Missouri Dept. of Agriculture600 North Road P.O. Box 630Naples, FL 34104-3464 Jefferson City, MO 65102USA USA

Tim Lindsay Ken LingleyF.A. Bartlett Tree Expert Co. P.E.I. Dept. of Agriculture & ForestryP.O. Box 6828 18 Rose StreetScarboro, ME 04070-6828 Charlottetown,, P.E.I. C1E 1V4USA USA

277

Grover Lollar Justin LorangerSimulation Technologies, Inc. Lucas Tree Expert Co.1700 N. Moore Street P.O. Box 958Suite 1650 Portland, ME 04104Arlington, VA 22209 USAUSA

Ivar Lund Mark MagnussonDanish Institut of Agricultural Science (DIAS) Minnesota Dept. of AgricultureDept. of Agric. Engineering Bldg. 4A East DriveResearch Centre Bygholm, P.O. Box 536 Suite 700EDK-Horsens, Denmark Fergus Falls, MN 56537DENMARK USA

Eugene Mahar Duane E. MaheuS.D. Warren - NE Timberlands RR 3, Box 5000P.O. Box 400 Houlton, ME 04730Mountain Avenue USAFairfield, ME 04937-0400USA

Roy Maki Jose Maria F. dos SantosMonsanto Canada Inc. Instituto BiologicoRR #15, Onion Lake Road Av. conselheiro Rodriques AlvesThunder Bay, Ontario P7B 5NI 1252 Vila marianaCANADA Sao Paulo, Sao Paulo

BRAZIL

Glenn A. Martin Dan MartinHelicopter Applicatiors, Inc. Louisianna State UniversityP.O. Box 810 2189 Broussard StreetFrederick, MD 21705 Baton Rouge, LA 70808USA USA

Adolfo R. MarvinGallo Maxwell L. McCormack, Jr.California Dept. of Pesticide Regulation Monsanto1020 N. Street P.O. Box 296Room 300 Deer Isle, ME 04627-0296Sacramento, CA 95814-5604 USAUSA

John McCue Sandra McDonaldUniversity of Maine, Highmoor Farm Colorado State UniversityP.O. Box 179 Bioag Sci & Pest ManagementMonmouth, ME 04258-0179 Fort Collins, CO 80523-1177USA USA

Miles McEvoy Murray L. McKayWashington State Dept. of Agric. New Hampshire Dept. of AgricultureP.O. Box 42560 Division of Pesticide ControlOlympia, WA 98504-2560 P.O. Box 2042USA Concord, NH 03302-2042

USA

278

Patrick McMullan Joyce MeaderAgrobiology Research, Inc. Cooperative Extension SystemBox 57 P.O. Box 4287777 Walnut Grove Road Brooklyn, CT 06234Memphis, TN 38120 USAUSA

Jim Meadows Feridoon MehdizadeganExacto Inc. Maine Seed Potato Board988 Ocean Overlook Drive P.O. Box 49Fernandina Beach, FL 32034 Ashland, ME 04732USA USA

Ted Melnik Wanda MichalowiczUnion Carbide Ontario Environment, Pesticides Section39 Old Ridgebury Road 135 St. Clair Ave WestDanbury, CT 06 Suite100USA Toronto, ON M4V 1P5

CANADA

Bob Mickle Karl MierzejewskiREMSpC Droplet Technologies Inc.12 Wels H Dr 937-1 West Whitehall RoadAyr, ONT N0B 1E0 State College, PA 16801-2906CANADA USA

Paul Miller Max MillerSilsoe Research Institute Maine Board of Pesticides ControlWrest Park 28 State House StationSilsoe, BEDFORD MK45 4HS Augusta, ME 04333-0028ENGLAND USA

Milan Miller Dave MillerWoodland Services Univ. of Connecticut & New MexicoP.O. Box 14 State UniversityWilliamstown, VT 05679-0014 Box 30003, MSC 3BEUSA Las Cruces, NM 88003

USA

Daniel A. Morgan Glenn MorinChampion International Corporation New England Fruit ConsultantsP.O. Box 309 66 Taylor Hill RoadRoanoke Rapids, NC 27870 Montague, MA 01351USA USA

Robert J. Morrison Charles MosesDole Fresh Fruit Company Nevada Division of AgricultureSuite C-101 c/o Rye Express Courier 350 Capitol Hill Avenue6964 NW 50th Street Reno, NV 89502Miami, FL 33166-5632 USAUSA

Aboud Mubareka Ross MunseySamco Forestry, Ltd. Dextrac Ent. Ltd.1125 Power Road RR #1St. Joseph/Madawska, NB E7B2M3 C-33 S.B.CANADA Falkland, BC VDE 1W0

CANADA

279

Glenn P. Nadeau Claire NadonMaine Public Service Co. New Hampshire Dept. of AgricultureP.O. Box 1209 Division of Pesticide ControlPresque Isle, ME 04769-1209 P.O. Box 2042USA Concord, NH 03302-2042

USA

Norm Nesheim Erdal OzkanUniversity of Florida Ohio State UniversityBldg. 847 Agricultural Engineering BuildingBox 110710 590 Woody Hayes DriveGainesville, FL 32605 Columbus, OH 43210USA USA

Brent D. Palmer Dick PalmquistCity of St. Albans FMC CorporationP.O. Box 867 Ag Products AgroupSt. Albans, VT 05478 1775 Marlot StreetUSA Philadelphia, PA 19103

USA

Bernard Panneton Jennifer PaulAgriculture & Agri-Food Canada Maine Board of Pesticides Control430 Boulevard Gouin 28 State House StationCentre de R&D en Horticulture Augusta, ME 04333-0028St. Jean-Sur-Richelieu, Quebec j3B 3E6 USACANADA

John Peckham Phillip PerryMinnesota Dept. of Agriculture Maine Board of Pesticides Control90 W. Plato Blvd. 28 State House StationSt. Paul, MN 55107-2094 Augusta, ME 04333-0028USA USA

Ray Perry Steve PerryDurand-Wayland, Inc. U.S. EPAP.O. Box 1404 MD80 USEPALangrange, GA 30241 Research Triangle Park, NC 27711USA USA

Jack Peterson Marlene PicheArizona Dept. of Agriculture Agriculture & Agri-Food Canada1688 West Adams 430 Boulevard GouinPhoenix, AZ 85007 Centre de R&D en HorticultureUSA St. Jean-Sur-Richelieu, Quebec j3B 3E6

CANADA

Rocco Pizzo Ricks H. PluennekeS.D. Warren - NE Timberlands Plant Pro Advisory ServiceP.O. Box 400 6155 Dick Price RoadMountain Avenue Fort Worth, TX 76140-7847Fairfield, ME 04937-0400 USAUSA

280

Robert Pond Roddy PrattMcSherry’s Nursery Agriculture & Agri Food CanadaP.O. Box 136 P.O. Box 1210Fryeburg, ME 04037 Charlottetown, P.E.I. C1A 7M8USA USA

Dean Radabaugh Carol RamseySouth Dakota Dept. of Agriculture Washington State University523 East Capitol Fass Bldg. P.O. Box 646382Pierre, SD 57501 Pullman, WA 99664-6382USA USA

Scott Ray Thomas ReedDow AgroSciences TeeJet Northeast Inc.Building 306/D2 P.O. Box 3979330 Zionsville Road 124A W. Harrisburg StreetIndianapolis, IN 46268 Dillsburg, PA 17019USA USA

Leo A. Reed Eri Borges RegitanoPurdue University Dow AgroSciences Ind. Ltda.Office of Indiana State Chemist R. Brigadeiro Franco1154 Biochemistry Building 2477 apto. 1101W. Lafayette, IN 47907-1154 Curitiba-PR, Brazil 80.250.030USA

Darryl Rester Sid ReynoldsLouisiana State University Cherryfield Foods, Inc.172 Knapp Hall P.O. Box 128P.O. 25100 Cherryfield, ME 04622Baton Rouge, LA 70894-5100 USAUSA

Christopher M. Riley Howard RileyNew Brunswick Research & Productivity Council H&M Riley Consulting, Ltd.921 College Hill Road 23 Ashford CloseFredericton, NB E3B 6Z9 Tantallon, Nova Scotia B3Z 1E5CANADA CANADA

Bradford Robinson Charles G. RockConnecticut Dept. of Environmental Protection Novartis Crop Protection, Inc.Pesticide Management Division P.O. Box 1830079 Elm Street Greensboro, NC 27419Hartford, CT 06106 USAUSA

Andrew R. Roth Ghislain RousseauPurdue University SOPFIMOffice of Indiana State Chemist 1780 rue Semple1154 Biochemistry Building Quebec, QB G1W 4B8 W. Lafayette, IN 47907-1154 CANADAUSA

Jo D. Saffeir Masoud SalyaniMaine Board of Pesticides Control University of Florida, CREC28 State House Station 700 Exp. Station RoadAugusta, ME 04333-0028 Lake Alfred, FL 33850USA USA

281

Sergio Sartori Thomas SavielloMaquinas Agricolas Jacto S.A. Maine Board of Pesticides ControlRUA Dr. 28 State House StationLuiz Miranda, 1650- Augusta, ME 04333-0028Pompeia - SP, Brazil 17590-000 USABRAZIL

Eric Schiedt Larry SchulzeRohm & Haas Co. University of Nebraska727 Norristown Road 101 Natural Resources HallP.O. Box 904 Lincoln, NB 68583-0818Spring House, PA 19477-0904 USAUSA

James Schupp Bill SeekinsUniversity of Maine Maine Dept. of AgricultureHighmoor Farm Food & Rural ResourcesP..O. Box 179 State House Station #28Monmouth, ME 04259-0179 Augusta, ME 04333-0028USA USA

Carmine Sesa Richa ShaunakRhodia, Inc. Zeneca AgrochemicalsCN 7500 Formulation Dept.Cranbury, NJ 08512-7500 Yalding Technology CenterUSA Yalding, Nr Maidstone, Kent

UK

Tom Short Ron ShrumS.D. Warren - NE Timberlands Durand-Wayland, Inc.P.O. Box 400 P.O. Box 1404Mountain Avenue Langrange, GA 30241Fairfield, ME 04937-0400 USAUSA

Daniel J. Simonds Breece SleeperMead Corporation Lucas Tree Expert Co.P.O. Box 738 P.O. Box 958Rangeley, ME 04970 Portland, ME 04104USA USA

Thomas P. Small William G. Smart, IIIInternational Paper Greenleaf Technologies, Inc.45 West Broadway P.O. Box 1777Lincoln, ME 04457 Covington, LA 70434USA USA

Wesley C. Smith Doug SnyderMaine Board of Pesticides Control BASF Corporation28 State House Station Box 13528Augusta, ME 04333-0028 Research Triangle Park, NC 27709-3528USA USA

Wendell W. Soucier Joseph SowersInternational Paper Co. Virginia TechP.O. Box Y 206B Hutcheson HallAshland, ME 04732 Blacksburg, VA 24060USA USA

282

Michael Spellman Helmut SpieserChampion International Ministry of Agric., Food & Rural AffairsP.O. Box 885 Box 400Bucksport, ME 04416 Ridgetown, ON N0P 2C0USA CANADA

Ples Spradley James A. StewartUniversity of Arkansas International PaperCooperative Extension Service P.O. Box 320P.O. Box 391 Stratton, ME 04982Little Rock, AK 72203 USAUSA

Richard H. Storch Brian StorozynskyUniversity of Maine Alberta Farm Machinery Research Centre15 Mainewood Avenue 3000 College DriveOrono, ME 04473 Lethbridge, Alberta T1K 1L6USA CANADA

Robert Stover Bob StutzmanWIL FARM LLC Safe-Way Exterminating Co., Inc.1952 W. Market Street RFD #3, Box 904Nappanee, IN 46550 Bangor, ME 04401USA USA

Paul E. Sumner Sherman TakatoriUniversity of Georgia Idaho State Dept. of AgricultureRural Development Center 2270 Old Penitentiary RoadP.O. Box 1209 Boise, ID 83712Tifton, GA 31793 USAUSA

Theresa Takiue Milton E. TeskeHawaii Dept. of Agriculture Continuum Dynamics, Inc.Pesticides Branch P.O. Box 30731481 South King Street., Ste. 431 Princeton, NJ 08543Honolulu, HI 96814 USAUSA

Alan B. Theis Norman ThelwellUnion Carbide Zeneca Ag. ProductsP.O. Box 670 Western Research CenterBound Brook, NJ 08805 1200 South, 47th StreetUSA Richmond, CA 94804

USA

Roger Theriault Harold ThistleLaval University USDA Forest ServiceDept. SGA MTDC, Bldg. 1, Ft. MissoulaSainte-Foy, Quebec G1K 7P4 Missoula, MT 59804CANADA USA

Lee A. Thomas Michael ThompsonMaine Department of Environmental Protection Arkansas State Plant Board1235 Central Drive Box 1069Presque Isle, ME 04769 Little Rock, AR 72203USA USA

283

Barry T. Tibbetts Ted TichyS.D. Warren - NE Timberlands Mead PaperP.O. Box 400 1598 State Rt. 2Mountain Avenue Sherburne, NH 03581Fairfield, ME 04937-0400 USAUSA

Robert Tomlins Prescott TowleMaine Board of Pesticides Control CWC Chemical, Inc.28 State House Station 2948 Simmons DriveAugusta, ME 04333-0028 Cloverdale, VA 24077USA USA

Andrew C. Triolo Allen K. UnderwoodUS EPA, Region I Helena Chemical Co.Pesticides, Toxics & Radiation 6075 Poplar AvenueCPT U.S. EPA, JFD Federal Bldg. Memphis, TN 38119Boston, MA 02203 USAUSA

David Valcore Gary R. Van EeDow-Elanco Bldg. 304 Michigan State University9330 Zionsville Road 226 Farrall HallIndianapolis, IN 46268-1054 Agr. Eng. Dept., MSUEast Lansing, MI 48824 USAUSA

Stephen P. Vinall Carrol M. VossAgro Chemical Eval. Unit, Univ. of Southampton AgRotors, Inc.Biological Sciences Building P.O. Box 70Bassett Crescent East New Harbor, ME 04556Southampton, U.K. S016 7PX USAUSA

Henry F. Wade, Ph.D Bob WagnerNorth Carolina Dept. of Agriculture University of MaineConsumer Services, Pesticide Section 5755 Nutting HallP.O. Box 27647 CFRU, UmaineRaleigh, NC 27611 Orono, ME 04469-5755USA USA

David G. Wagner John WainwrightPennsylvania State University New York State225 Agricultural Engineering Bldg. Dept. of Environ. ConservationUniversity Park, PA 16802 207 Genesce StreetUSA Utica, NY 13501

USA

Martin Waller Cliff WeedZeneca Agrochemicals Washington State Dept. of AgricultureJealott’s Hill P.O. Box 42589Nr Bracknell, Berkshire RG42 6ET Olympia, WA 98502-2589UK USA

284

Chris Weed Alan J. WestZeneca Ag Products Southern Crop Protection Assn.10648 Scottsville Road P.O. Box 52671Alvaton, KY 42122 Atlanta, GA 30355USA USA

Allen White J. Patrick WhiteU.S. Fish & Wildlife Service White’s Weed Control10711 Burnet Road 142 Raymond RoadSte. 200 Palmyra, ME 04965Austin, TX 78758 USAUSA

Fred Whitford Susan P. WhitneyPurdue University University of DelawarePurdue Pesticide Programs Dept. of Entomology & Applied Ecology1155 Lilly of Life Sciences 254 Townsend HallWest Lafayette, IN 47907-1155 Newark, DE 19717USA USA

Ray C. Whittemore Joseph E. Wiley, IIINCASI Maine Dept. of Inland Fish. & WildlifeP.O. Box 53015 Bureau of Parks & LandsMedford, MA 02153 22 State House StationUSA Augusta, ME 04333-0022

USA

Jeffrey J. Williams Rich WilsonMead Publishing Paper Division 1900 E. Andromeda P19 Main Street Tucson, AZ 85737Mexico, ME 04257 USAUSA

Lynn Wilson Jim WilsonS.D. Warren - NE Timberlands South Dakota State UniversityP.O. Box 400 Ag Hall 237Mountain Avenue Box 2207AFairfield, ME 04937-0400 Brookings, SD 57007USA USA

Terry L. Witt Dan WixtedOFS University of Wisconsin3415 Commercial St., SE Department of AgronomySuite B 1575 Linden DriveSalem, OR 97302-4668 Madison, WI 53706USA USA

Robert E. Wolf Robert WolffUniversity of Illinois New Hampshire Dept. of Agriculture360-N Agr. Engr. Sci. Bldg. Division of Pesticide Control1304 W. Pennsylvania P.O. Box 2042Urbana, IL 61801 Concord, NH 03002-2042USA USA

285

Nicholas Woods Allen WooldridgeC-PAS (Centre for Pesticide Application & Safety) ADAPCO, Inc.UNI of Old Gatton College 2800 South Financial CourtQueensland, Australia Sanford, FL 32773AUSTRALIA USA

John P. Wright Duncan WurmDow AgroSciences Nat. Ag Aviation Res. Edu. Foundation 9330Zionsville Road 1005 E Street S.E.Indianapolis, IN 46268 Washington, DCUSA USA

Kathryn ZahirskyDavey Tree Expert co.1500 N. Mantua StreetKent, OH 44240USA

north american conference on pesticide spray drift management - amazon...

Documents