for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture May 3, 2013Coordinator Weekly IPM report: Stanton Gill, Extension Specialist, IPM for Nursery, Greenhouse and Managed Landscapes, sgill@umd.edu. 301-596-9413 (office) or 410-868-9400 (cell)

Regular Contributors: Pest and Beneficial Insect Information: Stanton Gill and Paula Shrewsbury (Extension Specialists) Disease Information: Karen Rane (Plant Pathologist) and David Clement (Extension Specialist)Weed of the Week: Chuck Schuster (Extension Educator, Montgomery County)Cultural Information: Ginny Rosenkranz (Extension Educator, Wicomico/Worcester/Somerset Counties)Fertility Management: Andrew Ristvey (Regional Specialist, Wye Research & Education Center)Design, Layout and Editing: Suzanne Klick (Technician, CMREC)

In This Issue...

If you work for a commercial horticultural business in the area, you can report insect, disease, weed or cultural

plant problems found in the landscape or nursery to

sklick@umd.edu

TPM/IPM Weekly Report

- Azalea sawfly- Diagnostic program- Emerald ash borer program- Boxwood mites- Boxwood leafminer- Spruce spider mite- Tick activity- Emerald ash borer control- Carpenter bees- Brown marmorated stink bug- Ambrosia beetles- Aphids- White peach scale- White prunicola scale- Japanese maple scale- European lecanium scale- Cryptomeria sclae- Fall cankerworms- Frost damage- Liriope problems- Iris borer

Beneficial of the WeekWeed of the WeekPlant of the WeekDegree DaysPhenologyAnnouncements

Integrated Pest Management for

Commercial Horticulture

ipmnet.umd.edu

Sawfly Larvae Feeding on AzaleaBill Miller, The Azalea Works, brought in a sample of azalea sawfly larvae that was found feeding on azalea this week. They are not gregarious like other sawflies and blend in well with the green leaves so they may be hard to spot.

Azalea sawfly larvaPhoto: Bill Miller, The Azalea Works

Mark Your Calendar: May 29, 2013, Time: 4:30 p.m. to 8:30 p.m.Improving Your Diagnostic and Treatment Skills

A program on insect and disease identification and control and sprayer calibration and tree injection

Location: Central Maryland Research and Education Center (CMREC) 11975 Homewood Road, Ellicott City, MD Sponsors: University of Maryland Extension and MD Arborist Association

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Boxwood MitesExamine the foliage of boxwood for mites. On April 27, newly hatched boxwood mites were found on plants in Baltimore. If your customer has boxwood growing in sunny spots and has mite injury from last year, examine the foliage closely. Use a 10 -16 X magnifier to look at the undersides of the foliage for the mites.Control Options: At this point, boxwood are putting out new growth. Horticultural oil can be used at a 1 – 2% rate. We have used the insect growth regulators, Hexagon and TetraSan, with good success. Since the mites are young nymphs at this point the growth regulators are very effective. Other options include Sanmite and Avid. Make sure the sprayer puts out a fine mist and be sure to hit the undersides of the foliage.

Planning for the Invasion: Control Measures for Emerald Ash Borer for Managers of Urban Forest ResourcesIf you are a city manager and need to make decisions on how to deal with EAB in your city then look into attending the May 7th conference More information is available at http://eabcontrol.eventbrite.com/

Spruce Spider MiteWe have been examining branches of Alberta spruce from Clarksville and Westminster and are still just finding eggs. We should have hatch of eggs in city areas. If you are seeing hatch of spruce spider mites please let us know at sgill@umd.edu.

Boxwood LeafminerNancy Harding, UMD, observed boxwood leafminer adults flying around boxwood on April 28 in Bowie. Mike Raupp, UMD, reported boxwood leafminer adult activity on boxwood in College Park on May 1. The adult leafminers have a bright orange body. The pupal cases may still be found on the undersides of thefoliage where the adults emerged.Control: Systemic insecticides such as imidacloprid should provide 2 – 3 years of control of this pest. Applications of dinotefuran should provide one season of control and is uptaken into the plant faster than imidacloprid. If you are on a budget an application of a synthetic pyrethroid such as bifenthrin or permethrin will kill adults, but it will also kill many beneficial organisms in the process.

Boxwood leafminer pupal case (above) and adult (right)

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More on Control of Emerald Ash BorerFrom Dave Smitley – Michigan State University, in response to question about whether to make two applications for EAB control:The application rate for the homeowner product, Bayer Tree and Shrub Insect Control, is 1 oz per in of trunk circumference, not diameter. The reason for mentioning two applications is only for compliance with the label. The product is not supposed to be applied more than once per year. However a fall 2013 application could be followed by a spring 2014 application, and still be once per year.

The reason for considering two applications is that for larger trees (> 10” dbh) one application is not enough to protect them from intense EAB pressure. Two applications or a doubling of the labeled rate has worked for me and for Dan Herms for trees up to a 16” dbh. Spring (early May in Maryland) works better than fall, so if one application is made, spring is preferred. Watering-in and watering during dry periods helps immensely. There is also a group effect, so if you treat all the ash trees in a given area you will have better results than if you treated a single tree among untreated trees. So, for an irrigated site, or a site with moist soil, where you treat all the trees, one application should work well for trees up to a 12 or 15” dbh.

Also, for homeowners, we have recently had good results with ACECAPS, as a homeowner trunk implant. For larger trees, it is more economical for homeowners to hire an arborist to make a TREEage trunk injection. It can be done every 3rd year at the low rate or every 4th year at the high rate.

Brown Marmorated Stink Bug (BMSB)There are still a lot of reports of brown marmorated stink bugs buzzing around in peoples’ homes this week. Many of the adults have moved outside and should be mating. We have not found any egg masses yet, but they should show up soon.

Recently hatched BMSB nymphs by egg mass in June 2011

Tick ActivityWe continue to receive reports of high tick activity this season. Be sure to check yourself for ticks regularly when working outside.

Carpenter Bees Are Very Active This WeekYou may see male carpenter bees buzzing around the landscape and dive bombing each other to establish their territory. The carpenter bees are drilling into exposed wood surfaces to establish their nest for the season. We are getting several reports that they are attacking pressure treated wood. The old copper arsenate treated wood (banned several years ago) was rarely attacked, but the newer, safer treated pressure woods appear to be susceptible to the drilling activity of carpenter bees.Control: Paint exposed surfaces to reduce the drilling activity of carpenter bees. Once they bore into wood an aerosol spray can be applied into their hole after dark then plug the hole with a piece of steel wool.

Carpenter bee boring into wood on building

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Ambrosia Beetle ActivityWhat a wild spring it has been as far as the weather goes. On April 7 – 9, we had a real spike in temperatures reaching the high 80s and low 90s F for many areas of Maryland. There are two highly damaging ambrosia beetles we are concerned about which are Xylosandrus germanus and Xylosandrus crassiusculus. These two exotic ambrosia beetles are increasingly being recognized as a key pest of nursery trees, particularly deciduous hosts. Over the last 20 years a growing body of evidence indicates X. germanus and X. crassiusculus will colonize apparently-healthy trees. Nursery owners in Maryland have been reporting fairly heavy losses from these two beetles for the last 3 years.

After the original spike of flight activity in early April of 2013, the numbers we are catching in our baited traps in various parts of the state has dropped off as shown in the chart. Several nursery operators we contacted treated their susceptible tree species with Onyx (Bifenthrin). I called several of the nursery owners this week to see how this application worked and so far everyone is reporting very good control levels with the bifenthrin application. This generally gives about 3 weeks of control. If we had another spike in flight activity I might suggest a second application of bifenthrin, but from the trap counts it appears a second application is not necessary at this point.

We will continue to monitor and let you know if there is another upsurge in flight activity. Last year we had one nursery owner report damage from a second generation. The life cycle is 55 days from egg to adult. So far this season, the cold weather is working to our advantage and keeping flight activity down.

Damage to violas in landscape bedPhoto: Steve Sullivan, The Brickman Group

Aphids on Viola Steve Sullivan, The Brickman Group, sent in a photo last week of a landscape bed of violas with dead spots created by aphid feeding. Steve noted that it can often be mistaken for drought damage so look closely at plants for aphids. Assess the damge and look for the presence of predators and parasitoids to determine the control measures that are needed.

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Cryptomeria scale damage on fir (above) and female scale (below)

White Peach Scale Hatches on Eastern ShoreNorm Brady, Bartlett Tree Experts, sent a picture of female armored scale that had eggs under the covers. Norm collected the sample on April 12th just outside of Denton. The scale was identified by Lorraine at the Bartlett Research Lab as white peach scale. They were females with eggs. Norm noted that where the lab is located in Charlotte, NC there were crawlers of this scale on April 15th. White peach scale is Pseudaulacaspis pentagona and has a wider host range than white prunicola scale.We have found this scale commonly infesting holly, but it feeds on large variety of plant material.

European Lecanium ScaleWe are receiving reports that European lecanium scale females are starting to swell. We are not seeing eggs yet.

White Prunicola ScaleNancy Harding, UMD, examined the test site where we are monitoring white prunicola scale, Pseudaulacaspis prunicola, on cherry trees in Laytonsville. White prunicola scale is mainly found on Prunus species including cherry trees and cherry laurel. We also often find it on lilac. Last week, we only found females without eggs in the Laytonsville area. On April 30 (183 degree days), Nancy found 74 that are 3rd instar without eggs and 26 that are 3rd instar with eggs. Norm Brady, Bartlett Tree Experts, reports he is finding female scale with eggs on the Eastern Shore.

Japanese Maple ScaleNancy Harding found third instar females without eggs of Japanese maple scale in Laytonsville on April 30 (183 degree days). Japanese maple scale females are switching from 2nd instar to 3rd instar and the males are maturing into the 5th instar and will be coming out fairly soon to mate with the females. Both males and females turn a purplish color at this time.

Cryptomeria Scale, Aspidiotus cryptomeriaeWe were examining a blue spruce sample in Woodbine on May 1 and found an infestation of cryptomeria scale which is an armored scale that feeds on the foliage. This scale insect overwinters as 2nd instar males and females. In a normal year we would have 3rd instar present sometime in early May with eggs. What we observed this season were a a lot of 3rd instar females and we found a newly emerged male that was mating with a 3rd instar female. This means we can probably expect eggs and crawlers around early to mid June. Look for this armored scale on cryptomeria, hemlock, pines, fir, and spruce.Control: Distance or Talus can be used when the crawlers appear next month.

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Fall Cankerworms – Out in Southern MarylandBen Beale, Extension Educator in Southern Maryland, reported activity of fall cankerworm in northern St. Mary’s County and eastern Charles County for a second year in a row. Last year we had emails reporting its activity in College Park and the eastern part of Anne Arundel County. The Home and Garden Information Center is also receving calls of defoliation in Southern Maryland. Fall cankerworm, Alsophila pometaria, family Geometridae, is a native pest of hardwood trees in Maryland. This caterpillar feeds on foliage rapidly in spring, but it is not a problem every year in the same location. Isn’t it great to have a native pest rise up instead of an invasive species? Usually when there is an outbreak of a native pest, then the predators and parasites collapse the population within a year or so. The fall cankerworm is so called because adults are active in late fall even though larvae feed in the spring. The cankerworm caterpillar has prolegs on the front and back part of the abdomen with no prolegs in the middle section. They hump up to move about and are often called inchworms. Larvae have three pairs of true legs on their thorax and three pairs of prolegs on their abdomen. The first pair of prolegs, when looking back from the head, is much smaller than the last two pairs. The caterpillars are light green and some are dark brownish-green. The light green caterpillars have white lines running down their body from the head to the tip of the abdomen. The dark brownish-green caterpillars have a black stripe the length of their back. Generally, when more dark colored caterpillars are seen, it may be a sign of a heavy infestation. Common trees on which this species prefers to feed are ash, basswood, beech, black cherry, red maple, sugar maple, red oak, and white oak. It will also feed on the leaves of apple, birch, boxelder, dogwood, elm, hickory, and many other hardwoods. Nearly every year, the fall cankerworm causes at least some small areas of defoliation in some landscapes or in forest areas.

When populations build up it can cause alarming amounts of defoliation, but it is so early in the year the trees generally recover without control being applied. What customers are going to notice, besides the defoliation, is that the larvae, when finished feeding after 4 or 5 weeks will lower themselves by silken threads. Nothing more alarming to customers may be to see floating caterpillars suspended from trees.

Brown form of fall cankerworm

Frost DamageMark Schlossberg, ProLawn Plus, Inc., sent in a photo of hypericum with frost damage on May 1.

Frost damage on hypericumPhoto: Mark Schlossberg, ProLawn Plus, Inc.

Fall cankerworm damagePhoto: Ben Beale, UMD

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Liriope Problems Greg Stacho, Mainscapes, Inc., called to inquire what the problem was with liriope last season. Many plants died out in landscapes in 2012.

There are two common diseases of this plant that we have seen on clinic samples in the past few years. Red leaf spots and leaf dieback are often symptoms of anthracnose, caused by the fungus Colletotrichum sp.. Variegated cultivars are often more severely affected. Rainy weather or overhead irrigation will splash-disperse spores and increase the severity of the disease. The pathogen overwinters on infected leaves. Cutting and removing old foliage in early spring can help reduce disease severity on new plants. Avoid sprinkler irrigation to keep foliage as dry as possible. If the infection is severe, dieback of entire plants may occur and infected plants should be removed. We have also seen crown rot of liriope caused by a Fusarium sp., particularly in drier locations. The soil-borne pathogen attacks the bases of the leaves as well as the crown, resulting in death of foliage and plant collapse. Remove and discard plants with Fusarium crown rot and avoid re-planting with liriope in the same area.

If you are seeing crown rot problems on liriope in a bed that holds a lot of moisture then the culprit may be Phytophthora root rot. Excessive moisture from over-irrigation or poorly draining soils favor the development of this water mold. Crown rot caused by Phytophthora may have a blackened, slimy look to the rotted leaf bases, but symptoms can be very similar to Fusarium crown rot. Infected plants should be removed, and steps taken to improve drainage or alter irrigation practices. Application of a fungicide such as Subdue Maxx may help protect plants for a short time, but for long-term management, improving drainage in the site or altering irrigation practices to avoid excessive moisture is the most effective way to manage Phytophthora crown rot. Steve Sullivan, The Brickman Group, has observed that the cultivar ‘Big Blue’ is the most susceptible and replanting with other cultivars may also reduce disease.

Liriope crown rot. In this case, symptoms are due to anthracnose and Fusarium, but Phytophthora crown rot may look similar.

New shoots of liriope emerging at edge of older plant-ing. Spores from older leaves can infect this new growth. Cutting back and removing old liriope foliage, and keep-ing new foliage as dry as possible can help reduce the amount of infection on new plants.

Leaf spots on variegated liriope, caused by a Colletotrichum species (anthracnose)

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Iris BorerFrom: Stanton GillOn Sunday I was observing an iris planting in Glenwood. The iris fans were about 6 – 8” tall and iris borer larvae were chewing on the foliage causing small holes. The larvae will feed for a short time on the outside of the foliage before moving into the leaf folds. They then tunnel in the soft tissue and eventually work their way downward into the rhizome. Often a bacterial soft rot moves in which produces a foul odor.Cultural Control: Look closely for chewing damage and water-soaked streaks on foliage. If you find iris borers early in the season, you can crush the insect while it is inside the leaf or remove the infested leaf. Sanitation in July is critical if you are having problems with iris borer. If an iris plant has above-ground symptoms (brown leaf tips, early senescence), dig it up and examine the rhizomes. Discard rhizomes containing iris borer caterpillars and those with tunnels.Chemical Options: An insecticide application needs to be applied when the larvae are feeding on the outside of the foliage before they moves into the leaf olds. Two options are acephate (Orthene) or spinosad (Conserve). It is important to time the application when eggs are just hatching. This is approximately when new growth is about four to six inches high.Beneficial Nematodes: There are Heterorhabditis and Steinernema species of nematodes that have been shown to attack iris borer larvae. Nematodes need a moist environment to survive and move. The easiest time to apply is during a rain shower. If no rain, water iris before and after applying nematodes. Apply nematodes when iris leaves are almost fully expanded but before flowering.

Iris borer damage on foliage

Iris borer larva

Beneficial of the Week, Paula ShrewsburyPredatory caterpillar, Laetilia coccidivora, feeds on soft scales. It is spring and many of the soft scales (Family Coccidae) are sucking sap from the phloem of ornamental plants and excreting honeydew like crazy, all in preparation for making and laying their eggs. Fortunately, it is not uncommon to find a predacious caterpillar feeding on and killing these soft scales. This predacious caterpillar is the larvae of a snout moth (Family Pyralidae) Laetilia coccidivora. It is found in southern states and northward up into Maryland. The larvae are predatory on Coccidae species such as tulip tree scale, wax scale, pine tortoise scale, and other soft scales. They feed on the eggs and young of soft scales. Last week there was a report of Laetilia feeding on scales on the eastern shore. They are also known to be active in late summer / early fall.

Magnolia branch with tulip tree scale (see reddish “bump”) covered in silk produced by the predatory caterpillar, Laetilia coccidivora. Photo: P. Shrewsbury, UMD

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Weed of the Week, Chuck SchusterPlant Identification and Potential Control Options of the Week

What is a weed? All native plants have value, but some when they are found in a place that they are not desired causes some to look for information. A weed is nothing more than a plant out of place.

Our Plant of Interest this week is roughstalk bluegrass, Poa trivialis. This perennial grass is found in turf and has been showing up in some of our well managed turf areas this spring. It is classified as a fine textured, cool season grass with a prostrate spreading growth habit. Roughstalk bluegrass will spread quickly by way of stolons which can be a problem for the desirable turf species. Reaching a total height of up to three feet, it will produce a panicle seedhead which is typical of other bluegrass species. As the weather gets hotter, it will go into a dormant stage, returning to active growth when the temperature moderates and will grow through the cooler months.

The stems have small hairs and bands of purple at each node. Leaves have the boat-shaped tip found in most bluegrass species and are a shiny light green color that may discolor to a bronze when stressed by heat or drought. Each leaf blade can be up to seven inches in length and one quarter inch wide. Leaf blades are covered with small hairs. The leaf also has a large ligule that is membranous and occurs with a hook near the top. This weed will be affected by dollar spot and brown patch disease.

Control of this weed is difficult in established turf. Velocity herbicide is labeled for it in sod production and golf courses. It should be noted that in some stands of established turf, recent weather conditions have caused it to show some frost damage or bleaching of the blades. This is an extremely hard weed to control. Spraying back with a post emergent non selective material may be necessary, but will require two applications to eliminate all stolons. Check the label for reseeding interval.

These predacious caterpillars forage on the branches of plants with soft scale and produce webbing that appears to “coat” the branch while encompassing the scales. The branches have a dusty, messy appearance to them. When you look closely you can see the webbing and if you tease the webbing apart you may get lucky and find the predacious caterpillar! This caterpillar has been noted to reduce soft scale populations. When you are monitoring scale activity on your trees and shrubs, be sure to look closely for signs of this voracious caterpillar feasting on the scales.

Also of interest is that some soft scales produce a chemical for defense called carminic acid. This chemical deters many predators from feeding on the soft scale. Laetilia, however, is not affected or deterred and they just eat away. Moreover, this caterpillar uses carminic acid that it acquires from its prey, as a defense against its own predators - very cool.

Close up of silk covered branch showing the predaceous caterpillar that feeds on soft scale, Laetilia coccidivora. Photo: P. Shrewsbury, UMD

Roughstalk bluegrassPhoto: Penn State Turfgrass

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PLANT PLANT STAGE (Bud with color, First bloom, Full bloom, First leaf)

LOCATION

Chrysogonum virginianum First bloom Ellicott City (May 2)Podophyllum peltatum (mayapple) First bloom Elicott City (May 2)Viburnum rhytidophyllum First bloom Ellicott City (April 29)

Plant Phenology: What is in bloom

Degree Days (As of May 2)Baltimore, MD (BWI) 229 College Park 330Dulles Airport 264 Frostburg, MD 120 Martinsburg, WV 240 National Arboretum 330 Reagan National 330 Salisbury 310

To check degree day (DD) accumulations in your local area go to: http://www.weather.com/outdoors/agricul-ture/growing-degree-days/USMD0100

Plant of the Week, Ginny RosenkranzCamellia japonica ‘Blood of China’ is a spring blooming camellia that grows 6-8 feet tall and 5-6 feet wide with an upright growing habit. The leaves are shiny dark green in color and last all year long, shedding the former years leaves in the late spring. The flowers are its crowning glory. They are slightly fragrant, peony shaped, and double pealed in a dark salmon red with bright yellow stamens. The plant itself is cold hardy in USDA zones 7-9, and like all Camellia japonica, likes to grow in full to part sun with some shelter from the drying winter winds. It prefers moist, well drained soils that are acidic, but after becoming established in the landscape can handle some drought and some salt. If subject to dry weather, it is normal for some of the spring buds to drop unopened. Mites can cause harm to flowers and many scale insects are pests. Anthracnose, root rot and leaf spot are the major diseases.

Peony ‘Blood of China’Photo: Jean Scott

JOB POSTING/HELP WANTED: University of MarylandTitle: Associate Agent Functional Title: Master Gardener Trainer, Sustainable HorticulturePosition Number: 118930 Location: Ellicott City, MDClosing date will be 5/6/13 or until filledPosition Summary/Purpose of Position: The Master Gardener Trainer will develop, implement, and provide advanced training (face-to-face and online) for Master Gardeners in ornamental plants with an emphasis on native plants and sustainable landscaping. Create new content on the HGIC website, and develop online teaching modules. Provide support for HGIC horticulture consultants. Work as a team member with State Master Gardener Coordinator and Advanced Training Coordinator to determine training needs and methods of delivery and evaluation.Application Process: All candidates must apply online at https://ejobs.umd.edu

Stanton GillExtension Specialist

sgill@umd.edu

Paula Shrewsbury Extension Specialistpshrewsb@umd.edu

Ginny RosenkranzExtension Educatorrosnkrnz@umd.edu

Chuck SchusterExtension Educator

cfs@umd.edu

Karen Rane Plant Pathologistrane@umd.edu

Brian Clark Extension Educator bpclark@umd.edu

Andrew RistveyExtension Specialistaristvey@umd.edu

David ClementPlant Pathologist

hgic.umd.edu

The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied.

CONTRIBUTORS:

University of Maryland Extension programs are open to all citizens without regard to race, color, gender, disability, religion, age, sexual orientation, marital or parental status, or national origin.

Thank you to the Maryland Arborist Association, the Landscape Contractors Association of MD, D.C. and VA, the Maryland Nursery and Landscape Association, Professional Grounds Management Society, and FALCAN for your

financial support in making these weekly reports possible.

Photos are by Suzanne Klick or Stanton Gill unless stated otherwise.

Upcoming Programs

Planning for the Invasion: Control Measures for Emerald Ash Borer For Managers of Urban Forest Resources May 7, 2013 Location: Robinson Nature Center, 6692 Cedar Lane Columbia, MD 21044 http://eabcontrol.eventbrite.com/

Improving Your Diagnostic and Treatment Skills: An Evening SeminarMay 29, 2013Location: CMREC, Ellicott City, MD

MNLA Nursery Field DayJune 20, 2013Location: Waverly Farm, Adamstown, MDContact: MNLA, 410-823-8684

Nutrient Management Plan Writing – Nursery and Greenhouse ProductionJuly 10, 2013, 9 a.m. to 3:30 p.m.Location: CMREC, 11975 Homewood Road, Ellicott City, MD 21042Contact: Andrew Ristvey, aristvey@umd.edu, 410-827-8056 x113

MDA Pesticide Container Recycling Program

MDA is once again conducting a pesticide recycling program. For a list of dates and locations of collection sites, go to http://mda.maryland.gov/plants-pests/Documents/recycle.pdf.