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Combination Azobenzene—HETP Fumigationby

W. E. Blauvelt, Department of Entomology, and Jullue HoffmanRoees Incorporated Research Fellow, Cornell University

Fumigation with a combination of azobenzene and hexaethyl tetraphosphate has showngreater effeotivenesa against all stages ofred spider mite from a single treatment thaneither material used alone by any method yetreported. Like the "combined operations"used so successfully in World War II, thisnew method strikes at the enemy simultaneously with two different and powerful forcesacting together for the greatest combined effects.

By markedly increasing the effectivenessof azobenzene fumigation the combinationtreatment promises to reduce considerably thenumber of fumigations required. This wouldbe particularly valuable on roses, where themites are most resistant and where frequentfumigations are objectionable because of lossof color in the buds.

The combination fumigant, like the useof HETP Itself, Is still in the experimentalstage. Much additional researoh and largescale testing will have to be done before wecan recommend it with assurance for generalgrower use. However, the results to date areproraielng both aa to effeotiveneaa and plantsafety on a wide range of florist crops. Sinceno new method can be kept secret until fullydeveloped and teeted, we are giving here theexperience to date ao that growers who wishto experiment with It will have the benefitof this Information.

COMBINATION GIVES FASTER KILL

Azobenzene fumigation alone under properconditions has given kills of better than 99per cent of all stages of the red spider miteincluding active mites of all ages, the inactive molting stages, and egge in all stagesof development. These results have been obtained not only In many large and small scaleexperimental fumigations but in many routinefumigations by growers. The weak point incontrol has been that many of the mitea diedso slowly that they were able to lay quite afew eggs before dying. Although some of theseeggs are affected so that they do not develop,enough hatch to carry on the infestation. Sogreat is the rapidity of mite developmentthat small numbers of survivors soon increaseto-a large population, particularly at hightemperature. There was a need for some effective material that could be added to insure an immediate high kill of older mites toprevent this egg laying. HETP appears to flilthis need best, giving 100 per cent kill ofactive stages in twelve hours or less.

The question will be raised, If HETP 1bbo effective, why not use it alone and avoidthe loss of color in roses from azobenzene?The reason la that HETP, while remarkably effective against the active stages has littleeffect against the egge and also fails to killmany of the inactive molting stages. Thus It

is weak where azobenzene is strong, and themaximum effectiveness is obtained by usingthe two materials together. The egge andmolting stages make up from one half to threefourths of the total population; and threeoarefully timed treatments with HETP aloneare uaually required to give the same degreeof control aa is obtained with one combination fumigation.

EXPERIMENTS SHOW VALUE AS A FUMIGANT

Hexaethyl tetraphosphate was discoveredand developed in Germany during the war toreplace nicotine for control of aphlds orplant lice. Information on the formula andmethod of manufacture was uncovered by theUnited States government science teams whoentered Germany immediately after fightingceased. Tests in this country showed thatit was highly effective against mites as wellas aphlds and large amounts are now beingmanufactured and used as sprays on variouscrops.

The writers were particularly Interestedin determining whether HETP could be used asa greenhouse fumigant, since fumigation savesmuch time and labor and Is more thoroughthan spraying. The chances of using HETP asa fumigant were not considered promisingsince the material was known to vaporize onlyslightly at normal temperatures and chemistsreported that It could not be distilled orvaporized by heating without "breaking down".Experiments were first made by bubbling airthrough a flask of HETP and into a chamberIn which mite-lnfeated leaves were exposed.A complete kill of active stages of the miteswas obtained, proving that the material wasvolatile enough to be effective as a fumigant.

HETP was also found completely effective againat active atages of the mitea whendiatributed through the air of a greenhousein very fine mist or fog-like particles bymeans of the now familiar liquified gasaerosol bomb. There were strong indicationsthat the effect of HETP aerosol was also duelargely to fumigation, through vaporizationof the tiny particles of HETP in the air.The first and moat extensive work on use ofHETP as an aerosol has been done by Dr. FloydF. Smith and his oo-workers in the UnitedStates Bureau of Entomology. Their investigations have been reported in detail in the

cont'd, from pg. 11-New Azobenzene Fumlganteand may go out before completely burned, foavoid this they should be stored In a warm,dry plaoe.

For best results with Azofume Candles,follow the recommendations for proper Condl-tlona for Fumigation as discussed in the preceding article.

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florist trade Journals.

Next, experiments were made to determinewhether HETP could be vaporized by means ofthe steampipea as with azobenzene. Practically complete kills of active stages of themites were obtained by dosages of 3 to 5grams of HETP per 1000 cubic feet, eitherapplied undiluted or mixed to a paste withwater and celite powder and painted on thepipes. Although some of the material ie probably broken down by this method, enough Isvaporized to give good results at economicalcost. Steam pipe vaporization ia a particularly good method for vaporizing HETP by heatsince the temperature Is automatically controlled well below the point (300°F.) whereHETP is known to break down rapidly and maygive off ethylene gas harmful to plants.

TESTS ON MIXED CROPS

The first commercial scale trial of combination azobenzene-HETP fumigation was madeDecember 26, 1946 in a 30,000 cubic footgreenhouse of the Floriculture Department atIthaca. Seventy per cent azobenzene powderwas used at the standard rate of 1 pound per40,000 cubic feet and HETP was added at therate of 5 grams per 1000 cublo feet. TheHETP was mixed in with the azobenzene pasteand painted on the pipes in the usual manner.

The house contained 20 different flor

ists crops in addition to potted rose plantsof Better Times variety moved in for thetest. The plants were as follows: Carnatlons-mature plants of King Cardinal, Virginia Rose,Olivette, 3 benches; ChryBanthemums - 26varieties as listed in "article on AzobenzeneDevelopments, 400 plants 2 to 6 weeks oldin flats; Snapdragon - Cheviot Maid Supreme,1/2 bench 'in crop; Geraniums - Madame Landry,90 plant8 in 4-lnch pots; Cineraria - Slter'sRainbow strain and Creraers Strain, 150 plantsin 6-inch pots; Calceolaria - multifloranana, 20 plants In 5-lnch pots and many hybridseedlings; Tulips - 50 pans, tops about 3";Myosotls - Blue Bird, 60 plants in 4-lnchpot8; Camellia - 2 plants, pink and white,inbloom; together with 10 to 25 planta each ofAsters, Stocks, Larkspur, Easter Lilies,Lupine, Kalanchoe, Begonia, SaTntpaulla, Calendula, NarclssUs, ana Sweet PeasT

Due to a rapid drop in outside temperature from around 20 degrees at 4:30 p.m. whenfumigation was started to S degrees duringthe night, the houae temperature was heldbarely at 70 degrees and the house could notbe ventilated until 10 a.m. In spite of theunfavorable conditions the only injury of anyimportance was to Myosotls, which developednumerous burned spots In the leaves. Theseplants had Just been repotted and sprayedwith water to reduce wilting, and the injurywaa apparently greateat where the foliage waawet. Occaalonal leaves of lupines and larkspurs developed some marginal burn. Carnation and camellia blooms showed no noticeablebleaching or other injury, and snapdragonflowers were not noticeably damaged.

The treatment gave a 100 per cent killof active stages of red spider mite on both

roses and carnations. Counts at intervals upto 10 daya showed a 99«9S per cent kill ofall stages Including eggs and molting stageson carnations and 93 per cent on roses. Inaddition, there was a nearly 100 per centkill of the pink and green rose aphid.

COMMERCIAL TESTS ON ROSES

On roses, the first commercial scaleteat of the combination fumigation waa madein cooperation with Mr. Harold Koenig at theUnited State8 Cut Flower Company, Elralra,N.Y.on January 31, 1947* Three connecting ridgeand furrow houaes of 65,250 cubio feet eachwere treated. The varieties were Better

Tirae8, Brlarcliff, and Talisman. The standard dosage of 70 per cent azobenzene powderwas used but the dosage of HETP was cut tothree grams per 1000 cubic feet. Unfortunately, a rather high wind developed whichcaused rapid leakage in the narrow, ratherloose houses. The kill of active stages thefollowing morning was high but the kill ofeggs and molting stages was unsatisfactory.There was no foliage injury, tlpburn orbleaching of mature leaves.

In mid-February, Harold Koenig made asecond combination fumigation in these samehouses under more favorable conditions on a

sunny day, with a house temperature aroundSO degrees, and a 6-hour fumigation period.Vapotone, which contains 50 per cent of HETP,was used at the rate of S fluid ounces foreach pound of 70 per cent azobenzene powder(equal to 5 grams HETP per 1000 cubic feet).The results were excellent. Practically 100per cent of active stages of the mites werefound dead the following morning, and a veryhigh kill of eggs and molting stages was obtained. There was no foliage injury in theform of bleaching and only very slight tip-burn. A few buds showed a purple discoloration of the margins of outer petals the following morning, but there was very littleloss of color in the buds, Whether this result could be expected generally, and whetherHETP acts In some way to reduoe the bleaching effect of azobenzene on buds is notknown. A number of other growers have triedthe combination fumigation but detailed reports of results have not yet been received.

SUGGESTIONS ON TREATMENT

Much additional research and large-scaletesting will have to be done before the combination fumigation can be reoomraended. Forthose who wish to experiment with It at thepresent stage we suggest using 4 fluid ouncesof straight HETP or S fluid ounces of Vapotone (50 per cent HETP) for each pound of 70per cent azobenzene powder. Simply mix itwith the water used In making the pa8te forpainting on the pipes. All other operationsand conditions for fumigation are the sameae with the 70 per cent azobenzene powderalone.

HETP 1b not suggeeted for lamp vaporization with azobenzene cryetals because of thedanger of breaking down the material by thehigh temperature, with loss of effectivenessand possible production of ethylene. If a _•

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combination treatment is desired with lampvaporization or with azofume candles it canbe accomplished by using an HETP aerosol during the fumigation period.

PRECAUTIONS-

HETP is a highly poisonous material,-as poisonous as pure nicotine, and all necessary precautions as given on the containersshould be strictly observed. Rubber glovesshould be worn in handling and applying theconcentrated material. Operators should weara chemical cartridge respirator or a gasmask when exposed to the vapors during fumigation. We have used the Comfo ChemicalCartridge Respirator with G. M. C. cartridges,made by the Mines Safety Appliance Co., Pittsburg, Penna., and believe that this is probably satisfactory for the concentration ofvapor used. The price has been $5.50. Forgreater assurance of safety the Full VisionGas Mask, with G. M. C. cannlster, may beused as suggested by Dr. Floyd Smith for usewith HETP aerosols. This is made by thesame company and costs about $22.50.

More About Surface TubeAutomatic Watering

The tubes are fastened together withpieces of rubber tubing or garden hose. Theamount of water emitted from the 0.039 inchorifices ic as follows:

Stream height Gal. per Hour(inches) per orifice

I 1.07

1.155 1.236 1.51725

1.391.47

9 1.5410 1.61

Kenneth Post

Note on VermiculiteVermlcullte is an excellent medium for

rooting cuttings. (Refer to bulletins 13 and14) The coarse house fill or size no. 1grade is recommended for this purpose.

We have recently been Informed that thevermiculite sold by building supply dealersfor insulation purposes la being treated tomake it waterproof. Thia material ia notgood for propagation. Before buying vermiculite, find out whether It haa been treated.

Untreated vermlcullte for plant propagation ia being aold by several florist supplydealers.

School for Foremen and Growers

In spite of a six-Inch snowfall and subzero temperatures, more than 100 floristswere on hand when Dr. Kenneth Post openedthe .program. The morning sessions were devoted to discussions of Fertilizers, TimingCrops, Ventilation and Temperature Control,Automatic Watering, and How Diseases Spread.The afternoons were spent at the collegegreenhouses where the growers were able tosee How to Spray for Disease Control, Aerosols, Sodium Solenate, and Azobenzene Applications, Year-around Mum Production,, Automatic watering Methods, Automatic Ventilation and New Wrinkles in Propagation.

The following list was taken from ourregistration:

Connecticut 6Illinois 1Maryland 2Massachusetts^Michigan 2New Jeraey S

New YorkOhio

Pennsylvan laCanada

EnglandTOTAL

495

H1

TOT

Welcome to Our DepartmentCharles W. Fischer, Jr., eon of the

well-known florlat of Atlantic City, N.J.wasgraduated from Cornell In February 1947, andJoined our department to carry on graduateBtudiee In the field of commercial floriculture. In addition to chemistry which was hismajor subject during his undergraduate work,he completed many courses In botany and plantphysiology.

You will become better acquainted withhim ae you visit Cornell and see the resultsof his research.

Charles W. Fischer,Jr.