STATE PLANT BOARD
March 19k E-642
United States Department of Agriculture Agricultural Research Adminisetration Bureau of Entomology and Plant Quarantine
A SUIAY OF THE RESULTS OF THE WORK WITH DDT CONDUCED BY THE DIVISI O OF TRUCK CROP AND GARDEN INSECT IN VESTIGATIONS DURING TEE SEASON OF 1944
Cmpiled by W. H. White, Division Leader
Preliminary results on the work conducted in 1943 by the Division of
Track Crop and Garden Insect Investigations on DDT as an insecticide were reported in the February 1944 issue of the Journal of Economic Entomology.
Experiments were continued during the season of 1944. They consisted of
laboratory and small field-plot experiments, and in a few instances of
large fielA-plot experiments, against several conmon species of insects
which attack vegetables, tobacco, and sugar beets. With a few exceptions
the DD was used in dust mixtures containing pyrophyllite, and the final
product was prepared from a 10 percent MT-pyrophyllite mixture which was supplied upon order by Geigy Co., Inc., / in compliance with provisions prougated by the War Production Board on supplies of DI for experiaental purposes.
This statement has been prepared from reports received from the
various field laboratories of the Division, and is issued for the information and guidance of others interested in experimental work with DT as
a crop insecoticide.
The work on cabbage caterpillars vas conducted in field plots in
southern California, at Charleston, S. C., and at Baton Rouge, La., against
mixed populations, principally of the cabbage looper (Autographa brassioae (Riley)) = Trichoplusia ni (Hbn.), the imported cabbage worm (Pieris raa
(L.)), the larva of the diamondback moth (Plutella maculipennl Curt.
and the cabbage weborm (Hellula undalis (F.)). Several species of
Agrotinae and Heliothis armigera (Hbn.) were also present. In the Charleston
area the MT appeared to be more toxic to the cabbage looper than to either
the imported cabbage worm or the larva of the diamondback moth and also more toxic than either rotenone or pyrethrum to the cabbage looper. Thep results of this series of experiments seem to warrant the tentative conelusion that heavy infestations of these three species of caterpillars may
be controlled effectively by a 1 percent DIDT-prophyllite dust applied at 10-day intervals, the first application being made as soon as feeding injury is apparent. This conclusion is drawn without consideration or regard
for the residue factor. In one experiment consisting of plots of cabbage, collards, and broccoli, a 1 percent dust mixture applied at 10-day intervals from the time the first true leaves appeared on the plants effectively
controlled the cabbage looper, imported cabbage worm, and several species of Agrotinae. The 1 percent DDT dust mixtures were not effective against
the cabbage webrorm, but when the strength was increased to 2.5 percent
adequate protection was obtained.
1/ The Geigy Co. designated this material as "Neocoid 15."
Comparative tests with DIY dust mixtures, calcium arsenate, and
cryolite were nae in southern California against the toto fruitwom (Heliothis a era (Hbn.)). The results of these tests, based upon the relative number of damaged tomatoes at harresttime, showed that a 10 percent DDT dust mixture gave 92 percent control, a 5 percent DDT mixture 77 percent, and a 2.5 percent DIE mixture 81 percent. By comparison an undiluted calcium arsenate gave 81 percent control, and a 70 percent cryolite mixture 2/ 60 percent control. In this experiment three applications of dust were made at intervals of 2 weeks, at an average rate of 30 pounds per acre-application. In another heavily infested experimental field the following results were obtained; 10, 5, a 2.5 percent WT dust mixtures gave 97 percent, 84 percent, and 79 percent control, respectively, "whereas the undiluted calcium arsenate gave 65 percent and the 70 percent oryolite 53 percent control. At Norfolk, Va., a 5 percent DT dust mixture was as effective against this insect on Fordhook lira beans as undiluted cryolite (90 percent).
Flea Beetles on Potatoes
Experiments comparing cryolite, calcium arsenate, and DI dust mixtures against the tuber flea beetle (Epitrix tuberis Gentn.) and the western potato flea beetle (E. subrinita(Lec.)) were conducted in the
Yakima Valley, Wash. In these experiments the tuber flea beetle, fiw 1'ly designated as the western frrm of E. cucumeris (Hafrr.), was the predominant species. The main objective of flea beetle control in this area is to protect the potato tuber from larval or grub damage; therefore, the results of the experiments are measured in terms of injury to the potato' tubers. Four applications of a 10 percent WT dust applied at the rate of approximately 17 pounds compared with a 70 percent cryolite dust mixture applied at the approximate rate pf 10 pounds per acre-application yielded the following results: WDT plots 42 percent damaged tubers, cryolite plots % percent damaged tubers. While the number of damaged tubers from the DDT plots was about a third less than from the dryolite plots, the total yield of marketable potatoes was about the same for both treatments.
Mexican Bean Beetle
Studies during 1943 showed that DDT applied as a dust or as a Slpay suspensi'La bad little toxic effect on the Mexiaa bean beetle (Spilaebna varivesti4 aNls.). The experiments of 1944 have given similar results. In field experiments conducted in North Carolina, the control from a 10 percent MTJ dust, applied with hand dusters in two of the experiments and with a pwer duster in another, ranged from 41 to 49 percent; a dust containing 0.5 percent of rotenone gave from 96 to 100 percent control. In field experiments at Columbus, Ohio, spray suspensions containing as high as 100 pounds of the 10 percent EM dust per 100 gallons of water did not control the Mexican bean beetle.
_In this paper references to percentages of cryolite indicate the percentage of sodium fluoaluminate.
Plant Bugs on Beets Grown for Seed
In the Phoenix, Ariz., area a 4.5 percent I dust was compared with a dust mixture consisting of pyrophyllite containing 0.2 percent of pyrethrias to which equal parts of sulfur had been added. These dust mixtures were tested against three species of I bugs which infest suger
beet seed stocks at the same time. The species involved were oblineatus (Say), L. hesperus Knight, and. L. elisus Van D. In smll experimental plots the applications of the dust mixtures vere made at the rate of 50 pous per acre. Two applications ere made of the pyrethrum dust mixture, one on May 11 and the other on May 19; and one application of the D mixture was ade on May 11. The results of the applications were recorded on June 1. The MI) dust gave 77 percent control and the pyrethrum dust 67 percent. Germination tests of seed produced on the experimental plots showed 65 percent of viable seed from the undusted plots, 89 percent from the pyretbrum plots, and 91 percent from the MT7 plots.
At Albuquerque, N. Mex., 7 acres of a 20-acre field of sugar beets
which bad passed the blossoming stage were dusted on June 5 with a 5 percent W? mixture at the rate of 40 pounds per acre. The application was made with a traction duster. On June 6 and 16 the remaining 13 acres of the field were dusted with the pyrethrum dust mixture as described above at the rate of 30 pounds per acre-application. Examination of the fields on June 27 shoved a reduction da L bugs of 95 percent in the area treated
with DI and of 60 percent in th rea treated with the pyrethrum mixture. The percentage of viable seed was 78 from the DMT-treated area and 71 from the pyretbrm-treated area. In another field test at Safford, Ariz.,
5 acres of a W0-acre field of sugar beets were dusted with a 5 percent MT mixture and. 5 acres with a 2 percent DIT mixture, the application being by airplane at the rate of 50 pounds per acre. On June 15, 7 days after the applications, an examination of the treated and untreated acreage showed a 99 percent reduction of Lygus bug population in the 5 acres receiving the
5 percent IWf dust and 75 percent in the acreage receiving the 2 percent DDT dust. Germination tests shoved a viability of 88 percent in the seed taken from the acreage treated with the 5 percent WI an& of 76 percent in the seed from the acreage treated with the 2 percent DI mixture.
At Phoenix, Ariz., on May 31, an 80-acre field of garden beans infen ted with bugs and the Say utinkbug (Chloroobroa sayi Stal) was treated with 5 and 2 percent wTr dust mixtures. on TIM control of Lygus was recorded as 100 percent in both plots; the numbers of these species taken by 50 sweeps of an insect net in a comparable undusted plot increased from 83 on May 31 to 307 on June 3. Reduction of the Say stinkbug on June 3 was 92 percent for the 5 percent dust and 79 percent for the 2 percent dust. The percentage of viable seed produced was 92 in the
5 percent MV plot and 88 in the 2 percent DME plot. The undusted plot yielded 73 percent of viable seed.
Experiments conducted in southern Wisconsin showed that a 2.5 percent IM dust mixture reduced infestations of the potato leafhopper
(Rpoas fabse (err.)) on potatoes and beans 78 to 99 percent. These figures were obtained frm. counts of leaftpper nymphs 1 to 3 weeks after application. The WI dust mixture ave a greater reduction in leafqhopper populations than did a dust mixture containing 1 parent ofat didtro..9. cyolobezylphbnol1 and 50 percent of Iulfur.
In similar experiments in the Columbus, Ohio, areas I1 sprays an wr-sulfur dusts jpve better results than did the dinitro mixture a a pyrethrn-sulfur mixture contning 0.025 percent of pyretbrius and 50 percent of sulfar. The PDT sprays contained up to 0.08 percent ofat in a kerosene emlsion, and the dust mixtures consisted of 1.4 percent of WT, 50 percent of sulfur, and the reminder pyrophyllite.
In laboratory experiments at Moscow, Iaho, in 193 relatively lor mortalities of the pea weevil (ruchus pia (L.)) were obtained with
a 10 percent IE dust when the ieevils were transferred from treated ages to lean ages 5 minutes after treatment. Later tests showed that the mortality could be increased by retaining the insects in the treated cages for a longer time. In 194 rield experiments were c duoted. on plots 24 feet wide and located end to end around. the edges of larse fields of peas grown for seed. In 21 replicates a 5 percent ENT dust reduced the adult pea weevil infestation 99 percent in 2 days, whereas a (.75 percent rotenone dust reduced. the infestation 98 prcent in a like period. In these tests the insecticides vere applied with a power duster at the rate of 30 pounds of the DI dust mixture and 20 pounds of the rotenme dust mixture per acre. In 7 replicates 2.0 percent of the dried peas in the IE plots were weevily as compared with 2.7 percent in plots where rotenone dust vas used.
In a field experiment conducted at San Clemente, Calif., against the pepper weevil (Anthonom eugenii Cano) on bell peppers, MD dusts at strengths of 10, 5, and .5 parent yielded higher mortalities than did a 70 percent cryolite mixture. The mixtures were applied with rotary hand dusters at 7-day intervals, at the rate of 15 to 25 pounds per acre depending upon the size of the plants. In another experiment in which the 10- and 5-percent strengths of W were applied at 16-4ay intervals, the kill of weevils was greater than where the cryolite mixture was applied at 7-day intervals.
Cabbage Seedpod Weevil
In laboratory tests at Sumner, Wash., 10 percent DIT dust showed no toxicity to the cabbage seedpod weevil (Coutarhynchus assililis (Payk.)). A bait spray containins 6 pounds of the 0 percent 18T-pyrophyllite mixture and 45 pounds of sugar in 100 gallons of water was also ineffective.
Laboratory tests at Opelousas, La., indicate that DT is toxic, to
the uweetpotato weevil (Cylas formicarius elegantulus (Summers)) but not so toxic as potassium fluosilicate. The 10 percent DTY gave mortalities ranging from 82 to 98 percent, as compared with 98 to 100 percent with .undiluted potassium fluosilicate and 80 percent with undiluted calcium arsenate.
In the laboratory tests in 1943 DDT showed a toxicity to the pea
aphid (Macrosipu pisi (Kalt.)) comparable to that obtained with rotenone dust mixtures. Results of field experiments at Madison, Wis., did not substantiate these consistent laboratory results. For example, in one experiment the application of 5 percent DDTP dust with a power duster at the rate of 35 pounds per acre, followed by heavy rains, resulted in 99 percent control after 7 days, as compared with 88 percent for a 0.5 percent rotenone dust containing 2 percent of a light mineral oil. In this experiment the average yields of shelled peas per acre In five quarter-acre plots were 1,517, 859, and 495 pounds,, for the DDT, rotenone, and check treatments, respectively. In a second experiment, also followed by rains, a 5 percent DIYT dust gave less outstanding results than those obtained with several dosages and strengths of rotenone dust mixtures. In a third experiment, under wet conditions but accompanied by very little precipitation,, both the 5- and 10-percent strengths of DDTl were less effective than a dust containing 0.75 percent of rotenone and 2 percent
of a light mineral oil.
At Twin Falls, Idaho, in an experiment conducted in cooperation with the Idaho Agricultural Experiment Station, a 5 percent DDTl dust, applied to table onions at the rate of 25 pounds per acre with a power duster equipped with a 20-foot muslin hood, gave 69 percent control of the onion trips (Thrips tabaci Lind.). This figure was based upon the number of thrips surviving in the dusted plots after four applications as compared with those surviving in the undusted plots. In another experiment in which the material 'was applied with a hand duster the control was 63 percent. The DDYT dust yielded greater control than a spray containing 4~ pounds of 10 percent DDTl per 100 gallons of water, and applied with a traction sprayer under 350 Pounds pressure at the rate of approximately 100 gallons per acre. This dust also gave greater control than a spray containing 1 quart of nicotine sulfate and 3 quarts of corn sirup per 100 gallons of water. On the other hand, in California a 10 percent DT dust gave no better control then a spray containing 1 quart of nicotine sulfate, 14 pounds of sugar, and 8 ounces of a spreading agent per 100 gallons.. and this nicotine spray did not yield so good a result asc a Dill' spray containing 6 pints of a 10 percent DDTl emulsion per 100 gallons of water. The emulsion was prepared by dissolving unilu~lted DDYT in toluene and adding an emulsifying agent and water. In smftll-plot experiments at Beltsville, Md1., the performance of DDT has conformed In general 'with the results of the field experiments In Idaho and California.
In 11 replicates of a field experiment with the beet leafhopper
(Eutettix tenellus (Bak.)) on sugar beets at Twin Falls, Idaho, the application of 115 pounds per acre of 5 percent IOT dust resulted in an average reduction in populations of 95 percent after 3 days and 89 percent after 10 days. A spray containing 4 pounds of 10 percent DDT applied at 200 gallons per acre did not give so great a reduction.
In small field tests in California, only 12 adult squash bugs
(Anasa tristis (Deg.)) survived 13 days after the last of two applica.tions of a 10 percent DDT dust mixture. In comparable untreated plots
the survivors included 221 adults, 20 eggs, and 7 nymphs.
The harlequin bug (Murgantia histrionica (Han)) was confined in field cages on cabbage at Hendersonville, N. C. A 10 percent DDT dust killed only 64 percent of the adult bugs in 3 days. In small tests at Alhambra, Calif., a 2.5 percent DDT dust killed 35 percent in 3 days and 86 percent in 5 days.
At Walla Walla, Wash., where the sugar-beet wireworm (Limonius
califronicus Mann.) and the Pacific Coast wireworm (L. canus Lec.) were used in laboratory tests, the indications are that long periods of time are required to kill wireworms with DDT and that this material does not act as a repellent. The wireworms killed by DDT appear to be desiccated, as though affected by a strong alkali or exposed to drying, whereas those killed by funigants are usually found to be stiff and bloated. In one series of experiments begun in May and repeated in July and August 1944, DYT was thoroughly mixed with the top 9 inches of garden soil and wireworms were caged within the treated soil. The wireworm mortalities at the end of 5 weeks' exposure to different dosages of DDT were as follows:
Pounds per acre Pmeeent mortality
The surviving wireworms, many of which were inactive, were placed on moist blotting paper in salve tins and observed for an additional 5 weeks. The mortality at the end of the 10 weeks was 99 percent for the 16-pound dosage and 100 percent for the others. No data are available on the effect these dosages of DDT will have on subsequent plant growth.
Eornworms on tobacco
In field experiments at Florence, S. C., and, Oxford, N. C., the application of either a 5 or a 10 percent DDT mixture did not give a satisfactory reduction of the tobacco hornvorm (Protoparce sexta (Johan.)). In laboratory tests at Oxford the fifth instar of the tobacco hornworms was not affected by the 10-percent mixture but the eame instar of the tomato hornworm (P. quinquemaculata (Haw. ) succumbed readily. In comparable tests with third instars of the two species, 100 percent mortality of the tomato hornworm was obtained in 24 hours in each of seven replicates whereas the mortality of the tobacco hornworm averaged 12 percent in 2 hours and 35 percent in 96 hours. There was very little feeding of either species on the treated foliage.
In a field experiment at Florence, S. C., a 10 percent DDT dust mixture applied in the buds of the plants by different methods gave from 88 to 100 percent kill of the tobacco budvorm (eliothis virescens(F.)) in 4 days.
Tobacco Flea Beetle
In a field experiment at Oxford, N. C., a 5 percent MT dust gave 66 percent control of the tobacco flea beetle (Epitrix hirtipennis (Melsh.)) 3/ based on a comparison of the number of beetles surviving on treated and untreated plots following the first application, and 59 percent following the second application. In this experiment three 60 percent cryolite dusts, each in a different diluent, gave control ranging from 39 to 54 percent.
Tobacco Moth and Cigarette Beetle
In laboratory experiments at Richmond, Va., undiluted DI was used in an acetone-oil solution. The solution was atomized into a modified PeetGrady chamber. The test insects were adults of the tobacco moth (Ephestia elutella (Hbn.)) and the cigarette beetle (Lasioderma sorricorne (F.)T). A 5 percent DDT-oil solution, used at the rate of 100cc. per 1,000 cu.ft., resulted in 97 percent kill of the tobacco moth in 3 days and 71 percent kill of the cigarette beetle in 5 days. A 15-percent solution resulted in kills of 98 and 90 percent of the moths and beetles, whereas pyrethrum-oil spray containing 0.2 percent of pyrethrins gave mortalities of 100 and 46 percent of the moth and the beetle, respectively. A 10 percent D dust mixture, prepared by mixing pyrophyllite with an oil solution of DT and then blowing it into the dust chamber at the rate of 3 ounces per 1,000 cubic feet, killed 48 percent of the tobacco moths and 93 percent of the cigarette beetles. A 15-percent solution of DDT in oil sprayed on packages of cigarettes did not prevent them from becoming infested, during an exposure of 30 days to the cigarette beetle and the tobacco moth.
3/EReretofore erroneously identified as Epitrix parula F.
UNIVERSITY OF FLORIDA
3 1262 09230 4152
No ebaustive tests have been conducted on the tolerance of plants to DDI dust or spray mixtures or solutions. However, the vark that has been done with DDT dusts indicates that tomatoes, potatoes, oabba&e,. turnips, onions, beans, peas, and tobacco are tolerant to la strengths and reasonable dosages of this material, and that some injury to sq=6 or other cucurbits may be expected when this material is applied in dust form at low concentrations.