June 1945 E-662 LIBRARY STATE PLANT BOARD Waited States Department of Agriculture > Agricultural Research Administration Bureau of Entomology and Plant Quarantine IVSXCTABT AND 7IZLD-GA41 TESTS WITH DDT AGAINST WBTTJ-IR I N&ED BEETU ADULTS CONDUCTED AT ILORALA, ALA., DCRINU I9UU Hiram 0. Toung, Division of Cereal and Forage Insect Investigations Xnssctary and field-cage tests of DDT (l-trichloro-2,2-ble(p- chlorophenyl) ethane) were conducted against the adults of one species of white-fringed beetles ( Pantomorus leucoloma (Boh*)) at Jlorala, Ala., during the summer^ of I9UH, The results of these tests confirm those obtained in 19^3»~^ which showed that DDT is the most potent insecticide ever tested against adult white-fringed beetles* The DDT used in all the experiments reported was received from the manufacturers as a 10 percent DDT-pyrophyllite dust. A chemical analysis made by the Division of Insecticide Investigations of this Bureau showed that this material contained 8*9 percent of DDT. Lower concentrations were prepared by further diluting this dust with addi- tional pyrophyllite* The 10 percent DDT-pyrophyllite was also used for preparing all sprays* The adult white-fringed beetles were collected in the field* and all beetloe used in any one series of tests were collected from the same host plant on the same date* IKSSCTART TESTS Effectiveness of DDT as a Stomach Poison In these tests a total of approximately 50 beetles in five cages were used in each replication, and each series of tests was replicated two or three times during the season* The mortality was recorded 96 hours after the beetles had been released on the treated foliage* In each test an appropriate number of untreated check cages were included in order to determine the natural mortality* The net mortalities have been calculated by Abbott's formula* -/ Toung, E* C* 19hU # DDT against the white-fringed beetle and the velvetbean caterpillar. (Scientific Hote) Jour. Icon* Int. 37*lU5-lU7* UN 2 3 im Dusts .— In the insectary teste against the adult beetles, peanut and chrysanthemum foliage held in 2- ounce wide-mouthed bottles embedded in soil in 5-inch azalea flower pots was treated in a settling chamber with predetermined dosages of dusts containing different percentages of DDT* The foliage was held in a position similar to that existing under field conditions. After the dusts had been allowed to settle for 3 minutes, the beetles were confined on the treated foliage in screen cages 9 inches high and 5j inches in diameter. Prior to the dust treat- ment the foliage was moistened with a fine water mist from a hand atomiser* Zn two series of tests dusts containing different percentages of DDT were applied at a fixed rate equivalent to 11*6 pounds per acre on peanut foliage and 15*5 pounds on chrysanthemum. for comparison a synthetic cryolite dust (76.8 percent sodium fluoaluminate) in which 10 percent of wheat flour had been incorporated to improve its dusting fuality was applied at the same rates. The results are shown in table 1. In this series 0.13 pound of DDT per acre on peanut foliage and 0.16 pound on chrysanthemum foliage gave approximately the same mortalities as obtained with the cryolite dust at the same dosages of the dust mixture, from these results it is apparent that, when used as a stomach poison in dust form, DDT was 69 to 7U times as toxic to white-fringed beetle adults as sodium fluoaluminate. further tests were conducted to compare dusts containing various percentages of DDT when applied so as to give the same dosage of DDT regardless of the dilution. This dosage was 0*23 pound of DDT per acre on peanut foliage and 0.31 pound on chrysanthemum. The results are given in table 2, These tests indicate that, when DDT dusts are used as a stomach poison, the quantity of DDT applied per acre is the important factor affecting mortality, and not the percentage of DDT contained in the dust. - 3 - Table 1. — Iff ectiveness of DDT as a stomach poison against the white- fringed beetle when ppplied as a dust to foliage at fixed dosages of dust. Insectary tests, 2 replications on each foliage Tests on peanut foliage Tests on chrysanthemum foliage Concentration of DDT Dosage of DDT Net mortal- ity Dosage of DDT Net mortal- ity Percent 0.25 .5 1.0 1.5 2.0 2.5 1; Check (cryolite dust)—' Lb. per acre Percent Lb. t>er acre Percent 0.03 .06 .12 .17 .23 .29 1 u 36 50 83 73 39 0.0U .08 .16 •23 .31 .39 o 13 53 86 89 9U 55 1/ 76.8 percent NajAlTg. Table 2.— Sff ectiveness, of DDT as a stomach poison against the white- fringed beetle when applied as a dust to foliage at fixed dosages of DDT. Insectary tests, 2 replications on each foliage. Concentration of DDT Tests on peanut foliage Dosage of mixture Net mortal- ity Tests on chrysanthemum foliage Dosage of mixture Net mortal- ity Percent 0.25 .5 1.0 1.5 2.0 2.5 1/ Check (cryolite dust)"" Lb. t>er acre Percent Lb. per acre Percent 93.0 U6.0 23.0 15.5 11.6 9.3 11.6 65 83 77 87 83 82 50 123.9 61.9 31.0 20.6 15.5 12.U 15.5 96 97 93 99 96 9H U2 i/ 76.8 percent Na^AlP^. - 4 - Sprays . — Sprays containing different quantities of DDT and 0.1 pound of a wetting agent per 100 gallons of water were applied outside the insectary with a hand sprayer to peanut and chrysanthemum foliage held in an upright position in wide-mouthed "bottles. The spray was applied until it dripped from the foliage. When it was dry, "beetles were confined on the treated foliage in the manner described for dusts* A spray containing 8 pounds of synthetic cryolite (85.H percent sodium fluoaluminate) and 0.1 pound of a wetting agent per 100 gallons of water was used as a check. The results are given in table 3« Table 3» — Effectiveness of DDT as a stomach poison against the white- fringed beetle when applied as a spray to foliage at differ- ent concentrations. Insectary tests, 2 replications on each foliage Net mortality on— Concentration of DDT Peanut Chrysanthemum foliage foliage Lb. per 100 gal , 1/6H 1/32 1/16 V 2 1/ Check (cryolite)" 8 Percent 1 11 65 92 92 97 93 Percent 15 27 91 93 95 89 — / 85 .H percent Na^AlPg. The sprays were about equally effective on peanut or chrysanthe- mum foliage. The sprays containing 1/8 pound or more of DDT per 100 gallons gave a net mortality in excess of 91 percent, and 1/8 pound of DDT gave the same mortality as 8 pounds of cryolite. Effectiveness of DDT as a Contact Poison Dusts applied to the beetles .— Dusts containing different per- centages of DDT in pyrophyllite were also tested in the insectary as contact poisons. Adult beetles were placed in wooden-frame cages, 12 inches square and 1 inch high, covered on the top and bottom with l6-mesh screen wire. These flat cages were placed in a settling chamber, 1/h inch above the bottom surface. After the dust had been injected and allowed to settle for 3 minutes, the beetles were immediately transferred to untreated foliage in clean test cages, and the mortality was recorded. - 5 - The results of one series of tests in which the rate of applica- tion was equivalent to 11*6 poundn of dust ner acre arc shown in table k. Only the 5-percent dust gave any appreciable mortality. Treatments with cryolite and pyrophyllite were used as checks. Table U. — Effectiveness .of DDT as a contact poison against the white- fringed "beetle when applied as a dust to the beetles at a fixed dosage of dust. Insectary tests, 2 replications Dosage Concentration of DDT of Net mortality DDT Percent Lb. per acre Percent 0.25 0.03 i 2 .5 .06 2 1.0 .12 1 1.5 .17 3 2.0 .23 9 2.5 .29 7 5.0 .58 Checks: Cryolite dusti' 2 Pyrophyllite 1/ 76. 8 percent JTa^AlFg. Dusts containing 2.5 and 5 percent of DDT were also applied at different dosages in order to vary the quantity of DDT applied per acre. The results, which are given in table 5» show that, within the limits used, the mortality increased as the quantity of DDT per acre was increased. Treatments of O.Uj pound or more of DDT per acre showed more than 51 percent net mortality. The heaviest treatment, 0.93 pound of DDT per acre, gave 9° percent net mortality. Further tests were conducted to compare dusts containing different percentages of DDT when applied so as to give the same dosage of DDT. This dosage was O.3I pound per acre. There was considerable variation in the results with the different concentrations. The dusts containing 1.5 and 2 percent of DDT were the most effective, and both of them gave approximately 50 percent net mortality. The detailed results are given in table 6. Table p. & ; ieciiveneaB of LDI 0.0 e» J^ia^ i^ib^u t^eiuSit the white- fiiugoa beetle »heu a., lied as a dubt to the beetles at different dosages of DDT and dust, Insectary tests, 3 replications Concentration of DDT Dosage of — Mixture DDT Net mortality Lb. per acre Percent 9 *? O.23 13 12.4 .31 2 ? 15.5 36 18.6 # 52 12.4 .62 73 15.5 .73 88 IS. 6 .93 90 15.5 Pe rcent 2.5 5.0 Check (cryolite dust)- 1/ 88.9 percent Ka-jAlFg. Table 6.— Effectiveness of DDT dusts as a contact poison against the white-fringed beetle when applied as a dust to the beetles at a fixed dosage of DDT. Xnsectary tests, 2 replications Dosage * Concentration of DDT of Het mortality mixture Percent Lb. per acre Percent 0.25 123.9 2 .5 61.9 1.0 31.0 30 1.5 20.6 51 2.0 15.5 2.5 12.4 S , 5.0 6.2 22 Checks 1 Cryolite dust 1/ 15.5 Pyrophyllite 23.2 — / 76.8 percent Ha^AlPg. Dusts applied on the soil , — Dusts containing different percentages of DOT were tested by applying them directly on the soil surface. The soil was placed in 5-inch asalea flower pots, in each of which a wide- mouthed bottle was embedded, and exposed in the settling chamber for 3 minutes to predetermined dosages of the dusts. Clean foliage was then placed in the bottles. Newly collected beetles were introduced into screen cages and allowed to crawl on the wire before the cages were placed over the treated pots. This procedure avoided placing the adults directly in contact with the treated soil surface* The quantity of foliage used in these tests was approximately twice that used in other tests. The foliage touched the side of the cage at several points, permitting the adults to reach it without crawling on the soil, Under the conditions of this test most of the beetles moved from the foliage to the soil to oviposit or rest within U hours. Under field conditions adults are on the surface of the soil more hours during each day than on vegetation* Dusts containing 2.5 and 5 percent of DDT were applied at different dosages, as in the tests where the applications were made directly to the beetles* The results, given in table 7» show that the lighter dosages gave greater mortality when applied to the soil than when applied directly to the beetles (table 5). Since mortality continued to occur for a longer period, the tests were continued for 3 additional days, or a total of 7 days* The two heaviest dosages gave slightly greater mortal- ity at the end of 96 hours when applied to the beetles, but not at the end of 168 hours. Table 7»~W*>ctivenes8 f DDT as a contact poison against the white- fringed beetle when applied as a dust to the soil surface at different dosages of DDT and dust* Insectary tests, 3 replications Concentration of DDT Dosage of — T Mixture DDT get mortality after — 96 hours l68 hours Lb* per acre Percent Percent 0.23 } S 29 12.4 .31 US 56 15.5 60 68 18.6 £ 5U 69 12.4 .62 7H 85 15.5 .78 72 88 18.6 •93 8U 9U 15.5 2 5 Percent 2.5 5.0 Check (cryolite dust)- 1/ i/ 88.9 percent Ia~Airg - g - Sprays applied on the "beetles, - —Sprays containing different quantities of DDT and~T3.1 pound of a wetting agent per 100 gallons of water were tested by applying the sprays directly to the beetles. The beetles were held in wooden-frame cages exactly like those used in the dust tests. The sprays were applied with a small hand, sprayer until they dripped from the beetles. After the beetles had been allowed to dry, they were placed in clean cages and provided with untreated foli- age for food. The results are given in table g. H Table g.— Effectiveness of DDT as a contact poison against the white- fringed beetle when applied as a spray to the beetles at different concentrations. Insectary tests, 2 replications Concentration of DDT Net mortality Concentration of DDT Net mortality Lb* per 100 gal* Percent 1/6U 17 1/32 20 1/16 U7 1/g 6t 1/4 gu Lb. per 100 gal. Percent 1/2 93 Checks: Cryolltei/ g Water 1 g5.U percent UajAlFg. Spray 8 applied on cages .— Two sprays were tested to study the mortality caused by contact with treated surfaces. The sprays con- tained k pounds of DDT and 0.6 pound of a wetting agent per 100 gallons of water, and 20 pints of fish oil was used in one of the sprays. The inner surfaces of the cages were sprayed until dripping. After the spray had dried, newly collected adults were placed in the cages for different periods of time and then transferred to untreated foliage in clean cages* The mortality records were made at 2U-hour intervals for 96 hours, but since practically all the beetles affected died within Ug hours, the mortality was thereafter recorded at the end of Ug hours. A few tests were begun within 2U hours after the cages had been treated, a second series was started after 2 to 7 days and before the treated cages were exposed outdoors to weathering, and a third series after 13 to 22 days and the cages had been exposed outdoors for 6 days, during which time 5*6 inches of rain fell. - 9 - The results are shown in table 9* * n tests started within 2k hours after treatment, the two sprays were about equally effective when adults were confined In the treated cages for 1/2, 1, and 16 hours. In the second series the beetles confined for 1/U, 1/2, and 1 hour were much less affected by the spray containing fish oil than by the spray without fish oil, but both sprays were equally effective after 16 hours. The fish oil had dried and hardened at the time of this exposure* In testa conducted after the cages had been exposed outdoors, both sprays failed to kill beetles confined for 1 hour, but after 16 hours the spray containing fish oil was the more effective* Table 9 •"Effectiveness of DDT as a contact poison against the white- fringed beetle when applied as a spray, with and without fish oil, to the surface of 1 cages Time after treatment Length of Net mortality when tests were begun exposure Tests Without fish oil With fish oil Days Hours Number Percent Percent Before exposure to outside weathering 1 1 1 1 100 96 100 9* 98 100 2-7 1/U I 12 16 k 3 2 1 63 11 98 H 11 2U 98 After exposure to outside weathering 13-22 110 16 3 20 58 Toxicity of Plants Grown in DDT In December I9U3 DDT was thoroughly mixed with soil at the rates of O.U16, l.Oh, 2.08, U.17, and lO.Ul grams per cubic foot, which is equivalent to incorporating 10, 25, 50, 100, and 250 pounds of DDT with the upper 3 inches of an acre of soil. In I9UU peanut plants were grown in this soil. Approximately 50 adult beetles were fed for 22 days on the foliage from each treated plot. In no case was the foliage toxic to the beetles. - 10 - FIELD-CAGE TESTS Insecticide Applied on Foliage • To determine how long DDT would remain effective against the white- fringed "beetle under field conditions, 5 tests were made in which dusts and sprays were applied on peanut and chrysanthemum plants, 3 tests on potted plants and 2 on plants growing in the field* Either 3 or U field cages 2U by 2k by 30 inches were utilized for each treatment, and 25 to 35 "beetles were exposed in each cage. The dusts contained either 2.5 or 1.5 percent of DDT in pyrophyllite, and were applied at the rates of O.3H to 0.38 pound of DDT per acre. Two sprays were used, a concen- trated spray applied with a paint sprayer and a dilute spray applied with an ordinary pressure sprayer. The dilute spray contained 0.2 pound of DDT, 2 pints of fish oil, and 0.1 pound of a wetting agent in 100 gallons of water. The concentrated spray contained U pounds of DDT, 20 pints of fish oil, l.lU pounds of a wetting agent, and water to make 100 gallons. The quantity of DDT applied per acre was not determined for the sprays, "but it is known to have "been greater than for the dusts. The dilute spray was applied until it dripped from the foliage, and the concentrated spray "by enveloping the plant in a light, fine fog. In the tests on potted plants, after the treatments the pots were plunged in the soil outdoors, where the plants were exposed to weathering for different periods and then placed in field cages into which adult beetles, newly collected from the field, were introduced. In the tests on field-grown peanut plants, the plants were covered with cages immediately after treatment. Beetles were released immediately in some of these cages and at specified intervals thereafter in others. The mortality was deter- mined 96 hours later. The net mortalities and rainfall for the individual tests are given in tables 10 and 11. The dusts remained effective for a shorter period than the sprays. In the mortality te3ts begun immediately after treatment, the average net mortalities were 77» 96, and 9*+ percent, respectively, for the dust, the concentrated spray, and the dilute spray. After 5 days 1 exposure and an average rainfall of 3*12 inches the dust was only 39 per- cent as effective as initially, while the concentrated spray retained 93 percent and the dilute spray 6U percent of its initial killing power. After 10 days of exposure and an average rainfall of 5*07 inches, the dust gave 6 percent, the dilute spray 26 percent, and the concentrated spray 67 percent net mortality. In tests begun 15 days after treatment, and after an average rainfall of 7*95 inches, the dilute spray gave 13 percent and the concentrated spray 56 percent net mortality. - 11 - *J ft* 9 o ft rH ON ,C2> rH 8£S1 I CO • • • u cu c\j ir\ cr»o • i-i m o • • Ed I -it CTirH I 0>CU ir>cno o O O H I CO H k^vx> cvi to ct\*o vo eg O I I o CM ro whia vr> O O O aMno o o\rH • • • • • • O LT\0 ITv Olf\OlT\ rH rH rH rH I CD 12 - u +» >» ■*» ■H •a +» 6 O & J •H +» «H 5 s © R p. o +> 4» o d © d H O 4* «H Js J 8 - P H g is ^ © *i •a § © as © d M 4» o a o « rH © « i d o O -P at © o ■P -H jfl rH 5 H tO CO CTt h- 1 8 tc?ilrVr£\ cXj <^c^o>cr\iR3 to I I 8 H I I I I © Eh co oj CO o CWOVO • • • • CVi © o © © © 3 233 u • • • £< co to in • • • • • o V010VO r-to O mow oino inpin H H W H rH CO CO SI to - 13 - Insecticide Applied in Soil In July 19^ "beetles were introduced into outside rearing chamber* 15 inches in diameter "by 30 inches deep, in some of which DDT had "been mixed into the upper 3 inches of soil a month pre- viously at rates of 25, 50 » and 100 pounds per acre. Upon examina- tion in August the mortality was much higher in the treated than in the untreated chambers. Accordingly, a series of tests was set up to study the mortality of beetles caused by DDT when mixed in the soil. On August 21 field cages 2k by 2k by 30 inches were placed over soil treated with DDT in the upper 3 inches at rates of 5t 10 » 50, and 100 pounds per acre. In these tests potted chrysanthemum plants grown in untreated soil were placed in the cages as food for the beetles. Two cages were used for each treatment, and 25 to 35 beetles were exposed in each cage* Tests were started in these cages on August 22, August 30, and September 11. The first test was continued for 7 days, and the other two tests for 12 days. The average net mortality for the three tests was 31 percent for the 50-pound and 6l percent for the 100-pound dosage, and for the two lower dosages approximately the same as in the untreated checks, EFFECT OF DDT ON PLANT. FOLIAGE ■4 During I9I& field plots of cotton, peanuts, and corn inter- cropped with velvetbeans were treated with a number of applications of DDT. The DDT was applied in three ways — as a 2.5 percent dust in pyrophyllite, as a dilute spray, and as a concentrated spray. The sprays were of the same composition as those used in the field-cage tests. During the summer each plot received three or more applica- tions at the rate of approximately one- third pound of DDT per acre- application. No foliage injury to these crops was observed. SUMMARY Insectary tests were conducted at Florala, Ala., in 19^+H to determine the effectiveness of DDT against the adults of one species of white- fringed beetles ( Pantomorus leucoloma (Boh.)). DDT dusts and sprays were effective both as stomach and contact poisons. When used as a stomach poison DDT in dust form was 69 to 7^ times as toxic as sodium fluoalurainate, and a spray containing 1/8 pound of DDT per 100 gallons of water was about as effective as a spray containing 8 pounds of synthetic cryolite (85»H percent sodium fluo- aluminate). These tests indicate that, when used as a stomach poison, the quantity of DDT applied per acre is the important factor affecting mortality and not the percentage of DDT contained in the dust. As a contact poison DDT in dust form was effective when applied directly to the "beetles or on the surface of the soil. Dilute sprays containing 1/8 pound or more of DDT per 100 gallons applied directly to "beetles produced net mortalities in excess of 60 percent. Adults can accumulate a lethal dose of DDT from contact with surfaces treated with sprays or dusts. The use of fish oil as an adhesive in a DDT spray increased the period adults must remain in contact with a treated surface to accumulate a lethal dose when the treated surfaces were not exposed to weathering. Fish oil, when used in a spray, increased the adhesion of DDT on surfaces exposed to outside weathering. The foliage of peanut plants grown in soil containing DDT was not toxic to the "beetles. In field-cage tests DDT was applied as a dust, a dilute spray, and a concentrated spray to study the duration of effectiveness of these methods of application under different weather conditions. The concen- trated spray remained effective longest, and the dilute spray was effec- tive longer than the dust. Applications of 50 and- 100 pounds of DDT per acre in the upper 3 inches of soil gave appreciable mortality of "beetles caged on the treated soil. No foliage injury was observed on cotton, peanuts, corn, and velvetheanB in field plots that received repeated applications of DDT as a 2.5 percent dust, a dilute spray, and a concentrated spray.