LIBRARY STATE PLANT BOARD April 1945 E-651 United States Department of Agriculture Agricultural Research Administration Bureau of Entomology end Plant Quarantine UBOHafORY TESTS WITH NEW COMPOUNDS AS INSECTICIDES AGAINST THI PEA APHID By J. E. Dudley, Jr., T. E. Bronson, and P. H. Harries, Division of Truck Crop and Garden Insect Investigations In an attempt to find a more effective insecticide for the pea aphid ( Macro siphum plsi (Kith.)), tests hare been conducted under greenhouse or laboratory conditions with a number of new organic materials. 1/ With the exception of DDT, most of the materials listed were not sufficiently tox- ic to be very promising. The tests were made at Madison, Wis., by J. B. Dudley, Jr., and T. E. Bronson, in cooperation with the Wisconsin Agricultural Experiment Station, and at Columbus, Ohio, by P. H. Harries, in informal cooperation with the Ohio State University, during the period March 1941 to December 1943. For convenience, the results at the two locations will be presented separately. Experiments at Madison, Wis. Pea aphids were reared in the greenhouse on the English Broad Windsor bean ( Ylcla faba (L. )). After reaching maturity, the aphids were trans- ferred for testing to pea plants grown in soil in No. 2 tin cans, each can containing one plant. When from 4 to 6 inches high each pea plant was in- fested with 10 or 15 newly transformed adult apterous aphids and immedi- ately caged with a cylindrical screen-wire cage. Several hours later when the aphids had become settled on the plants, the cages were carefully re- moved, and all the plants for a treatment (1 to 6) were placed at the bot- tom of a glass cylinder 3 feet tall and 10 inches in diameter for dusting. Dust mixtures were prepared in lots of 100 to 200 grams in a high- speed electric drink mixer, the type which has the revolving blades mounted in its base. A dosage of 100 to 500 mg. of dust mixture was expelled into the top of the cylinder through a copper dusting nozzle at an air pressure of 15 pounds per square inch. The top of the cylinder was at once covered. and the dust allowed to settle for various lengths of time, after which the plants were removed, the wire cages immediately replaced over the plants, and the plants returned to the greenhouse benches for observation. In the 1941 tests each of 13 synthetic organic compounds was diluted with an equal quantity of talc and tested at a dosage of 200 mg. of dust mixture against 10 aphids. Two tests were conducted, and the aphid mor- tality was recorded after 1, 2, and 3 days. The temperature averaged 64° P. during the first test and 71° during the second test. The following Ma- terials did not give appreciable mortality within 3 days after treatment! 1/ Most of the chemicals tested were furnished by the Division of Insecticide Investigations. 1945 - 2 - Diphenylamine, ph t ha lo ni t rile, alpha, beta-dibromoethylbenzene ( styrene dibromide), dibenzofuran, £-chloroni tro benzene, acetone semicarbazone, j>-dibromobenzene, £-dichlorobenzene, arrtl 1-mercaptobenzothiazole. Dibenzothiophene and 2,5-dichloroaniline killed most of the aphids at each temperature. 9,9-Dimethylacridan and 2-chloro-6-nitro toluene were ineffective at 64° J. but within 3 days gave mortalities of 100 and 90 percent, respectively, at 71°. Foliage injury was caused by phthal- onitrile, 2,5-dichloroaniline, 2- chloro-6-ni tro toluene, dibenzothiophene, and dibenzofuran. "Each of the materials that gave appreciable mortality at either temperature was tested at approximately 64° F. in one or more mixtures with derris. The results, as summarized in table 1, show that the ef- fectiveness of derris was increased by the addition of the new materials. Incidentally, however, when mixtures containing 0.50 percent of rotenone, with and without 10 percent of 2,5-dichloroaniline, were applied to un- replicated field plots at the rate of 40 pounds per acre, both dust mix- tures gave the same results. Table 1. — Mortality of pea aphids dusted with 200 mg. of mixtures of synthetic organic materials and derris. Madison, Wis., 1941 Synthetic organic material Mortality after — Rotenone : : content > Aphids '< of mixture ; ' 1 day t 2 days J 3 days 2, 5-Di chlo roani line Dibenzothiophene 2-Chloro-6-ni tro toluene 25 9, 9-Dimethylacridan None (derris alone) None (check) Percent Percent Number 25 0.25 60 10 .25 90 10 .50 70 25 .25 20 10 .25 70 me 25 .25 20 25 .25 20 — .50 100 — — 100 Number Percent Percent Percent 90 100 100 75 86 96 67 77 33 lool/ 100 100 83 91 94 40 85 90 40 90 95 40 48 64 l/ Moderate foliage injury. - 3 - Undiluted ground thundergod vine ( Tripterygium wilfordii (Hook, f . ) ) caused no mortality of the 20 pea aphida in two laboratory teste conducted at average temperatures of 64° and 72° F. A mixture containing 50 percent of thundergod vine and 2 percent of peanut oil in pyrophyllite was also in- effective. During 1943 tests were made of a large number of specially prepared dust mixtures that had been sent to the laboratory by E. G. Beinhart, of the Eastern Regional Research Laboratory of the Bureau of Agricultural and Industrial Chemistry. Each mixture contained, in addition to other materials, 2 percent of nicotine derived from nicotine alkaloid, nicotine sulfate, or ground tobacco du6t impregnated with nicotine alkaloid to contain 10 percent of nicotine. Pyrophyllite was used as the diluent. In each test 30 aphids were given a dosage of 250 mg. of the mixture. The aphid mortality after 24 hours was 100 percent when the nicotine- pyrophyllite mixture contained 0.6 percent of a fractionated naphthalene oil. Lower mortalities were obtained when the same percentage of a re- fined oil, a lubricating oil (S.A.E. 10), a light and a heavy spray oil, or propylene laurate was substituted for the fractionated naphthalene oil. When the mixture contained 10 percent of sulfur and 1 percent of glycerol (C.P. ), all the aphids were killed in 24 hours. The mixture became less effective when either the sulfur or the glycerol or both ma- terials were omitted, and when either apple sirup (60 percent levulose) or a sulfonated oxidized petroleum hydrocarbon was substituted for the glycerol. The aphid mortality was 100 percent in 24 hours when the mix- ture contained 4 percent of a thiocyanate preparation (containing 50 percent of beta-thiocyanoethyl ester of an aliphatic acid and 50 percent of oil) but was less when smaller percentages of the thiocyanate were used. In one series of tests with 30 aphids in each, dust mixtures con- taining talc impregnated with rotenone-containing resins dissolved in oil to contain 0.15 and 0.25 percent of rotenone were about as effective as comparable mixtures containing these percentages of rotenone in ad- dition to 0.75 percent of phenoxathiin (phenothioxin). In similar tests a dust mixture containing 10 percent of talc and 90 percent of di(tri- methylcyclohexenone) had no effect on the aphids. Very low aphid mor- talities were obtained with various dust mixtures prepared from saba- dilla seed furnished by T. C. Allen, of the University of Wisconsin. The powdered sabadilla seed was diluted with pyrophyllite and with talc to contain 33 and 60 percent of sabadilla. Other dust mixtures tested contained 5 and 10 percent of sabadilla seed extract in pyrophyllite. Low mortalities were also obtained when small percentages of rotenone were included in some of these sabadilla mixtures. Tests were made of ground yam bean ( Pachyrhizus erosus (Urban)) 2/ with pyrophyllite as the diluent, 30 aphids being used in each test. 2/ Furnished by R. Hansberry, of Cornell University, who in a pro- cessed report, "Notes on experiments with the yam bean," has summarized results of tests by various organizations with this material on the pea aphid and other insects. - 4 - Mortalities of lets than 25 percent were obtained with dusts containing 10 and 20 percent of yam bean at dosages of 200 to 400 mg. of the mixture. The 40 and 60 percent yam bean mixtures, each at dosages of 300 and 500 ag . , gare mortalities ranging from 60 to 93 percent. The temperature during the tests averaged from 63° to 70° T. Results of tests with mixtures of DDT and pyrophyllite are summar- lted in table 2, These tests substantiate those reported by Harries (2) is shoving that DDT is toxic to the pea aphid at relatively low strengths. the mortalities were much higher at 63°-65° I. than at 51° -55°. Table 2. — Mortality of pea aphids dusted with 250 mg. of mixtures of DDT and pyrophyllite. Madison, Vis., 1943 DDT I average In i temperature ■ixture during test Percent 0- 10 63 5 63 55 1 64 53 0.6 64 53 .61/ 65 51 Checks 51-64 Mortality after — 1 day 8 days 3 days Ifnaber 135 105 45 166 105 195 105 106 60 330 Percent percent Percent 100 96 91 68 34 61 45 54 100 100 100 98 61 91 61 99 29 1 100 100 100 100 33 95 32 100 66 6 1/ Mixture also contained 1 percent of nicotine derived from ground tobacco dust impregnated with nicotine alkaloid to contain 10 percent of nicotine. - 5 - A series of tests was conducted on the residual effect of DDT when dusted on pea plants. The plants were dusted with mixtures of DDT and pyrophylli te and held for various periods before aphids were introduced. In all tests the average temperature was 64° P. The new plant growth (except as detailed in table 4) was removed from the plants prior to ex- posure to aphids in order to keep them from feeding on the untreated new foliage. In each test 45 adult aphids were used. The residues from 500 mg. of the 5-percent and 10-percent strengths of DDT dust applied 1, 3, 5, 11, 14, and 21 days before exposure to aphids gave 84 percent mortality of the aphids in 1 day and 100 percent mortality in 3 days. The mortality of comparable check lots of aphids was 22 percent after 3 days. In other tests, summarised in table 3, the 1-percent and the 0.5-percent strengths of DDT had greater residual effect than did dust mixtures containing 0.5 percent of rotenone. When the foliage was washed with tap water 8 days after being dusted with 10 percent DDT-pyrophyllite, enough residue remained to be very toxic to the 60 aphids that were placed on the foliage 1 day later (table 4). Table 3.— If feet of exposure of pea aphids to foliage previously dusted with DDT or ground derris root mixed with pyrophyllite. Madison, Wis., 1943 Material and strength Quantity ap'pli ed Interval between dusting of foliage and exposure to aphids : Mortality Aphids • in used : 3 days Percent by weight Milligrams Humber Percent DDT I 1 0.5 Botenone 0.5 itenone 0.5 plus mineral oil 2 250 250 250 500 500 10 20 7 9 9 1 3 5 1 3 5 Hone (check) 45 100 30 94 45 69 45 78 45 44 45 51 45 51 45 29 45 91 45 96 45 9 240 3 - 6 - Table 4. — Removal of DDT from pea foliage by washing 8 days after dusting, as indicated by the mortality of pea aphids placed on the foliage 1 day after washing. Madison, Wis., 1943 Treatment of foliage Mortality after — 1 day : 2 days 3 days Percent P< srcent Percent 70 92 98 18 38 64 97 100 100 88 96 100 Washed and new growth removed Washed Hew growth removed None Undue ted (check) Experiment at Columbus, Ohio The methods employed at Columbus were similar to those used at Madison. The chief differences were that each mixture was applied at a very low dos- age to 10 adult aphids by use of a bell- jar duster designed by Harries (1), and that the tests were usually replicated (repeated on different days.) Pea plants for use in the teste were sprouted in trays of sand in the lab- oratory and were prepared by transplanting two plants into each can of sand and adding 60 ml. of nutrient solution. The plants were placed under a bank of fluorescent lights, operated 12 or 14 hours daily with an electric time switch, and were ueed when about 3 to 4 inches high. After treatment the infested pea plants were ringed with a barrier to obviate the necessity of a screen cage and to avoid the effect of a loss of light. The plants were randomized in position under the same light conditions at temperatures of 70° to 80° ?. and 40 to 60 percent relative humidity during the obser- vation periods of 3 or 4 days. The results, as summarized in tables 6 and 6, demonstrated that most of the materials were inferior to derris, although many of them were tested at the 50-percent strength. The mortalities were generally low even with derris, owing to the low dosages employed. DDT, however, was very effec- tive and appeared to be more effective than derris at comparable strengths. Promising results were obtained with 2 percent of beta.beta'-dithiocyanodi- ethyl ether, 10 percent of yam bean, and 50-percent strengths of 4,6-dini- tro-o-cresyl acetate, 2-chlorofluorene, 4,6-dinitro-o-cresyl methyl ether, and phenazine. The only other mixtures giving mortalities over 30 percent were those containing m-bromoacetanilide, phenoxathiin, and 2'-hydroxy- 2,4,4,4', 7-pen tame thy If la ran. - 7 - Table 5. — Mortality of pea aphids and the number of progeny 3 days after dusting with synthetic organic materials. Columbus, Ohio, 1943 Material Mortality of adults » prog ! ny Sunriring progeny per plant Percent Number Mixtures with equal parts of pyrophyllite, dosage 70 mg. , 10 aphids in each of 7 replicates: Derrisi/ 43 18 m-Bromoacetanilide 33 40 Hydrazobenzene 20 34 Azobenzene IS 34 o-Iodo nitrobenzene 16 31 m-Iodonitrobenzene 14 43 E-Xodoacetanilide 14 37 o-Iodoacetanilide 10 44 o_-Chloroacetanilide 9 54 m-Chloroacetanilide 7 48 £- Promo ace tanilide 7 53 2-Chloroacetanilide 6 44 £-Iodoni trobenzene 6 48 Hone (check) 3 52 Mixtures with equal parts of talc, dosage 100 ag. , each tested with 10 aphids repeated 6 times the same day: 4, 6-Dinitro-o-cresyl acetate 2-Chlo rof luo rene 4, 6-Dinitro-o-cresyl methyl ether Phenazine Derrisl/ Phenoxathiin (phenothioxin) Phenothiazine None (check) 98 90 1 75 3 63 4 62 7 55 10 45 16 7 54 is of 20 aphids eac 45 88 40 94 40 97 33 110 34 86 4 196 Botenone 0.25$ plus phenoxathiin 0.75$ Rote none 0.25$ Botenone 0.15$ plus phenoxathiin 0.75$ Botenone 0.15$ Botenone 0.5$ (from ground cube) None (check) 1/ Diluted to contain 1 percent of rotenone. 2/ The first four dusts also contained 2 percent of oil and were pre- pared by combining derris resins and oil, with or without phenoxathiin, in acetone and spraying the mixtures into talc with thorough mixing. - 8 - Table 6. — Mortality of pea aphlds and the number of progeny 3 days after dusting with various materials in comparison with rotenone; 10 aphids for each material in each replicate. Columbus, Ohio, 1943 Material ' Mortality 1 of adults Percent Series At Dosage 100 mg. , 5 replicates DDT 10$: In pyrophyllite 100 Technical DDT diluted with proprietary 3$ DDT dust 100 Rotenone 0.5$ in derris-pyrophyliite 94 Yam bean 10$ in diatomaceous earth-pyrophyllite 62 None (check) 4 Series B: Dosage 50 mg. , 10 replicates Beta, beta 1 -dithiocyanodiethyl ether 2$ in talc- magnesium carbonate: Lot 1 Lot 2 Rotenone in derris-pyrophyliite: 0.3$ from Derris malaccensig 0.5$ from Derris elliptica 2 , -Hydroxy-2,4,4,4',7-pentamethylflavan 5$ in diatomaceous earthj Lot 1 Lot 2 None (check) 98 71 40 33 31 34 2 Series C: Dosage 100 mg. , 5 replicates 74 Rotenone 1$ in derris-pyrophyliite Piperine in pyrophyllite: 16$ 8$ 2* 1$ None (check) 10 6 14 22 4 Surviving progeny per plant Number 9 17 59 1 25 65 62 70 67 137 13 54 55 72 53 72 96 - 9 - Table 6. — (Continued) Mortality j Surviving Material of adults progeny per plant Series B: Dosage 100 mg. , 7 replicate 8 Rotenone 0.5^ in derrie-pyrophyllite 46 21 Black pepper, undiluted 9 58 Black pepper in uyrophyllite: 80# 11 49 40# 16 42 204 7 56 10% 17 37 None (check) 3 80 Series E: Dosage 50 rag, 11 DDT in pyrophyllite: 10J6 100 5* 100 Ot 2.5# 98 2 1.25$ 100 2 .625$ 100 2 Rotenone rjf> in derris-pyrophyllite 96 5 None (check) 21 108 Series F: Dosage 50 mg. , 10 repliqates=/ DDT in pyrophyllite: H# 100 Of 556 100 2.5$ 99 3 1.25$ 99 3 .625$ 100 4 .325^ 93 9 .156$ 92 16 .078^ 89 21 Rotenone 0.5$ in derris-pyrophyllite 83 16 None (check) 3 123 1/ 80 aphid s per treatment. 2/ Results with 9 of these replicates have been reported (Harries 2). UNIVERSITY OF FLORIDA I I Hill HUH I - 10 - 3 1262 09238 7132 Literature Cited (1) Harries, T. H. 1943. A duster for laboratory experiments with insecticides. U. S. Bur, &nt. and Plant <}uar, ET-214, 3 pp. [Processed. ] (2) 1944. Laboratory tests with W$ a^inst the pea aphid and the Mexican beaz? beetle I Scientific Hote) Jour. Icon. Int. 37 1 151,