3R^YROARD November 1944 E-628 United States Department of Agriculture Agricultural Research Administration Bureau of Entomology and plant Quarantine TESTS OF DDT MIXTURES AGAINST CODLING MOTH LARVAE By L. F. Steiner, S. A. Summerland, and c» H. Arnold, Division of Fruit Insect Investigations, and J. g. Fahey, Division of Insecticide Investigations Introduction Because of the promising results obtained with DDT (2,2-bis (p-chlorophenyl)-l,l,l-trichloroethane) as a codling moth (Carpocapsa pomonella (L.)) insecticide when used alone or with certain supple- ments in preliminary tests at Vincennes, Ind., during 1943,-=/more extensive laboratory tests were undertaken during the winter of 1943-44. These tests were designed to compare the effect of various materials, including wetting agents, adhesives, and fungicides, as well as methods of preparation and application, on the efficiency of the DQT deposits on apples both before and after exposure to tap-water sprays. It is believed that the results obtained, although not conclusive, will be of interest and use to other investigators. Experimental Methods Whole Rome Beauty apples, picked green early in September, washed in 2 percent hydrochloric acid to remove arsenical deposits, and held in cold storage until needed, were used for the tests, shortly before being sprayed, the apples were run, one by one, through two acetone baths to remove excess wax and provide a uniform and natural fruit surface. For most tests 80 apples were treated with each mixture. The de- posits were allowed to dry overnight at 60-70°F., ana then the apples were divided in equal lots. One lot was used without further treat- ment; the other lot was exposed five times for 4 aeconas each to sprays of tap water, with a 30-second interval between applications, in order to estimate the probable effect of dashing rains on the residual efficiency of the treatment. In a few tests in which the effect of rain was not studied only 40 apples were treated. 1/ Steiner, L. F., Arnold, C. H. , and Summerland, s» A. Laboratory and field tests of DDT for control of the coaling moth. Jour. Econ. Ent. 37: 156-157. 1944. -2- Sprays were applied with an orchard-type sprayer, remodeled for laboratory uae. It was operated at a pressure of 300 pounds per square inch.. The discharge was from two nozzles set 16 inches apart in a vertical plane, and so directed that the spray cones would converge on the fruit 36 inches from the nozzles, jhe exposure time was 4 seconds, during which the apples, mounted on wire pins, were revolved twice, in certain tests of mixtures having deposit-building characteristics the apples were exposed to the spray three times at 30-second intervals. The combined output of the two nozzle a was 1.5 gallons per minute. Although most of the formulas were used in sprays, a few dust mixtures were tested. Dust applications were made with an orchard- type power duster arranged so that the discharge would be 20 feet from the apples. The entire lot of 40 (or 80) pinned apples was dusted at once, being turned after half the material had been applied. Ten newly hatched codling moth larvae were placed on each apple after it had been ringed with sticky tree-banding material at tne calyx. One lot of 40 unsprayed apples was included in each experi- ment. The result of each test is expressed as the percent larvicidal efficiency and is "calculated in accordance with Abbott's formula: Percent efficiency = 100 -flOO x number of worm entrances fr sprayed, jp4t J) \ number of worm entrances in unsprayed fruit/. Materials Used The DDT used for these tests was obtained in three forms. A coarse grade of undiluted materials' was ground in a pebble mill, either with water to make a paste or in dry form with bentonite, walnut-shell flour, diatoaaceous earth, sulfur, or lead arsenate. This material was also used with various solvents. The other two forms consisted of a 50:50 DDT-pyrophyllite (Pyrax ABB) mixtureS/and a 39:61 mixture of micronized DDT and talc J? 2/ supplied by the Division of Insecticide Investigations. %f Supplied by the Division of Insects Affecting Han and animals, -3- The composition op characteci sties of certain of the supplements used in the experiments followt-a/ 301 oilj A paraffin-base 100 percent petroleum oil, with s^yholt viscosity 57 seconds at 100°F., unsulfonated residue (A.O.A.C.) 84.3 percent Crude cottonseed or soybean phosphatides, containing 55-60 percent of acetone-insoluble phosphatides Dreft: Sodium lauryl sulfate, technical Bnulsive-type summer spray oil (98.7 percent), Saybolt viscosity 57.6 seconds at 100°F., unsulfonated residue (A.O.A.C.) 90.6 percent Fermate; Ferric dimethyl dithiocarbtunate 1N-2503: A» oil-soluble alcohol sulfate product Mississippi bentonitex &Lue Itawamba class having a low swelling value Soybean oil, containing approximately 3 percent of acetone- insoluble phosphatides Triton 1956: A phthalic glycerol alkyl resin Triton x-100: Polyethylene glycol phenyl! sooctyl ether Wyoming bentonite, pellets Yelkin C and ST: Proprietary water-dispersible mixtures contain- ing 55 percent of soybean lecithin ana cephalin. C also contains 45 percent of carbitol, ana ST 25 percent of soybean oil and 20 percent of carbitol ij fov convenience of the reader the proprietary wetting agents and other supplements used have been listed by name. Such mention does not imply a recommendation of tiny particular material in preference to many others that might have served similar purposes. -A- Preparation of spray Mixtures The usual method of mixing the 3pray materials was to make a slurry with any supplements not combined in dry form with the DDT and a small quantity of water in an electric mixer, and tden add the DDT. This mixture was then added to water in the spray tank and the volume made up to 5, 8, or 10 gallons, depending upon the number of apples to be sprayed. In the absence of wetting agents it was not possible to break up all the small agglomerates of the DDT-pyrophyilite, DDT-talc, or similar dry mixtures when they were stirred into water. They appeared as a suspension of particles ranging for the most part up to 1 mm. in diameter. When such mixtures were sprayed, however, the agglomerates were broken up and effectively dispersed in the spray droplets. The DDT-water paste was prepared by grinding J+ parts of DDT with 6 parts of water in a pebble mill. This paste had the consistency of a thick batter, which dispersed readily upon further dilution. Effect of Time of Grinding on Larvicidal Efficiency of DDT-Water Paste In two experiments DDT was ground with water for different periods up to 64. hours. DDT was used at 3 ounces per 100 gallons in one experiment and at 4- ounces in the other. The average results of these experiments are summarized in table 1. t -5- T&ble 1. — Larvicidal efficiency of DDT-water pastes ground in a pebble mill for different lengths of time i : Mean surface t » particle t Larvicidal efficiency Time of Undisturbed : i After 5 grinding t diameter : deposits i i water sprays Hours Microns Percent Percent 1 9.2 91.5 71.0 2 7.9 90.9 67.0 k 7.0 91.2 58.4 8 6.0 89.8 62.9 16 5.1 94.2 57.1 32 4.4 95.1 66.6 64 4.3 95.6 62.7 -6- Larvicidal Efficiencies of DDT Spray Treatments Twelve experiments were conducted to determine the larvicidal efficiency of DDT when combined in different proportions with various supplements and applied as sprays. Because of differences in larval vigor or average ability of the mixture of strains of larvae U3ed to enter the fruit, and in the condition of the fruit as the work pro- gressed, each experiment must be considered separately. The spray J formulas and the results obtained with them are given in tables 2-13. The quantities of materials given in the formulas are on the basis of 100 gallons, and refer to the amounts present in the diluted spray mixture. Formulas have been numbered for convenience in identifying these formulas, particularly those tested more than once. -7- Table 2. — Comparison of various concentrations of DDT-pyrophyllite (50:50) and DDT-talc (39:61) mixtures, DDT-water paste (40:60), and DDT- soybean oil-ben tonite : DDT ! • concentration : per 100 gallons : : Formula i : Larvicidal efficiency Supplement : Undisturbed : deposits I, , - t After 5 : water sprays • • Pounds Percent Percent Pyrophyllite 0.25 .50 1.00 1 2 3 96.3 98.9 100.0 83.0 Talc .25 .50 1.00 5 6 94.7 97.3 98.9 70.8 Water (paste) .25 .50 1.00 7 8 9 99.5 100.0 100.0 83.5 Soybean oil 1 qt. + Hiss, bentonite 0.5 lb. .25 10 91.5 — Lead arsenate 3 lb. (check, no DDT) — 11 56.9 — Table 3. — Effect of various supplements on larvicidal efficiency of DDT-pyrophyllite mixtures applied in sprays at 0.25 pound of DDT per 100 gallons : % Formula t Larvicicial efficiency Supplement t Undisturbed : After 5 : e t deposits : water sprays Percent Percent None 1 99.4 76.0 Dreft 0.5 oa. 12 97.4 69.5 Yelkin C 0.5 oz. 13 97.4 57.8 Soap (neutral) 1 oz. H 96.8 67.5 301 oil 1 pt. + Miss. bentonite 0.5 lb. 15 98.1 85.1 No. 15 + soybean phosphatides 2 oz. 16 92.9 85.1 No. 15 + soybean phosphatides 4 oz. 17 94.2 78.6 'v Table 4* — Evaluation of soybean oil in DDT sprays applied at 0.25 pound of DDT per 100 gallons Formula : Larvicidal efficiency Mixture s x Undisturbed : After 5 2 : deposits « : water sprays • Percent Percent DDT-water paste 7 94.4 68.8 DDT-water paste + Miss. bentonite 0.5 lb. 18 99.2 69.6 No. 18 + soybean oil 1 qt. 19 98.4 88.0 DDT in soybean oil 1 qt. + Miss, bentonite 0.5 lb. 10 94.4 80.8 DDT-water paste + bordeaux (1/2:1:100) 20 92.8 72.0 No. 20 + soybean oil 1 qt. 21 88.0 75.2 DDT in soybean oil 1 qt. + bordeaux 22 77.6 73.6 -9- Table 5« — Comparison of various dry supplements whew applied with DDT in sprays at 0.25 pound of DDT per 100 gallons Supplements/ '< : Formula ! : Larvici dal efficiency : Unuisturbed • • After 5 : deposits * • • « water sprays percent Percent Water paste (check) 7 95.1 76.0 Pyrophyllite (50:50) 1 96.7 82.0 Talc (39:61) 4 98.4 77.9 Diatomaceous earth (1:2) 23 92.6 72.1 Miss, bentonite (1:3) 24 91.8 67.2 Aalnut-shell flour (1:3) 25 100. 0 75.4 Hyd rated lime (1:3) 26 88.5 70.5 1/ Ratios indicate DDT: supplement, Table 6. — Evaluation of mixtures containing lead arsenate (3 lb.), with and without DDT (2 oz. in water paste) or a fungicide : x Formula) AS2O3 residue :Larvicidal 5: Undisturbed efficienc; Material added to [Undisturbed: After L: After 5 lead arsenate • 1 ; deposits : water : deposits :water • • spray, s • • ; sprays 1 iicrograms per sq.cm. Percent Percent None 11 10.7 6.6 39.8 35.6 DDT-water 27 11.0 6.3 84.5 48.5 Fermate 1 lb. 28 9.6 7.6 34.3 36.0 Fennate 1 lb. + DDT-water 29 13.1 9.3 82.4 41.0 Bordeaux (1/2:1:100) 30 9.5 7.0 31.0 28.5 Bordeaux (1/2:1:100) + DDT-water 31 11.6 10.5 84.1 47.3 DDT-water (check, no lead arsenate) 32 — — 59.4 36.8 -10- Table 7. — Evaluation of sulfur in DDT-water paste mixtures, applied in sprays at 0.25 pound of DDT per 100 gallons Supplement Formula None 7 lettable sulfur 1.5 lb. 33 Dusting sulfur 1.5 lb. + Drsft 0.25 oa. 34. Fermate 0.25 lb. 35 Flotation sulfur paste 2.5 lb. 36 Liquid lime- sulfur 3 pt. 37 Larvicidal efficiency Undisturbed deposits Percent 95.1 95.1 93.2 94.6 79.5 89.3 After 5 water sprays Percent 79.5 59.0 36.1 A3. 4 38.6 52.2 Table 8. — Evaluation of DDT-lead arsenate dry mixtures (10:90) appliea in sprays : : AS2O3 residue •Formula: Undisturbed: After : Larvicidal efficiency Spray material 5: Undisturbed: After 5 : deposits : water : deposits : water * • : sprays • • : sprays Micrograms per s^.cm. Percent Percent Lead arsenate 2 lb. 11 oz. (check) 39 8.8 6.6 39.6 23.4 DDT (2.4. oa.) -water paste (check) 40 — — 90.5 32.4 DDT-lead arsenate dry mixture (1.5 lb. ) gr jund into paste with water 41 8.1 6.6 86.0 46.9 DDT-lead arsenate dry mixture (1.5 lb. ) 42 6.0 5.6 64.9 30.6 Ho. 42 + bordeaux (1/2:1:100) 43 7.1 5.7 47.3 21.6 No. 43 + 301 oil 1 qt. 44 6.9 6.2 46.8 33.8 No. 44 + Yelkia ST 2 oz. 45 6.8 6.1 45.5 28.4 -11- Table 9. — Comparison of various ary supplements in formulas containing DDT (0.25 lb.) and soybean oil (1 pt.) applied in sprays i Supplement : Fo rmula : Larviciual efficiency Undisturbed : After 5 deposits : water sprays Pyrophyllite No. 1 + soybean oil + Wyoming bentonite 0.25 lb. Water paste + soybean oil + Wyo. bentonite 0.25 lb. Talc mixture + soybean oil + wyo. bentonite 0.25 lb. Diatomaceous earth (1:2) + soybean oil Miss, bentnnite (1:3) + soybean oil Walnut-shell flour (1:3) + soy- bean oil Percent Percent 1 82.6 39.3 46 82.2 47.1 47 75.8 70.8 48 86.4 58.0 49 68.0 43.8 50 68.0 55.3 51 78.5 47.5 -12- Table 10. — Effect of various wetting agents added to the DDT- pyrophyllite mixture when applied in sprays at 1*0 pound of DDT per 100 gallons : Weight l i i j Larvicidal : of ! r i . Surface tension j efficiency Wetting agent t wetting i Formula t of spray mixture t after 5 : agent t at 25°C. ; water spra; * Ounces Dynes per cm. Percent None: DDT 0.5 lb. — 2 — 84.5 DDT 1.0 lb. — 3 72.5 83.9 Draft 0.1 52 71.0 76.8 .2 53 69.0 83.9 .4 54 58.5 77.4 IN 2503 .1 55 71.9 82.2 .2 56 67.0 84.5 .4 57 61.2 83.9 Triton b 1956 .1 58 72.5 77.4 .2 59 69.0 81.0 .4 60 64.5 81.0 Grandpa1 s Pine Tar Soap .5 61 65.0 79.2 1.0 62 62.5 79.2 2.0 63 60.5 82.7 -13- Table 11. — Effect of various supplements, with ana without oil, adaed to the DDT-pyrophyllite mixture, when applied in sprays at 1.0 pound of DDT per 100 gallons V • • : Larviciaal : ft eight of ; : Surface tension : efficiency Supplement ! : supplement : Formula : of spray mix : after 5 ! : tare at 25°C. : water sprays • Ounces Dynes per cm. Percent None: DDT 0.5 lb. — 2 — 64.9 DDT 1.0 lb. — 3 72.5 81.8 lelkin ST 0.5 U — 79.1 1.0 65 71.0 81.1 2.0 66 68.0 73.6 Soybean flour 2.0 67 72.5 88.5 4c0 68 • 67.6 73.6 8.0 69 63.5 68.9 Soybean phosphatides 1.0 70 — 85.1 2.0 71 52. A 81.1 301 oil 1 pt. + Mi .38. bentonite 0.5 lb. 72 — 93.9 No. 72 + soybean phos- phatides 1 oz. — 73 — 93.2 jcjnulsive-type oil 1 pt. + Miss. bentonite 0.5 lb. 1U — 91.2 Soybean oil 1 pt. + Miss, bentonite 0.5 lb. — 75 — 92.6 -14- Table 12. — Comparison of several emulsion formulas with DDT-pyrophyllite mixture when applied in sprays at 0.25 pound of DDT per 100 gallons Solvent Emul3ifier ;Larvicidal efficiency Formula : Undisturbed : After 5 : deposits : water : : sprays Benzene 9.7 oz. Ethylene dichloriie 13.3 oz. Aylene 13.3 oz. DDT-pyrophyllite mixture (check) Triton B-1956 1.5 oz. Sulfonated castor oil (50%) 1.3 oz. Triton X-100 1.3 oz. 76 77 78 Percent 57.6 46.3 47.9 81.5 Percent 36.2 36.1 28.6 41.2 Table 13 . — Effect of spraying time on efficiency of DDT-pyrophyllite mixtures when applied in 3pr<*ys at 0.25 pound of DDT per 100 gallons Material added to DDT-pyrophyllite : Larvicidal efficiency : when spraying time was Formula • • • • 4 seconds * 12 seconds F ercent Percent 82 97.1 98.9 83 93.7 100.0 84 93.1 98.3 Miss, bent^nite 0.25 lb. and Fermate 0.25 lb. in slurry + 301 oil 1 qt. No. 82 + soybean phosphatides 2 oz. suspended in oil No. 32 + cottonseed phosphatides 2 oz, suspended in oil -15- Larvicidal Efficiencies of DDT Dusts The few tests made with dust mixtures are presented in table 14 . It will be noted that formula 38 cannot be compared directly with the other formulas, because the test was conducted at a different time. * Table 14. — Larvicidal efficiency of various DDT-talc mixtures applied as dusts : Quantity : : Larvicidal efficiency Mixture t applied t Formula : Undisturbed : After 5 : to 80 : : deposits : water sprays : aDDles : • • : Ounces Percent Percent DDT-talc (39:61) 2 38 99.0 63.9 DDT-talc (10:90) 6 79 97.1 40.0 DDT- talc-sulfur (10:40:50) 6 80 98.3 U.5 DDT-talc-301 oil (10:88:2) 6 81 98.7 46.7 -16- Discuasion Because of the high toxicity of DDT, in order to bring out differ- ences it was applied in lower concentrations than woula be practical under field conditions. On this account it seemed desirable to reduce proportionately most of the supplements, where wetting agents were employed, however, only the maximum quantities tested increased notice- ably the ease with which the i->DT could be dispersed in water to make a moderately thick slurry. The higher concentrations required for field use (approximately 1 lb. of DDT per 100 gal. for the codling moth) would therefore require more of the wetting agent to make a 3lurry of the same consistency. One of the most important developments in these tests was the performance of those mixtures not containing wetting agents, particularly the water paste and the pyrophyllite and talc preparations. There was no evidence that the wetting agents would improve the efficiency of any of the DDT formulas, and in many instances they tended to reduce the efficiency both before and after exposure to tap-water sprays. The probable usefulness of DDT in paste form was suggested by results obtained in laboratory-field tests in 19-43 after DDT had been ground for short periods with water in a thin slurry. The differences between the paste and the DDT-pyrophyllite mixture, however, were not mathematically significant (tables 2 and 5). DDT combined with crude soybean oil and enough Wyoming bentonite to prevent "breaking" in the tank (formula 4-7) proved more effective after the tap-water sprays than mixtures containing pyrophyllite, talc, diatomaceous earth, Mississippi bentonite, or walnut- 3hell flour. Length of grinding had a definite effect on particle size (table 1). The results indicate that the efficiency of unweathered deposits might be improved by grinding to a mean surface particle diameter of 4 to 5 microns but that the ability of the deposits to withstand the artificial rain weathering diminished as the diameter was reduced below approximately 9 microns. The paste used in most of the experi- ments was ground approximately 36 hours. DDT dissolved in soybean oil (formulas 10 and 22), benzene, ethylene dichloride, or xylene (table 12) was much le3S effective than when used alone in a water suspension. After the tap-water sprays the DDT paste or pyrophyllite mixture gave better results when added to bentonite- soybean oil or petroleum oil emulsions (tables 3» At and 11) than when used alone. Such mixtures are promising, particularly where some deposit- building action can be obtained, as with formulas S3 and 84. In these formulas the presence of ferric dimethyl dithiocarbamate increased the deposit-building action of the DDT- oil-phospha tide mixture. Other metallic salts would probably uo likewise. Fruit sprayed con- tinuously for 30 seconds with these mixtures acquired a thick,, even, coal-black aeposit. V -17- Although a weak bordeaux can be used with DDT without seriously reducing Its efficiency (table U) , the various forms of sulfur (table 7) reduced the efficiency of deposits exposed to the tap-water sprays. DDT in combination with lead arsenate (tables 6 and 8) was laost effective when the two were added to the spray mixture separately or ground with water to form a paste. The dry mixture was too granular. DDT promises to be a very effective fortifying agent for lead arsenate at dilutions as low as 2 ounces per 100 gallons. In formulas 29 and 31 it appeared to increase the deposits of arsenious oxide. Among the most promising developments in this series of tests were the results obtained with the dust mixtures (table M), particularly those containing sulfur and oil. Since the completion of these experiments a technique for the analysis of DDT deposits on fruit has been developed at the Vincennes laboratory .2/ On fruit similar to that employed in the larvicidal efficiency experiments, but not treated to remove excess wax, deposits of 5.2, 10.9, 22.0, and 48,8 micrograms a£.DDT per square centimeter were obtained with spray mixtures containing DDT paste equivalent to 0.5, 1, 2, and 4 pounds of DDT to 100 gallons. Sprays of DDT-pyrophyl- lite employing 3 pounds of DDT to 100 gallons, alone and with Missis- sippi bentonite and soybean oil (formulas similar to Nos. 1 and 75) , gave deposits of 21.7 and 38.0 micrograms of DDT per square centimeter, respectively* 2/ Fahey, J. E. The determination of DDT spray deposits on apples. Assoc. Off. Agr. Chem. Jour. Submitted for publication. UNIVERSITY OF FLORIDA llllllllillilllilllllllll 3 1262 09230 3899 /'