l: y STAT^^^ty.i 9 ^ ARD E-743 United States Department of Agriculture Agricultural Research Administration Bureau of Entomology and Plant Quarantine INVESTIGATIONS OF SPRAYS FOE CONTROL OP THE EUROPEAN CORN BORER, TOLEDO, OHIO, 19I+5-I9U6 By D. D. Quest el and R, V. Connin, Division of Cereal and Forage Insect Investigations Investigations of insecticides applied as sprays for control of the European corn "borer (Pyrausta nubilalis (Hon.)) were continued during the seasons of 19^5 and i$P+6 in the vicinity of Toledo, Ohio, and the results obtained are presented herewith. Small-Plot Tests Small plot 8 were laid out in randomized "blocks, each plot "being H rows wide and 20 feet long, and each treatment was replicated U times. A wheelbarrow sprayer powered with a gasoline engine and equipped with nozzles that produce solid cones of spray was used in the application of water suspensions. All buffer rows were treated with a spray containing ground cube root (U.8 percent rotenone) applied with a self-propelled boom sprayer. All the insecticides were tested as water suspensions, and sodium butylhydroxyphenylbenzene sulfonate (Areskap) was used as the wetting agent at the rate of l/3 pound per 100 gallons of water. The plants were thoroughly sprayed, enough spray being applied to cause free run-off at the base of each plant. The quantities used were increased during the season as the plants grew larger. No accurate record of the gallons used per acre was practical, but the dosage was estimated at 150-175 gallons per acre in 19^5 and 170 gallons in 19^. In 19^+5 borer development was late but corn development was later. The egg-hatching period began in the earliest fields on June 25, or 10 days later than in 19^ t and ended after July 11, 11 or more days later than in 19^-. The first spray application was made on June 29, when the corn was 9 inches high. This is in contrast with the 19^- season, in which the first application was made on June 17, when the corn was 36 inches high. Additional applications in 19*+5 were made on July h f 9, and lU. Only slightly more than 1 inch of rain fell during the spraying season. In 19^+6 egg hatching began on June 25, and the first spray was applied on June 28, when the corn was 38 inches high with tassels begin- ning to emerge. Three additional applications were made on July 3, &, and 13. At the time of the second application the corn was fully tasseled and silking. -2- In both years 100 corn plants, 25 from each plot, for each treatment were dissected at the roas ting-ear stage to determine the effectiveness of the treatments. The results are presented in tables 1 and 2. In 1945 the compounds l-itSobutyryl-2-phenylhydrazine and 1-phenyl- 2-(phenylsulfonyl) hydrazine were among the more effective of the insecti- cides tested. l-Trichloro-2,2-bi6(3,5-dichloro-2-hydro3yphenyl)-ethane, tetrachlorodiphenylethane, benzene hexachloride, and 1-phenyl-semioxama- zide were apparently somewhat less effective, though not significantly bo, at odds of 19 to 1* Both bis(3,5,6-trichloro-2-hydroxyphenyl)methane and l-phenyl-2-(jD-tolysulfonyl) hydrazine greatly reduced borer populations in both plants and ears, but were significantly less effective than the first eight materials listed. However, a rather heavy dosage of all these chemicals except benzene hexachloride was used. The particle size of the hig^h-rbtenone (9.6 percent) cube powder tested in 194-5 was very small (300-500 mesh) • Although this material gave satis- factory control, it did not reduce the borer population in the plants so much as did the cube of lower rotenone content which had a somewhat larger particle size. Rvania . l-trichloro-2 . 2-bis ( 3 , 5-dicaloro-2-hydroxyphenyl) ethane , l-phenyl-2-(phenylsulfonyl) hydrazine, cube, and DDT gave good spray sus- pensions. The remaining materials gave poor to medium suspensions. Of the nine materials tested in 194-6, five showed very promising results. Chlorinated camphene and 2,2-bis(3-bromo-5-chloro-2-hydroxyphenyl)- 1-trichloro ethane were both about as effective as DDT but were used at considerably heavier dosages. The sample of methoxy analog of DDT (trichloro-bis(methoxyphenyl)- ethane) used in these tests was highly effective, although a different, highly purified sample that was tested at the same strength in the labora- tory during the winter of 194-5 caused no appreciable mortality of corn borer larvae. In view of these results, a comparative test of both samples was run in the laboratory. The 194-5 material again caused no mortality, whereas the 1946 material was quite toxic at low concentrations. This discrepancy was apparently due to some difference in the preparation of the two samples. o o ft o a •H > •H O •H P O © to CT\ VO vo ir> CT\ CA OS CO CTi ft © © u 1? •H u SrH v_x © rH ft © rH © o> a rH O CM d ir» 3 ft © s ft I?! •H A JO *> £-3 *H .3 a ft o • rH lb O © rH rH ft a 5' H -h P U T •»» ^ S^ d © .2 N (D ;3 «h © E a © CVl p! ^ A ft •d >» © id 1 © a^ ft o © O -H (0 o > % p u ? 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She same materials were tested in 19^6 except that the DDT dust contained 50 percent of DDT. t&trawet (an aromatic monosodium sulfonate) was used as the wetting agent in all sprays at the rate of 1/3 pound per 100 gallons of water • In 19^3 the first application was made on June 25, when the corn was approximately lU inches high and in the whorl stage. Joditional applic** tione were made on June jJO and July 5 a&d 10* from 1J0 to 190 gallons of spray were applied per aore-*appllcation, larger Quantities being used as the plants grew larger. In 19**6 e all four applications were made at the uniform rate of 175 gallons per acre® At the time of the first applica- tion, June 26, the plants were 38 inches high with the tassels beginning to emerge. .Additional applications were made on July 1, 6, and 10, and at the roasting-ear stage in both years a total of 50 plants were dissected from the three replicate strips for determining the borer populations* She results are given in table 3* Jm in the small^lot tests, the DDT mleronised on fuller's earth gave the best control in both years, even though the dosage was only 1/2 pound of DDT per acre in 19ty>. *ho results obtained with Jfranla were practically the sane as those obtained with rotenone in 19ty>» each giving satisfactory control, but the Sfyania appeared to be somewhat more effective in 19^6. Ghder the comparatively heavy infestation in 19*H> there were only 8 Ho. 1 borer-free ears per 100 plants in check plots as compared with 96 in the plots treated with DDT. The higher control obtained in 19^5 than in I9U6 with ftranla and rotenone may have been due partially to the fact that the com was in the whorl stage in 19H5 at the time the applications were made, as higher control is usually obtained at this stage than at the tasseling and silking stages. Bcsidues of DDT on Sprayed Corn Plants Samples of green corn plants that had been treated four times with DBf at Impound and ~J**poTxxitiL dosages in the small^lot tests were taken at roastlng-ear harvest time and sent to the Division of Insecticide Investigations for determination of DDT residues, fhe chemical analyses showed that, based on the green weights and the organic chlorine found, 0.8 p.p»m« of DDT was present on the unhusked ears and 17.8 p.p.m. on the leaves and stalks of the plants that had been sprayed with DDT at a total of h pounds per acre, and 15*0 p.p.m. on the unhusked ears and 190.2 p.p.m. on the leaves and stalks of the plants that had been sprayed with DDT at a total of 28 pounds per acre. 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H H O -p u a H X O CD k r-l •H .0 CD cd 25 O 0» t0 O •H P cd ■g i o i4 CD p 3 «« o 0) p CH o cjn cr\ CM CM CM a « « o CM O a in a p a •»> •d CD .1' ■P. 4» a) a o CD CD CO •H u O - O p u u CD 9 © CD P«H 6 •8 &2 •H CO .0 o I s p 9 O u to p o 2 •d p CJ h o *> CD • *» •d ct CD P 13 ttOP •H 9 1! o o Cfl -P 3 § CD CO •H CD -10 Summary Investigations of insecticides appliable as sprays for control of the European corn borer ( Pyrausta nubilalis (Hbn.)) were continued during the seasons of 1945 and 1946 in the vicinity of Toledo, Ohio, In small-plot tests thirteen preparations applied with a wheelbarrow sprayer in 1945 re- duced the borer population in the plants 89 percent or more. Of the new materials tested in the small-plot tests in 1946, five gave satisfactory control — technical DDT micronized on fuller^ earth, l,l-dichloro-2,2-bis- (p-chlorophenyl) ethane, chlorinated camphene, 2,2-bis(3-bromo-5-chloro-2- hydroxyphenyl)-l-trichloroethane, and trichloro-bis(methoxyphenyl) ethane. None of the five caused spray injury when applied to growing corn plants. Highly refined airplane-engine oil, one of the carriers used with DDT as an aerosol, caused severe injury to corn plants, but crude soybean oil similarly used caused no apparent injury. Twenty-eight pounds of DDT per acre applied in four applications as a water suspension caused no observable injury to growing plants. In comparisons of DDT, Ryania speciosa . and cube powder applied with a self-propelled power sprayer in commercial fields of early-market sweet corn, DDT was the most effective against the borer although very good con- trol was obtained with the other two. DDT residues amounting to 0.8 and 15.0 p. p.m. were present on roasting ears taken from plots that had been sprayed with DDT at totals of 4 and 28 pounds per acre. 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Of the new materials tested in the small-plot tests in 1946, five gave satisfactory control— technical DDT micronized on fuller's earth, l,l-dichloro-2,2-bis- (p-chlorophenyl) ethane, chlorinated camphene, 2,2-bis(3-bromo-5-chloro-2- hydro2yphenyl)-l-trichloroethane, and trichloro-bis(methoxyphenyl)ethane. None of the five caused spray injury when applied to growing corn plants. Highly refined airplane-engine oil, one of the carriers used with DDT as an aerosol, caused severe injury to corn plants, but crude soybean oil similarly used caused no apparent injury. Twenty-eight pounds of DDT per acre applied in four applications as a water suspension caused no observable injury to growing plants. In comparisons of DDT, Byania speciosa . and cube powder applied with a self-propelled power sprayer in commercial fields of early-market sweet corn, DDT was the most effective against the borer although very good con- trol was obtained with the other two. DDT residues amounting to 0.8 and 15.0 p. p.m. were present on roasting ears taken from plots that had been sprayed with DDT at totals of 4 and 28 pounds per acre. Samples of leaves and stalks from the same plots bore DDT residues amounting to 15*0 and 190.2 p. p.m. , based on their green weights.