Toxicity Studies on Cyclodiene-Susceptible and Cyclodiene-Resistant Strains of the Cabbage Maggot1

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Abstract
Collections of larvae of Hylemya brassicae (Bouche) were made in areas of Ontario where resistance had not yet developed, and where high levels of resistance were known to occur, and laboratory cultures were established. Base-line toxicity data were obtained on adults. The results indicated that the level of resistance of a homozygous resistant strain to aldrin was ×1127. No resistance was apparent with either DDT or diazinon. Cross-resistance occurred within the cyclodiene-insecticide group (dieldrin ×971.6, endrin ×35.2) and to related materials such as isobenzan (×42A) and lindane (×19.7). Analysis of soil samples collected in 2 areas where resistance had developed indicated that the soil contained from 1.3 to 1.4 ppm of aldrin and dieldrin and from 0.3 to 2.6 ppm of DDT. A possible alternative to the use of soil insecticides for maggot control would be an adult spray program. Tests conducted on adults with 9 insecticides indicated the following order of toxicity: Nia 10242 (2,2-dimethyl-2,3-dihydrobenzofuranyl-7 N-methyl carbamate) >Bayer 25141 [O, O-diethyl O-p-(methylsulfinyl)phenyl phosphorothioate] >Dursban (O, O-diethyl 0-3,5,6-trichloro-2-pyridyl phosphorothioate) >parathion>Bayer 37289 (O-ethyl 0-2,4,5-trichlorophenyl ethylphosphonothioate) > U.C. 211,19 [2-methyl-2-(methylthio) propionaldehyde on (methylcarbamoyl) oximeazinphosmethyl>phorate>carbaryl. In studies on the influence of temperature on the toxicity to adults, DDT exhibited a pronounced negative temperature coefficient, lindane a slight negative temperature coefficient, while the remaining materials showed positive temperature coefficients. Posttreatment temperature appeared to be more critical than pretreatment temperature.