Smirle_1998_Pestic.Biochem.Physiol_61_183

Larvae of the obliquebanded leafroller,Choristoneura rosaceana(Harris Lepidoptera Tortricidae were collected from apple orchards in Larvae of the obliquebanded leafroller,Choristoneura rosaceana(Harris) (Lepidoptera: Tortricidae), were collected from apple orchards in Deux-Montagnes, Qubec, Canada, where leafroller populations were documented to be resistant to azinphosmethyl. Larvae were bioassayed for azinphosmethyl resistance over five generations of rearing in the laboratory in the absence of insecticide selection pressure; resistance levels reverted to susceptibility in approximately four generations in 1995 and three generations in 1996. In 1996, activities of esterases and glutathione transferases were assayed in adult moths concurrently across generations. Reversion of resistance was significantly correlated with decreasing esterase activities in both male and female moths when either alpha-naphthyl acetate or -naphthyl butyrate was used as the test substrate. Glutathione transferase activities were correlated with resistance levels only in male moths when 3,4-dichloronitrobenzene (DCNB) was the test substrate; no correlations between activity and resistance were observed for females with DCNB or for either sex when activity was assayed with 1-chloro-2,4-dinitrobenzene (CDNB). The instability of azinphosmethyl resistance in the obliquebanded leafroller, coupled with the apparent involvement of esterases in resistance development, should make this pest amenable to a resistance management strategy involving the rotation of azinphosmethyl with other control materials that are not primarily metabolized by esterases.