Correlated insecticide cross-resistance in azinphosmethyl resistant codling moth (Lepidoptera : Tortricidae)

Resistance to several classes of insecticides was correlated with azinphosm ethyl resistance in codling moth, Cydia pomonella (L.), in California. In t ests of laboratory and field populations, cross-resistance was positively c orrelated with azinphosmethyl and two organophosphates (diazinon, phosmet), a carbamate (carbaryl), a chlorinated hydrocarbon (DDT), and two pyrethroi ds (esfenvalerate and fenpropathrin). Additionally, negatively correlated c ross-resistance was identified between azinphosmethyl and two other organop hosphates, chlorpyrifos and methyl parathion. Patterns of resistance observ ed in laboratory colonies were confirmed with field bioassays. In bioassays of field populations, azinphosmethyl resistance was observed to increase f rom 1991 to 1993, although levels of resistance remained <13-fold. Because orchards with azinphosmethyl resistance have had difficulties with suppress ion of codling moth, and cross-resistance was found for all tested classes of insecticides, strategies for managing resistance will need to be develop ed so as to protect current and future control tactics. The two insecticide s with negatively correlated cross-resistance are discussed as potential to ols for resistance management.