SURVEY OF AZINPHOSMETHYL RESISTANCE IN CODLING MOTH (LEPIDOPTERA, TORTRICIDAE) IN WASHINGTON AND UTAH

A bioassay in which azinphosmethyl was incorporated into the adhesive of a sex pheromone trap was developed to detect resistance in populati ons of male codling moth, Cydia pomonella (L.). Experiments were done to evaluate the influence of the length of the bioassay, moth body pos ition in the adhesive, moth age, and extremes of temperature and relat ive humidity (RH) experienced by moths caught in traps in the field. M oth's body position and age for moths <5 d old were not significant fa ctors affecting moth mortality. Exposure to low humidity (45% RH) or l ow to high temperature (10-20-degrees-C) for up to 12 h did not signif icantly affect mortality. Forty-eight populations were surveyed in Was hington, and three populations were surveyed in Utah during 1991-1992 with a discriminating concentration, 75 mug (AI)/g adhesive; moth mort ality was scored after 64 h at 20-degrees-C and >85% RH. Populations f rom crabapple plantings, certified-organic, abandoned, and conventiona l orchards were sampled. Twenty of 44 populations monitored in 1991 an d 12 of 17 populations monitored in 1992 had significant levels of res istance compared with a susceptible laboratory strain based on nonover lapping 95% CL. All but one of these resistant populations were from c urrent conventional or recently abandoned conventional orchards. Resul ts from the 10 orchards sampled in both years were not significantly d ifferent. Resistance in a population collected in 1991 reverted rapidl y when removed from exposure to azinphosmethyl and reared on apple in the laboratory.