Azinphosmethyl Resistance in the Tufted Apple Bud Moth (Lepidoptera: Tortricidae): Reversion, Diagnostic Concentrations, Associated Esterases, and Glutathione Transferases

Abstract

In 1989 sticky-card bioassays performed on adult males collected in pheromone traps showed 41-fold resistance to azinphosmethyl in a field population of tufted apple bud moth, Platynota idaeusalis (Walker). After 17 generations under laboratory rearing conditions without azinphosmethyl selection, azinphosmethyl resistance in neonates and male adults reverted to a level approaching that of a susceptible strain. Estimated LC95s and LC99s (340 and 760 µg [AI]/g adhesive, respectively) of susceptible moth populations were selected as diagnostic concentrations of azinphosmethyl and used to assay three field populations of adult males for azinphosmethyl resistance in 1990 and 1991. Glutathione-transferase activities were not associated with azinphosmethyl resistance in laboratory strains. Elevated nonspecific-esterase activities were found in resistant laboratory strains and a field population with a high level of resistance. Among the nonspecific esterases, the presence of one esterase (E6) was closely associated with azinphosmethyl resistance in field populations. In this study, nonspecific-esterase assays gave an accurate assessment of azinphosmethyl resistance in this tortricid species, but a specific assay that detects the E6 will provide the sensitivity necessary to detect moderate to low levels of resistance in field populations.