SUSCEPTIBILITY OF REDBANDED LEAFROLLER (LEPIDOPTERA, TORTRICIDAE) TO AZINPHOSMETHYL DURING THE APPLE SEASON

Six field populations of redbanded leafroller, Argyrotaenia velutinana (Walker), were monitored for azinphosmethyl resistance during the aut umn flight of 1989 with a sticky-card bioassay in which adult males ca ptured in sex pheromone traps were exposed to a concentration series o f azinphosmethyl. This field bioassay, plus a laboratory bioassay perf ormed on neonates from two of the field populations, did not detect az inphosmethyl resistance in this tortricid, even in an orchard where he avy reliance on azinphosmethyl led to azinphosmethyl resistance in ano ther tortricid, Platynota idaeusalis (Walker). The sticky-card bioassa y with a diagnostic concentration of 90 mug (AI) azinphosmethyl/g adhe sive killed the expected 95% of the adults captured in a population du ring the summer and autumn flights, but killed only 89% of the males c aptured during the spring flight of 1990. We attributed the greater to lerance to azinphosmethyl in adult males from the spring flight to the significantly larger weight (1.4-fold) of males captured in the sprin g than in the autumn. A new diagnostic concentration of 120 mug (AI) a zinphosmethyl/g adhesive, adjusted for adults captured during the spri ng flight, was evaluated during the 1991 spring flight and better appr oximated a concentration that killed 95% of the susceptible adult male s during this flight. Our report describes baseline data on the suscep tibility of redbanded leafroller to azinphosmethyl.