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 autumn flight of 1989 with a sticky-card bioassay in which adult males captured in sex pheromone traps were exposed to a concentration series of azinphosmethyl. This field bioassay, plus a laboratory bioassay performed on neonates from two of the field populations, did not detect azinphosmethyl resistance in this tortricid, even in an orchard where heavy reliance on azinphosmethyl led to azinphosmethyl resistance in another tortricid, Platynota idaeusalis (Walker). The sticky-card bioassay with a diagnostic concentration of 90 mug (AI) azinphosmethyl/g adhesive killed the expected 95% of the adults captured in a population during the summer and autumn flights, but killed only 89% of the males captured during the spring flight of 1990. We attributed the greater tolerance to azinphosmethyl in adult males from the spring flight to the significantly larger weight (1.4-fold) of males captured in the spring than in the autumn. A new diagnostic concentration of 120 mug (AI) azinphosmethyl/g adhesive, adjusted for adults captured during the spring flight, was evaluated during the 1991 spring flight and better approximated a concentration that killed 95% of the susceptible adult males during this flight. Our report describes baseline data on the susceptibility of redbanded leafroller to azinphosmethyl.