Monitoring Azinphosmethyl Resistance in the Light Brown Apple Moth (Lepidoptera: Tortricidae) in New Zealand

Abstract

The extent of azinphosmethyl resistance in light brown apple moth, Epiphyas Postvittana (Walker), in the Nelson region of New Zealand was determined in 1982. Light traps were used to capture females from which laboratory colonies were established for testing. Resistance was detected by spraying larvae directly with a Potter tower. In later resistance surveys (1983–85) topical application to pheromone-attracted males was used to assess resistance. Two populations (at Mariri and at the Moutere Bluffs) resistant to azinphosmethyl, but of confined distribution, were found. Resistant male moths were collected from apple orchards and nearby scrub areas and were more abundant outside orchards during the period of insecticide spray application. Subsequent reinvasion of orchards by moths from nearby scrub areas within the orchard area was indicated by the similarity in proportion of resistant individuals in the two habitats and by catches in pheromone-baited sticky traps from orchards and scrub areas. Two percent fruit damage occurred in an affected orchard in which the grower applied azinphosmethyl, compared with a normal level of ca. 0–0.2% damage elsewhere in the district.