LARGE-SCALE TRIALS OF MATING DISRUPTION OF LIGHTBROWN APPLE MOTH IN NELSON, NEW-ZEALAND

Mating disruption of lightbrown apple moth (Epiphyas postvittana (Walk er)) was assessed in combination with reduced insecticide programmes c overing 321 ha of trials in commercial Nelson apple (Malus domestica B orkh.) orchards from 1990/91 to 1993/94. The aim was to compare insect control and insecticide residues under a combination of reduced insec ticide plus pheromone, compared to the standard insecticide programme alone, on a commercial scale. The combination of the pheromone and two fewer spray applications post-Christmas, including the omission of th e final application 2 weeks before harvest, provided an equivalent lev el of leafroller control to the standard insecticide programme in 3 of the 4 years. Reduced insecticide use in the absence of pheromone had increased fruit damage. Individual sites where poor control was obtain ed with pheromone were characterised by a small treated area or poor a pplication technique, indicated by trap catch inside the treated area. High rate pheromone (2000 dispensers/ha), yielded significantly less fruit damage at harvest than the standard pheromone rate (1000/ha). Az inphos-methyl residues were reduced on fruit at harvest in the pheromo ne treatments, and the incidence of fruit with low or non-detectable r esidues was increased. Prospects for managing leafrollers using pherom ones in combination with reduced insecticide programmes are promising, although further work is needed to make this alternative more cost-ef fective.