Potential for outbreaks of leafrollers (Lepidoptera : Tortricidae) in California apple orchards using mating disruption for codling moth suppression

Two species of leafrollers, Argyrotaenia citrana (Fernald) and Pandemis pyr usana Kearfott, represent serious obstacles to the implementation of mating disruption for control of codling moth in coastal California apple orchard s. Larval and adult densities of A. citrana and P. pyrusana and subsequent fruit damage were compared under different codling moth control treatments. Leafroller larval counts and levels of fruit damage were significantly hig her in most plots that were untreated or treated only with codling moth phe romone. Leafroller fruit damage levels in these plots were commonly between 10 and 15% at harvest. As summer larval counts were good predictors of fru it damage levels, larval sampling could be a useful tool for predicting lea froller outbreaks. Use of pheromone trapping for A. citrana to detect local ized outbreaks within an orchard was not useful and failed to correlate wit h larval numbers, whereas adult monitoring for P. pyrusana appears more pro mising. Efforts to implement a codling moth mating-disruption program in Ca lifornia must include changes in strategies for monitoring and controlling leafroller species.