Predation on eggs of codling moth (Lepidoptera: Tortricidae) in mating disrupted and conventional orchards in Washington

Abstract

Predation on eggs of codling moth, Cydia pomonella L., was assessed in Washington in June and August, 1995 in eight apple orchards treated with organophosphate insecticides (OPs), four orchards treated with mating disruption (MD) and some OPs, and four treated with MD but not with OPs. Sentinel codling moth eggs laid by caged moths on 10 shoots in each orchard were scored as alive, dead, or missing after 7 d, and beating tray samples of arthropod predators were collected at the beginning and end of each trial. Levels of egg predation (dead + missing eggs) did not differ significantly among orchard types in June but varied among orchard types in August (MD alone> MD + OPs > OPs). The percentage of dead eggs in August was significantly higher in the orchards receiving only MD than in orchards treated only with OPs. The percentage of missing eggs was significantly lower both months in orchards not treated with MD. Densities of spiders and all predators on both sample dates and for earwigs in August were significantly higher in orchards not treated with OPs. Densities of heteropteran predators did not vary significantly by orchard type. No significant correlations were found among predator densities and egg mortality within an orchard type. However, the percentages of dead eggs and dead plus missing eggs were significantly and positively correlated with densities of earwigs, spiders, and all predators in tray samples across the 16 orchards.

Key words: Codling moth; eggs; predation; mating disruption; biological control