Predation removes 10-20% of the codling moth eggs laid in unsprayed orchards, and usually less in treated orchards. Is this any different when mating disruption is used for control of codling moth as it is on over 20% of Washington's apple acreage?
The major predators of codling moth eggs are minute pirate bugs, mirid bugs, earwigs, lacewings, and predatory thrips. Densities of these insects and spiders were measured, along with egg mortality, in 16 test orchards in central Washington. (Even though spiders are not likely to eat codling moth eggs--they may feed on larvae, though--their absence is a good indication of the ecological disturbance created by insecticide use.)
Egg mortality ranged from 7-52% in individual orchards. No one type of predator was primarily responsible for egg mortality. Where there was a higher number and diversity of predators there was higher egg predation. Predators were more numerous in orchards where mating disruption was used for codling moth control than in those treated with insecticides, and the unsprayed orchards had the highest percentage of dead eggs. Levels of egg predation did not differ signficantly among treatment programs in June, but were significantly higher in the unsprayed orchards by the end of the season.
The importance of predators in the biological control of codling moth in apple orchards should not be overlooked. In this study, using organophosphate insecticides early in the season to supplement mating disruption or to manage secondary pests greatly reduced biological control of codling moth.
Knight, A. L., J. E. Turner, and B. Brachula. 1997. Predation on eggs of codling moth (Lepidoptera: Tortricidae) in mating disrupted and conventional orchards in Washington. J. Entomol. Soc. Brit. Columbia 94, Dec. 1997.
Return to Commodity Menu Vol. V No. 11
Return to Contents Menu Vol. V No. 11
Go To Index