Woolly apple aphid, Eriosoma lanigerum (Hausmann), has become a pest of increasing importance in Washington apple orchards in the past decade. The increase in aphid outbreaks appears to be associated with changes in pesticide programs and disruption of biological control. We sampled woolly apple aphid colonies in central Washington apple orchards for natural enemies of this pest from 2006 to 2...

Parasitoid disturbance populations in agroecosystems can be maintained through the provision of habitat refuges with host resources. However, specialized herbivores that feed on different host plants have been shown to form host-specialized races. Parasitoids may subsequently specialize on these herbivore host races and therefore prefer parasitizing insects from the refuge, avoiding foraging on...

Aphids are major pests in apple orchards, debilitating the crop and spreading disease. We investigated whether early-season predation by canopy spiders may be effectively controlling aphid numbers in three organic orchards. For this purpose, we monitored the aphid population dynamics from the winter eggs to colony stages and compared this to spider abundances and rates of predation on aphids de...