Syrphid fly larvae attack woolly apple aphids. The woolly apple aphid overwinters as a nymph on the roots of apple trees, but can also overwinter on the aboveground part of the tree in protected areas on the trunk or main limbs. In the spring, overwintering aphids produce live young that migrate up and down the tree. Adult aphids are a reddish-brown to purple color but are usually concealed beneath a white, cottonlike ­substance secreted from the aphid’s abdomen. Galls form on the plant where aphid colonies feed. Roots of infested trees have large, abnormal swellings. Continued feeding can kill roots […]