Treatments with horticultural oils during dormant periods in spring can provide adequate control of these Insects. Aphids on fruit trees spend the winter as eggs clustered near the buds. After eggs hatch in spring, the aphids feed on the emerging leaves, causing slight leaf curls. Diazinon, malathion and insecticidal soaps also can help suppress aphid outbreaks after leaves emerge. However, aphid infestations typically are short-lived on apples.
Aphids usually leave the tree by late spring, flying to alternate summer host plants.
If aphids are not seriously damaging the majority of terminals or injuring fruit, there is little benefit from insecticides for aphid problems after leaves emerge. Woolly apple aphid on stem. This insect has long, thread-like strands of wax that cover its body. They infest twigs, callous tissues around pruning cuts, and sometimes roots of apple trees. Sustained infestations of woolly apple aphid over several years cause cankers to develop that can girdle and kill parts of the plant.