Large numbers of both species may build up on growing terminals on apple trees during summer, particularly when there is an abundance of succulent new foliage. Despite our dearth of rainfall so far this season, there have been several reports of high populations here and there. Both species are apparently common during the summer in New York orchards, although no extensive surveys have been done to compare their relative abundance in different production areas throughout the season. Nymphs and adults of both species suck sap from growing terminals and water sprouts. High populations cause leaves to curl and may stunt shoot growth on young trees.
Aphids excrete large amounts of honeydew, which collects on fruit and foliage.
Sooty mold fungi that develop on honeydew cause the fruit to turn black, reducing its quality. Aphids should be sampled several times throughout the season starting in mid-June. Inspect 10 rapidly growing terminals from each of 5 trees throughout the orchard, and record the percentage of infested terminals. The larvae of syrphid and cecidomyiid flies prey on aphids throughout the summer. These predators complete about three generations during the summer.