Green Apple Aphid
Overwinter as eggs in protected areas on limbs and start hatching at half-inch green. Green apple aphids remain on apples all season.
Curled leaves; copius honeydew supports black, sooty mold; stunted shoots.
Look for shiny black eggs in early spring. If aphids are a problem later in the season, start after petal fall and select a random shoot on the major cultivar in the block and count the number of leaves that have one or more wingless aphids; repeat on 10-20 more shoots, and determine an average number leaves/shoot that have aphids.
Delayed dormant oil will usually take care of this aphid. Otherwise, 4+ leaves/shoot infested with aphids during the season will require treatment.
Degree Day Model
Numerous beneficial insects including lady beetle adults and larvae, lacewing larvae, and syrphid fly larvae help suppress aphid populations.