These leaves may later turn bright red. Feeding on the leaves around fruit clusters often results in the bunching, stunting and malformation of the developing fruit. These abnormalities become worse as fruit develops and can eventually render the fruit unsalable. Large aphid populations may produce large amounts of honeydew as waste from the sap on which they feed. Honeydew excreted onto fruit will serve as a growing ground for sooty mold fungus, which will affect the finish of the apple.
Untrimmed trees render favorable conditions for the aphids and greatly handicap methods of control.
A cool, wet spring favors aphid development because it provides conditions unfavorable for aphid parasites and predators. A large proportion of the overwintering eggs do not hatch. Males are scarce and make up only a small portion of the total population. Many females deposit eggs before mating, and these eggs do not hatch in the spring. The aphid passes the winter in the egg stage.