The life history of most aphids is complicated with many variations and exceptions. Aphids cause damage by piercing the tender plant tissue and drawing large quantities of plant sap. They often feed in groups. Aphids can cause galls, curled leaves, swollen branches, and discolored or wilted leaves. They usually do not cause permanent damage to forest, shade and ornamental trees.
Some aphids excrete excessive amounts of a sticky substance called honeydew.
This honeydew can be extremely annoying when it is deposited on sidewalks, cars and other objects. Honeydew attracts insects such as ants, bees, flies and wasps, whose presence may be the first sign of an aphid infestation. Aphids have many natural enemies including lady beetles and birds. Weather conditions such as heavy rains or cold temperatures are major factors in reducing aphid populations. However, under favorable conditions, aphid populations can rapidly increase and may require chemical control.