Aphids
Aphids commonly appear in the early spring in large colonies. Nymphs and adults can all be found feeding on the new growth at the ends of branches. We commonly find aphids on Spirea, Viburnum, Tulip Trees, and even oaks. Some ants tend these colonies to collect the sweet honeydew that aphids secrete and to protect them from attacking insects. If ants are controlled, the number of aphids usually drops, because beneficial insects, such as lacewing and syrphid fly larvae, find and destroy them. When immediate control is necessary, we hose the plants off with water as needed.
NOTE: The photos in this Gallery of Pests are taken from the University of California, Davis, IPM website, which is a great resource for further information.