In spring, silk webs appear in the crotches of trees or on the ends of branches. The leaves are chewed and the tree may be completely defoliated. Groups of bluish or black hairy caterpillars with yellow or white stripes and blue or white spots are feeding in or around the webs.
Spray with an insecticide labeled for these pests, following label directions. Cut out and destroy large webs. To prevent damage the following year, destroy the brown egg masses that encircle the twigs during the winter.