Spider mites frequently attack severely during dry years. Caterpillars Tent caterpillars and fall webworms attack flowering crabapples. Tent caterpillars are hairy black worms. They have a white stripe and a row of blue spots on their back and brown and yellow lines along each side. They are about 2 inches long.
Tent caterpillars feed on young leaves in the spring.
They live in webs in the crotches of trees at night and feed during the day. Fall webworms are pale green or yellow and have a dark stripe down their back and a yellow stripe along each side. They are about 1 inch long. Webworms feed on leaves from May to September. They form loose, unsightly webs at the ends of branches.