The wooly apple aphid, which is bluish black and has white wax covering, sometimes is found in cracks or pruning wounds. Spider Mites Spider mites are red or greenish-red pests that feed on the underside of leaves. They are barely visible to the naked eye but sometimes can be detected by fine webs on the underside of leaves. Infested leaves become yellow, gray, or brownish, and flowers become discolored or faded. Severely infested trees become stunted.
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.