Premature leaflet drop and complete defoliation can result. They feed primarily on under surface of leaflets. A black sooty mold may grow on the sugary honeydew secreted by the aphids. Heavy honeydew and sooty mold on the surface of leaflets may interfere with photosynthesis. They feed primarily along the midribs and veins on the underside of leaflets, causing dark brown blotches which later appear as scorched, dead areas.
Infestations normally begin on the lower branches and spread upward.
Heavily damaged leaflets turn entirely brown and drop, often resulting in premature tree defoliation. Piercing-sucking mouthparts arise on the front of the head. Infested nuts are usually held together at their base by silken webbing containing conspicuous, dark, grass eliminated by the larvae. One larvae can destroy all the nuts in a cluster. Second generation larvae also attack the nuts but damage is usually less severe.