The abdomen is covered with white, fluffy wax. Plump, gray, wingless aphids on maple leaves are about 2 mm long and are concealed beneath dense, white, waxy strands. On alder, wingless aphids have short, dense strands which are divided into small squares. Each egg is covered with a white woolly coat.
Nymphs resemble wingless adults but are somewhat smaller.
The woolly alder aphid is found east of the Mississippi River. Woolly alder aphids require both alder and silver maple to complete their life cycle. Woolly alder aphid on red maple has been reported rarely. Plants infested with the woolly alder aphid are easily recognized by the presence of large, fuzzy, white colonies of these insects on the foliage, twigs or bark. Although their presence usually causes alarm and is a real nuisance, these aphids apparently cause little permanent damage to their host plants.