Adults first appear in late May to mid-June. They are most abundant in late June and July. The first-generation females deposit eggs in midribs of young leaves. In Pennsylvania, second-generation adults, which may develop as early as the first week of July, often are numerous during August and early September. The occurrence and timing of a second generation is not documented in Vermont.
Symptoms range from a light stippling to a severe chlorotic or bleached appearance of entire leaves.
In heavy infestations, the leaves may curl, turn brown, and drop prematurely. Black spots of excrement render an unaesthetic look to the lower surfaces of infested leaves. Infestations were especially severe in Chittenden County. Small, oval adults, black or brown with yellow markings, lay eggs in stems of new growth. There is only one generation a year, the eggs hatching the next February or March when leaves are developing.