Pest description and damage The cotoneaster webworm is a dark brown caterpillar, 0.25 to 0.5 inch long. It typically webs leaves together and feeds within tubes snaking along the branches. Besides unsightly webbing, larvae skeletonize leaves. Death of branches can occur. The webworm is primarily a problem on Cotoneaster horizontalis (rock cotoneaster) and only in some years.
Biology and life history The caterpillars feed during the summer and fall, overwintering in nests on the plant. They pupate in the spring giving rise to dark gray, night-flying adult moths. Eggs are laid in spring.
Pest monitoring Search for webbing that follows along the main branches among the leaves.
Hand-pick and destroy larvae; prune out nests.
The fact that populations rise and fall indicate that natural enemies are present in most years.
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