Pest description and crop damage The cotoneaster webworm is a dark brown caterpillar, 0.25 to 0.5 inch long. It typically ties clumps of leaves together with webbing and feeds within the nests, skeletonizing leaves. The webworm is primarily a problem on Cotoneaster horizontalis (rock cotoneaster).
Biology and life history The caterpillars feed during the summer and fall, overwintering in nests on the plant and pupating in the spring. The dark gray, night-flying adult moth emerges in the spring to lay eggs.
Hand-pick and destroy larvae; prune out nests.