Fall webworm, Hyphantria cunea (Drury), caterpillars feed on more than 100 species of forest and shade trees. Wild Cherry seems to be the preferred host.
The adult of the fall webworm is an almost pure white moth with a wing-spread of about 1¼ inches. The forewings are often marked with small black dots. Two generations a year probably occur in West Virginia. The first adult emerges from May to late June and the second generation adults emerge in July and August. After eggs are laid by the adult, hatch soon occurs and the young larvae or caterpillars begin to spin a silken web over the foliage, enlarging the web as they grow. These webs are toward the tips of branches rather than in the branch crotches as in the case of the Eastern Tent Caterpillar. Young caterpillars are pale yellow, with two rows of black marks along the body. When full grown, they are covered with whitish hairs.
In general, the caterpillars of the first generation are active in June and July, while the second generation is active from July to October. Complete caterpillar development usually requires 5 to 6 weeks. Full-grown caterpillars leave the web and the resting period takes place in a thin cocoon in debris under a tree or in crevices around a building or fence.
Outbreaks of this insect may occur, encompassing tracts several miles in extent. On shade trees, the webs usually occur on an occasional branch. This may not injure the tree appreciably, but reduces its ornamental value. However, occasionally the tree may be almost defoliated, if control measures are not employed.
Natural enemies of various kinds help to control this insect. Birds, insect predators, and internal parasites attack the caterpillars. Clusters of eggs may be destroyed by predators and internal parasites.
