Oak and chestnut
Evidence: In winter, look on the bark or fallen leaves for the characteristic white cocoons. During the growing season, examine leaves for caterpillars, molting webs along veins on the underside of leaves, and skeletonized patches. The tiny pale-yellow larvae tend to hang from leaves on silken threads.
Life Cycle: There are two generations per year. Winter is spent as pupae in white cocoons on trunks and leaves. First generation moths emerge in April and May and lay eggs on undersides of fully-grown leaves. Newly-emerged larvae feed as miners, but later instars (full-grown larvae are about 1/4 inch long) feed externally on the lower leaf surface. Molting takes place in small silken webs. Second generation adults appear in July and August.
Management: Ornamental trees are especially vulnerable to this insect. Repeated attacks may result in weakened trees with thinning crowns, dieback, and increased susceptibility to attack by wood-boring insects. Fallen leaves should be raked and burned to destroy cocoons. Population levels can vary widely from one year to the next.
Figure a: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT
Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 128-129;
Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs. 2nd edition. Cornell University Press. p 220-221;
Martineau, R. 1984. Insects Harmful to Forest Trees. Agriculture Canada Government Publishing Centre, Supply and Services, Ottawa. p 144-146;
Rose, A.H. and Lindquist, O.H. 1997. Insects of Eastern Hardwood Trees. Canadian Forest Service Publication, Forestry Technical Report 29. p 150-151.