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The Fall Webworm
Fortunately, most of the damage he does by munching leaves is aesthetic. Because they are active in the late summer / early fall when the leaves are weeks away from falling and have already done their job, only trees that are weak to begin with are affected. In New England there is one generation yearly. It winters as a "pupa" in the soil and in June / July the adults emerge and the females begin laying their eggs. The eggs hatch by early August and the larvae spin their web that both protects them from predators and encloses the leaves which they eat for about a month. By late August / early September they begin to crawl down the tree, construct a cocoon and "pupate".
The webworm feeds on at least 88 species of trees in the U.S. As about 36 species of predators eat the webworm, lately the birds, toads, and large insects have been feasting. The webworm should not be confused with either the gypsy moth or the eastern tent caterpillar which also spin webs in treetops. The first obvious difference is timing: the webworm defoliates in the fall, the other two in the spring. The eastern tent caterpillar always forms its thick web in crotches or forks and he ventures OUT to feed, returning to the web at night or during rainy weather. Neither the fall webworm or the tent caterpillar pose the threat of the gypsy moth which is twice the size of the webworm and a voracious eater who can defoliate entire stands in a few weeks. Controlling the webworm is usually limited to removal of the nests by hand, or pruning infected branches and burning them. Spraying is NOT recommended.
© 2001 by David Mather. All rights reserved. No parts of this publication may be reproduced in any form or by any means without the written permission of the author.