THE VIRGINIAN-PILOT
Copyright (c) 1995, Landmark Communications, Inc.
DATE: Sunday, November 19, 1995 TAG: 9511171162
SECTION: HOME PAGE: G8 EDITION: FINAL
SOURCE: ROBERT STIFFLER
LENGTH: Short : 43 lines
THOSE FLIMSY WEBS you see on the tips of branches of wild cherry, crabapple and other trees are the tents of fall webworms. They are active each fall and often encase an entire tree or shrub.
A similar pest, the Eastern tent caterpillar, feeds in the spring and builds tents in the crotches of trees.
Like tent caterpillars and other defoliators, fall webworms can strip leaves from trees. But because they feed in late summer and early fall, when leaves are near the end of their good life, the webworm rarely causes serious damage to trees, says Michigan State University entomologist Dave Smitley.
``Other pests feed early in the growing season,'' Smitley says. ``When they defoliate a tree, the tree dips into its food reserves to produce a new set of leaves. Repeated spring defoliations can weaken trees and make them vulnerable to other insects, diseases and environmental problems.''
To help you identify a fall webworm, they are 1 inch long, pale-colored, hairy caterpillars. They feed in groups within the silken webs they construct in trees and shrubs.
Because they do little damage, some entomologists say to leave them alone. If necessary, they can easily be removed and destroyed by hand when worms and webs are small.
If webs are large and numerous in hard-to-reach places, you can spray the foliage with Baccilus thuringiensis kurstaki (Bt), which is a bacterial disease considered preferable to spraying with chemical insecticides. Bt affects only caterpillars and does not harm beneficial insects, birds or pets. It can be used on edible fruits just before harvest.
As fall webworms feed and grow, they enlarge the web, which becomes littered with excrement, molted skins and bits of leaves. After feeding and completing that cycle of life, the caterpillars weave silken cocoons under bark or in litter on the ground. Then they emerge as adult moths in July and begin the cycle again. by CNB