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Feeding Inside a Tent of Silk

While very hungry, the webworm caterpillar won’t harm your trees

It’s the fall webworm that’s eating your trees from the comfort and security of webby nests.
    The greenish larvae’s appetite is huge and undiscriminating, extending to 636 different species of trees. Redbuds, walnut, hickory, fruit trees and some maples are favorites of these fuzzy worms.
    Late summer through early fall, when the larvae are most active, is prime time to spot webworms chowing down.
    The webs they spin over foliage give them netted protection against predators as they feed.
    As the larvae grow, they finish off entire leaves, leaving only skeletons. Eventually, they enshroud whole branches in a loosely spun tent of silk.
    Feeding continues through mid-September, when full-grown larvae wander from their host plant in search of protected pupation sites.
    Disturb the larvae and they may twitch and wave their bodies synchronously to ward off predation.
    Devastating as their occupation looks, there’s no need for any but aesthetic concern. Webworms chew on tree leaves late in the season when leaves have done their work and are soon to fall. They don’t eat tree bark or branches, so they rarely cause any extensive damage.
    Don’t confuse fall webworms with bag worms, tent caterpillars or gypsy moths. Bag worms are big now, and they can kill a tree, but each worm is a single individual. Tent caterpillars are active in early spring. More dangerous gypsy moths, which can defoliate a tree, appear in late spring to early summer. Fall webworms attack in late summer or early fall.
    The easiest and most environmentally safe way to get rid of the worms from your trees is to remove the nest. Cut out infested branches or use a garden rake or a strong stream of water from a hose to knock the nest out of a tree.
    Then let Mother Nature do her work. Once the webworms are freed from their nests, birds and stinkbugs devour them.

The Next Stage of Webworms

    What’s next for webworms? a reader called to ask.
    The fall webworm, Hyphantria cunea of the family Arctiidae, lives in larval stages in nests for four to six weeks. Next it pupates in a thin, dark-brown, silk coccon overwoven with bits of detritus. This stage overwinters in the bark and leaf litter at the base of trees. Eventually the moth emerges, hairy with orange and bright yellow patches on the front legs and a wingspan of about an inch and a half.

How can you get rid of these pests. This year they destroyed my hundred year old Butternut tree. It is usually a gorgeous tree but looks awful this year. This is the worst invasion ever. Help.