Fall Webworms

by Wizzie Brown

Webworms can be found on a variety trees and are most well-known for the webbing they create on the tips of branches. Webworms are caterpillars (larvae) of a moth. Caterpillars cause damage by feeding on foliage contained inside their protective webbing.

There are 2-4 generations of webworms that occur each year. The first generation appears April-May and the last generation occurs in the late fall. The last generation is the most damaging generation, which provides these creatures with the name fall webworm.

Webworm larvae are about an inch long when fully grown. They are pale green to yellow with tufts of long hairs projecting from their body. While these are fuzzy caterpillars, they do not sting. Most people notice webbing that webworms create on the tips of branches. Webworms feed within the webbing and use it as protection from predators. When the caterpillars run out of foliage to feed on, they expand the web to encompass new leaves.

To manage webworms, the size and accessibility of the tree needs to be considered. Egg masses can be pruned from trees before they hatch in early spring. Egg masses are on the underside of leaves and are covered with hairs. Small webs can also be pruned from the tree when they begin to form in the spring. Larger webs can be knocked out of the tree or opened with a stick or jet of water which allows predators inside the web to feed on caterpillars. Do NOT use fire to burn the web from trees! This causes more damage to the tree than if the caterpillars continued to feed.
Insecticides are also available for webworm management. Look for active ingredients such as Bacillus thuringiensis var. kurstaki (this product specifically targets caterpillars), spinosad, azadirachtin, or pyrethrins. Webs need to be opened before treatment with a pesticide so that pesticide gets inside the web where caterpillars are located.

Please note that webbing will remain in trees even after caterpillars are dead. Webbing needs to be removed by you or a strong weather event.

For more information or help with identification, contact Wizzie Brown, Texas A&M AgriLife Extension Service Program Specialist at 512.854.9600. Check out my blog at www.urban-ipm.blogspot.com

This work is supported by Crops Protection and Pest Management Competitive Grants Program [grant no. 2017-70006-27188 /project accession no. 1013905] from the USDA National Institute of Food and Agriculture