Fall Webworms Are Likely to be Found Soon

The fall webworm, Hyphantria cunea (Drury), is usually noticed when the light gray silk webs are discovered on trees in late summer and early fall. They are considered pests of shade and ornamental trees in urban areas, by attacking more than 88 plants as they enclose leaves and small branches with their webs. Four generations occur in the south Texas, with 2 to 3 generations occurring in northern Texas. The last generation in the fall is usually the most damaging.
The caterpillars build webs soon after hatching and they will remain inside the web consuming the tender parts of the leaves. If the caterpillars eat all of the leaves within the web, then new foliage will be enclosed within the webbing. These caterpillars are 1 inch in length, pale yellow or green in color, and covered with white and black tufts of long hair. The caterpillars will molt 6 or 7 times before dropping to the ground to pupate. The pupae overwinter and the adult moths emerge the following spring.

Some Control Options:
Some Non-Chemical Control Options:
1)Small webs can be removed by pruning and destroying the infested portions of branches.
2) A stick or pole can be used to snag individual webs to allow natural enemies such as yellow jackets, paper wasps and birds to eat the webworms.
3)Bacillus thuringiensis, B.t,. is effective against fall webworms if it is applied when the caterpillars are small. It is better to apply after the eggs hatch and the web is not so dense.

Some Chemical Control Options:
Chemicals should be applied after eggs hatch, since they are most effective on young caterpillars. Insecticides such as those containing spinosad and tebufenozide as active ingredients can be used. Multiple applications may be needed as generations continue.

Fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae), web on pecan. Photo by Bart Drees, Professor and Extension Entomologist, Texas A&M University.