Fall Webworms

It seems early, but fall webworms have hatched their early season brood. This is the less abundant race of fall webworm that develops in mid-summer and defies their common name. The web starts at the branch tips and becomes enlarged to encompass fresh, green leaves until the web may become two to three feet long. This is more noticeable with the later season race. Because fall webworm damage accrues over the summer, they usually cause little long-term health damage to the trees they defoliate. At any one location, the populations of fall webworms wax and wane so that they are conspicuous and damaging for a year or two and then the populations seem to thin.

Webworms feed on over 600 types of trees, shrubs and other plants. In North Carolina they are most often reported on pecans, persimmons, sourwoods and willows. Small trees infested with several broods of caterpillars may be entirely enclosed in webs. After feeding for four or five weeks, the caterpillars crawl down, spin cocoons and pupate in mulch or soil.

Fall webworms can be managed by pulling down the webs and destroying the caterpillars if the webs are within reach by a pole. If the webs are within reach of a sprayer, several insecticides can be sprayed for control. Only spray foliage adjacent to the web. Insecticides work best when the caterpillars are young, so it is best to treat as soon as the webs are first noticed. A product containing Bacillus thuringiensis or carbaryl is appropriate for homeowner use, while commercial applicators can use B.t. (e.g., Dipel), Conserve, Talstar or one of several other options. View a QuickTime movie clip about fall webworms at http://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/note07/fallwebworm.mov. For more information about fall webworms, see Ornamentals and Turf Insect Information Note No. 46 available on the “web” at http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note46/note46.html.

From: Steve Bambara, Extension Entomologist