Fall Webworm

HOSTS; The favourite hosts of the Fall Webworm include Walnut, Cherry, Hickory, Crabapple and Birch trees.  They have been known to feed on at least 88 species of plants.

DESCRIPTION AND LIFE CYCLE; Unsightly tents are appearing everywhere at this time of year.  Fall Webworm is just another insect to plague our trees this season.  Larvae hatch as goldenrod begins to bloom and the (caterpillars) pass through as many as 11 instars on their way to developing into adults.  They create silken tents on the ends of branches.  As they occur so late in the growing season, there is usually no need to control webworm. 

MANANGEMENT; If deemed necessary, the unsightly nests in the lower canopy of the tree can be dislodged with a strong stream of water or with a pesticide such as Bt. (Bacillus thuringiensis).  The nests can be removed but this also removes potentially healthy branches with buds for next year’s growth.  Pruning can be done at any time of day as these caterpillars stay in the web while feeding.

Webworms have many natural enemies including birds, predaceous bugs and parasitic wasps.  Leaving the webs intact allows populations of their natural enemies to develop.

Reference; A Pocket IPM Scouting Guide for Woody Landscape Plants Diane Brown-Rytlewski