Darrell Blackwelder column: Fall webworms are making their presence known

Published 12:00 am Sunday, September 13, 2020

In late summer, shade trees throughout the county are often covered with large, light gray, silken webs. Fall webworms enclose leaves and small branches in their nests, making trees around the county look ugly. Fall webworm larvae feed on over 85 species of trees in our area including pecan, walnut, American elm, hickory, persimmon and fruit trees.

This pest begins its feeding in late summer, concentrating its nests to limited areas. Because of this, little real damage is done to most trees.

Fall webworms

This pest over-winters in the pupae stage in the ground but can be located in old nest remains, under loose bark and in fallen leaves. The adults emerge from late May into July, laying eggs. Eggs hatch into hungry larvae, feeding for about six weeks, at which time they drop to the ground to pupate. Two or more generations may occur during the summer.

The nest of sticky material is nature’s way of protecting the vulnerable larvae. Pesticide sprays cannot effectively penetrate large nests. Control of the pest is best done by physically removing the nest. Small nests can be pruned out of small to medium trees. These small nests can be easily destroyed with a stick or cane pole. Do not burn or torch the nests in trees. This causes additional damage to the tree and is a hazard.

Parasites and predators will also control fall webworms. Yellow jackets, wasps and hornets as well as birds, predatory stink bugs and parasitic flies are important predators.

Darrell Blackwelder is the retired horticulture agent and director with the North Carolina Cooperative Extension Service in Rowan County. Contact him at deblackw@ncsu.edu .