Garden Column for the Salisbury Post
Darrell Blackwelder
August 8, 2003

    There is a persimmon tree in my yard that is covered with fall webworms. The large, light gray, silken webs make the tree look downright ugly, not to mention the mess on the sidewalk associated with their ferocious feeding habits.
    Webworms enclose leaves and small branches in their nests making trees around the county look ugly. The late summer pest emerged about two weeks ago and the larvae are preying on trees throughout the county. Outbreaks of fall webworms follow a cycle. This season's outbreak is significant, but outbreaks in other years been much worse.
    Fall webworm larvae have feed on over 85 species of trees in our area. Most of the damage I have observed is on 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.
    This pest over-winters in the pupal stage. Pupae are usually 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 generation 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 crushed 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.
    Bacillus thuringiensis (Dipel) the bacterial insecticide is effective against fall webworms if it is applied when the larvae are small. Spray the leaves when they are incorporated into the nest and eaten.
    As mentioned earlier, fall webworm infestations are generally scattered and do little harm to the tree. Generally, trees will survive these attacks with little or no real damage.

Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. For archived garden columns or other information, visit the Rowan County Master Gardener web site at www.rowanmastergardener.com , e-mail Darrell_Blackwelder@ncsu.edu or phone at 704-633-0571.