I don’t know about you but I have certainly seen enough ‘webworms’ to last me until fall of next year! Sometimes the fall webworm is mistakenly called the tent caterpillar, and I don’t like those either. But there are two major differences, the tent caterpillar forms webs in the fork of a tree in late spring into summer while the webworm forms webs at the end of the tree branches in late summer into fall. If you want to get technical about it, their scientific names differ, too each having a different genus and family but in the same order ‘Lepidoptera’. For this article it is about the fall webworm that we see at the end of branches in many trees during this time of year.
The fall webworm (Hyphantria cunea) is a moth known principally for its larvae stage. Generally, the moth is white in color although some may have dark colored marks. It is native to North America, ranging from Canada to Mexico. It is one of the very few insect pests that has been introduced from North America to other continents. And the bad news is that they can now be found around the world even in the coldest of countries. There is usually only one generation produced per year in cold countries but unfortunately for us, there may be as many as four generations in South Carolina. The female webworm moth after mating in spring will lay between 400 to 500 eggs on the underside of leaves of most of our hardwood trees and fruit trees with pecan and hickory being the preferred. These eggs hatch in about a week producing hundreds of tiny, hairy worms with yellowish-white bodies and black heads and some with brownish bodies with red heads. The fall webworm will feed for about four to six weeks. They immediately begin to spin a small silken web over the foliage on which they feed. As they grow, they enlarge the web to enclose more and more foliage; and, can occasionally defoliate a tree but rarely kill it. My Yoshino Cherry Trees are a favorite of these worms leaving behind only their ugly webs. Once these webworms are full grown, the larvae wanders from the tree in search of protected areas usually on or in the soil to pupate. This cycle repeats itself with the last generation surviving the winter in cocoons in the pupae stage and can be found in leaf litter and crevices of tree bark. Adult moths emerge in the spring, mate and unfortunately , start the life cycle again.
The good news is that you can control them by removing and destroying most of their webs. Also, Conserve Insecticide (spinosad) can be used when the webworms are small. Just be sure to tear apart the web so the insecticide can make contact with the worms. Conserve is a very safe insecticide that will not harm beneficial insects that feed on fall webworms. But as a bird lover, I like best of all, tearing the webs open and giving birds the opportunity to feed on hundreds of fall webworms!