How To Control Fall Webworms
Ever notice a big mass of webbing on a tree? It’s most likely made by a tent caterpillar or Fall Webworm. Fall Webworms are not to be confused with the eastern tent or the forest tent caterpillars. The main difference between them is the time frame in which they are active. According to Jerome F. Grant (Professor-Entomology and Plant Pathology), the eastern and forest tent caterpillars are only active in the spring. The fall webworm, however, is active from in the spring through fall with three generations occurring each year here in Tennessee. Read on to learn how to control Fall Webworms.
The fall webworm forms large web nests that cover the ends of the branches. They enlarge the nest as they continue to feed. Each generation can feed four to eight weeks. You may see two races of fall webworms here in the Knoxville/Oak Ridge area. The Blackheaded Fall Webworm is yellowish or greenish with two rows of dark bumps that border a dark stripe. The Redheaded Fall Webworm is brownish orange or yellowish tan with orange red bumps.
Fall webworms can attack many types of trees including but not limited to persimmon, pecan, hickory, black walnut, sweetgum, American elm, maples, and sourwood. Although they are not considered a serious forest pest, fall webworms can completely defoliate small trees in the landscape.
Controlling Fall Webworms
To control Fall Webworms and prevent defoliation, it is probably best to use a chemical control on smaller trees and shrubs that are infested. Willow Ridge recommends using Thuricide® at the rate of 4 teaspoons per gallon of water. Using Ortho® Dial N Spray hose end sprayer with the setting on 4 teaspoons and the spray nozzle in the jet position. You can penetrate the web nest with the jet spray. This will thoroughly saturate the leaves on which the worms are feeding. On larger trees, remove the web nests that can be reached. Don’t worry too much about the nests high up in the tree.
As always, read instruction label on any chemical product you use and call Willow Ridge Garden Center at 865-481-3825 with any questions you may have.