WSU Extension

Hortsense

Common Insects & Mites : Tent caterpillars
(revision date: 4/30/2013)


Biology
The most common tent caterpillar in home landscapes is the western tent caterpillar. It typically has a dark body with white and orange or yellow markings and a bluish dashed line down the center of the back. Long whitish or yellowish hairs are found along the length of the body. Adult moths lay eggs in a foamlike mass around current-year twigs, where the caterpillars overwinter as tiny larvae inside their eggshells. In spring and early summer, characteristic tents are made on the tips of branches. Young caterpillars typically feed in large groups in the protection of the nests. Older caterpillars feed in small groups or as individuals. They can partially or completely defoliate trees, causing some loss of vigor. Badly weakened trees may be killed, but damage is rarely this severe. The western tent caterpillar is famous for 2- to 3-year epidemic cycles on many kinds of trees. They almost disappear for several years following outbreaks.
Management Options

Non-Chemical Management
  • Pick out and destroy the foamy-looking, grayish, 1/2" egg cases during the fall and winter. These may be found in bands around twigs or in flattened masses on trunks.
  • Several natural parasites and predators help control tent caterpillar populations. Avoid use of broad-spectrum insecticides which kill beneficial insects.
  • Strip or prune out and destroy nests and caterpillars as soon as noticed. This is best done in early morning or evening, when caterpillars are gathered in the nests.
Select non-chemical management options as your first choice!

Chemical Management

Pesticides are generally not recommended. If you choose to make an application, make certain that the pesticide applied is registered for the host and effective against the pest. Carefully read and follow label instructions. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Images
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Caption: Tent caterpillars
Photo by: S.J. Collman
Caption: Tent caterpillar egg mass
Photo by: A.L. Antonelli
Caption: Tent caterpillars and webbing
Photo by: R.S. Byther