Common Insect & Mite: Tent caterpillars

Photo by: S.J. Collman

Use IPM (Integrated Pest Management) for successful plant problem management.

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

• 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.

Revision Date:5/6/2009

Bacillus thuringiensis (Bt) can be applied within tents. Make certain that the product that you purchase is labeled for the target host. Carefully read and follow label instructions. Use a spreader-sticker with Bt.

---