Poplar: Tent caterpillars

categories: Ornamental trees Ornamentals Poplar Poplar Insects

last review date: 2025-06-28 09:29

Biology

Two species of tent caterpillar are common in Washington. The forest tent caterpillar is about 2″ long at maturity and has a bluish body with black and white markings. This species makes silk mats on branches and trunks.

The western tent caterpillar is the most common species in western Washington. It is dark with orange and black markings. 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.

Tent caterpillars are present in spring and early summer. They can partially or completely defoliate trees, causing some loss of vigor. Badly weakened trees may be killed, but damage is rarely this severe.

Management Options

See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.

Non-chemical Management

Select non-chemical management options as your first choice!

• Pick out and destroy the foamy-looking, grayish, 1/2″ egg cases during the 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.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

• Apply in spring when caterpillars are seen and have begun feeding.
• If Bt is chosen, be sure to apply when insect is feeding.
• Best time is when caterpillars are young.
• Use a spreader-sticker with liquid Bt formulations.
• 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.

Approved Pesticides

Examples of pesticides that are legal for home use in Washington State are listed below.
The list may not include all products registered for this use.

• Monterey Garden Insect Spray [Organic]
  Active ingredient: spinosad (spinosyn A+D) (EPA reg. 62719-314-54705)
• Natural Guard Spinosad Bagworm, Tent Caterpillar & Chewing Insect Control
  Active ingredient: spinosad (spinosyn A+D) (EPA reg. 62719-314-7401)
• Safer Brand BioNEEM Multi-Purpose Insecticide and Repellent Concentrate [Organic]
  Active ingredient: azadirachtin (EPA reg. 70051-6-42697)
• Safer Brand Caterpillar Killer for Trees, Shrubs and Vegetables Concentrate II [Organic]
  Active ingredient: Bacillus thuringiensis subsp. kurstaki (EPA reg. 70051-106-42697)