WSU Extension

Hortsense

Caption: Juniper webworm damage
Photo by: A.L. Antonelli
  
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Juniper : Juniper webworm
(revision date: 2/14/2019)


Biology
The adult juniper webworm is a copper-brown moth with white bands on the edges of the front wings. The moth is about 1/2" across. The webworm caterpillars initially feed by mining inside leaves, then gather to feed in small colonies or nests of webbed foliage as they mature. They are yellowish to brownish with dark brown lines on the back and a dark head. The caterpillars overwinter in the nest and resume feeding in spring. Fully mature caterpillars are about 1/2" long. Due to their habit of feeding deep in the plant canopy, damage may be easily overlooked. Damaged foliage turns brown and is covered with dirty webbing.
Management Options

Non-Chemical Management
  • Hand-pick caterpillars.
  • Prune and destroy webs with caterpillars.
  • Several natural enemies help control juniper webworm populations. Avoid use of broad-spectrum insecticides which may kill these predators and parasites.
Select non-chemical management options as your first choice!

Chemical Management


Applications made in late fall, winter or early spring at relatively low temperatures are effective against this pest. 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.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bayer Advanced Power Force Multi-Insect Killer R-T-S
    Active ingredient: cyfluthrin  |  EPA reg no: 72155-39
  • Bonide Captain Jack's Deadbug Brew RTSpray [Organic]
    Active ingredient: spinosad  |  EPA reg no: 4-471
  • Safer Brand Caterpillar Killer/Trees, Shrubs, & Vegetables Conc
    Active ingredient: Bacillus thuringiensis subsp. kurstaki  |  EPA reg no: 42697-23
  • This list may not include all products registered for this use.
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Caption: Juniper webworm damage
Photo by: A.L. Antonelli
Caption: Juniper webworm larva
Photo by: K. Grey