Oak: Western oak looper
categories: Oak Oak Insects Ornamental trees Ornamentals
last review date: 2025-06-30 10:57
Photo by: S.J. Collman
Biology
The Western oak looper feeds mainly on the foliage of the Oregon white (or Garry) oak (Quercus garryana).
Mature larvae of the Western oak looper are about 1″ long and light brown with black spots when mature. They move in a characteristic “looping” or measuring-worm fashion.
The adult moth is yellowish to dark brown. Severe infestations are rare but can result in almost total defoliation of trees. No permanent damage is done by occasional outbreaks.
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!
- Severe outbreaks seldom occur.
- Provide proper culture. Healthy trees can better tolerate insect damage.
- Hand-pick caterpillars when practical.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
- Apply in July, or early August when larvae are feeding.
- It is mostly a pest in Oregon.
- 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.
WSU Extension programs and employment are available to all without discrimination.
Evidence of noncompliance may be reported through your local Extension office.