Elm: Elm leafminer
Photo by: J. O'Brien
Biology
Elm leafminers feed by removing green tissue from between upper and lower surfaces of the leaves. Symptoms of feeding by the yellowish or green larvae include large brown to gray-brown blotches on the leaves.
These damaged leaves may remain on the tree throughout the growing season.
The adult elm leafminer is a small black sawfly. This pest attacks Scotch, Camperdown, English and American elm.
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!
- Natural predators may help control populations.
- Pinch, or pick and destroy, infested leaves to kill larvae.
Chemical Management
IMPORTANT: Always read and follow label directions when working with pesticides.
For more information on using pesticides visit :
- If you choose to use a pesticide, apply when mine blotches are first noticed or at least before late spring when larvae begin to leave the leaves to pupate in the soil.
- Insecticidal soaps must be applied to the exposed larvae.
- 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
If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.
Additional Image
Photo by: A.L. Antonelli
WSU Extension programs and employment are available to all without discrimination.
Evidence of noncompliance may be reported through your local Extension office.