Elm: Elm leafminer

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

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

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

• 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

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

• Bonide Captain Jack's Deadbug Brew R-T-U [Organic]
  Active ingredient: spinosad (spinosyn A+D) [EPA registration number: 4-472]
• Safer Brand Insect Killing Soap Concentrate II [Organic]
  Active ingredient: potassium salts of fatty acid [EPA registration number: 42697-60]
• This list may not include all products registered for this use.

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