Oak: Pit scale

categories: Oak Oak Insects Ornamental trees Ornamentals

revision date: 2024-06-05 02:04

Small branch appears rough due to brownish scale.
Oak pit scale
Photo by: A.L. Antonelli


Pit scales of oak may be brown, gold, or greenish in color. They feed on twigs and small branches, with young wood most commonly infested. Pit scale feeding causes the tissue of the twig to swell around the insect. The growth makes the scale appear to be in a pit on the bark. Numerous scales on a twig cause it to appear roughened. Adult scales are covered with a hard shell and are about 1/16″ in diameter. Severe infestations cause twig dieback. Heavy infestations of pit scale combined with drought stress or anthracnose, a fungal disease can result in severe weakening or death of trees.

Management Options

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

Non-chemical Management

Select non-chemical management options as your first choice!

  • Prune out and destroy severely infested twigs to help control localized infestations (when practical).
  • Provide proper culture. Healthy trees are more able to tolerate insect damage and are more disease-resistant.
  • Natural enemies may help control scale populations. Avoid use of broad-spectrum insecticides which kill beneficial insects.

Chemical Management

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

  • Apply to control the immature crawler stage, usually in late spring to early summer.
  • 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.