Oak: Pit scale

• Categories: Oak Oak Insects Ornamental trees Ornamentals
• Last review date: 2026-08-29 08:19

Biology

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

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!

• 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

• 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

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.

• Hi-Yield Dormant Spray
  Active ingredient: Paraffinc oil
  EPA registration number: 7401-428
• Safer Brand Insect Killing Soap Concentrate II [Organic]
  Active ingredient: potassium salts of fatty acid
  EPA registration number: 42697-60
• Azera Gardening [Organic]
  Active ingredient: azadirachtin, pyrethrins
  EPA registration number: 1021-1872
• This list may not include all products registered for this use.