Douglas Fir: Spruce spider mite

• Categories: Conifers Douglas Fir Douglas Fir Insects Ornamentals
• Last review date: 2026-04-28 08:10

Biology

The presence of spruce spider mites is indicated by yellow or bronze stippling beginning near the needle bases. Infestations usually begin on older needles of the lower branches and spread upwards as the mite population increases.

Damaged needles may turn brown or reddish-brown. Fine webbing may cover the needles and twigs. The actual spider mites are very small and vary in color from greenish to orange, dark green, or black, with orange legs.

Spruce spider mites attack many species of conifers. They are easily spread by wind. These mites are often worst on dusty roadside 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!

• Spider mites are probably controlled naturally by predatory mites and rain.
• Try to avoid broad-spectrum insecticides that will kill predatory mites and insects and allow a spider mite population explosion.
• Hose trees with strong stream of water to wash off spider mites (where practical).

Chemical Management

• Apply oils in early spring to smother over wintering eggs.
• Begin monitoring for spider mite in the late spring or especially during hot weather.
• Soaps should be applied in May or early June if mites are present.
• Repeat applications may be necessary.
• 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.

• All Seasons Horticultural and Dormant Spray Oil Concentrate [Organic]
  Active ingredient: mineral oil
  EPA registration number: 4-80
• Hi-Yield Dormant Spray
  Active ingredient: Paraffinc oil
  EPA registration number: 7401-428
• R-T-U Year-Round Spray Oil
  Active ingredient: mineral oil
  EPA registration number: 6218-78
• 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.