Spruce: Spruce spider mite

Biology

The presence of spruce spider mites is indicated by yellow stippling near the needle bases, usually on the lower branches and spreading upwards as the mite population increases. Damaged needles may turn 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. These mites are often worst on dusty roadside 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!

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

Chemical Management

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

• Begin monitoring for spider mite in the late spring or especially during hot weather.
• Horticultural oils, soap-based products and some other products may cause discoloration of spruce needles, particularly on Colorado blue spruce.
• Read labels carefully and test on a small area before application.
• DO NOT APPLY Safer Brand Insect Killing Soap Concentrate II to Colorado blue spruce.
• 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.

• 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.

Additional Images