WSU Extension

Hortsense

Caption: Spider mites under microscope
Photo by: L.K. Tanigoshi
  
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Pine : Spider mites
(revision date: 2/14/2019)


Biology
Spruce spider mites feed on older needles, causing yellowish to gray stippling (tiny spots) and needle chlorosis or yellowing. Fine webbing is usually present on infested needles and twigs. The mites are tiny and greenish or yellowish in color. They overwinter as eggs on the host and can hatch as early as April or May.
Management Options

Non-Chemical Management
  • Wash mites off trees with a strong stream of water where possible.
  • Reduce levels of nitrogen in foliage to decrease spider mite reproduction. Switch to a slow-release or low-nitrogen formula.
  • Avoid use of broad-spectrum insecticides which kill parasites and predatory mites.
Select non-chemical management options as your first choice!

Chemical Management


Apply oils in early spring to smother over-wintering eggs. Begin monitoring for spider mites in the late spring or especially during hot weather. Apply one of the following for nymph or adult mites. 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.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • R-T-U Year-Round Spray Oil
    Active ingredient: oil/pet distillate  |  EPA reg no: 6218-78
  • Safer Brand Insect Killing Soap Conc II [Organic]
    Active ingredient: potassium laurate  |  EPA reg no: 42697-60
  • This list may not include all products registered for this use.
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Caption: Spider mites under microscope
Photo by: L.K. Tanigoshi
Caption: Spider mites and eggs under microscope
Photo by: Unknown