WSU Extension

Hortsense

Caption: Spider mites under microscope
Photo by: L.K. Tanigoshi
  
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Ornamental Cherry : Spider mites
(revision date: 3/10/2017)


Biology
Spider mites are tiny, eight-legged, and yellowish to brown in color. Their feeding causes mild to severe stippling (little specks or dots) on leaves. Usually yellowish or bronzish, stippling can, in severe cases, cause leaves to drop. Fine webbing is often present, especially on the underside of leaves. Mites may be found on either leaf surface and can be more damaging during dry, dusty conditions. Spider mites overwinter as fertilized females in litter and duff, usually away from the tree.
Management Options

Non-Chemical Management
  • Predaceous mites and insect predators such as ladybird beetles may naturally control spider mite levels. (Predacious mites can be purchased and released.) Avoid use of broad-spectrum insecticides that can kill these natural predators.
  • Wash spider mites from plants with a strong stream of water.
  • Keep plants healthy to increase pest tolerance.
  • Switch to slow-release or lower-nitrogen fertilizers. High levels of nitrogen in the leaves can increase spider mite reproduction rates.
Select non-chemical management options as your first choice!

Chemical Management


Begin monitoring for spider mite in the late spring or especially during hot weather. Soaps may need to be applied several times. 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.
  • 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.
Images
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Caption: Spider mites under microscope
Photo by: L.K. Tanigoshi
Caption: Spider mite damage on leaf
Photo by: A.L. Antonelli
Caption: Spider mite webbing
Photo by: A.L. Antonelli
Caption: Spider mites and eggs under microscope
Photo by: Unknown