WSU Extension

Hortsense

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


Biology
Spider mites are tiny, eight-legged and variably colored from yellow or green to red or brown. When viewed through a hand lens, they appear as tiny moving dots. Spider mites typically feed on the underside of leaves, causing yellowish to bronze stippling or speckling. Severely infested leaves may turn yellow and drop from the tree. Fine webbing may be present on leaves or in branch crotches. Hot, dry, dusty conditions are especially favorable for development of severe spider mite infestations.
Management Options

Non-Chemical Management
  • Predacious mites and insect predators such as ladybird beetles may naturally control spider mite populations. Avoid use of broad-spectrum insecticides that kill these beneficial insects.
  • Wash spider mites from plants with a strong stream of water.
  • Provide proper plant culture. Healthy plants are more tolerant of damage.
  • High levels of nitrogen in the foliage encourage spider mite reproduction. Switch to a slow-release or low-nitrogen fertilizer.
Select non-chemical management options as your first choice!

Chemical Management


Begin monitoring for spider mites in the late spring or especially during hot weather. 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