WSU Extension


Crown gall 
European canker (Nectria canker) 
Fire blight 
Pacific Coast pear rust 
Pear trellis rust 
Powdery mildew 
Pseudomonas blossom blast and dieback 
Stony pit 
Virus diseases 
Apple-and-thorn skeletonizer 
Brown marmorated stink bug 
Codling moth 
Cutworms and armyworms 
Pear psylla 
Pear slug (pear sawfly) 
Pearleaf blister mite 
San Jose scale 
Spider mites 

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Caption: Spider mites under microscope
Photo by: L.K. Tanigoshi
Pear : Spider mites
(revision date: 3/22/2021)

Several species of spider mites may be found on pear leaves, including the twospotted and McDaniel spider mites and the European red mite. They may be various colors including yellow, greenish, brown, or red. All species feed on the leaves, causing a whitish to yellow stippling. More severe damage results in leaves taking on a bronzed appearance. Infested pear leaves often develop small to large necrotic brown spots during hot weather. This is known as transpiration burn and is a common symptom of mite feeding on pears. Severe cases of transpiration burn can result in premature leaf drop. Most spider mites spin webbing which may be found on the lower leaf surfaces and between leaves and twigs. The European red mite typically produces smaller amounts of webbing than other species.
Management Options

Non-Chemical Management
  • Provide proper culture for trees. Healthy plants are more tolerant of damage, while drought-stressed plants are more susceptible.
  • Predatory mites and insects such as ladybird beetles and green lacewings aid in control of mite populations. Avoid use of broad-spectrum insecticides which kill beneficials.
  • Hose mites from plants with a strong stream of water.
  • 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

Apply superior type oils in early spring just prior to bud swell to manage overwintering eggs for European red mite control. Apply insecticidal soap for other mites. Insecticidal soap sprays must cover all leaf surfaces to be effective. 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.
  • Hi-Yield Dormant Spray
    Active ingredient: oil/pet distillate  |  EPA reg no: 7401-428
  • R-T-U Year-Round Spray Oil
    Active ingredient: oil/pet distillate  |  EPA reg no: 6218-78
  • Safer Brand Insect Killing Soap with Seaweed Extract II [Organic]
    Active ingredient: potassium salts of fatty acid  |  EPA reg no: 42697-59
  • 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
Caption: Spider mite damage on leaf
Photo by: A.L. Antonelli