WSU Extension

Hortsense

Caption: Pearleaf blister mite damage
Photo by: C.R. Foss
  
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Ornamental Pear : Pearleaf blister mite
(revision date: 2/14/2019)


Biology
Pearleaf blister mites are tiny, white to yellowish eriophyid mites that feed on leaves and fruit. Damage on leaves is caused by mites feeding inside the leaf tissues, resulting in the formation of pale green to reddish blistered areas on the leaf. Later in the summer these blistered areas will turn brown to black as the leaf tissue dies. Leaf blisters are typically 1/8" to 1/4" in diameter. Severe blister mite infestations can cause leaves to drop. Blister mite damage to fruit consists of russetted, somewhat sunken areas on the skin. These mites overwinter under bud scales, attacking emerging leaves in the spring. Severely infested buds can fail to develop in the spring.
Management Options

Non-Chemical Management
  • Predatory mites help control populations by feeding on exposed mites. They cannot attack mites inside blisters. Avoid use of broad-spectrum insecticides which kill predatory mites and beneficial insects.
  • Provide proper culture. Healthy trees easily tolerate some insect damage and leaf loss. Neglected trees are more likely to be attacked.
  • Removing and destroying infested leaves may help control mite populations on small trees.
Select non-chemical management options as your first choice!

Chemical Management


Apply oil plus lime-sulfur in early spring just prior to bud swell. Chemical management is not effective after mites are protected within the plant tissues. 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.
  • All Seasons Horticultural & Dormant Spray Oil Conc [Organic]
    Active ingredient: oil/pet distillate  |  EPA reg no: 4-80
  • R-T-U Year-Round Spray Oil
    Active ingredient: oil/pet distillate  |  EPA reg no: 6218-78
  • This list may not include all products registered for this use.
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Caption: Pearleaf blister mite damage
Photo by: C.R. Foss