WSU Extension

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Caption: Pear leaf blister mite damage on mountain ash
Photo by: R.S. Byther
  
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Mountain Ash : Leaf blister mite
(revision date: 6/24/2015)


Biology
The leaf blister mite is a very tiny white, sausage-shaped eriophyid mite. They are seldom visible to the unaided eye. Eriophyid mite feeding on the underside of mountain ash leaves causes development of blister-like spots on the upper leaf surface. These raised spots are generally light green, round and somewhat wrinkled in appearance. Older leaf blisters may turn brown. Severe infestations may result in premature leaf drop.
Management Options

Non-Chemical Management
  • Avoid use of broad-spectrum insecticides which kill natural predators, especially predaceous mites.
  • A strong, direct spray of water may help wash mites from trees. It also reduces dust, which seems to favor eriophyid mite infestations.
  • Hand-pick and destroy damaged leaves to improve appearance of small trees.
Select non-chemical management options as your first choice!

Chemical Management


None recommended.

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Caption: Pear leaf blister mite damage on mountain ash
Photo by: R.S. Byther