WSU Extension


Anthracnose (Blotch) 
Thousand cankers disease 
European fruit lecanium 
Walnut aphid 
Walnut blister mite 
Walnut husk fly 
Walnut twig beetle 

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Caption: Walnut blister mite damage
Photo by: R.S. Byther
Walnut : Walnut blister mite
(revision date: 5/20/2014)

The walnut blister mite is an eriophyid mite. These tiny, whitish, sausage-shaped mites cause raised green to yellowish blisters on the upper leaf surfaces. Beneath the blister, on the underside of the leaf, is a yellow to orange felt-like mass, in which the mites can be found. Later in the season, the velvety areas turn brown. The blisters can be large and unsightly, but damage caused by the walnut blister mite is primarily aesthetic.
Management Options

Non-Chemical Management
  • Provide proper culture. Healthy trees are unharmed by some blister mite feeding.
  • Avoid use of broad-spectrum insecticides which kill natural predators, especially predacious mites.
  • A strong, direct spray of water may help wash mites from trees. It also reduces dust, which seems to favor eriophyid mite infestations.
Select non-chemical management options as your first choice!

Chemical Management

None recommended


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Caption: Walnut blister mite damage
Photo by: R.S. Byther
Caption: Walnut blister mite damage
Photo by: A.L. Antonelli