Walnut Blister Mite
Aceria erinea
7 host plants
Last updated
Walnut blister mites (Aceria erinea) cause small, blister-like galls on walnut leaflets that eventually turn brown and fall out, leaving shot holes. Affected foliage appears stippled and eventually yellows. This microscopic mite favors warm, moist conditions. Cool-climate walnut plantings rarely experience significant damage due to climate conditions that limit mite reproduction.
Monitor walnut foliage for the first appearance of blisters in late spring. For severe infestations in warmer years, spray sulfur starting at bud break and repeat every two weeks through early summer. In cool-climate regions with limited walnut cultivation, no routine control is typically needed. Maintain tree vigor and provide adequate water during hot spells.
Quick Reference
Adults of these mites (Eriophyidae) are very tiny and can be seen only under magnification. They are light to amber yellow, cylindrical, tapered at the posterior end, with two pairs of short legs at the front of the body. The overall appearance is that of a small worm. Immatures appear similar to the adult but are smaller. Feeding on leaves causes reddish to yellowish green blisters; blisters turn brown or black as the tissue dies later in the season. Leaves may drop prematurely. Loss of...
Cultural Controls
- 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.