Walnut Blister Mite

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. Western Washington 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. Since western Washington has minimal walnut disease pressure overall, no routine control is needed. Maintain tree vigor and provide adequate water during hot spells.