Blister Mites (Appleleaf & Pearleaf Blister Mites)

HOSTS

• Apple 
• Pear

DESCRIPTION

Blister mites are tiny mites (too small to see without the aid of a microscope) in the eriophyid group. They burrow under the lower surface of leaves and cause “blisters” that start out green and then turn brown as they age.

BIOLOGY

Adults overwinter under leaf bud scales and emerge with new leaf growth in the spring. They migrate to leaves and feed and reproduce inside tiny blister-galls.

SYMPTOMS

• Raised "blisters" on leaves that start green in spring and by mid-summer become brown
• Leaf yellowing and early leaf drop

GENERAL MANAGEMENT

Treat large infestations in early fall, before leaf drop, when mites are migrating from leaves to buds. Options include carbaryl, horticultural oil, or lime sulfur. Dormant oil applications in spring are also effective. Blister mites cannot be treated in summer.

Monitoring:

Watch leaves for blisters starting in mid spring.

Treatment Threshold:

Very high populations can reduce photosynthesis and thus, tree vigor, and may need to be treated. Trees can tolerate lower populations.

Insecticides:

• Residential: dormant oil alone or with carbaryl; sulfur (single application, do not mix oil and sulfur)\
• Commercial: for delayed dormant application click here; for post-harvest application click here