Blister Mites (Appleleaf & Pearleaf Blister Mites)

    Blister Mites (Appleleaf & Pearleaf Blister Mites)

    Early apple blister mite damage. Early apple blister mite damage.

    Mid to late apple blister mite damage.
    Mid to late apple blister mite damage.

    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

    Precautionary Statement: Utah State University and its employees are not responsible for the use, misuse, or damage caused by application or misapplication of products or information mentioned in this document. All pesticides are labeled with ingredients, instructions, and risks, and not all are registered for edible crops. “Restricted use” pesticides may only be applied by a licensed applicator. The pesticide applicator is legally responsible for proper use. USU makes no endorsement of the products listed in this publication.