Leaf Blister Mites

Hosts

Apple, pear

Biology

Pear-leaf and apple-leaf blister mites are microscopic worm-shaped mites in the eriophyid group.  Adults overwinter under leaf bud scales and emerge with new leaf growth in the spring.  They migrate to leaves and feed in colonies inside tiny blister-galls.

Symptoms/Damage

Newly formed leaf blisters are green and then turn brown as the leaves age; severe infestations can deform fruit and reduce tree vigor.

Monitoring

Watch leaves for blisters.

Treatment Threshold

High populations can reduce photosynthesis and thus tree vigor.  Lower populations can be tolerated.

Degree Day Model

None

Management Considerations

Cannot be treated in summer.  Horticultural oil, sulfur, or carbaryl in fall or spring is most effective.