Pest profile

Pearleaf Blister Mite

Eriophyes pyri · Sarcoptiformes: Eriophyidae[2]

Pearleaf blister mites are microscopic mites that feed inside pear leaves, raising reddish to yellowish-green blisters that turn brown or black as the tissue dies.[1]

Pear leaf dotted with brown blisters caused by pearleaf blister mites
Pear leaf dotted with brown blisters caused by pearleaf blister mites. (c) Jon Mortin, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Adults are about 0.009 inch long and visible only under magnification: light to amber yellow, wormlike and tapered, with two pairs of short legs at the front.[1]
  • Blisters are reddish to yellowish green at first and turn brown or black later in the season.[1]

Where it lives

The PNW Insect Management Handbook covers it on flowering pears in Pacific Northwest landscapes.[1]

US map: public records from 18 states since 1990 (GBIF).

Biology and life cycle

Mature females overwinter under outer bud scales and burrow into swelling buds in spring, so blisters are already there as leaves unfold.[1]

At petal fall they move to more leaves or fruit; several generations develop inside the blisters each year.[1]

Mites spread from tree to tree on the wind or carried by birds and insects.[1]

Damage and signs

  • Leaves may drop early, and losing foliage weakens trees and cuts shoot growth and flowering.[1]

Health risk

It feeds on plants; the PNW Insect Management Handbook mentions no risk to people.[1]

Control

Prevention

Scouting doesn't help in the current season, since mites are already inside when blisters show; plan any action for the following fall or winter.[1]

Water trees properly, since drought-stressed trees are more susceptible, and avoid excess nitrogen.[1]

Traps and physical control

Wash mites from the tree with a strong stream of water.[1]

Biological control

Phytoseiid predatory mites almost always keep it under control if broad-spectrum insecticides are avoided; heavy rain and cold also suppress it.[1]

Common questions

What are the red blisters on my pear tree's leaves?
Likely pearleaf blister mite, a microscopic mite that feeds inside the leaf.[1]
Should I spray when I see pearleaf blisters?
No. By then the mites are inside the leaves; plan any action for the following fall or winter.[1]

Sources

  1. Pacific Northwest Pest Management Handbooks (OSU, WSU, University of Idaho), “Pear, flowering (Pyrus): Pearleaf blister mite (Insect Management Handbook).” pnwhandbooks.org/insect/hort/landscape/hosts-pests-landscape-plants/pear-flowering-pyrus-pearleaf-blister-mite (accessed 2026-10-06)
  2. iNaturalist, “Eriophyes pyri taxon page (order and family).” www.inaturalist.org/taxa/389186 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.