Pear leaf blister mite, Eriophyes (=Phytoptus) pyri , is an eriophyid mite found on pear, Pyrus sp. Young trees can be damaged by severe infestations.
The mite is difficult to manage once it moves into the blister-like domiciles it creates by feeding on the leaf tissue in the early spring. By petal fall, the mites will lay eggs and remain protected from predators within the leaf blisters. The mites overwinter under the outer scales where they feed on the developing buds.
Management is often timed for the fall to treat the mites while they are in the outer bud scales. Delayed dormat applications also target the bud scales with oils. Timing during the season is best done prior to their movement into the leaf blisters after petal fall. A Degree Day model developed by Bergh and Judd showed 50% of the population emerge from overwintering sites by DD 112 (base 42.8 F.). The predatory mite, Typhlodromus occidentalis, will feed on the exposed mites but do not provide economic control. See Chemical Control of Nursery Pests section of the PNW Insect Management Handbook.
UC IPM Online: Pearleaf blister mite
This is a good site for biology and images and management ideas although it is geared to fruit production rather than nursery stock. Degree day information can be found here.
Pearleaf and appleleaf blister mite. Orchard and Pest Management Online. Washington State University. Good life cycle information the PNW.
Bergh, J. and G. Judd. 1993. Degree-Day Model for Predicting Emergence of Pear Rust Mite (Acari: Eriophyidae) Deutogynes from Overwintering Sites. Environmental Entomology 22(6):1325-1332.
Orginal publication: 9-18-2008
Latest update: 4-17-2019
Author: R.L. Rosetta, Extension Nursery Integrated Pest Management, Department of Horticulture, Oregon State University
Page last modified 4/17/19
Pear leaf blister damage
Pearleaf blister mite damage on 'Chanticleer' pear
Pearleaf blister mite damage on new growth of 'Chanticleer' pear
Pear leaf blister mite damage
Pear leaf blister mite early damage on "Trinity" pear
Pear leaf blister mite damage, older blisters on leaf underside