Pear leaf blister mite
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
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
Author: R.L. Rosetta, Extension Nursery Integrated Pest Management, Department of Horticulture, Oregon State University
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