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Eriophyid Mites on Conifers (05/27/21)

A recent spruce sample found Eriophyid mites feeding on the discolored needles.

A recent spruce sample found Eriophyid mites feeding on the discolored needles. Eriophyid mites are in the Order Acari and Family Eriophyidae, and they feed on many deciduous and coniferous (spruce and pine) trees and shrubs. These mites are minute (<1 mm in length), white to yellow, carrot-shaped and have only two pairs of legs located near the head. A dissecting microscope is usually needed to see them. If you can’t find the mites, look for the white threadlike cast skins of eriophyid mites giving the plant a fuzzy appearance. These mites like ‘cool’ springs.

For damage symptoms, this spruce Eriophyid rust mite are vagrants on leaf surfaces causing chlorotic, browning, stunting or red patches on spruce needles/branches. Other species cause bladder galls or distorted flowers and foliage.

If mite populations are known to be high, a dormant oil can be applied in early spring before bud break to suffocate the eggs and any recently hatched mites. Other biorational pesticides are insecticidal soap and abamectin. Synthetic insecticides available include bifenthrin, carbaryl and lambda-cyhalothrin. The best timing for chemical control is 7-10 days before bud break.

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Presley Mosher

Interim Diagnostician Director

 

Patrick Beauzay

Research Specialist

 

Janet J. Knodel

Extension Entomologist

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