NC State Extension Publications

Description and Biology

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Beech erineum mites, Aceria ferruginea, are microscopic eriophyid mites that feed only on American beech trees. The mites are very small (0.2 mm long). They apparently overwinter on the bark or in the buds of beech as a special reddish females that crawl to the petioles in early spring just as the new growth emerges from the buds. These mites feed on the leaves and cause the cells on which they feed to develop into a velvety pale yellow to pink patch in which the reddish forms lay their eggs. From these eggs, whitish females and males develop and reproduce throughout the growing season. Once the leaves are fully expanded, the mites can no longer induce gall formation. In late summer as the erineums dry out, a generation of reddish mites migrates to the buds where they overwinter inside, becoming active in the following spring. The galls are not likely to cause lasting injury to the beech nor will these mites infest any other kind of ornamental plant.

Erineums caused by Aceria ferruginea on beech

These unusual galls are caused by the beech erineum mite, Aceria ferruginea.

Photo by Charles Smith (Strick Tree Services)

Eriophyid mite Illustration. A typical eriophyid mite has only four legs at the front end (two on each side)

Eriophyid mite.

Host Plant

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American beech is the only known host of the beech erineum mite. The mite causes velvety bumps on the lower leaf surface that eventually dry out and turn brown. Beech erineum mites cause neglegible damage to the overall health of an established tree.

Residential Recommendation

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Eriophyid mites in general are susceptible to Sevin insecticide. Should the decision to treat be made, the infested tree could be treated in late winter to kill the overwintering mites or anytime once the new growth has emerged and hardened off a little.


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For assistance with a specific problem, contact your local N.C. Cooperative Extension Center

This Factsheet has not been peer reviewed.


Professor and Extension Specialist
Entomology & Plant Pathology
Professor Emeritus
Entomology & Plant Pathology

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Publication date: Nov. 5, 2013
Revised: Oct. 9, 2019

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