Ash flower gall mite

Eriophyes fraxiniflora

This cigar-shaped mite is one of a group of eriophyid mites that cause galls to form on plants. It affects only male ash trees, causing a proliferation of flower buds to form, which results in unattractive galls. Although the galls are unsightly, they aren’t harmful to the tree since they only affect the flowers. Galls start out green, then turn brown to black and persist over the winter. The size of the mite is less than 0.5 mm.


No treatments are necessary, but galls may be pruned off to improve the tree’s appearance.

Ash flower gall mite
Ash flower gall affects only male flowers.

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The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the AgBioResearch, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.