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Ash Flower Gall

July 3, 2006
Ash flower gall is caused by the eriophyid mite, Eriophyes fraxiniflora. Although present every year, this gall is particularly numerous this year. After overwintering near buds, the mites attack the male flowers as they are opening in the spring. Their feeding causes the bud tissue to greatly proliferate, resulting in the clusters of 1/2- to 1-inch, round green galls with irregular surfaces that are being seen now. Not only are these galls more numerous this year, but also the extra attention paid to ash this year in looking for emerald ash borer will cause more of these galls to be noticed.

Because only the male flowers are attacked, this gall-producing mite is not a problem to tree health. However, when the leaves drop to the ground in the fall, these galls, which are then shrunken and brown, hang on the tree through the winter. As a result, the galls are typically noticed during the dormant season.

We primarily recommend that people ignore or learn to live with these ash galls. If the galls are a serious aesthetic problem, the mites can be sprayed in the spring with carbaryl (Sevin) or bifenthrin (Talstar) when the flowers are opening.

Author: Phil Nixon


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