Flowering Ash Gall Mite ( Aceria fraxiniflora Felt)

Host: Ash Tree

Description: Though most galls are caused by insects, this one is caused by an eriophyid mite called Eriophyes Fraxinivorus. These tiny mites feed on the male flower clusters of the ash tree in the early spring season & in doing so; transform the male flowers into irregular, fringed masses. These masses persist for up to two years and become more noticeable when the leaves drop in the fall. The masses will be green early in the season when they are newly formed, but will turn black as they dry.

Recommendations: As with most galls, the Ash Flower Gall is unsightly but does not harm the health of the tree. The mites are also difficult to control because they are able to enter the flower bud before it is visibly open. If you wish to try insecticidal control, apply the insecticide 7 to 10 days before the bud is expected to open. Try insecticides labeled carbaryl, dicofol, and horticultural oils (dormant oils to be used prior to the buds bursting).

References:

1. Ash Flower Gall Mite, Bugwood, www.bugwood.com
2. Insect and Mite Galls in the Landscape, University of Minnesota Extension, FO-06704, http://www.extension.umn.edu/distribution/horticulture/ DG6704.html
3. K-State Research & Extension