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Problem: Ash Flower Gall Mite (Aceria fraxiniflora Felt)
Hosts: Ash
Description: Though most galls are
caused by insects, this one is caused by an eriophyid mite, Eriophyes
fraxinivorus. These tiny mites (about 0.5 mm long) feed on the male flower
clusters of ash early in the season, transforming 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 they form 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 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.
Labeled insecticides include carbaryl, dicofol and horticultural oil.
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
Last Update: 03/10/2005
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