Ash Flower Gall Mite
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Acari: Eriophyidae Hosts: Ash species Evidence: These tiny mites (0.5 mm) feed on male flowers, causing swelling of the tissues. Flower clusters become irregularly branched, fringed, distorted gall-like masses (a). The galls are initially green but become black later in the season. Many galls stay on the tree well after the mites have vacated and may be visible until the following spring. Life Cycle: There are several generations during the spring and summer. In the spring, overwintering female mites move to developing male flowers to feed, which stimulates gall formation. Eggs are then laid in the developing galls. After hatching, the nymphs live and feed within the gall tissue. A generation of overwintering females is produced in the fall. These females mate and then move to bark crevices under bud scales to spend the winter. |
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a. Feeding on male flowers by ASH FLOWER GALL MITES causes irregularly-branched, gall-like growths to form. These aborted male flowers may turn black and persist through winter. |
Management: Although the galls caused by these mites detract from the appearance of ornamental trees, infestations do little actual damage to their health. Control measures are not usually necessary.
References:
Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs. 2nd edition. Cornell University Press. p 20;
Rose, A.H. and Lindquist, O.H. 1982. Insects of Eastern Hardwood Trees. Canadian Forest Service Publication. Forestry Technical Report 29. p 225.
