Gall Mites and Midges
Hosts: Bladdergall: silver and red maples; Spindlegall: sugar maple; Erineum: many species of maple; Gouty vein midge: sugar and red maples.
Evidence: In spring as leaves expand, look for characteristic gall formations on the upper surfaces of leaves (a,b,c,d).
Life Cycle: For gall mites, there are several generations per year. Adults overwinter in cracks in bark. Gall development is initiated as adults feed on developing buds in spring. The female becomes enclosed in the abnormal growth, and lays eggs within. Eggs hatch and mites reach adulthood and leave the galls rather quickly. These adults may initiate the development of more galls. The gall midge probably has one generation per year, with the winter spent in a cocoon in the soil. Adults emerge in spring and lay eggs in developing buds.
Management: Though these mites and midge cause galls that may be aesthetically undesirable, they are not a serious threat to the host tree. Handpicking infested leaves, which tend to be most common on lower branches, can help reduce populations. Systemic insecticides can be applied in spring or early summer to kill mites.
Figure a: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT.
Figure b: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.
Figure c: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT.
Figure d: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.
Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 31-32, 442;
Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs. 2nd edition. Cornell University Press. p 482-483;
Martineau, R. 1984. Insects Harmful to Forest Trees. Agriculture Canada Government Publishing Centre, Supply and Services, Ottawa. p 183-186;
Rose, A.H. and Lindquist, O.H. 1982. Insects of Eastern Hardwood Trees. Canadian Forest Service Publication, Forestry Technical Report 29. p 121-123.