Maple Gall Mites
Author(s) P. J. Pellitteri, C. F. Koval, D. L. Mahr
Maple leaves frequently develop growths or swellings known as galls. These are caused by microscopic mites. If a tree is heavily infested, its foliage becomes distorted and drops prematurely. But usually the injury is only temporary, and the tree vigor does not deteriorate significantly.
Three common types of gall mites infest various maple species in Wisconsin: maple bladder, maple spindle, and erineum gall mites. This fact sheet covers all three types of mites as well as effective means of controlling these pests (2 pages; 2006).