Maple Leaf Galls

Question

We have a couple of maple trees that are a couple of years old. They have got what look like red eggs on almost every leaf. We would like to find out what they are and what we can do for them.

Minnesota Master Gardeners say:

 These abnormal growths are probably maple leaf bladder galls. They seldom result in harm to the tree so control is not warranted.

A University of Minnesota fact sheet, Insect and Mite Galls in the Landscape, is available on line at http://www.extension.umn.edu/distribution/horticulture/DG6704.html

The fact sheet discusses how the galls are formed and also contains images of several different types of galls.