Question
I have a young autumn blaze maple with thousands of raised red spots covering the leaves.  They are about 1/16 inch in diameter, cluster at the base of the leaf & seem to follow the veins outward.  Is this a pest, disease, or fungus?  If so, is it detrimental to my young maple?  I have a second young maple with just a few of these raised red spots, and am concerned for the health of both trees.

Answer
Hi Christine:

This may be a gall insect rather than a disease.  I am not aware of it having a significant impact on the tree health.  Try Google-Images- "Maple bladder gall" insects to look for a match. We usually don't recommend a chemical- just rake up and dispose of leaves.

Steve