Question
We live in Wisconsin and have an Autumn Blaze maple.  We noticed tiny balls on some of the leaves.  The colors of the tiny bumps are pale green, redidsh or dark black.  Is this a disease or an insect infestation?  The tree is young, probably about 5 years old.  Thank you for your time and expertise.

Answer
There are insects that cause small galls on the leaves.  I believe this is what is wrong with your tree.  They will not kill the tree, but will make it look bad.  If you want to treat the tree, I would treat with Bayer Advanced Tree and Shrub Insecticide.  This product is mixed with water and poured on the soil around the base of the plant.  It is taken up systemically and will kill the bugs within a week or so.  It also provides protection from reinfestation for up to a year.  The existing ball will not go away but the product will keep more from forming.  Good Luck.