Question
I have a tree in my back yard that we here when I moved in. I have noticed since I moved in that the leaves on the tree have green lump on the back. Is there anything that I can do about them and what are they? I live in Central Ohio if that is any help.

Answer
These are called leaf galls they are made by an insect. Generally the insect lays its eggs on the leaf and the chemical from the egg laying will cause the cells on the leaf to expand and cover the egg. the eggs hatch and the young insect feeds inside the gall.
These galls are not a health problem to the tree and cause little more than a spot on the leaf. the worst case would be the leaves may drop a little sooner than normal. No control is needed. The population will vary greatly from year to year so next year you may not see any galls.
I would not be concerned about this since it will not damage the tree.