Tall bumpy growths on tree leaves
We just noticed that a large old tree in our backyard seems to be infested or have some kind of disease. The majority of the leaves have growths that are tall and skinny. Some parts of the tree have just a few, but in other areas each leaf might have 30 to 50 growths. We have noticed a large number of small green caterpillars in the area of this tree as well, but we aren't sure if the two go together. Is there anything we can do to treat this tree either now or in the fall or next spring to prevent these growths in the future? Attached is a picture of the tree as well as closeups of leaves with the growths on them.
These are cool looking leaf galls caused by a microscopic mite (an eriophyid mite). Though they may look nasty, they are harmless to the tree. There is no recommend control either. The caterpillars would be a separate issue.