What am I dealing with?

I have many many leaves on a mature maple with these bumps. What am I dealing with? Will it harm or kill the tree?

 

Maple leaf galls probably induced by mites

 

There's a fungus among us. A toad peed on the leaf?
Not sure what it is but ive seen similar on multiple species.

 

I've seen that a lot but don't know what it is. Didn't seem to stress the trees though.

 

There's a bunch of little insects that lay an egg and take advantage of the tree leaf growing around it. . Some times it's not an insect at all but just the tree reacting to damage a bug,mite, fungus, etc did by growing a gall around the wound. I see them a lot on oak tree and maple tree leafs quite often here. There's a wasp that lays an egg on oak tree leafs here that (either the wasp or the wasp egg) excretes a hormone that really makes the leaf respond by growing a big round fuzzball with a shell around the "egg"/larvae. Doesn't hurt the tree.

 

They are mites and once they are encapsulated you can't, kill them. They start out crawling on the bark so you can spray and prevent further propagation. They DO NOT harm the tree as they are parasites and need the tree. They overwinter in the bark and spraying in early spring is best.