Warts on oak tree leaves?

Question

I have two oak trees in my yard and they have these wart-like growths on the leaves. They are over all the leaves. They are hard and you rip the leaf when you try to peel them off. Is this a disease? I don't pay too much attention to these trees so it is the first time I'm noticing it. Any ideas?

Answer 1

No it is not a disease. They are called oak galls and they are harmless to the tree...they're also common on maples. They are caused by a tiny wasp that injects her eggs under the leaf surface, which later swells as the young wasp develops inside. No need to do anything about it...I actually think they're kind of neat.