I have a oak tree that has developed some sort of illness. on some of the leaves there is a wad of yellowish brown fur around the center of the leaf. I looked around on the internet but could not fined anything. I live in southern illinois.If any one has any Idea what this is that would be great, also how bad is it for the tree?If you can, how would you get it to stop growing. Thanks. I will try to get a picture up some time soon.
My first thought is that it could be a caterpiller but that is very unlikely at this time of year.
Could be bird droppings
Could also be deposits from insects such as eggs.
Here in CT it is normal to see some leaves on oak trees developing small brownish / orange spots. These are scars that have healed. The source of the scars can be from insects feeding or even damage from hail. The spots are caused by sap leaking out of the wound and then drying into a hard mass.
I don't know the local weather history through the last few months. If it has been wetter than normal it may be a fungus.
If the tree in question is a deciduous oak that will be dropping its leaves soon I wouldn't worry much about it since any treatment that gets applied may end up being a waste since the leaves will soon be falling off. In that case my suggestion is wait until spring when the new leaves come out and then regularly check the foliage to make sure that its not comming back.
Other than the spots on the leaves do they appear healthy, (wilting)