The leaves look sort of like a hickory. Do the small branches have a lot of curves and angles? It could be that. With sap oozing, there probably is disease involved.

My hickories keep the squirrels alive, along with the acorns, and give good shade. Lot of small branch drop, though.
Sunny

I think it is a wild black cherry but I can't see the bark. Cherry has little horizontal lines on the younger limbs.

Here is a link that might be useful: black growth

This post was edited by helenh on Mon, Sep 23, 13 at 12:25

Here is a remedy if that is what you have:

Here is a link that might be useful: what to do about the black growth

I think you're right about it being black cherry, Helen.
Sunny

Most certainly black cherry. The black knots are so widespread among black cherry in this region that you might as well resign yourself to never totally getting rid of it. We usually just cut them down if it is too bad or at least cut out the bad parts. They are kind of a nuisance tree anyway, spreading everywhere from seed. Almost invasive.

Sandy