I have a weeping cherry tree in my yard that was trouble free for a few years then last year I noticed it had about three spots very near the base of the tree oozing sap which dries like tar. I don’t believe the tree has had any damage from mowers, deer etc. Is there something I should be doing with this or just let it be?
It could be that there are borers (insects) that have punctured the bark and the trees is bleeding sap which then turns black due to mold. In this case you could treat it with a systemic insecticide (Bonide annual tree and shrub insect control) when it leafs out later. I’d postpone the treatment until after the flowers finish to make sure you aren’t harming the bees. One application is enough.
Another possibility is that it has picked up a disease called “canker” or “black knot” and, if this is the case, there isn’t much that can be done.
HERE’s a link to a page that you might find helpful in determining what exactly the problem is. If you can take some pictures of the problem and show them to the folks at the garden center, they may have a better chance at an accurate diagnosis.