Sap bubble at base of weeping cherry tree
I found this at the base of my weeping cherry tree and figure it could be some kind of borer pest. Any idea what is causing it and what I can do to treat it, if anything?
The sap indicates an injury of some kind. Can't guarantee it's a borer. However, it is extremely common for weeping cherry to be infested and killed by peach tree borer.
One of the ways to prevent this is to keep mulch away from the base of the tree (this attracts egg laying there.)
Actually, mulch should never touch the base of any tree or shrub. It should be kept back a few inches and not be more than 2-3" deep.
Here is a page on managing borers: https://extension.umd.edu/hgic/topics/borers-trees