That lumpy looking thing is some kind of fungus - does anyone know what kind? Could this kill my Santa Rosa plum tree? Should I dig it out or will that just spread it? Note: There is a very large Valley Oak tree in the yard behind mine and about 25-30 feet away from my plum tree. I have tried to look up photos of Oak Root Fungus but haven't come up with anything that resembles this yet. I once tried to grow a greengage plum which lasted about 2 years then shriveled up and when I finally dug out the rootstock roots, one had something like this on it, though smaller. I am in San Mateo, CA and the soil (in this tree's little hill) is 2-3 ft of topsoil, then 3-4ft of clay+crushed sandstone, then ancient bay bottom clay pillow.

Thanks, Jane