What is this fungus like growth on my plum tree?

[NoviceGrower]

It started out small but has begun to spread, what is it and what can I do to kill it without killing the tree?

[imafan26]

It is a fungus. Unfortunately it does not bode well for the health of the tree. most fungus live on decaying matter. The bark is peeling and I don't know if your tree has exfoliating bark or not. It usually means the tree is already dying. The fungus is probably not the cause but the result of the tree's decay.

[applestar]

These ARE fungus/mushrooms that grows on dead wood -- so by the time they appear (fruit) on the surface like this, the particular portion of trunk/branch is dead and colonized by the fungal mycelia. I would think there are no living branches above this point? It's best to cut this section off, sterilizing the cutting tool with alcohol or bleach water and making/repeating with a new clean cut until the cut surface is completely clear of deadwood and you are down to living tissue.

[NoviceGrower]

Yeah you're right that branch the fungus is on is dead. The tree was a graft of a peach and plum tree, and I believe that's the peach side (that never produced anyway) that's dead. I'm going to cut off the dead branch this weekend, is there anything I should put on the stump, something to help seal and heal?