Just spread the ashes from pellet stove around lilacs, and found a trunk with 4 or 5 fungal growths. Should these be removed? Should the trunk be cut out after blooming? Should the fungus be left alone? It's an old trunk with lots of buds coming.
The plant appears healthy with lots of new growth, but is among many other lilacs that have no fungus. Can this spread? Is it potentially damaging? Just looked at it again and am leaning to cutting out the old trunk after blooming, don't think we would miss it.
Oh yeah, this can spread. Depending on the type of fungi, spores can be shot from 1 to 10 meters away (3 and 30 feet).
If it is an opportunistic pathogen it could be harmful. Might be a wise idea to cut the area off and remove all traces of the fungus and burn the removed parts.
I'm not by any means saying that all fungi are pathogen, far from it. Actually, less than 1% of known fungi are pathogens but, given that you have lilacs in the immediate vicinity, might be better to ere on the safe side.