Q.fungus on plum tree
Is this white fungus on one main branch of our plum tree likely to be dangerous to fruit on the other main branches? Should I cut off the affected branch or, as the tree just beginning too bud after the winter, is it too late? The tree was pruned in the autumn but there was no sign of this fungus then.
This could be just a Lichen on the tree branch, which would be harmless.
A fungus would likely spread and could be more of an issue for the health of the tree.
Inspect the tree more closely, the leaves, trunk. Look for any other signs of disease.
This article will help with the most common issues.