Oak Trees

[Affordabletree]

I have stopped pruning oak trees now due to the warm weather really starting. But I saw an oak tree with what looks like black knot. Can oaks get black knot? I thought it was only cherries and flowering plumbs. This tree is approx 32" DBH and 80' tall with 80% of the canopy covered in what looks like black knot. I told the home owner tree should come down but would investigate whether it could be saved. So is there any treatment? I know cherries and plumbs you can prune if caught early but you have to sterilize the tool you are using in a bucket of bleach water. I think that this tree is far to big and far to covered to save if it is black knot.

 

[Twindad]

I don't believe oaks get black knot. Like you said, it is specific to cherries, plums, and others in the genus Prunus.
What you are seeing is most likely some type of gall. While most galls don't usually cause serious harm to the tree, heavy infestations can. It could also be indicative of other issues weakening the tree.