I'm attached two pictures of holes in the trunk of a mature Stewartia pseudocamelia. Can anyone tell me if this is an indication of a problem with the tree? or what has made these holes. Thank you. Susie
The holes look like the work of a sapsucker, probably the Red-breasted Sapsucker. The holes don't indicate any problem with the tree but can be entry points for disease. Wrapping something around the trunk to discourage the sapsucker from feeding on your tree would definitely be beneficial.
Good irrigation during times of drought can create greater sap and water flow. The bugs don't like this and usually don't damage trees. That can go for Bronze Birch Beatles and Pine Mountain Beetle problems as well as others.
I have similar looking damage on my Mountain Ash trees. Unfortunately, it took me some time to notice the growing damage and after that to catch the culprits in the act. By then the damage became so bad that nothing could be done to help the trees. You can see two of them on the picture. But there were literally swarms of hornets slowly killing my trees. They use chewed bark as a building material for their nests.
Regardless of what types of hornets they are, they didn't create those holes in the tree. Hornets and paper wasps use dead wood for building their nests; they don't carve holes in living trees. They might chew around the edges of the holes after the wood dries out, but they don't initiate the holes, which were originally created by a sapsucker. Most likely, the hornets are after the insects attracted to the sap in the holes.