It sounds like not the exotic epidemics these other theorists are guessing at. SOD is caused by Phytophthora ramorum , which makes many smaller bleeding lesions with a little black sap which I haven't seen attracting insects. We in NC have Phytophthora attacking a lot of red oaks but no one has ID'd ramorum yet. It's already here, I suspect, or at least a matter of time...
Doesn't sound like wilt either, but a bacterial infection. Are the insects feeding on stinky, fermented sap? If yes, this is a pathological type of "slime flux", which kills the bark and eventually can kill the whole tree.
You need to tap the bark to see where it is hollow, then remove those portions because they are dead. Pull away what's loose, but don't tear into attached, living bark, the kind with hard and bright-colored tissue underneath. After you get all the rotten stuff off, hose it down real good.
Now to disinfect the bacteria: Put a solution of 1 part bleach to 9 parts water. Spray the infected wood but don't let too much get on the living bark or get down to the roots. You may need to retreat the infection later if you see it is still active. It's usually most active in June up here but with the weather so crazy now, I'm not surprised you're seeing it now in SC.
I get a lot of calls about hornets on old oaks, and it's always pathogenic slime flux. Can you post a picture? The usual response to a post like yours is "Call a local arborist", but to be honest most of them have read a 20-year old book which describes slime flux as a non-problem so they do not treat it. They are mistaken, imvho.
