gld, your poor oak tree. I've never seen anything like that either. I thought june bugs only ate fruit. Can you spray them with something? The samething that kills Japenese Beetles will kill june bugs.

Could the Junebugs just be going after the sap? Maybe something else is actually causing the damage. You should post this in the Pest and Diseases forum and see what they say there. I think it's a pretty active forum so maybe someone will know.
I'm worried that some of my trees were weakened by the ice storm damage and might be more likely to have problems with borers and diseases this summer.

christie, that's a good idea. I took another shot this morning. I am sure that is what is happening.

My hunch is a trig girdler or stem girdler. Look it up on google and see if that's it. They cause little damage, but you can stop the cycle by cleaning up under the tree because they lay eggs in the small twigs that fall to the ground. Keep it tidy all summer and into the fall, and the problem should be much less severe in the following years.