Have you seen this?

We are seeing damage to our oak trees this year. Small limbs are just falling off, and as you can see by the photos, the limbs are almost hollow.
We have only seen this on our oaks. A friend of ours is a tree guy, and he believes it is possibly a gall wasp, or some sort of borer insect, and is possibly drought related.
We are going to take some samples to our Clemson ext. office to identify and possibly find out if there is a treatment available.
Any one seen this on their trees????