Question
I have a pin oak about ten years that appears to be dying.  It has kill all grass in a perfect circle at the drip edge. The gall wasps have been on other oaks this one doesn't have a single gall.  While the other oaks are leafing out normally this one seem to leafing out about 50% with most of the dead limbs being in the top.

Answer
William:
If this tree looked good last year, something rather than a disease or insect may be the culprit. Check the tree for any loose bark near the base or any visible damage to the bark near the affected part of the canopy. Have there been any lightning (electrical storms)strikes?  If you care to, send a photo of the tree and this circle.  Review your image on your computer to be sure it is in focus before sending.

Regards
Steve