Had them bad in WV about three years ago. It was so bad, you'd ride through the woods and think it was winter with little leaf cover. There is some kind of blight that kills them after it rains though. The key is to kill enough that next year's numbers are much lower. If trees get hit a few years in a row, they're done.

Edit: Sorry Doug........I was trying to edit MY post. LOL After 7 yrs you'd think I would know whatI'm doing here.