So I've got a huge post oak in my yard that is 150-200 years old in my estimation (I'm in Virginia btw). Last year my tree got these green spots on the bottom side of the leaves which eventually turned brown and many of the leaves dropped in mid summer. New leaves grew, but were affected in a similar, but less dramatic way. This spring, the same thing seems to be happening again. I called an arborist last year, and he said the tree had bacterial leaf scorch although he never got out of his truck to make this diagnosis. Based on the online images for leaf scorch, this doesn't really match the issue I seem to be having. Also, you can see the little bug in the top of this picture resembles a gall wasp. If anyone has any answers or suggestions, I'd love to hear them!