Unlike Oak Leaf Scorch, Oak Wilt is caused by a fungus, Bretziella fagacearum (was Ceratocystis fagaceae). I've sampled 15 tress randomly in the Knoxville area and another 3 outside of Knoxville and had 12 of those tested with molecular techniques - the only method to be certain whether bacterial or fungal infected; I'm happy to report none of them had OLS. Five came back positive (not through molecular analysis but visual estimation, as anthracnose infected. The oak wilt fungus is coming in on rhododendrons, one of the nearly 200 plants that can "host" this fungus. Identifying and differentiating the three diseases can only be done by either growing the pathogen from leaf material or through molecular analysis. My instincts are to not trust visual diagnoses. All three pathogens can kill a tree under the right circumstances and unfortunately, hot dry weather and hot weather can favor death by anyone of them. So - please review the links provided here and water your trees when the temps are >85 with more than 6 days w/o rain.