Howdy, I have a huge oak tree that last year lost some leaves from one side of the canopy. I got concerned and had an arborist come out. He really didn't give me any info but did a dna test and recommended a treatment once he got the results back from the lab. I couldn't tell you what he said it was diagnosed with, but the treatment was drilling holes around the base of the tree and injecting something in it. That apparently didn't help anything because it is doing the same this year and is slightly worse. I'd love to hear opinions on here about what it is. I just hate to lose it because it's so old and beautiful.