I have a large native oak tree in our back yard where there has been no recent soil movement or other activities (where its root system was not likely damaged or exposed to hot air). The tree is about 50 feet tall and the leaves are beginning to turn brown at the outer edges (fairly rapidly) even though one right next to it is fine. A similar oak tree within 100 feet away (behind our property) appears completely dead in a very short period of time. Is this being caused by a root or leaf fungus? Can it be treated quickly to prevent death of the oak tree?
I have both good and bad news. The good news is that Post Oaks only very rarely become infected with the fungus that causes oak wilt, the most serious fungal disease killer of oaks. The bad news is that I really cannot tell what is going on with your tree. Your consideration of root disturbance is smart. I have seen similar situations where there was a sewer line leak--sewage is salty and can cause those symptoms, and where fracking liquid was accidentally released.
Try to get a good look at some new growth. If it looks healthy, whatever happened is probably only temporary and the tree will recover by growing new leaves to replace those. If the new growth looks distorted, It may be possible that there is some other cause such as herbicide damage. Post Oaks are great trees and very tough, but they are sometimes killed by too much water, usually from irrigation, but it may be that the excess rainfall we had this spring was hard on the m.
You can of course call upon an ISA certified arborist to evaluate the situation: http://www.isa-arbor.com/findanarborist/arboristsearch.aspx
While I am reasonably certain this is not oak wilt, an arborist might be able to come up with a definitive diagnosis.
Last week, we had an arborist from Southlake view our Black Jack Oak. He had bad news. 17" of rain in May had encourage a fungus to kill the feeder roots to the tree. Until the hot months began, the need for the feeder roots to gather moisture for the tree was not required. By the time the tree needed water, it had few feeder roots to provide it. There is NO new growth and less than 5% green leaves on the tree after about 10 days (even while watering it lightly every day). The arborist indicated that the fungus had done its damage and treating the tree was a waste of money. Hard to believe that a tree that took that long to get that big could die so quickly.
I am so sorry to hear about your tree. Unfortunately, too much rain can be almost as difficult to deal with as too little rain. Thank you for sharing this information with me.