Question
Hi. I live in Texas and there was a terrible drought here. We have a mature oak tree (approx 30yrs old) that had all the leaves at the top turn brown and wilt but not fall off.  there is a small branch that is still green about 3-4ft from the ground. the tree stayed this way for about three months but i have just noticed the bark is coming off all over except for the 3-4ft from the base. large patches are missing and small, and where the bark is missing there is a light greyish brown fungus. it is near a power line and the street. we also lost a couple bushes right near the base of this tree. there are a few small holes in it here and there, i am unsure whether these were here previoulsy or not. we did have a woodpecker a year or two ago, but it is now gone to my knowledge. the bird did not seem to have done much damage. considering the location of the tree, it falling is a big concern.

Answer
Hi Annie,

Unfortunately, I suspect that your oak tree may have hypoxylon canker.  This is a common disease of oaks and tends to show up more often in drought years.  One of the major symptoms of the disease is that the bark falls off.  The dark growth that you are observing in these areas is a sign (physical evidence of the fungus) and where the fungus produces spores.  Usually, when you see this the tree is near death.  The one branch that is still hanging on has probably not been invaded yet, but it is a matter of time.  This pathogen will affect the structure of the tree and the tree will become hazardous.  You will want to have it removed as soon as possible so it doesn't come down in a storm.

Here are some links to information on this disease produced by the Texas Extension Service.  You can compare the damage on your tree with the images to confirm if this is the problem or not.
http://txforestservice.tamu.edu/main/popup.aspx?id=1262
http://easttexasgardening.tamu.edu/homegardens/hypoxylon.html
http://plantclinic.tamu.edu/helpful-factsheets/hypoxylon-fact-sheet-1/

Feel free to contact me if you have additional questions.

--Jen