Question

Picture of tree proble   HI Jennifer, I am hoping you can help me. I have a huge old oak tree on a 2nd property and when I left a few weeks ago the tree was beautiful but when I came back a couple weeks later, every leaf on the tree was dead. Then I notice some spots where the bark was missing and in it's place was a grayish powdery mildew and a white film around the edges of the missing bark spots. I pulled off some of the bark around it and underneath was a white film completely separating the bark from the trunk. What's wrong with my tree and will it kill my other old-growth trees? Any help is appreciated!

Answer
Hi Ashlie,

I think your oak tree has a disease problem and I have narrowed it down to the two most likely problems.  You will have to do some investigation to determine which it is.  Unfortunately, both of these diseases will kill the tree.  I would recommend that you have the affected tree removed as soon as possible so the level of inoculum (spores) is reduced and the other trees are less likely to be infected.  Unfortunately, they may already be infected but not symptomatic at this point.

I think that the problem you are describing is hypoxylon canker.  This disease is common on oaks and when the bark falls off to reveal a grayish white or black color, the tree is usually near death.  Please take a look at the images at the following website to see if this fits with your symptoms:
http://txforestservice.tamu.edu/main/article.aspx?id=1262
You can find more information about hypoxylon at that website and also off this fact sheet:
http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2312/EPP-7620web.pdf

I also want to make you aware of another disease that causes similar symptoms.  This disease is Armillaria root rot.  The roots rot, but the fungus will also invade the lower trunk and make symptoms similar to your image.  Although I think hypoxylon is more likely, it is possible that armillaria is the problem.  In my experience, armillaria root rot has not made the bark fall off like hypoxylon, but it could be possible.  For information about armillaria root rot, please review:
http://na.fs.fed.us/spfo/pubs/fidls/armillaria/armillaria.htm
and
http://www.rainbowtreecare.com/tree-knowledge/disease-2/armillaria-root-rot/

After reviewing the images and deciding which you think is most likely, please feel free to post follow up questions.  There is a great deal of information in the fact sheets, but I can certainly try to address other questions.

Good luck with your trees.
--Jen