Question
The 50+ year old willow oak has developed a couple of branches that have areas of distorted leaves.  When I took some of the leaves off to examine them I found that the leaves are curled under.  Along the underside there is a strip about 1/4" wide running down the center the whole length of the leaf.  This strip is the same green as the leaf and includes a midrib.  On the upperside of the leaf it looks as though the midrib had been cut out.  There is a gully where it once was. The leaf is leathery and I see no other spots or markings on it.  I hope you can help me identify this and let me know what to do about it (if anything).  By the way when the arborist was here about 6 wks ago to clean out dead wood from my trees, he said that this oak is approximately 85' tall so I would really hate to loose it especially since its twin is on the other side of the house. The problem did not exist when the arborist was here and I had not noticed it until today so I can't tell you how long this leaf thing has been around.  Thanks for your help.

Jean Blanton  

Answer
Jean,

These trees must be a slight standing side by side.

Two things could be happening.  There are nutritional stresses that can cause the leaf curling, but I not think this is it.

I would be willing to bet a cup of coffee that there is an insect pest causing the problem.  Take a sample to the extension office and let their entomologists take a peek.  If this turns out to be the cause follow their directions to eradicate.

Good luck

Gary