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Wednesday - June 17, 2015

From: Austin, TX
Region: Southwest
Topic: Diseases and Disorders, Trees
Title: Red oak leaves have a swelling along the veins
Answered by: Guy Thompson

QUESTION:

I have red oaks in my back yard, approx 30 or more have a disease that are wilting the leaves. Looking at the back of the leaf there is swelling along the spines. I've gone to one nursery in town that confirmed it was not oak wilt, but had not seen this symptom before. I can send a picture on request. The trees all seem to be fully affected on all branches.

ANSWER:

The disorder of your Quercus texana (Nuttall oak) is caused by the action of a small midge with a name, Macrodiplosis quercusoruca, much longer than itself. It llays its eggs near the leaf vein.  Chemicals secreted by the midge's larva as it feeds by the leaf vein cause the tissues by the veins to swell.  It seems common in the Austin area this year.  I have noticed infested oaks in my yard for the first time.  Perhaps the midge prospered because of the unusually wet weather.  There is apparently no remedy for this infestation, but I believe that the trees will survive.

 

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