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Friday - July 30, 2010

From: Austin, TX
Region: Southwest
Topic: Trees
Title: Dying Bigelow oaks in Austin
Answered by: Barbara Medford

QUESTION:

I have several stands of Bigelow Oak (Q.sinuata var. breviloba) in NW Austin mixed with Yaupon and Cedar Elms. Several have died each year for the past 8 years. Two now have brown, dry leaves which is the first sign I notice of a problem. How do I stop more from dying and find out the cause?

ANSWER:

There is no doubt you have, and have had, serious ongoing problems with your Quercus sinuata var. breviloba (bastard oak). We have looked at your question several times, wondering exactly how to approach it. We are not plant pathologists, and even if we could see the trees and had an exact history of when they died and all the symptoms around their deaths, we would not be able to give you a diagnosis or treatment, if there is one.

The first thing we think of when someone mentions problems with oak is Oak Wilt Disease, which has been the scourge of red oaks and live oaks in Central Texas for some time. Please go to this site from the Texas Oak Wilt Information Partnership, of which the Lady Bird Johnson Wildflower Center is an active partner. A specific section of that site is on identifying oak wilt.

The problem for us in trying to decide what your problem might be is that the Bigelow Oak is a white oak; while they can contract oak wilt disease, they are not very susceptible to it and seldom die from it. However, like live oaks, which are very susceptible, your oaks grow in clumps, which makes transmission of disease via connected roots a large problem.

Another possibility is what is called "oak wilt decline." From the University of Tennessee Extension we found this article on Oak Wilt Decline. We suggest you read it also, although both diseases have many similar symptoms.

Obviously, we cannot give you a definitive answer. You need a certified arborist to actually look at your trees, try to diagnose the problem, and suggest what you might be able to do to alleviate it. You are in an area where oak wilt is definitely a problem, so the best thing you can do is contact the Texas Forest Service. You are in the Austin District for that, and your contact would be:

Austin
Jim Houser
Oak Wilt Coordinator
8317 Cross Park Drive, Suite 425
Austin, TX 78754
512-339-4589
[email protected]

They might be able to send someone to look at your trees, or recommend an arborist who is trained in the diagnosis of diseased oak trees. We urge you to take some action right away, before you lose all your oaks, and/or see the disease transmitted to other oaks in your vicinity.

From our Native Plant Image Gallery:

Quercus sinuata var. breviloba