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Wednesday - April 04, 2012

From: Austin, TX
Region: Southwest
Topic: Diseases and Disorders, Pruning, Trees
Title: Red oaks that didn't drop leaves in Austin
Answered by: Barbara Medford


I have a number of Red Oaks on land that did not drop leaves this past fall. Now these same trees seem to be dead? It seems there's some type of mold/fungus on the trees. Some trees have small patches of this stuff while others have it up and down the whole trunk. If I cut the trees down will it spread? Is it bad, should I worry? Anything help?


A group of volunteers at the Lady Bird Johnson Wildflower tree were looking at  Quercus buckleyi (Texas red oak) on the grounds of the Center. It also had not lost its leaves, which were quite brown. Damon Waitt, the Senior Botanist, did the "thumbnail" test, scratching a very thin sliver of bark off a large limb, and found a layer of green beneath it, which indicated the tree was still alive. The stems were also limber. The conclusion was that the tree would probably survive. Even though the Wildflower Center does do some irrigation, we were limited, like everyone else in Austin, to as little as possible last year, and as you know, it did not rain. Now, of course, some things we thought were dead, shrubs, trees, etc. are popping leaves out and carrying on. Hopefully, so will your tree. In fact, more recently, we passed that tree and it is leafing out like crazy.

However, (isn't there always a "however"?) the description of the fungi on your tree trunks is pretty alarming. Oak Wilt, a scourge of red oaks, is a fungus transported by the nitiludid beetle. A wound in the bark, as from an unpainted pruning scar or damage from a weedeater or lawnmower, will exude a sap, which is ambrosia to the beetle. If he has been feeding somewhere else in oak sap, perhaps from a tree already infected by Oak Wilt, the fungus spores will infect the new tree.

Since we are not plant pathologists and certainly couldn't diagnose this problem sight unseen, we want to refer you to a website that should be able to help you. First of all, you are going to need professional help from a trained, licensed arborist. The Texas Oak Wilt Partnership, in which the Lady Bird Johnson Wildflower Center is an active partner, should be looked at closely. Under "Getting Help" you will find out you are in the Austin District, and get names and contact information on Oak Wilt specialists.

This is the time of year when the nitiludid beetle, spreader of Oak Wilt, is most active, so if the tree is infected, you will need to take the advice of the expert you bring in on whether to cut it down now or wait until the dormant months of December and January and also on how to protect other oak trees in the vicinity.


From the Image Gallery

Texas red oak
Quercus buckleyi

Texas red oak
Quercus buckleyi

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