Oak WIlt in the Texas Hill Country

Late January/early February is the beginning of the most dangerous season for our oaks-red oaks especially and live oaks. Oak wilt is an infectious disease that kills trees in a relatively short time by destroying their ability to take in water; the trees die of thirst. Fungal mats form under the bark of red oaks, and sap beetles feed on them then spread the fungus over long distances from the infected tree to a fresh cut on a healthy one. Once a tree has oak wilt, healthy trees around it are likely to become infected through the roots, so even if you're careful when you trim your oaks, once a tree is infected, you'll probably lose the entire stand.

Of course you have to trim your trees. When you do, paint the cuts immediately to prevent the beetles from being attracted to the sap. Do this year-round; the weather is too unpredictable, and we can't count on it being cold, hot or dry enough to prevent spreading. In fact, the city of San Antonio has an ordinance that requires you or any tree-trimming service to paint the cuts on oak trees. Many of the tree trimmers don't paint cuts. Make sure you ask them if they do; some will argue with you and tell you it's not necessary. If they don't paint, hire another company or follow them around with a can of paint. For more information on oak wilt and a list of susceptible species, go to http://www.texasoakwilt.org/About/introduction.html. For some very sad pictures I took in Bandera County, go to http://www.shurgot.net/Oak_Wilt.htm and follow the link. For the ordinance (Chapter 21, Article VIII), click on www.municode.com/resources/gateway.asp?pid=11508&sid=43