The Texas Hill Country is known for its beautiful live oak, red oak and even post oak and blackjack oak species. These trees seem to thrive here with little trouble except from people and nature. People affect these trees by building houses, driveways or yards around these fine trees and nature affects them by the drought we are currently in now. Droughts put these trees under significant stress and this stress sets the tree up for the possibility of disease infection. Besides oak wilt we have another problem disease of these oaks called Hypoxylon canker caused by the disease organism Hypoxylon atropunctatum. This disease is found everywhere in abundance but it is not a problem for healthy trees. Stressed trees unfortunately are susceptible to this fungus through wounds and then the disease grows easily in the sapwood. The first symptoms are yellowing and wilting of leaves, and death of top branches of the tree. The fungus is capable of spreading over 3 feet in all directions in a single year from the infection point. Hypoxylon canker is characterized by the large pieces of bark that fall from the tree as it dies because the disease works on the cambium layers that hold the bark in place. Underneath the bark are the fruiting structures of the fungus that are dusty brown spores. These blow from tree to tree to spread the disease further to weak, drought stressed trees.
Before you think all your oaks are going to die please be assured that this disease is not that widespread in our beautiful oaks but it is more of a problem in droughts. Watering all trees but especially oaks in our landscapes a little more this summer will help prevent the stress and consequently the disease.
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- Bob Whitney
- As an Agriculture Extension Agent for Texas AgriLife Extension Service I have had an opportunity to be involved in just about every aspect of agriculture. From the 5,000 cow dairy to the types of trees to use in a home landscape I have had a chance to learn how the different parts of an agriculture systems work together. Seedless watermelons, drip irrigation, pecan orchard management, fruit crop development, dairy nutrient management, environmental issues confronting agriculture, producer tours, field days, research projects and more have been a part of my life for over 30 years as I lived and breathed agriculture. Since 2004 I have been actively involved in consulting internationally working in Honduras, Guatemala, Egypt, Jordan, Iraq, India, and China. I have worked with missionaries and other groups dedicated to alleviating poverty among third world farmers. I lived in the Middle East in 2007-2008 working on a project for the Borlaug Institute of International Agriculture at Texas A&M University. In this project I was the Chief of Party and Team Leader for a $5.7 Million dollar effort to train Iraqi Extension agents and specialists in all aspects of agriculture.