Oak Tree Diseases by Byron Chitwood
Probably the most dreaded disease problem that attacks oak trees in Texas is Oak Wilt. Fortunately, we do not have that problem in Hunt County. However, it is as close as Collin County to the west of us so be vigilant and take precautions to prevent this disease from attacking your oak trees. It can attack any variety of oak trees but seems to be one that infects Live Oaks. One of the easiest precautions that can be taken is to buy only seasoned fire wood, preferably from this immediate area. Also, do not trim any of your oak trees except in the hottest and coldest month: August and February respectively. The spoor that causes oak wilt is transmitted by a small beetle that feeds on the sap of trees and can smell a newly cut tree from over a mile away. In order for the oak wilt spoor to infect a tree it must be transmitted in a fairly mild temperature range.
The disease that has been the most prevalent in this area for the last several years is Hypoxylon Canker. This disease is transmitted by windblown spoors from an infected tree to other ones especially those in a distressed state such as we have been witnessing as a result of the extended drought. Post oaks are the variety most affected by this disease. This area has a lot of post oaks, especially in sandy areas. Post oaks have a relatively shallow root system which does not hold water very well. Drought conditions dry out the topsoil very quickly and leave the trees in a very distressed and vulnerable condition. If there is Hypoxylon canker infected trees in the area, the spoors are transmitted by the wind and can infect ones that are not already infected.
The first signs of Hypoxylon canker are peeling of bark from the infected tree. These spoors have somehow gotten under the bark and feed on the trees vital fluids. The canker grows under the bark creating pressure causing the bark to burst and fall off. The tree cannot survive if the tree is “girdled” and will very quickly die. There is no known cure for a tree in this condition. The best way to prevent trees from contacting the disease is to keep the “high value” ones watered. These are the ones in yards and close to homes. If a large acreage is involved, there is not much that can be done economically to prevent the disease from occurring.
Post oaks are very sensitive to root damage. Do not grade or fill with topsoil on the root system. Do not park vehicles on the root system. If a tree dies from Hypoxylo0n canker, cut it down and stack away from other trees. Cover with a clear plastic sheet and the heat will kill the active spoors. It can be safely burned without transmitting the disease.
There are too many tree diseases to describe them all in this article. If you do have a tree problem, contact the Texas A&M AgriLife office at 903-455-9885 with a description of the tree problem and the variety of tree if available. The office will alert one of the local Master Gardeners and you will be contacted with advice on what the problem is and how to handle it if there is a solution.