Preventing Oak Wilt by Byron Chitwood
There are many diseases and insects that attack Oak Trees in Texas. . One of the most devastating of the diseases is Oak Wilt. Hunt County has managed to dodge the Oak Wilt problem even though it is as close as Collin County. Oak wilt will be discussed later in this article but first it is important to recognize some of the more prevalent conditions that attack Oaks and some other trees in our area.
The prolonged drought has been an enabler for many of the diseases and insects to attack our Oak Trees. One of the ones that have been the most devastating in our area is Hypoxylon Canker. Hypoxylon is a wind borne fungus that attacks the trees by entering through wounds in the bark. Hypoxylon Canker attacks the cambium layer under the bark and at the same time, white rot attacks the sap bearing wood under that layer. Both grow and expand causing the bark to peel and fall to the ground around the base of the trunk of the infected tree. Presently, there is no cure for this disease and trees that reach this state will eventually die. The only safe treatment is to keep the high value trees in the urban lawn well watered. Healthy trees have the ability to resist Hypoxylon Canker.
Oak Tree Decline is also a fungus that we do see some of in this area. The fungus gradually stops the flow of liquids to the top branches which dieback. This disease gradually kills the infected tree over a period of time.
Borers usually attack unhealthy and stressed trees. They are not the cause of death of many trees but are a symptom of other problems. High value trees can be sprayed with an insecticide that will at least kill the borers. A proficient Arborist should be contacted if treatment is desired.
One problem that we see in this area is from Oak Twig Pruner and Oak twig girdler. The symptom of this problem is a multitude of very small branches fall from an otherwise healthy tree. Both insects lay eggs in a small branch. The eggs only hatch after the branch dies. The best suggestion for this problem is too keep all the fallen branches picked up and destroyed or put in a secure trash bag and dispose of them.
Oak Wilt develops from a fungus spread by the Nitidulid Beetle. They feed on the sap of Oak Trees. Unfortunately, some of these trees they feed on are infected by Oak Wilt. They then transport Oak Wilt fungus to otherwise healthy trees. Since the Nitidulid Beetle is a sap feeder, the most convenient dinner table for them is a very recently trimmed tree that is oozing sap. The oak wilt fungus can only survive in a very narrow temperature range that occurs between early spring and the hottest part of the summer. Therefore, limit trimming oak trees to only the coldest and hottest months of the year, namely February and August. Even then, paint the trimmed ends of branches with a pruning solution or latex paint.
One of the major ways Oak Wilt has been spread is through the purchase of firewood that comes from an area that already has Oak Wilt. Only purchase fire wood that has been well seasoned.
If Oak wilt is a suspect in one of your trees, please contact the Texas A&M AgriLife at 903-455-9885. A specialist will contact you to assess the symptoms and advise the next steps to take.