Central Texas Oak Wilt: What You Need To Know

Updated September 2026 by Levi Williams, ISA Certified Arborist TX-4955A, TRAQ Qualified.

The Short Answer

Oak wilt is a fungal disease that kills a red oak in as little as 4 to 6 weeks once symptoms appear, and moves between live oaks underground through grafted roots. Red oaks cannot be saved after infection. Live oaks often can, with fungicide injections repeated roughly every 7 months. Prevention is injections before the disease reaches your area, sealing every oak cut immediately, and trenching to sever root connections from an infected tree. If oaks near you are browning in a line across the yard, get a diagnosis this week.

What is Oak Wilt?

Oak wilt is the most destructive fungal disease in Texas and one of the most destructive tree diseases in the United States. It is caused by the fungal organism Bretziella fagacearum. The organism infects the tree and blocks water moving through the xylem system of oak trees.

All oak species can be infected by oak wilt, but some are more resistant than others. Managing it takes proper diagnosis and a real understanding of how the disease behaves in different oaks. 

How does it spread?

Oak wilt spreads in two major ways.

1. Sap Beetles

Physical contact with a family of sap beetles called Nitidulids. As shown in pictures below:

These beetles find the scent of the oak wilt fungus and rub their bodies in the spores while feeding on the fungal mats. They then find wounds on oak trees and feed on the sap. That contact with a fresh oak wound spreads the disease into the tree. This is exactly why a cut on an oak has to be sealed within minutes, in every season.

2. Root-to-Root Contact

Through the connected roots of oak trees. This is the most common way the disease spreads. Some white oaks such as white shin oak, lacey oak and chinquapin oak can carry it, and live oaks are the species best known for spreading it through the root system. 

How to Identify Oak Wilt

Shown below are symptoms from a confirmed live oak with oak wilt, photographed in the field by Levi Williams. 

Foliage discoloration

• Leaves may develop yellow or brown veins and fall prematurely

Below is the symptom oak wilt causes on live oak foliage. 

Branch dieback

• Branches may die off from the tips inward

Below are common branch dieback symptoms on a live oak.

Another diagnostic tactic is to look at the other live oaks nearby. You will rarely see just one live oak with symptoms. Live oaks in a given area generally show similar symptoms together. 

Red oaks show similar symptoms in the canopy branches and foliage, as shown below.

Fungal mats on the trunk of a red oak:

Foliage symptoms on a red oak leaf:

The only way to know for certain is laboratory testing of samples. Our certified arborists handle that process for you. 

Can Oak Wilt Be Treated?

• Red Oaks: once symptoms appear, red oaks typically die within 4 to 6 weeks and cannot be treated successfully after infection.
• White Oaks: not technically resistant, they simply decline more slowly. They can still root graft with other species.
• Live Oaks: can often be saved with aggressive intervention. Without treatment they typically succumb.

Live oaks can survive oak wilt, but a high percentage die from it without treatment. 

Below is a common oak wilt chemical treatment method. 

Oak wilt can be treated preventatively, before the disease reaches your area, with an annual fungicide micro injection. Preventative treatment significantly raises the survival odds of your oaks and is the only way to protect red oaks.

Trees that already have oak wilt, live oaks for example, can be treated with the same micro injection roughly every 7 months. 

Preventing Oak Wilt on Your Property

There are several things you can do to plan ahead. In active oak wilt centers, consider species other than oaks when you plant, which removes the exposure entirely on that part of the property. Preventative injections protect the oaks you already have. And every wound on an oak, whether from pruning, storm damage or a mower, gets sealed immediately.

Texas A&M Forest Service publishes the state guidance on oak wilt identification, suppression and trenching at tfsweb.tamu.edu. Our diagnosis and treatment plans follow it, and we will tell you when a case is better handled by a suppression trench than by injections alone.

Conclusion

If you are worried about oak wilt on your property or in your area, Tree Scouts can help. Our ISA Certified Arborists identify and treat oak wilt across Georgetown, Leander, Austin and the surrounding Hill Country, and will give you a plan you can act on.

Contact Tree Scouts today for a free oak wilt consultation and treatment plan.