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The Hill Country Steward: The Texas Live Oak – A Symbol of the Hill Country

By Central Texas Conservation Partnership

If you’ve spent any time driving around the Hill Country, you’ve likely seen large areas of dead oak trees – or worse, maybe you have those skeletal oak trees on YOUR property! The likely culprit is oak wilt, a disease caused by the fungus Bretziella fagacearum, which has become widespread throughout Central Texas.

An oak wilt infection begins when fungal spores are transferred to a healthy tree by way of tiny beetles in the nitidulid family commonly referred to as sap-feeding beetles. These beetles are attracted to sweet smells, including the fungal mats of oak wilt. Fungal mats are the reproductive structures found under the bark of some infected red oaks. 

When these beetles crawl on a fungal mat, they can pick up oak wilt spores. If a beetle then comes into contact with an open wound on another oak tree, fungal spores are spread to that tree. From there, the fungus can travel through that tree to other oaks that are connected through the roots. 

Disease prevention is key. This includes:

• Avoid pruning all oak trees from February 1 – June 30 because this is the time of year the sap-feeding beetles are most active.

• When pruning (or accidentally wounding) an oak tree, paint the exposed wood immediately to deter beetles from the fresh wood smell that would attract them to the tree. Regular paint will do the trick – tree-specific wound closure products are not necessary. 

• Infected RED oaks need to be destroyed as quickly as possible to prevent a fungal mat from growing. Infected red oaks can be cut down and burned (responsibly), chipped for mulch, or buried underground or under a clear tarp. 

Why should we be so diligent with oak wilt prevention? Oaks are not only special to us and our landscape, but they also provide many ecosystem services.

With live oaks especially, these trees are typically much older than any of us – possibly older than even our great-grandparents. Their long lives and large size equate to thousands of tons of carbon stored away from our atmosphere while providing oxygen and clean air for our benefit. Oaks also filter stormwater by slowing down runoff, allowing the water to gradually soak into our soils to replenish our aquifers, creeks, and rivers.

Live oaks are semi-evergreen, meaning they have green leaves almost year-round. They start dropping their old leaves while simultaneously growing new ones in late winter/early spring, giving us shade and a green tree to enjoy all year long. They also provide shelter and food to many wildlife species. For example, the golden-cheeked warbler, an endangered bird that exclusively breeds in the Texas Hill Country, not only needs mature Ashe juniper trees for habitat, but also the insects found on oaks and other hardwood trees for food. 

When pruning or working around oak trees, keep oak wilt prevention at the forefront of your mind. Treating cuts on a single tree to prevent a new oak wilt infection can potentially save hundreds of trees. And a tree saved today may live to see another century and continue providing benefits to future generations of Texans.

To learn more and connect with folks who care about your piece of Texas just as much as you do, visit www.texasconservation.org. Looking forward to learning more with you. – The Hill Country Steward

The Hill Country Steward – not a person, but a partnership of local experts dedicated to sharing the best information, tips, and lessons learned. Have questions? Send them to DearStew@texasconservation.org. Learn more at www.texasconservation.org.

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