Why are oak trees dying? Oak wilt in Texas

November 25, 2022

Learn how to spot and prevent oak wilt from killing trees on your property!


A red oak with oak wilt 
Trees are a valuable part of many homes here in Texas. For one, they provide a home and habitat for many of our beloved animal species and are a vital part of the ecosystem. But for homeowners, they provide a natural beauty that complements any house, increasing the aesthetic appeal and in many cases, the property value. 

However, like any living thing trees need care and attention and many homeowners may not recognize the signs of tree diseases, like oak wilt, before it's too late. Oak wilt is a highly destructive tree disease that has now been identified in over 20 states and has claimed more than a million trees in 76 Central Texas counties. It not only impacts the environment but can also be costly to remedy.

That’s why it’s so important for homeowners to be proactive in preventing oak wilt from happening. Read on to find out everything you need to know about how to prevent oak wilt and your options should it happen.

What is oak wilt?


Oak wilt occurs because of the fungus commonly known as Bretziella fagacearum (also known as Ceratocystis fagacearum). Once infected, the fungus travels throughout the xylem vessels, also known as the main waterways of the tree. From there, two things typically happen: The oak wilt fungus creates a blockage within the vessels, OR the tree, in its attempt to fight the infection, tries to deploy its own structures, which inadvertently also block its vessels.

However, no matter how the blockage comes to happen, water movement throughout the tree will, at one point or another, begin to slow down until it finally comes to a stop. When this happens, the tree starts to die, and the “wilting” appearance begins to set in.

Although any oak variety can contract oak wilt, red oaks are perhaps the most susceptible to oak wilt, especially Spanish oaks; the disease quickly kills these species. White oak species, like post oak and bur oak, have a natural resistance to the fungus and do not regularly die as a result of the infection, but can still cause it to spread. 

Live oaks are not as susceptible as red oak as the disease usually doesn't kill them as quickly. That said, they are the species that has been affected the most by oak wilt because of how quickly and easily it spreads through their complex, interconnected root networks. For this reason, you will almost assuredly find oak wilt wherever you find live oaks.

How does the oat wilt infection happen?


Like many human diseases, the transmission of oak wilt infection can happen in a couple of different ways. Here are just some of the causes of oak wilt:

The oak wilt beetle


Oak wilt beetles (also known as picnic beetles) are a part of the Nitidulidae beetle family, and they are one of the main culprits in the above-ground transmission of oak wilt. Attracted to the mycelial mats (spores of the decayed Bretziella fagacearum fungus that appear as a black and fuzzy-like substance), the oak wilt beetles frequently seek out and visit the spores. By coming into contact with them, they then attach the fungal spores to their bodies—similar to how one may pick up a common cold.

However, the problem is that the oak wilt beetle is not only attracted to mycelial mats. Because they’re also attracted to sap that fresh wounds on live oak trees may produce, they are also common visitors to oak trees.

If these sap-feeding beetles visit an Oak tree with an open tree wound while having the fungal mats on their bodies, the fungus is then transferred onto the tree as the beetle feeds on the sap. When this happens, the oak tree is officially infected.

Neighboring trees


Even without the aid of the oak wilt beetle, the disease regularly spreads through the infection of neighboring trees. As mentioned, this is a particularly large problem for live oaks, especially in areas where it is the predominant species.

Because live oaks are interconnected to neighboring live oaks through their highly advanced root system, they’re constantly open to infection. If the fungus gets into the root connections of one Live Oak, then it’s only a matter of time before the spread of oak wilt gets into the root connections of neighboring trees.

With the disease holding a capability of spreading at 75 to 100 feet per year, on average, it becomes very clear how big of a problem oak wilt is and will continue to be for Texas.

Oak wilt symptoms


Whether you’re concerned about trees in your own yard or neighboring trees close to your home that may affect your healthy oak, you'll want to be able to spot the signs. Some oak wilt symptoms or signs of oak tree dying include:

Browning color


The browning color of a leaf is most evident in the “veins” of the leaf. Also known as veinal necrosis, this happens when a brown line appears right up the middle of the leaves of a tree suffering from oak wilt or other signs occur that signify the leaf “drying out.” This could include browning on the edges of a leaf or any major type of discoloration in its veins instead of the leaf on the whole.

For diseased red oaks now beginning their (fatal) battle with oak wilt disease, it is common to find that some brown veined leaves will live next to new infections or leaves that have yet to be affected.

Wilting


Another common sign or symptom of oak wilt is, of course, the signs of wilting. Aside from the brown colors on the leaves, a tree suffering from oak wilt will also experience falling leaves that are not due to seasonal changes. With wilting happening rapidly, a tree can wilt away and die within a matter of months or weeks; live oaks typically die within two to four months and red oaks two to four weeks. This end result is evident by a completely bare crown (no leaves).

And once the complete arc of the disease has made its way through a symptomatic tree, leaving it bare, you’ll also see the fungal disease begin to produce fungal spores on mycelial mats on the tree to continue the cycle all over again. Again, they will appear as a black, furry, cotton-like substance on the tree.

It’s also important to note that seeing neighboring trees that are suffering from oak wilt is another symptom and sign that trees in the area may already be battling oak wilt, even if the signs are not yet visible on all the trees.

In those instances, if the browning color, wilting, or the end result of mycelial mats (aka oak wilt spores) have not presented themselves, the only other option to confirm oak wilt would be to have a tree lab tested.

Treating trees that have oak wilt


Unfortunately, due to the aggressive and subliminal nature of the fungus, there is currently no cure or way to treat trees that have oak wilt. In fact, by the time a tree is diagnosed with oak wilt, it’s already too late to be treated.

Therefore, if you suspect that a tree has already been infected, the only thing that can be done is to help prevent it from spreading the infection and affecting any other trees in the area.

How to prevent oak wilt


With no cure for oak wilt available and with the destruction of so many native oaks (especially live oaks) in the Texas area, learning how to prevent oak wilt from spreading to trees in your neighborhood should be a priority to any homeowner.  

Here are some ways you can do that:

Avoid puncturing oak trees


One of the best ways to prevent oak wilt from happening is to avoid puncturing oak trees. This is also referred to as “wounding” the tree. However, it’s common that man-made puncturing sometimes must occur for various reasons and some types of natural puncturing are unavoidable.

This can include:
  • Broken branches
  • Animal damage
  • Fire
  • Other physical impacts
If you do find yourself dealing with any of the above, it’s important to practice wound dressing or sealing the wound as soon as possible. With oak wilt beetles known to settle into a fresh wound in as little as 10-15 minutes, time is of the essence. You can dress and seal a wound using a commercial pruning sealer or wound paint. You can also use a simple latex paint to cover wounds. Although the color isn't important for dressing the wound, black, brown, dark green, and other dark earth tones are likely to stand out the least.

Avoid pruning too early


Another variation of puncturing your oak tree is through pruning cuts. There are a number of valid and even advisable reasons to trim, cut, and prune your trees. For example, you may need to remove a limb to keep it from damaging your home in a storm, or to create defensible zones around your house to potentially stop the spread of a fire. No matter what the reason, if you prune oaks in your yard, you'll want to do so during the right time of year. 

Like many insects, oak wilt beetles prefer mild temperatures and seasons; not too hot, not too cold. For this reason, avoid pruning or wounding your oaks from February 1st through July 1st. This is the time of year when the oak wilt fungus is most likely forms mats and the beetles are most active. You may not enjoy being active outdoors during the hottest or coldest points in the year, but neither does the beetle! That's why these are the most favorable conditions for pruning oaks. 

In addition to dressing wounds after pruning, it's also important to clean your pruning equipment after using it on an oak of any kind. The fungal spores can easily stick to surfaces only to infect a healthy tree in the future. You can do this by thoroughly rubbing them down with isopropyl alcohol or any household disinfectant. 

Avoid spreading from infected trees


As you've probably realized, this fungus is difficult to contain. Even if you prevent oak wilt beetles from visiting your trees, neighboring trees that have become infected are disease centers and can easily spread it to healthy oaks in the area. 

Apart from proper pruning and wound dressing practices, there are a few ways that you can protect your oaks if the fungus has latched onto nearby trees:

Look out for oak wilt in neighboring trees

Before you can take any preventative action, awareness is key. Although it's important to look out for symptoms on your trees, you also need to keep an eye on any oak in the area. If you look out for oak wilt in neighboring trees and notice signs of the disease, you’ll be in an excellent position to stop it from spreading as soon as possible!

If the oaks in question are on a neighbor's property, talk to them about your concerns if they are not already aware and work with them to develop a plan of action. Depending on the type of oak, number of trees, and severity of the infection, it may be necessary to call in professional help. 

Burn or bury dead red oaks

Red oaks die quickly when infected with oak wilt, but even a dead tree can still form fungal mats and attract beetles that in turn spread it. If any red oaks in your area have perished due to this fungus, it's important to cut them down and either burn or bury them as quickly as possible.

Work with your neighbors, community members, or government officials (if trees are on public land) to ensure this is done properly and promptly while observing local regulations. 

Trench around live oak root systems

Unlike red oaks, it isn't enough to remove and burn or bury live oaks. Because live oak trees form sprawling root networks and interconnected communities, preventing the spread through root systems can be a difficult but necessary step to save neighboring oaks from the disease. 

Reach out to oak wilt infection centers or oak wilt management specialists such as the Oak Wilt Specialists of Texas to find out how they can help you take action. They may suggest trenching an area in order to preserve it and section off or quarantine the disease as best a possible. This is especially necessary if a large group or cluster of trees have an infection.

The process involves cutting a trench about a hundred feet away from the infected group of trees, forming a perimeter around them. The trench likely needs to be at least four feet deep, sometimes more, in order to sever the roots and stop the fungus from using them as a conduit to other healthy oaks. After the trench is made, the trees within may be uprooted or removed over time. 

This is a rather extreme measure, but it's important to evaluate the costs and benefits. Although the process is time and labor-intensive, expensive, and can pose a risk to healthy trees within the area, it may be the only way to prevent every single oak in the area from dying.

Use a fungicide treatment

Although there is no “cure” or treatment for oak wilt, you can use a fungicide treatment called Propiconazole, which has been tested and proven effective as a preventative treatment to help extend the life of oak trees. In conjunction with the recommendations above and even extreme measures such as trenching to preserve truly healthy trees, this fungicide can help your oak tree go the extra mile!

However, success of the treatment depends on a number of factors, including the health of the tree but also the method of application. For this reason, it is best to have it performed by a trained professional. 

Avoid infected firewood

Although burning infected wood does not transmit oak wilt, collecting, storing, and transporting unseasoned oak wood that has been infected can cause the fungus to spread to healthy trees in the area. Seasoned firewood is wood that has been dried for at least a year and has lost all or most of its moisture content. Unseasoned firewood can still contain enough moisture for the fungus to thrive and spread, so avoid collecting or buying it if at all possible.

Be proactive: Prevent oak wilt!


When it comes to preventing oak wilt from touching trees in your yard or in the surrounding areas, the key is to stay vigilant!

Remember to:
  • Avoid wounding any oaks and dress the wounds properly if you do.
  • Know when to prune oak trees (avoid February to July).
  • Keep your eyes peeled for browning or wilting stages on trees nearby or on your own so that they can be sectioned off appropriately.
Oak wilt is an insidious and destructive disease that has spread like wildfire throughout the state of Texas. Not only does it pose a serious risk to the trees that give your property that extra bit of natural Texas beauty, it threatens the environment and ecosystem as a whole. 

By following these steps and sharing information with our communities, together we can fight the spread of the oak wilt epidemic. 

Source: Texas A&M Forest Service 

Dead red oak leaves on the ground 

For more information about Germania and our insurance products, request a free quote online, or reach out to your local Germania Authorized Agent today!

by Geoff Ullrich

About the Author

Geoff Ullrich is a writer and Content Marketing Specialist at Germania Insurance.

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