Overview

Oak wilt is the leading cause behind a growing fungal tree epidemic in many parts of Texas. In this blog, Adam's Tree Service’s certified arborists dive deep into how the disease spreads, which trees are most at risk, and how you can help protect your landscape.

Highlights

Introduction

A tree can be a treasured and integral part of your property. Maybe it has shaded generations of backyard barbecues, held a tire swing, or stood quietly through every storm since you moved in. That’s why it’s so unsettling when something starts to change. Across Texas, a growing number of oaks are being infected by oak wilt, a fast-moving fungal disease that can take down the strongest trees.

This blog is here to help you understand what oak wilt is, why it’s so destructive, and what you can do to protect your trees before it’s too late.

What Is Oak Wilt?

Oak wilt is a serious fungal disease that affects oak trees in many parts of Texas. It’s especially common in Central Texas but has also been confirmed in other regions, including North Texas. Over the years, it’s caused the loss of thousands of trees across both residential and rural properties, making it one of the most significant tree health concerns in the state. While it doesn’t affect every neighborhood, it's essential for homeowners to be aware of it.

How Does the Fungus Affect Trees?

This fungus affects trees by interfering with the internal system that moves water and nutrients from the roots to the branches. Once inside, it invades the vascular tissue and triggers a natural defense response, causing the tree to form blockages within its own vessels. These blockages, while intended to isolate the threat, ultimately cut off the flow of essential resources. Without the ability to stay hydrated, internal tissues begin to dry out and shut down.

The process can escalate quickly. This is especially true during the growing season, when water demand is at its highest. Depending on the tree’s condition and the timing of the infection, visible decline can follow soon after the initial disruption. In many cases, the damage is severe enough to lead to complete loss.

Which Trees Are Most at Risk?

As the name suggests, oak wilt only affects oak trees, though different species of oak have different vulnerabilities. There are also specific biological and environmental characteristics that can increase a tree’s risk.

Some have internal structures that make them less capable of limiting the impact of infection once it begins. Others tend to grow in dense groups, which increases their overall vulnerability. Trees that are already under stress from drought, construction damage, or poor soil health may also struggle to respond effectively to the disease.

These combined factors make some trees more susceptible than others, especially when early signs are missed or left unaddressed. Professional evaluation can help identify which trees are most at risk.

Why Are Red Oaks Highly Vulnerable to Oak Wilt?

Red oaks are considered highly vulnerable to oak wilt. Once infected, these trees often experience a rapid decline, sometimes within just a few weeks. They rarely recover, and their quick deterioration can increase the risk of infection for other nearby oaks. Trees in this category are also known to support the conditions that facilitate the spread of this fungal disease within a landscape. Since the fungus progresses so quickly, there is often little time to respond once symptoms become visible.

How Does Oak Wilt Affect Live Oaks?

Live oaks are vulnerable to oak wilt and often develop the disease in a distinct pattern. Unlike some oak types that decline rapidly, these trees typically exhibit a slower, more gradual decline. Since these trees commonly grow in close groups with interconnected root systems, multiple trees in the same area can be affected. This makes early identification especially important, as this disease is capable of decimating a colony of live oaks.

How Resistant Are White Oaks to Oak Wilt?

White oaks are generally more resistant to oak wilt than other species. Their internal structure slows the movement of the fungus, which gives these trees a better chance of compartmentalizing the infection before it spreads. In some cases, the disease may not always progress beyond a small area, allowing the tree to continue growing without significant issues. However, resistance does not mean immunity. This oak species can still become infected, especially if it’s already stressed or damaged. Since the progression is slower, symptoms may also be harder to notice early on.

How Does Fungus Spread Between Trees and Yards?

Fungus can spread between trees and yards in ways that aren’t always obvious. Once the disease is present in a landscape, it may continue to affect nearby trees through a combination of natural and environmental factors. It doesn’t always stay confined to the tree where it started, and even healthy-looking trees can be at risk. Spread may occur gradually or advance more quickly depending on site conditions, tree placement, and stress levels. The movement of this fungal disease isn’t always visible, which is why a broader look at the surrounding area is important.

Can Insect Activity and Pruning Wounds Spread Fungal Disease?

Insect activity and pruning wounds spread fungal disease by creating openings that allow fungal spores to enter otherwise healthy trees. Certain beetles are attracted to the sap released from fresh cuts or storm damage, especially during the growing season. If these insects come into contact with infected material, they can transfer spores from one tree to another.

This possibility of disease transfer makes the timing of pruning especially important, as pruning between February and June in Texas increases the risk of exposure. To reduce the chance of infection, seal accidental wounds right away and schedule any non-emergency pruning during the dormant season.

Can Underground Root Systems Spread Fungus Infections?

Underground root systems spread fungus infections in oak trees that grow in close proximity to one another. As these trees mature, their roots often expand outward and form natural grafts with nearby trees. These shared connections allow water and nutrients to move between trees, but they can also create an unseen pathway for disease.

When one tree becomes infected with oak wilt, the fungus may pass through these interconnected roots and reach neighboring trees without any visible warning signs. This type of spread is especially concerning in landscapes with clusters of oaks, where multiple trees may be linked below the surface.

How Do People Spread Tree Fungus?

People can unintentionally contribute to the spread of tree fungus, particularly when infected materials are moved from one property to another. One common source of transmission is firewood from diseased trees. If logs or branches from an infected oak are transported and stored near healthy trees, the fungus may remain active and continue to spread.

Unintentional injury to trees, such as from improper trimming or construction damage, can also increase the risk of harm, as can the use of unclean tools. While not all movement or damage leads to infection, these factors can create opportunities for the disease to take hold.

What Are the Warning Signs of Fungal Infection?

Fungal infections, such as oak wilt, often present clear warning signs once they begin to affect a tree.

Watch for the following issues during the growing season:

  • Leaf discoloration: Sudden browning, bronzing, or dulling of leaf color
  • Canopy thinning: Noticeable gaps or sparse foliage in the upper crown
  • Premature leaf drop: Shedding that occurs well before seasonal changes
  • Wilting: Leaves that appear limp or curled, even with adequate moisture
  • Dead branches: Limb loss or dieback starting at the top of the tree

If your oak is showing one or more of these signs, early diagnosis is critical for the survival of your trees.

How Can an Arborist Help Protect Your Trees?

An arborist can help protect your trees by identifying signs of oak wilt early and recommending the proper steps to manage it. With professional training and local experience, they can evaluate overall tree health, rule out other causes, and determine whether treatment, monitoring, or removal is the most effective approach.

In cases where the disease is detected early, a fungicide injection using propiconazole may be recommended to slow the spread and support the tree’s defense. Tree experts also understand how and when to prune properly, minimizing the risk of exposing your trees to further infection.

If the disease is already established, they may suggest removing infected trees and installing root barriers to protect nearby oaks. Their guidance helps safeguard your property’s long-term health.

Save Your Trees With Professional Help

Oak wilt may start quietly, but the damage it causes can be fast and far-reaching. If you’re seeing changes in your trees or want to stay ahead of potential issues, the time to act is now. Our team of arborists at Adam's Tree Service has the experience and training to assess your trees, identify early warning signs, and guide you through the next steps with care and clarity.

Worried about oak wilt? Contact us at (817) 357-2931 to speak with a member of the Adam's Tree Service team.