Ridgmar Neighborhood Association

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How to Identify and Manage Oak Wilt in Texas


Oak wilt is one of the most destructive tree diseases in the United States and is killing oak trees in central Texas at epidemic proportions.  Oak wilt is an infectious disease that invades and disables the water-conducting system in susceptible trees.  All oaks are susceptible to some degree however red oaks are extremely susceptible.  Live oaks are intermediately susceptible, but the most seriously affected due to their growth from root sprouts and interconnected root systems.  Burr oaks are less susceptible than red and live oaks and with proper pruning and treatment may survive living with the fungus.  The successful management of oak wilt depends on diagnosis and understanding how the disease is spread.

Texas counties with confirmed oak wilt in red.



Identification of Oak Wilt


Foliar symptoms, patterns of death, and fungal mat presence can be used as identifiers of oak wilt.


Patterns of Death

Red oaks seldom survive and often die within 3-4 weeks following the initial appearance of symptoms.

Most live oaks defoliate and die over about a 6 month period following initial appearance of symptoms, due to death in stages.


Foliar Symptoms

Foliar symptoms on red oaks are less distinct.  In early spring, young leaves simply wilt and turn pale green and brown.  Mature leaves turn pale green to bronze, starting at the margins (edges) and working its way inward.

Leaves on diseased live oaks are very distinct.  Veinal necrosis is the most reliable in diagnosing live oaks.

Veinal necrosis in live oak leaves.


Oak wilt pattern in red oak leaves.


Fungal Mats

Fungal mats are a reliable indicator in the diagnosis of oak wilt.  They are specialized spore-producing structures that form on red oaks in the spring and develop visible signs of oak wilt in late summer and fall.  Infections in late spring and summer do not tend to develop because of the warmer temperatures and low soil moisture.  Fungal mats can appear in small cracks in the bark of dying red oaks that lead to hollow areas between the bark and wood.  The odor produced by fungal mats is closely related to the smell of rotting fruit.

Fungal mat on bark of red oak.

Spread of Oak Wilt


New Infections

Red oaks play a key role in the establishment of new infection centers.  Red oaks produce spore mats that attract the insect vector, the nitidulid beetle.  This beetle accounts for about 10% of new infections. While the red oak is its preferred path, it is possible that this beetle is responsible for infections of the other oak categories.


Spreading through Root Systems

Live oaks are most likely to be infected through root grafts, when roots from one tree fuse to roots of another.  The infection rate among live oaks can expand at a rate of 75-150 feet per year in any one direction.  It is possible for a live oak roots to graft to roots of a red oak, but the transmission of the disease is shorter in distance.


Disease Management


There are currently 3 approaches used for oak wilt management.  Successful control depends on which measure is taken.


Preventing New Infections

Infected red oaks that die late summer or fall should be cut and burned or buried as soon as discovered to prevent the spore mat from producing in the spring.

All wounding (including pruning) should be avoided from February to June.  The least hazardous periods are the hot summer days or cold days of winter.

If wood is kept for future firewood use, the wood should be covered in clear plastic (with edges buried) for no less than one year to allow the fungal mat to decompose and not spread.  You should never use freshly cut red oak wood that has been infected for firewood.


Stopping Spread through Roots

This method is not typically used in city settings.  Approximately 4 feet from the base of the trunk a trench is dug to sever the roots.  This allows for a trench to be made.  This is easier to perform on smaller trees than established mature trees.


Fungicide Treatment

Alamo™ is the only fungicide scientifically tested and proven effective for use as a treatment to prevent infection.  Alamo™ does not cure your oak of oak wilt and does not stop root transfer.  It stops the fungus from spreading further into the tree causing more damage.  Trees with more than 50% display of infection are normally not worth trying to save.


Beware of any tree service that treats Oak Wilt with any other product than Alamo injected directly into the roots of the trees.

    A typical charge is $10 per diameter inch for oak wilt treatment.  For example, a 30 inch diameter tree will cost $300 plus tax to treat.  Removal of the same tree can run 4-5 times that amount.  Treat as many trees as possible.  It is important to understand that one treatment will not cure or prevent the tree from developing signs in the future.  Trees are an investment to your property and should be re-evaluated in approximately 3 years to determine the need for re-treatment. 

Listed below are several companies that Ridgmar residents have recommended. 

                  Thompson Tree Service
 Fred Rodgers, their Certified Arborist and Oak Wilt Specialist, is available to provide you with a proposal for treatment.

                       Archie's Gardenland 

If you have had good luck with some other tree service let us know and we will post the info here.

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