Oak Wilt

Oak Wilt in Angus Valley

Sep 7, 2014

This is a summary of information provided by Chris Dolan, Environmental Program Coordinator and Arborist for the City of Austin’s Oak Wilt Suppression Program.  If you have questions after reading this, you may reach him at 512-974-1881 or Chris.Dolan@austintexas.gov.  The best time to call him is from 7:00 – 9:00 a.m.

Over the past twenty years, Austin has lost more than 10,000 trees to oak wilt.  This infectious and destructive disease is caused by the fungus Ceratocystic fagacearum which is spread primarily through interconnected or grafted root systems once an oak wilt disease center has been established.  Sap beetles can also carry oak wilt fungal spores from infected trees to fresh, open wounds on healthy oaks.

Unfortunately, oak wilt exists in Angus Valley.  The red lines on the map below indicate the two oak wilt mortality centers in our neighborhood.  As you can see, the areas have almost merged.  Since such a large area is infected, trenching is not an option for disease containment.  While there is cause for alarm, Mr. Dolan urges residents not to panic.  Even if your tree is in or near the diseased areas, it is not a certainty that you will lose it.  Some live oaks in infected centers may be unaffected by the disease.  And there are important precautions and steps you can take to lessen the chance of losing a tree to oak wilt.

Provided by the City of Austin, this map was last updated circa Feb. 2013

Provided by the City of Austin, this map was last updated circa Feb. 2013

Protect Healthy Trees

Preventing healthy trees from getting oak wilt is essential, as there is no permanent cure.  Since oak wilt can be spread by insects that are drawn to fresh cuts on a tree, remember the following:

  • Never prune an oak tree from February to June
  • Only prune when temperatures are above 90 or below 50
  • Always seal cuts, wounds, and fresh stumps immediately (wounds include damage caused by wind, hail, vehicles, construction, squirrels, birds, or pruning)
  • Use a certified arborist
  • Disinfect all pruning tools with 10% beach solution or Lysol between sites and/or trees
  • Debris from diseased oak trees should be immediately chipped, burned or buried
  • Unseasoned oak firewood should be stored under clear plastic, tightly sealed at the edges with soil or bricks
  • Burn all oak firewood before spring
  • Never store unseasoned oak wood from infected trees near healthy oaks

How to Spot Signs of Oak Wilt

  • You can visually see the foliar symptoms of oak wilt
  • Leaves on diseased live oaks develop veinal necrosis (yellow veins that eventually turn brown)
  • Diseased red oaks can be spotted from a distance for their bright autumn-like coloration in contrast to surrounding greenery
  • Diseased trees will defoliate (all the leaves will fall off)
  • Look for patterns of defoliation in the neighborhood – you can literally see it march down the street
  • Detailed information and photos to aid in oak wilt identification www.texasoakwilt.org

Foliar Symptoms on Live Oak                                                     











Foliar Symptoms on Red Oak











How and When to Treat for Oak Wilt

  • Good candidates for treatment are high-value oaks that are close to infection centers
  • Treatment works best as a preventative measure and should be applied before the tree is infected
  • A fungicide, propiconazole (AlamoTM), can be injected into the trees
  • Getting the right person to apply the treatment is critical
  • Use an Oak Wilt Certified Arborist – search at  http://texasoakwilt.org/find-a-vendor/certified-arborists/
  • The timing of the treatment is important – DO NOT wait until the disease is 50 feet away
  • Treat your trees when the disease is about 150 feet (roughly ½ a football field) away because oak wilt spreads at a rate of approximately 100 feet per year
  • The treatment only lasts 1½-2 years before needing to be reapplied
  • You can only treat the tree a total of 2-3 times because it is invasive to drill holes and inject the fungicide into trees and their root systems

Oak wilt is the most deadly disease affecting live and red oaks in Central Texas.  Even though many long-time residents of Angus Valley have known about the presence of oak wilt for years, new neighbors constantly move into the neighborhood.  Please help spread the word to them.

If you suspect your tree has oak wilt disease, please call Chris Dolan and let him know.  He may be willing to come out and inspect your tree.  Also, please report it to Chris if you plan to or already have treated your trees for oak wilt disease.  This will help him track the disease as it progresses.

Links and More Info.

An excellent website managed by the Texas Forestry Service (includes list of oak wilt certified arborists): www.texasoakwilt.org

City of Austin’s Oak Wilt Policy: Links to PDF

Pruning Guidelines for Prevention of Oak Wilt in Texas: Links to PDF