Oak Wilt

City Pruning Gidelines for Oak Wilt | General City Oak Wilt information | Texas Oak Wilt (includes videos on identification and treatment)

from the January/February 2011 newsletter 

Unfortunately oak wilt has again been discovered in Northwood. If caught in time, an infected tree can be injected with a fungicide to try to save the tree. Some species die fairly quickly after being infected; other can survive longer, which means the fungicide has a better chance of working.

Examples of red oak leaf with oak wilt | live oak leaf with oak wilt from TexasOakWilt.org

Treating a tree by injecting it with a chemical MAY save that tree – if it is injected in time – but does NOT stop the oak wilt fungus from traveling through the roots to nearby oak trees with intertwined roots. Fortunately the fungus doesn’t travel through the roots of other species. So if the only way two oak trees’ roots are connected is by going through the roots of another species tree, the fungus will not reach the “second” oak tree.

Digging a trench deep enough to cut the intertwined roots is the only way to do prevent the spread of oak wilt to nearby oak trees, and is both very expensive and is somewhat temporary, as the roots may eventually intertwine again over a number of years. But it may be enough to stop that particular infection from spreading to nearby oak trees.

Most oak wilt infections extend through the root system when oak tree roots intertwine; oak wilt travels 75 to 150 feet per year through the roots. New outbreaks are often due to the tiny sap beetle, which visits an infected tree, picks up the spores and then deposits them on a healthy tree that has an open wound, such as a just-pruned branch or damage from a lawnmower. The sap scent attracts the beetle. That is why it is so crucial to paint immediately after pruning or otherwise injuring an oak tree…and to sterilize tools before pruning, as the oak wilt spores can be transferred on pruning tools. Use a 10% bleach solution or Lysol to sterilize the pruning tools.

The sap beetle, which is responsible for many new infestations of oak wilt, is most active between February and June, so it is best to avoid pruning oak trees during those months. If you must prune or the tree is wounded and has an opening not covered by bark, PAINT IT IMMEDIATELY! (Spray paint works.) Don’t give a (possibly nearby) sap beetle time to scent and fly to the wound and spread the oak wilt fungus.

As spring approaches and the trees begin to bud, watch your oak trees for signs of illness. If the leaves don’t develop normally, you may have oak wilt. If you suspect oak wilt, contact one of the Association officers. We can have a professional evaluate the tree and recommend the appropriate treatment.

Who to notify about poor pruning practices

If you see someone pruning oak trees without painting (at any time of year) and you are not comfortable talking to them, email or call the City Arborist. (use their email form) or 512.974.1876. Include at least the address of the problem pruning and as much other details as possible, such as if the pruner is the resident or a contractor – and if a contractor, what company? (Is there a company truck or sign?)

If you can’t reach the  City Arborist, you may call 311.

Minimizing the threat of oak wilt

There are a number of effective measures that can minimize the threat of oak wilt:

* Prune oaks only in deep winter or deep summer. Any wound on an oak tree when the bark beetle is active is likely to get visited by the beetle. If the wound and the visit occur during spring or fall, when the fungus is also active, there is a chance that the tree will be infected with the disease.

Immediately treat every oak wound with pruning paint, regardless of its size or the time of year. Paint wounds with a high quality tree wound dressing, which will not impede the tree’s natural healing process. Although there is controversy over the benefits of horticultural wound dressing, its use in live and red oaks does reduce the risk of oak wilt infection. Wounds must be treated immediately; treating old wounds is not necessary because after two days, wounds are no longer attractive to beetles.

Remember that pruning is only one of the ways trees get wounded. Automobiles, lawn mowers, string trimmers, wind, ice breakage and bulldozers are other common causes of wounds.

  • Manage firewood to avoid infection. It is not necessary to avoid using the fireplace to stop the spread of oak wilt; smoke from infected wood burning is not a threat. The fungus is destroyed by heat and will not even survive in dry firewood.
  • If you use red oak firewood, try to buy wood from trees that have not been infected or killed from oak wilt. Only wood that has been cured for an entire summer should be stored near uninfected red or live oaks. If you buy oak firewood and are unsure of its age or origin, use it up before spring.
  • Diversify your shade tree plantings. Large blocks of red and live oaks are susceptible to the spread of the disease. Plant Afghan pines, redbuds, cedar elm, chinkapin oak, bur oak, Chinese pistache and Monterrey cypress in addition to red and live oak.

 Association may help with oak wilt treatment cost

For eligible residents, the Association may pay half of the cost of treatment, up to $500.

Eligibility requirements:

  • Homeowner must be current on dues and any other obligations with the neighborhood association (NNA)
  • Homeowner must use treatment specialist selected by the NNA
  • Homeowner must pay his/her portion in full at the time services are rendered
  • Homeowner must agree in writing to all requirements, including cost-sharing provision

If a homeowner has not paid the current year’s dues, the Board can consider allowing a homeowner to become current and therefore eligible for the program if the homeowner has been mostly compliant dating back to 2005, the year the program was adopted.