Oak Wilt - Know Before You Trim

Oak Wilt – Know Before You Trim
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Early detection & prompt action are essential for successful management of oak wilt. The specific measures taken depend on several circumstances but should include appropriate combinations of the following:

Prevent New Infections

  • Cut and dispose of diseased red oaks immediately
  • Avoid wounding oak trees, including pruning, from February through June
  • Sterilize/sanitize all pruning equipment between trees and paint all wounds and fresh stumps regardless of season
  • Handle oak firewood cautiously, burn all firewood before spring, and never store unseasoned oak wood from infected trees near healthy oaks
  • Cover unseasoned firewood (from infection centers and unknown origins) with clear plastic and bury the edges of the plasticInfected red oaks that die in late summer, fall or early winter should be cut down & either burned, buried, or chipped soon after discovery to prevent fungal mats that may form on these trees the following spring
  • If not possible, trees should be injected with herbicide or deeply girdled with an ax and stripped of all bark 2 to 3 ft above the soil line
  • Drying of the wood before spring discourages formation of fungal mats
  • All wounding of oaks (including pruning) should be avoided from February (this year in March) through June
  • The least hazardous periods for pruning are during the coldest days in winter and extended hot periods in mid- to late summer

Regardless of season, all pruning cuts or other wounds to oak trees, including freshly-cut stumps and damaged surface roots, should be treated immediately with paint to prevent exposure to contaminated insect vectors. Any type of paint (latex, oil-based, spray-on, brush-on, or wound dressing) will suffice. Transporting unseasoned firewood from diseased red oaks is a potential means of spreading the oak wilt fungus. Oak wilt can’t be transmitted by burning infected firewood; however, fungal mats may form on unseasoned oak firewood in storage.

Presently, no vectors have been proven to transmit the fungus from live oaks to other oak trees, but diseased wood from any oak species should never be stored near healthy oak trees unless precautions are taken.

It is best to purchase wood that has been thoroughly dried for at least one full year. If firewood from diseased trees is stored near healthy oak trees, it should be covered with clear plastic with the edges buried to prevent insects from leaving the pile

Trees cannot get oak wilt from the smoke of burning diseased wood - the fungus that causes oak wilt is very heat sensitive. The problem with firewood is the potential for storing contaminated wood. If the wood came from an oak wilt center and has fungal mats, then the beetles visit the fungal mats & fly off & infect the healthy trees in your yard. The best precaution is to always buy well-seasoned firewood

If you cut down infected oaks, cover the wood with a clear plastic for one year - this will ensure that the fungus is killed by the summer heat. Once the wood has dried out to the point where the bark is falling off & the wood is cracked, then the fungus that causes oak wilt is no longer viable (alive).

For more information on Oak Wilt please contact:
Mark A. Kroeze, CF, CA, Leon Valley Community Forester
Texas A&M Forest Service
15110 Jones Maltsberger, San Antonio, TX 78247
C: 210-859-9253  O: 210-494-4771  email: