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Oak Wilt Diagnostic Guide

Ceratocystis fagacearum

Oak wilt is a vascular disease of oak (Quercus sp.) caused by the fungus Ceratocystis fagacearum. The fungus is spread below ground via root graft transfer and above ground by nitidulid picnic beetles and possibly oak bark beetles. Members of the red oak family die rapidly (4-6 weeks) while members of the white and live oak family have more tolerance and may live longer. The disease is widespread throughout the eastern and central United States as well as Texas. Oak wilt is considered one of the most economically important diseases affecting oak trees in America.

Trees at Risk

All oak species within the range of the oak wilt fungus are susceptible.

Black Oak

Bur Oak

Live Oak

Pin Oak

Red Oak

White Oak

Signs of DamageOak Wilt Signs

RED OAK GROUP (Red Oak, Black Oak, Pin Oak)

  • Individual leaves wilt from the tips and margins toward the base, turning bronze to brown.  There is often a distinct line between living and dead leaf tissue.
  • Sapwood streaking underneath the bark consistently appears in the red oak group.
  • Oak wilt spreads mainly through the root systems of adjacent trees, so nearby dead trees are a good indicator that oak wilt is present.

WHITE  OAK GROUP (Bur Oak, White Oak)

Oak Wilt Signs

  • Individual leaves wilt from the tips and margins toward the base, turning bronze to brown. There is often a distinct line between living and dead leaf tissue.
  • Sapwood streaking underneath the bark consistently appears in the red oak group.
  • Oak wilt spreads mainly through the root systems of adjacent trees, so nearby dead trees are a good indicator that oak wilt is present.
Oak Wilt Signs

Spore mat under bark of red oak.

Physical Appearance

RED OAK GROUP ONLY

Spore mats may be found on the trunk and large limbs of infected trees that are in advanced stages of wilt.

Treatment Strategy

Red Oak Group: Treat only asymptomatic red oaks that are within root-grafting distance (50 ft) to an infected red oak. Alamo does not work on red oaks that are showing symptoms.

White Oak Group: Treat high value asymptomatic white oaks that are within root-grafting distance of infected white oaks. Symptomatic white oaks which display less than 30% canopy loss from oak wilt can also be treated successfully with Alamo™.

White oaks are more tolerant than red oaks and may survive for several years after becoming infected. Research has demonstrated that therapeutic treatments on white oaks are effective.

Live Oak Group: Treat asymptomatic live oaks that are within root-grafting distance (75 – 200 ft.) of infected live oaks. Live oaks are intermediate in resistance and typically die within 12 months of initial symptom expression, although a small percentage of the population of infected trees may live for extended periods of time in varying states of decline.

Symptomatic live oaks which display less than 30% canopy loss from oak wilt can also be treated successfully with Alamo™.

  • Tree Injection using Alamo

    Notes: FOR RED OAKS
    Dosage: 20 ml/DBH” in 1 Liter water/DBH”
    Timing: All Macro-Infusions should be performed prior to any root-graft disruption treatments and before removal of infected trees. After full leaf expansion in the spring and may continue through the growing season until there is significant fall color.
    Re-Treatment: Retreat with Alamo during the second full season after the initial treatment. Closely monitor for the reappearance of symptoms.
    Alamo
    Alamo
    $64.00
  • Tree Injection using Alamo

    Notes: FOR WHITE OAKS
    Dosage: Preventive: 10 ml/DBH” in 1 Liter water/DBH” Therapeutic: Trees less <25 inches: 10 ml/DBH”, Trees >25 inches: 20 ml/DBH”
    Timing: All Macro-Infusions should be performed prior to any root-graft disruption treatments and before removal of infected trees. After full leaf expansion in the spring and may continue through the growing season until there is significant fall color.
    Re-Treatment: Preventive: Monitor but re-treatment may not be necessary. Therapeutic: If disease symptoms progress during the growing season following application, a second application should be made.
    Alamo
    Alamo
    $64.00
  • Tree Injection using Alamo

    Notes: FOR LIVE OAKS
    Dosage: Preventive: 10 ml/DBH” in 1 Liter water/DBH” Therapeutic: 20 ml/DBH” in 1 Liter water/DBH”
    Timing: All Macro-Infusions should be performed prior to any root-graft disruption treatments and before removal of infected trees. Macro-Infusions with Alamo on live oaks can be performed year round except during leaf exchange in early spring (February/March).
    Re-Treatment: Preventive: if pressure remains high, reapply during the second full season. Therapeutic: Reapply if symptoms progress during growing season after initial application. When symptoms recede, re-treated as a preventative or when symptoms re-develop.
    Alamo
    Alamo
    $64.00

A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org

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