Laurel Wilt Disease: A Threat to Kentucky Sassafras Trees

Laurel wilt is a new disease that was recently detected in southwestern Kentucky. This disease, which is transmitted by the redbay ambrosia beetle, has the potential to rapidly kill sassafras trees. Currently no management options are available for this disease. However, it is important to avoid movement of infected plants or dead wood to prevent spread of the disease. As this disease is new to Kentucky, efforts are ongoing to determine the extent to which it is present in the state. If laurel wilt is suspected, please contact a local county Extension agent for further assistance.

Laurel Wilt Fast Facts

  • Symptoms include sudden wilt and rapid death with dead red-brown leaves still attached (Figure 1). Death can occur within weeks to months after infection. Sapwood may exhibit a dark, streaky staining when bark is cut away (Figure 2).
  • The fungal pathogen is moved by the invasive redbay ambrosia beetle, Xyleborus glabratus. These small insects (approximately 1/16-inch long) bore into trees or shrubs leaving a small circular hole in the bark, accompanied by a thin “toothpick” of sawdust. These beetles carry fungal spores with them that infect the xylem of trees resulting in disease. However, keep in mind that not all ambrosia beetle damage on sassafras is related to laurel wilt and laurel wilt can still be present even if there are no visible signs of no ambrosia beetle.
  • Human movement of contaminated wood, such as firewood, may aid in the spread of the pathogen and the insect responsible for laurel wilt.
  • In Kentucky, sassafrass trees are likely the species most at risk from laurel wilt. However, redbay, spicebush, and other members of the Lauraceae family are also susceptible to the disease. Potential hosts do not include mountain laurel, which, despite its name, is not in this family.
  • Laurel wilt is caused by the invasive fungal pathogen Raffaelea lauricola, which colonizes sapwood and travels through the xylem. The disease clogs the flow of water in the tree’s trunk, resulting in the “wilt” symptoms similar to those of a tree without enough water. This effectively strangles the tree and rapidly kills it.

Figure 1: Symptoms of laurel wilt include sudden wilt and rapid death with dead red-brown leaves still attached. (Photo: Ellen Crocker, UK)

Figure 2: Sapwood of infected trees may exhibit a dark, streaky staining when bark is cut away. (Photo: Ellen Crocker, UK)

Disease Prevention Options

No management options are currently available for laurel wilt. Thus, techniques that prevent infection are critical to limit spread and incidence of this disease.

  • Do not move wood products, such as firewood, from infected trees/shrubs, or from species susceptible to laurel wilt.
  • If laurel wilt is suspected, contact a local county Extension office for additional assistance.

Additional Resources

  • Laurel Wilt Information from the University of Kentucky Department of Forestry and Natural Resources – Link
  • Kentucky Cooperative Extension Service County Offices – Link

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By Ellen Crocker, Forest Health Extension Specialist; Tyler Dreaden, US Forest Service Research Plant Pathologist; Kim Leonberger, Plant Pathology Extension Associate; and Nicole Gauthier, Plant Pathology Extension Specialist

Posted in Forest Trees, Landscape Trees & Shrubs