Laurel wilt, a devastating fungal disease, poses a significant threat to certain native Kentucky trees. The University of Kentucky Martin-Gatton College of Agriculture, Food and Environment, in conjunction with the Kentucky Division of Forestry and the University of Tennessee Institute of Agriculture, is hosting a series of workshops to help alleviate the problem.  

Since its 2003 detection in the United States, laurel wilt disease has spread to twelve southeastern states, including several bordering Kentucky. While laurel wilt causes widespread damage to several species within the laurel family, such as redbay, spicebush and avocado, sassafras and spicebush are the primary Kentucky species at risk.  

“We really want to raise awareness about this destructive disease, and these field days have proven very effective,” said Clay Turner, UK forest health technician. “Laurel wilt disease plays havoc with sassafras and spicebush and we want to get the word out to save these native Kentucky trees.”  

Early detection and management are crucial. Laurel wilt disease can quickly kill the tree by infecting the xylem and cutting off circulation, keeping it from accessing water. Tree death can be quick, just weeks to months after initially becoming infected. In most laurel wilt diseased trees and shrubs, the fungus will cause distinctive, dark-staining streaks within the sapwood.  

Affected trees show sudden wilting and foliage discoloration, often resembling drought or water stress. The leaves eventually turn reddish-brown and die. The first signs of the disease in Kentucky were discovered in 2019 in Christian, Todd and Logan counties and have since spread.  

“The severity of the dieback can vary, affecting localized areas or the entire tree,” said Ellen Crocker, Department of Forestry and Natural Resources assistant professor who recently co-authored a laurel wilt study. “Inevitably, laurel wilt leads to tree death, with sassafras typically succumbing to the disease within several months of infection. Underneath the bark, dark streaky staining in the sapwood can be observed, accompanied by small circular holes and sawdust, signs of redbay ambrosia beetle tunneling activity.”  

Laurel wilt is caused by the fungus Raffaelea lauricola, which overwinters in infected wood and beetles, such as the ambrosia beetle. Once a tree becomes infected, the fungus colonizes the sapwood and spreads through the tree's water-conducting tissues. As the infection progresses, the tree's water uptake is restricted, leading to rapid wilting and eventual death. The ambrosia beetle, primarily responsible for spreading the fungus, creates galleries in the sapwood and cultivates the fungus as a food source for larvae and adult beetles. The beetles also carry fungal spores in their mouthparts, facilitating disease spread. Natural beetle movement and human-mediated transportation of infested wood contribute to the disease's dispersion.  

Currently, no effective management options exist for laurel wilt. Therefore, preventing the movement of infected wood is crucial to minimizing the incidence and spread of the disease.  

“It is essential to avoid transporting wood products, such as firewood or debris, from infected trees or susceptible species, especially in areas where the disease has been confirmed,” Crocker said. “Prompt removal and destruction of infected trees on-site can help reduce disease spread. By taking proactive measures and limiting the movement of infected wood, we can work towards preserving the natural beauty and biodiversity of Kentucky's forests and landscapes.”  

UK hosts the first and third field days; July 6 at the Jefferson Memorial Forest in Louisville and Aug. 11 at Lake Barkley State Resort Park. To register for either, email Clay Turner at cmturn2@uky.edu. UT hosts the second workshop July 18 at the UT Arboretum. To register, email Hannah Hollowell at Hannah.Hollowell@tn.gov. For more information on laurel wilt disease, visit https://forestry.ca.uky.edu/laurel-wilt.