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Watching over the sassafras trees: Federal and state forestry agencies monitor deadly tree disease together

Laurel wilt is a tree disease that rapidly kills sassafras and other trees in the Laurel family. The impact of laurel wilt on sassafras trees in the Appalachian Mountains and the Piedmont is likely to be severe, as a collaborative three-year monitoring project recently showed. The partners include the USDA Forest Service and eight state forestry agencies.

Bryan Mudder stands next to a sassafrass tree.
Bryan Mudder examines a sassafras tree along the Hiawassee River in Tennessee. A recent collaboration between the USDA Forest Service and eight state forestry agencies assessed the impact of laurel wilt as it spreads into the Piedmont and Appalachian Mountain regions of the eastern U.S. USDA Forest Service photo by Albert E. Mayfield III.

Laurel wilt is a deadly vascular disease of trees in the Laurel family. It is caused by a nonnative insect-pathogen complex. The USDA Forest Service and eight state forestry agency partners recently completed a three-year project to assess the occurrence and impact of laurel wilt spreading into sassafras trees in the Piedmont and in the Appalachian Mountains of the eastern U.S.

Sassafras grows in more than 28 states and reaches its largest form in the Appalachian Mountains. Sassafras is valued for its ecological functions and durable wood. There are also long cultural and culinary traditions around the tree’s fragrant leaves and roots.

As the monitoring effort showed, sassafras mortality due to laurel wilt increased rapidly from 2018 to 2020. Death occurred in small and large trees alike. Trapping for the redbay ambrosia beetle, which spreads the disease, did not improve early detection of latent laurel wilt infections. Seasonal flight activity of the redbay ambrosia beetle in the Piedmont and Mountains suggests two generations per year with little to no flight from December through March.

The results suggest that laurel wilt will continue to spread, killing sassafras trees wherever it goes. However, a georeferenced network of plots was established during the project. This network can provide baseline data for future monitoring efforts and can be revisited to look for evidence of sassafras resistance to laurel wilt.

Principal Investigators
Albert E. Mayfield III, Research Entomologist
Rabiu Olatinwo, Research Plant Pathologist
Bryan Mudder, Biological Science Technician
Stephen W. Fraedrich, Plant Pathologist (Retired)
4552 - Insects, Diseases, and Invasive Plants
Spread, vector flight behavior, and impact of Laurel Wilt in Sassafras beyond the Gulf-Atlantic coastal plain
Research Partners
Jaesoon Hwang, State and Private Forestry, Forest Health Protection
Wood Johnson, State and Private Forestry, Forest Health Protection
Jessica McKenney, State and Private Forestry, Forest Health Protection
Paul Merten, State and Private Forestry, Forest Health Protection
Robert Rabaglia, State and Private Forestry, Forest Health Protection
Marc Digirolomo, State and Private Forestry, Forest Health Protection
Karen Reed, Southern Research Station
Matt Cloud, Southern Research Station
Susan Best, Southern Research Station
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Ashleigh Hillen, Southern Research Station
Deanna Tipton, Southern Research Station
External Partners
Alabama Forestry Commission: Dana Stone, Mary Claire Smith, Kacey Gordon
Arkansas Forestry Commission: Chandler Barton, Brady Bradley, Brayden Fisher
Georgia Forestry Commission: Chris Barnes, Mark McClure, Lynne Womack, Greg Klett, Chip Bates
Kentucky Division of Forestry: Alexandra Blevins, James Morris, Abe Nielsen
North Carolina Forest Service: Jim Slye, Wayne Langston, Brian Heath, Craig Lawing, Kelly Oten, Rob Trickel
North Carolina State University: Cavell Brownie
South Carolina Forestry Commission: David Jenkins
Tennessee Department of Agriculture, Forestry: Nathan Hoover, John Henderson, Sam Gildiner
Virginia Department of Forestry: Lori Chamberlin, Katlin DeWitt, M. Mulroy-Goldman
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Virginia Department of Conservation and Recreation: Erik Molleen, Nathan Curtis, M. Fulford