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

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.