Laurel Wilt

Laurel wilt disease has been spreading through the U.S. since 2002 and is fatal to tree species in the laurel family. Forest Service researchers are continuing to monitor the disease, search for treatment methods, and develop a better understanding of how it is affecting sassafras and other susceptible species.

Since 2002, forests in the southeastern U.S. have struggled against a disease called laurel wilt. In 18 years, laurel wilt has spread to 11 southeastern states and killed hundreds of millions of trees. A review article by USDA Forest Service scientist Rabiu Olatinwo reflects on the origins and spread of laurel wilt throughout the last several years. Olatinwo, a research plant pathologist at the SRS, published this research with recently retired plant pathologist Stephen Fraedrich and research entomologist Bud Mayfield in the journal Forests.

Laurel wilt is a disease of woody plants in the laurel family (Lauraceae). Hundreds of millions of redbay (Persea borbonia) trees have been killed by laurel wilt in the southeastern Atlantic Coastal Plain region of the United States (US). The disease has also killed large numbers of sassafras (Sassafras albidum) trees in forests and landscapes, and avocado (Persea americana) trees in commercial production. As of October 2019, laurel wilt was known to occur from Texas to North Carolina, south through Florida and north to Kentucky. Laurel wilt is expected to continue spreading through sassafras in the eastern US, and is a potential threat to California bay laurel (Umbellularia californica) in the western US and to lauraceous species elsewhere in the world.
See also: Region 8 - Forest & Grassland Health for more information.

Laurel wilt has devastated plants in the Lauraceae family – redbay, sassafras, pondberry, avocado, and others – since it was first detected in the southeastern U.S. around 2002. There is no widespread, effective treatment for laurel wilt. Genetics research is focused on learning more about the pathogen's genetic structure in order to improve detection methods and screening for possible resistance in Lauraceae host species. "We have developed genetic markers to describe the population of the pathogen in the U.S.," says USDA Forest Service plant pathologist Tyler Dreaden. "Knowing which genotypes to use contributes to a quicker, more cost-effective resistance screening process." Dreaden led a new study to shed light on the genetic structure of the pathogen and its reproductive strategy. The research team included Marc Hughes at the University of Hawaii at Manoa, Randy Ploetz and Jason Smith at the University of Florida, and Adam Black, horticulture director of the Peckerwood Garden Conservation Foundation in Texas. Their findings were published in Forests.