Spread, Vector Flight Behavior, and Impact of Laurel Wilt in Sassafras Beyond the Gulf-Atlantic Coastal Plain

Abstract

Abstract Laurel wilt is a destructive vascular disease of trees in the laurel family (Lauraceae) caused by a nonnative insect/pathogen complex. This study monitored the recent spread and impact of laurel wilt in sassafras (Sassafras albidum [Nutt.] Nees) from the Gulf-Atlantic Coastal Plain region of the southeastern United States (US) into the adjacent Piedmont/Sandhills and Mountain regions. Laurel wilt was detected at thirteen of forty-six sassafras sites including seven outside the Coastal Plain. Compared to nondiseased sites, sassafras mortality due to laurel wilt increased rapidly from 2018 to 2020 and occurred in all diameter classes monitored (≥ 5 cm diameter at breast height, dbh). Flight trapping for the laurel wilt vector, the redbay ambrosia beetle (RAB, Xyleborus glabratus Eichhoff), with α-copaene lures did not enhance early detection of latent laurel wilt infections. Seasonal flight activity of the RAB in the Piedmont and Mountains suggested two generations per year with little to no flight from December through March. Study Implications Sassafras is the most widely-distributed lauraceous tree species in the US and is valued for its ecological functions, durable wood, and numerous cultural uses. Our results strongly suggest the potential for substantial loss of the existing sassafras resource as laurel wilt continues spreading through the eastern US. Survey traps baited with current lures for the primary insect vector are unlikely to improve early detection of new laurel wilt infections. The georeferenced network of plots established for this project provides baseline data for future monitoring efforts and could be revisited to look for evidence of sassafras resistance to the laurel wilt pathogen.