Monitoring Laurel Wilt in Redbay Trees at Cannon’s Point Preserve
Authors: Will Daniell, Alex James, Darrah Mitchell, and Katie Brill
Faculty Supervisors: James B. Deemy, Ph.D. and C. Tate Holbrook, Ph.D.
Laurel wilt is a destructive vascular disease known to cause widespread mortality of tree species from the family Lauraceae, particularly redbay (Persea borbonia), in the southeastern United States. The disease is caused by an invasive species of beetle known as the redbay ambrosia beetle (Xyleborus glabratus). The redbay ambrosia beetle hosts a symbiotic fungus (Raffaelea lauricola) that is the source of the infection, triggering a plant defense response that blocks water transport, causing systemic wilting of leaves and then death. As part of a service-learning project in BIOL 4020 Conservation Biology, we monitored a redbay population at Cannon’s Point Preserve, St. Simons Island, GA. Remarkably, the population contains numerous mature redbay trees that survived the initial outbreak of laurel wilt in the mid-2000s. We located and mapped overstory redbay trees (diameter at breast height > 10 cm), measured their size, and noted reproductive state, percentage of foliar wilt, and other signs of redbay ambrosia beetle infestation. Unfortunately, between 2016 and 2018, seven out of 26 previously healthy trees acquired laurel wilt. Five of the seven infected trees had 100% wilt and were presumed dead. There was no relationship between tree size and the presence of laurel wilt. Spatial analysis showed no clustering among the diseased trees. The increase in susceptibility of redbay trees to laurel wilt could be a result of immune stress caused by recent hurricane activity. Future research and management should include continued monitoring of surviving trees, screening for genetic resistance, and removal of diseased trees.