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Title: An uncertain future for American Lauraceae: A lethal threat from redbay ambrosia beetle and laurel wilt disease.

item Kendra, Paul
item Montgomery, Wayne
item Niogret, Jerome
item Epsky, Nancy

Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2013
Publication Date: 3/29/2013
Citation: Kendra, P.E., Montgomery, W.S., Niogret, J., Epsky, N.D. 2013. An uncertain future for American Lauraceae: A lethal threat from redbay ambrosia beetle and laurel wilt disease.. American Journal of Plant Sciences. 4 (3A) 727-738.

Interpretive Summary: Laurel wilt is a new destructive plant disease that kills trees in the family Lauraceae, and it has already decimated populations of redbay and swampbay trees throughout the southeastern U.S. The disease is caused by a fungus that is carried by a small wood-boring insect, the redbay ambrosia beetle. The beetle, native to Asia, was first detected near Savannah, GA in 2002. Since then, it has spread quickly and now is established in portions of North and South Carolina, Georgia, Florida, Alabama, and Mississippi. In Florida, the redbay ambrosia beetle and laurel wilt have reached Miami-Dade County where they threaten avocado, a close relative of native bay trees. Avocado production represents $14 million yearly for the state of Florida. In addition, conditions are favorable for establishment of the disease in bay laurel trees along the Pacific Coast, which would potentially threaten the California avocado industry, worth $415 million annually. This report summarizes our current understanding of laurel wilt disease, the susceptible tree species, and the beetle vector, and includes research conducted by USDA-ARS (Miami, FL) on development of attractants for better detection and monitoring of the insect pest. This review article will increase public awareness of laurel wilt disease and be informative for researchers and action agencies engaged in mitigation and management of this disease epidemic.

Technical Abstract: Laurel wilt is a destructive vascular disease responsible for high mortality of American tree species in the family Lauraceae, particularly redbay (Persea borbonia) and swampbay (P. palustris), two dominant components of Coastal Plain forest communities in the southeastern United States. The disease syndrome emerged as a result of establishment of an exotic wood-boring beetle, Xyleborus glabratus. During gallery excavation, females of X. glabratus introduce a newly-described, obligatory fungal symbiont, Raffaelea lauricola. This fungus proliferates within the gallery and provides food for the beetles, but it has proven to be pathogenic to American lauraceous hosts, which have had no co-evolved history with R. lauricola. Presence of the foreign fungus elicits secretion of resins and formation of extensive parenchymal tyloses within xylem vessels. The extreme defensive response results in blockage of water transport, systemic wilt, and ultimately tree death. The beetle vector was first detected near Savannah, Georgia in 2002, and since has spread throughout the Southeast to become established in six states. The epidemic spread south through Florida more rapidly than predicted and currently threatens commercial production of avocado (Persea americana). Recent research indicates that California bay laurel (Umbellularia californica) can serve as a reproductive host for X. glabratus and is susceptible to laurel wilt disease. Thus, the U.S. Pacific coastal forest ecosystems (and the California avocado industry) would be negatively impacted should the vector become established along the western coast. This review article summarizes our current understanding of the insect vector, the mycopathogen, and the susceptible host tree species. It also addresses elements of disease management and current methods for detection of X. glabratus.