Forest Health Protection
1720 Peachtree Road, NW
Room 816 N
Atlanta, GA 30309
Phone: (404) 347-7478
Fax: (404) 347-1880
In 2002, as part of the USDA Forest Service Early Detection & Rapid Response Pilot Project, three specimens of the redbay ambrosia beetle (RAB), Xyleborus glabratus Eichhoff, were captured in detection traps near Port Wentworth, Georgia. This was the first record of this Asian species in North America . Later in 2002, in coordination with APHIS, additional traps were placed in the Port Wentworth area to delimit a possible establishment, but no further catches of this beetle were made. Due to the small number of beetles collected and the location of the traps near warehouses, it was thought likely that the beetles had come directly from solid-wood packing materials and had not become established in native vegetation.
In 2003, significant redbay mortality on Hilton Head Island , South Carolina was reported to the South Carolina Forestry Commission (SCFC). Much speculation ensued about the possible causes of redbay decline and mortality, including drought and water table fluctuation. In late 2004, an investigation by USDA Forest Service Southern Research Station staff eventually found the RAB and an unknown wilt fungus in redbay trees on Hilton Head. After initial inoculation experiments, the combination of the fungus and beetle was suspected to be the primary cause of redbay death.
In 2004, the Georgia Forestry Commission (GFC) was also receiving reports of redbay mortality in coastal areas. A multi-disciplinary team from the USDA Forest Service, SCFC, GFC, Florida Division of Forestry, and other agencies and organizations began to cooperatively evaluate the problem and its causes. In early 2005, the wilt fungus was tentatively identified as a species of Ophiostoma , and was further identified as an unknown Raffaelea species ( Raffaelea is an asexual genus of ambrosia beetle symbionts related to Ophiostoma species) and later described as R. lauricola . Growth chamber inoculations by USDA Forest Service researchers showed the fungus to be a highly virulent wilting agent in several Persea species and other members of the Lauraceae family (e.g., sassafras, pondberry). The fungus was isolated from the redbay ambrosia beetles, indicating that the beetle was a vector of the fungus.
Based on Forest Service-supported surveys, the extent of establishment of laurel wilt in 2005 was so extensive that eradication was deemed unfeasible. In 2006, lab and field studies indicated that sassafras, avocado, and two rare plant species ( Lindera melissifolia and Litsea aestivalus ) were susceptible to attack by RAB and the laurel wilt fungus, although the speed and rates of mortality for these species seem to be lower than that for redbay.
In early 2007, a symposium was held to share what was known about the beetle and fungus and to strategize the forest health community's next steps (See Meetings, 2007 Jekyll Island Redbay Symposium). Interest was expressed for continued surveys, insecticide/fungicide studies, host studies, mechanical control, ecological response, and other miscellaneous projects. A Laurel Wilt Working Group was formed to strategize/prioritize next steps, to educate the public and land managers about the issue, and coordinate efforts among interested agencies, organizations, and individuals.
A second symposium was held in early 2009 in conjunction with the national Forest Health Monitoring annual meeting (See Meetings , 2009 Laurel Wilt Conference, Savannah, GA). The threat to Florida 's avocado was a major source of discussion. Other topics included redbay resistance research, the effects of laurel wilt on plant communities, host plant susceptibility, management via chemical control, redbay seed/genetic conservation efforts, pathways and possible regulations, RAB biology, host chemistry and attraction, pathogen-vector relationships and the laurel wilt website hosted by the USDA Forest Service.
The rate of spread of the beetle is estimated at about 20 miles per year (without help from humans, who may inadvertently transport it in firewood or infested plants). 2009 saw the expansion of laurel wilt into south Florida and coastal Mississippi while it continued its spread in Georgia and South Carolina as well. The detection of the problem in avocado-growing areas of Florida is generating significant concern among commercial growers and residents with avocado yard trees. The detection of laurel wilt in Jackson County, Mississippi reflects a very large geographic jump for the beetle and fungus; it is not known how the problem got there, but human-aided movement or a separate introduction in cargo seem to be more likely causes than “natural” spread. If the beetle had dispersed there on its own, symptoms of laurel wilt would presumably be present in the redbay range between coastal Mississippi and the infested counties in Florida. As of August, 2009, greater than 60 counties in coastal Florida, Georgia, Mississippi, and South Carolina are infested.
- Laurel Wilt in Georgia, James Johnson , Georgia Forestry Commission, Laurel Wilt Conference 27-Feb-09 (Slideshow 2.1 MB).
- Laurel Wilt Disease in Georgia (Poster). C. Bates, J. Johnson, and S. Cameron, Georgia Forestry Commission, Laurel Wilt Conference 27-Feb-09 (342 KB).
- Redbay Ambrosia Beetle and Laurel Wilt in Georgia: History and Summary
of Activities - January 2007 - James Johnson , Georgia Forestry Commission, 1/19/2007 (Abstract, 43 KB) (Slideshow, 2.6 MB).
- Redbay Ambrosia Beetle and Laurel Wilt in Florida's Forests - Albert E. Mayfield, III, FL Division of Forestry, 1/19/2007 (Abstract, 12 KB) (Slideshow, 4.4 MB).
- Redbay Mortality Survey in South Carolina - Andrew Boone for the South Carolina Forestry Commission, 1/19/2007 (Abstract, 12 KB) (Slideshow, 3.6 MB).
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