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December 3, 2008

DNR requests landowners leave dead red bay trees onsite

The S.C. Department of Natural Resources and the S.C. Forestry Commission is asking landowners with red bay (Persea borbonia) trees that died because of laurel wilt to leave the cut wood in place and not allow the wood to be moved to a landfill. Movement of infested firewood, wood chips and logs may be a major factor in spreading the disease into new locations not contiguous with main areas of infestation. Landowners, loggers, and others are asked to leave dead red bay trees and not salvage them for logs, chips or firewood unless the wood products are retained or used on site (burning, or burying in the case of chips, may actually help control the spread of the beetle and fungus). 
Movement of infested red bay wood could potentially dramatically expedite the spread of laurel wilt.   Swamp bay (Persea palustris) is nearly identical to red bay but is more prevalent in damp soils of the inner Coastal Plain.   Laurel wilt has similar impacts on swamp bay, and infested plants of this species should be treated as described for red bay.

Laurel wilt, a new disease of red bay and other plant species in the family Lauraceae, is causing widespread mortality in the coastal regions of South Carolina, Georgia, and Florida.  The disease is caused by a fungus (Raffaelea species) that is introduced into trees by an exotic insect, the red bay ambrosia beetle (Xyleborus glabratus).  The red bay ambrosia beetle is native to Asia and is the 12th new species of ambrosia beetle introduced into the United States since 1990. 

Laurel wilt has been confirmed in eight South Carolina counties including Jasper, Beaufort, Hampton, Allendale, Bamberg, Colleton, Dorchester, and Charleston. There are also 21 coastal Georgia counties and 14 Florida counties with reported infestation.

Find out more about laurel wilt from the USDA Forest Service.

Red bay trees grow in the Coastal Plain region from eastern Texas to Virginia and are ecologically and culturally important, although of minor commercial timber value.  Red bay trees provide fruit for song birds, turkey and quail. Deer and black bear browse on the foliage and fruits.  The larvae or caterpillars of the Palamedes swallowtail, one of the most abundant and most widespread large butterflies of the State’s Coastal Plain, require red bay leaves for development. Impacts on populations of Palamedes Swallowtail are not yet determined. 

The red bay ambrosia beetle was discovered in Savannah’s Port Wentworth area in spring 2002, but it is likely to have been established in the area prior to 2002 when the three adult specimens were trapped at the port.  Red bay trees began dying in Georgia and South Carolina near the Savannah area in 2003. By early 2005, officials with the Georgia Forestry Commission (GFC), South Carolina Forestry Commission (SCFC), and USDA Forest Service began to suspect the newly discovered ambrosia beetle was associated with this mortality.  Subsequent research since 2005 has found that the mortality is caused by a pathogenic fungus that is carried by the red bay ambrosia beetle.  The fungus is believed to be transmitted to healthy red bay trees when they are attacked by the beetle, resulting in a wilt disease.  The disease has also been discovered in individual plants of the federally endangered pondberry (Lindera melissifolia), the threatened pondspice (Litsea aestivalis), sassafras (Sassafras albidum) and avocado (Persea americana).

Many native ambrosia beetles (40 plus species) occur in the United States and primarily target stressed or dying trees.  In general, ambrosia beetles carry specific fungi that are introduced into the trees as they tunnel into the wood, and are fed upon by the developing insects.  In the case of the red bay ambrosia beetle, one of the associated fungi also acts a pathogen as it spreads through the tree’s vascular system, causing the trees to wilt and die.  This associated fungus is in the same class of fungi as those that cause Dutch elm disease and blue stain in pines.

All of Georgia’s coastal counties now have confirmed laurel wilt and the disease is moving northward in South Carolina, southward in Florida, and inland at a rate of about 20 miles per year. Recent infestations of red bay discovered on Folly Beach and James Island, Charleston County, are currently the most northern extent of the known occurrence of laurel wilt along the South Carolina coast. Both of these areas are somewhat isolated from prior known areas of infestation, suggesting the possible dispersal of the red bay ambrosia beetle and associated fungus via movement of infested wood by humans.

DNR protects and manages South Carolina’s natural resources by making wise and balanced decisions for the benefit of the state’s natural resources and its people.

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