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April 9, 2009

Private tree service company works to save new state champion Red Bay tree

An unusually large Red Bay (Persea borbonia) tree was discovered by S.C. Department of Natural Resources wildlife biologist and ecologist Billy McCord at Marine Resources/Ft. Johnson, James Island, near Charleston Harbor in March 2009.  The Red Bay was submitted to Clemson University for consideration as a State Champion and was officially designated as such on April 3. The new State Champion is 7.5 feet in circumference from 4.5 feet off the ground. The Red Bay is 48 feet tall and likely would have been taller as a large top section was destroyed in Hurricane Hugo. Find out more about champion trees at the S.C. Champion Tree Database.

The newly recognized State Champion Red Bay at Ft. Johnson is extremely vulnerable to an invasive insect, the Red Bay Ambrosia Beetle, that carries a fungal disease called Laurel Wilt Disease (LWD). Red Bay trees killed by LWD have been found within a few hundred yards of the new State Champion. LWD is causing widespread mortality of Red Bay and Swamp Bay (Persea palustris), a closely related species, in the coastal regions of South Carolina, Georgia, and Florida.

Barlett Tree Experts, a renowned tree service company since 1907, volunteered to treat the valued tree free of charge in an attempt to protect the new State champion Red Bay at Ft. Johnson.

Bruce Fraedrich, PhD and laboratory scientist with Bartlett, treated the Ft. Johnson State Champion Red Bay on April 6 with the systemic fungicide injection technique that has been shown to be effective in the prevention of LWD by University of Florida researchers. Barlett Tree Experts has also offered to fund and participate in experimental treatment of addition Red Bay trees at Ft. Johnson using additional systemic fungicide application techniques that have not yet been tested to prevent LWD in Red Bay.  Should any of the new experimental treatments prove successful, such procedures may offer less labor-intensive and less expensive options for preventative treatment of LWD.  

Systemic fungicide treatment does not provide long-term protection of plants.  Fungicides will likely need to be applied to target trees at least every 18 months to provide long-term protection from LWD unless an extremely effective control program is developed for Redbay Ambrosia Beetle.   

The beetles bore into trunks of trees and inoculate the plants with a non-native fungus. North American plants respond very negatively to the foreign fungus, which blocks the transport of water through cells of infested plants and causes the plants to wilt and die.

Redbay Ambrosia Beetles and LWD have spread rather quickly along the coast and into the Coastal Plain of Georgia and South Carolina since the disease and vector insect were first identified in the Savannah, GA area in May 2002.  Both the beetle and the associated fungus are thought to have been accidentally introduced through the Savannah port from wooden shipping materials imported from Asia.  Currently, LWD has been documented in all coastal counties in Georgia and nine Coastal Plain counties in South Carolina.  LWD has also been confirmed in 15 Florida counties. In late summer 2008, the disease was documented in central Charleston County at Folly Beach and on James Island near Ft. Johnson by McCord and Laurie Reid, South Carolina Forestry Commission entomologist. The disease was documented in Berkeley County, SC in early 2009 by Dr. Joel Gramling of The Citadel. These recently documented areas of infestation in Charleston and Berkeley Counties represent the most northern known progression of LWD at this time.

Sadly, Redbay Ambrosia Beetle and LWD also use other members of the Lauraceae as host-plants, and the beetle population may remain in an area for many years or indefinitely. Swamp Bay (Persea palustris) is very similar in appearance to Red Bay, and both species occur primarily in only the Sandhills and Coastal Plain of South Carolina and other southeastern states.  Swamp Bay typically occurs in damp soils, while Red Bay generally colonizes drier, sand-based soils characteristic of the lower Coastal Plain. Red Bay is often a primary component of the understory in maritime and other coastal forests.

Four lesser-known, shrubby, native members of the Lauraceae also occur in South Carolina, three of which are considered to be rare in the State. Northern Spicebush (Lindera benzoin) occurs in scattered sites, usually in rich, neutral to basic soils, throughout the State and much of the eastern half of the United States. Bog Spicebush (Lindera subcoriacea) is native only to the Southeast and is found in scattered colonies, usually in peaty seepage bogs.  Bog Pondspice, which is found in our area primarily in the Sandhills, is a SC-listed rare species, as it is throughout its range.  Pondberry (Lindera melissifolia), a specialist requiring seasonally-flooded wetlands, is federally endangered and also occurs primarily in the Southeast.  Pondberry is known from only a few isolated Coastal Plain populations in South Carolina  Pondspice (Litsea aestivalis) is restricted to the Southeast Coastal Plain and forms colonies, usually near the outer slopes of open, isolated wetlands.  Pondspice is listed as a rare species in South Carolina and throughout its range.  These species are all believed to be vulnerable to mortality and potential population loss from LWD.
     
Sassafras (Sassafras albidum) is another rather common tree species that frequently occurs in the same general habitats as Red Bay, and it too can be killed by LWD. However, Sassafras has a much broader distribution than other native members of the Lauraceae, occurring throughout the eastern half of the United States and into southeastern Canada. A major concern is the potential spread of Redbay Ambrosia Beetle and LWD throughout much of the vast range of Sassafras.  Some believe it likely that Redbay Ambrosia Beetle and LWD may have already been transported via firewood or other wood products into the Appalachian region by the uniformed public. Since Sassafras is currently widespread and common, it may provide a conduit for dramatic range expansion of Redbay Ambrosia Beetle and LWD and potential infestation of rare members of the Lauraceae.

Camphortree (Cinnamomum camphora) is native to Asia, but is persistent as an "old-fashioned" landscaping plant at scattered locales along the Southeast coast, and particularly within and near older cities such as Charleston and Beaufort.  It is also slightly invasive, having escaped and become naturalized in native plant communities.  Camphortree, also a member of the Lauraceae, is used as a host-plant by Redbay Ambrosia Beetle, but the associated fungus apparently does not cause mortality in this Asian species, presumably because all co-evolved in the same world region. However, Camphortree may function as a long-term host for Redbay Ambrosia Beetle and LWD, thereby sustaining populations of these invasive species which may repeatedly spread to native plants.

The secondary impacts of LWD are potentially far-reaching.  Red Bay and other native species in the Lauraceae are members of natural plant communities, and all species produce fruit that provide important forage for birds and other animals.  Such native plants also provide diversity and complexity of habitat at various levels above-ground within natural plant communities, thereby creating important wildlife habitat for cover and protection from weather and predators and nesting habitat for birds.  A full diversity of native plant species within natural plant communities also prevents or deters colonization by non-native or invasive plants that can out-compete native species and reduce the overall biodiversity, resiliency and productivity of habitats or communities.  Native plants such as Red Bay are also ecologically important because they are well-adapted to soils that may suffer increased erosion with the loss of stabilizing roots.  Red Bay is usually most common in near-coast forest and shrub thickets as occur on coastal islands, and the species has evolved with other coastal forest specialists to be resistant to wind and salt, thereby providing valuable stabilization to otherwise dynamic coastal forests and secondary dunes.

Another potential negative secondary impact of LWD, particularly in the coastal Southeast, is population declines of the Palamedes Swallowtail (Papilio palamedes). Palamedes Swallowtail is perhaps the most common large butterfly (wingspread 3.5-5.5 inches) in this region and its range is reflective of that for Red Bay and Swamp Bay since the butterfly’s larvae or caterpillars only use such plants as hosts.  Many butterfly enthusiast fear that the large dark brown and yellow butterfly, symbolic of the South Carolina Coastal Plain, may become significantly less common as LWD continues to diminish populations of Red and Swamp Bay. There is some hope in the realization that some bays stricken by LWD sprout from the lower trunks or roots that survive the fungal attack. McCord and Brian Scholtens, a PhD and professor at College of Charleston, hope to initiate a tagging study of Palamedes Swallowtail at Ft. Johnson in 2009 to gain insight into LWD impacts on the butterfly.  Ultimately, any such impacts may also be revealed in populations of the Spicebush Swallowtail (Papilio troilus), since this large butterfly only uses Sassafras and other members of the Lauraceae as its larval host.

The S.C. Department of Natural Resources (DNR) is asking landowners with Red and Swamp Bay trees that died because of LWD 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 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).

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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