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USDA Forest Service
Forest Health Protection
Region 8
1720 Peachtree Road, NW
Room 816 N
Atlanta, GA 30309

Phone: (404) 347-7478
Fax: (404) 347-1880

United States Department of Agriculture Forest Service.

Florida Forest Service USDA-APHIS Georgia Forestry Commission South Carolina Forestry Commission USDA Forest Service

Laurel Wilt

Ecological Concerns

The following section was extracted from Recovery plan for laurel wilt on redbay and other forest species. Caused by Raffaelea lauricola, vector Xyleborus glabratus (Mayfield et al. 2009).

 

Laurel wilt is devastating to redbay trees and kills nearly all mature redbay stems in impacted stands within 3-5 years. Small size classes (<1 inch diameter) of redbay regeneration appear to be generally less affected, and such regeneration has been observed in abundance in areas where virtually all the overstory and midstory redbay trees have otherwise been eliminated by laurel wilt (Cameron et al. 2008, Fraedrich et al. 2008). An explanation for the survival of this regeneration is still uncertain, but it may be that smaller redbay trees are relatively less apparent or attractive to the RAB. While the presence of redbay regeneration and the occasional discovery of live, larger-diameter saplings in the aftermath of a laurel wilt epidemic suggest that redbay will not go extinct, populations of mature redbay are nonetheless being dramatically reduced. Hanula et al. (2008) found that RAB populations dropped dramatically, but did not completely disappear, after most suitable redbay host material had been eliminated. Low-level populations of RAB were still present in 2009 in the areas where laurel wilt was first discovered and almost all suitable redbay trees for RAB brood had been eliminated at least 3 years before (J.L. Hanula, unpublished). It is not yet clear whether redbay regeneration will be able to eventually grow into mature canopy trees in such areas, or whether RAB populations will persist at low levels and continue to attack and inoculate trees with the laurel wilt pathogen once the trees reach a certain size. If low level RAB populations can be maintained in dead or weakened stems of other tree species that are not hosts for laurel wilt, then the beetle and pathogen may persist indefinitely.

 

To date, the ecological impacts of drastic reductions in redbay populations are not well researched or have not yet been reported in the scientific literature. Redbay produces blue drupes in the fall, and its fruit, seed and/or foliage are eaten by several species of songbirds, wild turkeys, quail, deer, and black bear (Brendemuehl 1990). Leaves of Persea species are the primary larval food source of the Palamedes swallowtail butterfly (Papilio palamedes (Drury)) (Hall and Butler 2007) and the only known hosts of the redbay psyllid (Trioza magnoliae (Ashmead)) (Hall 2009). Redbay (sensu lato, including swampbay) occurs in a very wide variety of habitats and forest types, and although not typically known as a large tree, it can reach sizes in excess of 70 feet tall and 40 inches diameter. A better understanding of the potential impacts of the local reduction or elimination of redbay on trophic, habitat or other ecological relationships is needed.

 

Potential ecological impacts on host species other than redbay are even less certain at this time. In a survey of more than 180 wetlands in northeast Florida, Surdick and Jenkins (2009) observed pondspice populations at 15 locations and documented varying percentages of pondspice with laurel wilt symptoms (up to 90%), but they confirmed the presence of the laurel wilt pathogen from only one site. The threat posed by laurel wilt to extirpate pondspice and pondberry populations is still unclear and deserves additional research attention. Furthermore, there are numerous other species in the Lauraceae, both in the United States (including California) and in other parts of the Western Hemisphere (including the Carribean, Mexico , Central and South America) that could be affected by laurel wilt should the vector become established within their ranges.  

 

Additional Information

  • What Forest Compositional Changes Can We Expect Following Redbay Mortality on a Barrier Island? - Rebecca S. Effler and Theron E. Menken, UGA Marine Institute, Sapelo Island, GA, 1/19/2007 (Abstract, 15 KB) (Slideshow, 1.6 MB)
  • What Else Is at Risk from the Redbay Ambrosia Beetle and Laurel Wilt? - Laurie Reid, South Carolina Forestry Commission (Abstract, 12 KB) (Slideshow, 4 MB)

 

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USDA Forest Service - Forest Health Protection, Southern Region
Last Modified: Monday, 16 December 2013 at 14:18:30 CST


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