Principal source: Cameron, R. Scott; Chip Bates and James Johnson., 2008. Distribution and Spread of Laurel Wilt Disease in Georgia: 2006-08 Survey and Field Observations . Georgia Forestry Commission September 2008 Funded partially by the USDA Forest Service Forest Health Protection Region 8
\r\nFraedrich, S. W; Harrington, T. C; Rabaglia, R. J; Ulyshen, M. D; Mayfield, A. E. III; Hanula, J. L; Eickwort, J. M; Miller, D. R., 2008. A fungal symbiont of the redbay ambrosia beetle causes a lethal wilt in redbay and other Lauraceae in the southeastern United States Plant Disease. 92(2). FEB 2008. 215-224.
Harrington, T.C., Fraedrich, S.W., Aghayeva, D.N. 2008. Raffaelea lauricola, a new ambrosia beetle symbiont and pathogen on the Lauraceae. Mycotaxon, Volume 104, pp. 399-404 (April - June 2008).
Compiler: National Biological Information Infratsructure (NBII) & IUCN SSC Invasive Species Specialist Group (ISSG)
Review: Stephen W. Fraedrich, Insects, Diseases, and Invasive Plants, USDA Forest Service
Publication date: 2010-06-07
Recommended citation: Global Invasive Species Database (2024) Species profile: Raffaelea lauricola. Downloaded from http://www.iucngisd.org/gisd/species.php?sc=1549 on 08-12-2024.
The redbay ambrosia beetle and its accompanying R. lauricola have spread the wilt through forests of coastal southeastern United States, killing almost all redbays over 2.5 cm in diameter in its path. A survey of redbays in counties near Savannah, the point of introduction of X. glabratus and R. lauricola in Georgia, found mortalities of redbays as high as 70% to 90% in the most heavily infested locations. Other known, susceptible hosts include: sassafras (Sassafras albidum), silkbay (Persea borbonia humilis, California bay (Umbellularia californica), avocado (Persea americana), pondspice (Litsea aestivalis), which is endangered in Florida and threatened in Georgia, and pondberry (Lindera melissifolia), which is federally endangered. Additionally R. lauricola has been isolated from camphor (Cinnamomum camphora) trees with branch dieback. However the collapsing wilt seen in redbay and other species has not been observed (Smith et al., 2009).
Laurel wilt has essentially eliminated mature redbay trees from a large portion of the South Atlantic Coastal Plain and maritime forests. R. lauricola and X. glabratus may continue to expand throughout coastal plain forests from Virginia to Texas. This invasive complex is considered a “very high risk”. R. lauricola and the ambrosia beetle are also a major threat to the avocado industry in south Florida, Mexico, and elsewhere. The invasion of Florida’s avocado groves, valued around $13-30 million annually, by X. glabratus and R. lauricola could be devastating.
Redbay is important to wildlife as its fruit, seed and or foliage are eaten by several species of songbirds, wild turkeys, quail, deer, and black bear, particularly in winter foraging. Two butterflies, the spicebush swallowtail (Papilio troilus) and the Palamedes swallowtail (P. palamedes) use Lauraceae species as hosts. Although P. palamedes larvae may feed on redbay or sassafras, adult females strongly prefer to oviposit on redbay. Reduction in redbay densities may have significant negative impacts on P. palamedes populations in their current range (Mayfield & Thomas, 2006; Koch & Smith, 2008).
R. lauricola and X. glabratus are thought capable of spreading throughout the entire range of redbays in the U.S. in less than 40 years. It may eventually become even more widely distributed if it continues to spread in sassafras, which is found in much of the eastern half of the U. S. There are many additional genera and species in the laurel family, concentrated mainly in the tropical and subtropical areas in Central and South America, which may also be susceptible (Cameron et al., 2008; Koch & Smith, 2008).
Chemical control: The fungicide propiconazole may be a useful method of preventing infection of redbay trees by R. lauricola. Research results found that propiconazole completely inhibited mycelial growth of Raffaelea spp. in vitro at concentrations 0.1 parts per million (ppm) or greater and was fungitoxic at 1 ppm or greater. Ten mature redbay trees received root-flare injections of propiconazole and none developed crown wilt symptoms for at least 30 weeks after being inoculated with Raffaelea spp., whereas nine of ten untreated control trees wilted in more than one-third of their crowns. Concentrations of propiconazole diminish in trees over time but the fungicide was retained in the stem xylem for at least 7.5 months after injection. Fungicide injections may not be a viable technique for avocado crops because at this time there are no fungicides registered for use on avocado. Control of the redbay ambrosia beetle is complicated by the fact that adult beetles must be in the immediate area of aerial sprays to be controlled. Detection of adult beetles involves monitoring traps and/or scouting groves. Once adult beetles bore into the trees contact insecticides are ineffective. The current recommendation is to periodically apply permethrin to the trunk and major limbs of uninfested, potential host trees up to about 10 ft above the ground beginning in early March. If an infestation is taking place, an application of permethrin is recommended to knock down the population as soon as possible (Mayfield et al., 2008a; Crane, 2009).