Photographer: R. Scott Cameron Affiliation: Advanced Forest Protection, Inc Source: www.bugwood.org Copyright: CC BY 3.0
Laurel wilt is caused by an insect-disease complex formed between the redbay ambrosia beetle (Xyleborus glabratus) and the vascular fungus (Raffaelea lauricola) it transmits to host plants in the family Lauraceae. The redbay ambrosia beetle transfers R. lauricola to the host plant through a specialized mouthpart called the mycangia. Beetles in the genus Xyleborus feed on the fungus inoculated in sapwood which is stored in the mycangia and spread to host plants utilized by adult females.
Symptoms: External symptoms are not readily noticeable upon initial infection from laurel wilt. Small strings of sawdust may appear where the redbay ambrosia beetle attacked the host, but these strings can blow away or disintegrate easily erasing signs of invasion. If the bark is removed at the point of attack small black holes are visible indicating the trees defense against infection from the fungus Raffaelea lauricola. The fungus spreads through the outer sapwood of the host plant causing the tree to exhibit wilted foliage with a purple tint. As foliage begins to wilt and die the tree weakens and becomes vulnerable to colonization of additional ambrosia beetles such as Xylosandrus crassiusculus, Monarthrum mali, and Xyleborus affinus.
Host(s): Redbay (Persea borbonia), sassafras (Sassafras albidum), avocado (Persea americana), swampbay (Persea palustris), pondspice (Litsea aestivalis), pondberry (Lindera melissifolia), and camphor (Cinnamomum camphora)
Laurel wilt causes the host plant to wilt and die within a matter of months or even weeks. Lauraceae hosts are in danger of significant damage and population decrease from the introduction of the redbay ambrosia beetle. Laurel wilt is known to spread rapidly, with an increase of redbay mortality from 10% to 15% within 15 months in Florida. Areas in South Carolina are near complete mortality of redbay populations. The loss of redbay is detrimental to wildlife that utilize the plant as fruit. Foliage and seed of redbay is eaten by songbirds, wild turkeys, quail, deer, and black bear. Economic concern arises from the patterns of host use seen in avocado plants by the redbay ambrosia beetle. Avocado plants are a crucial part of Florida, California, and other state's agriculture. Damage potential to the avocado trade is uncertain if laurel wilt spreads to avocado plants in Florida and other states that export avocados.
The fungus Raffaelea lauricola reproduces asexually by spore production and is transferred to host plants by a female redbay ambrosia beetles.
In 2002 the redbay ambrosia beetle was discovered near Port Wentworth, Georgia by chance in a survey trap. Within three years the beetle spread through the southeast U.S. and laurel wilt became the known cause of death to ambrosia and sassafras trees in Florida. Experts believe introduction of the redbay ambrosia beetle was facilitated by solid wood packing materials such as crates or pallets that the beetle was feeding on undetected.
NOW IN TEXAS: Spring 2015, dying redbay trees, infected with laurel wilt fungus, were detected by a U. S. Forest Service pathologist in Hardin County, Texas and the red bay ambrosia beetle was trapped in the same vicinity shortly thereafter. Currently, the disease has been found in southeast Texas in Hardin and Jasper counties, and in 2016 it was confirmed in Tyler County.
Native Origin: India, Japan, Myanmar, and Taiwan
U.S. Habitat: Laurel wilt is found in agricultural areas, natural forests, and planted forests where host plants are available. Transferred by the redbay ambrosia beetle (Xyleborus glabratus), laurel wilt is most commonly found on redbay and sassafras plants.
U.S. Present: FL, GA, MS, SC and TX
You can help prevent the spread of laurel wilt by avoiding the transport of firewood. Wood chips of infested trees should not be transported out of the area, but left on-sight as mulch. If its not possible to use the wood chips as much, try and leave them as locally as possible to prevent further spread. There are currently no chemical management options, but the experts at the University of Florida-Institute for Food and Agricultural Sciences are developing possible products.
Douce, G.K. and J. Johnson. 2005. Xyleborus glabratus in Georgia’s coastal forests. Georgia Forestry Commission Pest Alert, October 31, 2005.
Hanula, J.L., A.E. Mayfield III, S.W. Fraedrich, and R.J. Rabaglia. 2008. Biology and Host Associations of Redbay Ambrosia Beetle (Coleoptera: Curculionidae: Scolytinae), Exotic Vector of Laurel Wilt Killing Redbay Trees in the Southeastern United States. J. Econ. Entomol. 101(4): 1276-1286.
Mayfield, A.E. III, J.A. Smith, M. Hughes and T. J. Dresden. 2008a. First report of laurel wilt disease caused by Raffaelea sp. on Avocado in Florida. Plant Disease 92(6): 976.
Mayfield, A.E. III, J.E. Peña, J.H. Crane, J.A. Smith, C.L. Branch, E.D. Ottoson, and M. Hughes. 2008b. Ability of the redbay ambrosia beetle (Coleoptera: Curculionidae: Scolytinae) to bore into young avocado (Lauraceae) plants and transmit the laurel wilt pathogen (Raffaelea sp.). Florida Entomologist 91(3): 485-487.
Pest Alert Fact Sheet - Provided by Florida Department of Agriculture and Consumer Services, Division of Plant Industry
P.E.S.T. (Spring 2015) Quarterly Newsletter on Forest Pest MAangement Issues. Texas A&M Forest Service.
Riggins, J.J., S.W. Fraedrich, and T.C. Harrington. 2011. First report of laurel wilt disease caused by Raffaelea lauricola on Sassafras in Mississippi. Disease Notes 95(11): 1479.
Smith, J.A., L. Mount, A.E. Mayfield III, W.A. Lamborn, S.W Fraedrich. 2009. First report of laurel wilt disease caused by Raffaelea lauricola on Camphor in Florida and Georgia. Plant Disease 93(2): 198.