The redbay ambrosia beetle, Xyleborus glabratus, is a type of ambrosia beetleinvasive to the United States. It has been documented as carrying the fungus that causes laurel wilt, a disease that can kill several tree species in the Lauraceae family.
The beetle, first detected in the United States in 2002, is native to Asia and may have arrived in wood products, packing materials or pallets. Laurel wilt has been found in South Carolina and Georgia, and notably in Florida, where it has reached as far south as Miami-Dade County and as far west as Bay County. In 2009, state officials in Mississippi confirmed the positive identification of the disease in Jackson County. In 2011, it was confirmed as present in North Carolina and Alabama.
The redbay ambrosia beetle is a small, black or amber-brown, cigar-shaped beetle under two millimeters in length. The dorsal surface is mostly hairless and shiny when compared to other ambrosia beetles. They can be specifically identified by characters present on the elytral declivity, including its steep and convex shape when compared to other Xyleborus, and by the large size of indentations on the elytra.
The redbay ambrosia beetle is believed to originate from Asia or southeast Asia. Males are haploid, smaller in size, and flightless. The beetle's biology is poorly documented, but presumed to be similar to that of other ambrosia beetles, with larvae and adults feeding on the symbiotic fungus it carries with it, and not the wood of the host tree. The spores of the fungus are carried in mycangia at the base of each mandible.
Larval development time takes from fifty to sixty days. Studied populations increase steadily in size until late summer and early fall without distinct population peaks, leading researchers to believe that there are overlapping generations with year-round reproduction for the insect.
Laurel wilt can spread in at least two ways: one is via the beetle's natural reproduction and migration. A second way is through the sale and transport of beetle-infested wood, a result of redbay's use as firewood and for outdoor grilling.
The beetle was first detected in the United States in 2002, in Port Wentworth, Georgia. It has been suggested that this insect was introduced to the country on the wood of packing crates. The significance of these detections became apparent when the beetle was linked to and identified as the vector of laurel wilt, a fungal disease that had been killing large numbers of redbay trees. The fungus grows throughout the xylem of the tree, preventing the flow of water and nutrients throughout the plant. Death can occur from four to eleven weeks after inoculation.
^ abcHanula, JL. Mayfield, AE. Fraedrich, SW. Rabaglia, RJ. 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. Journal of Economic Entomology. 101(4):1276–1286.
^"Laurel Wilt". Gallery of Pests. Don't Move Firewood. Retrieved 7 November 2011.
^Griffiths, KM and Derksen, AI. 2010. 2009 – 2010 Florida CAPS laurel wilt and redbay ambrosia beetle survey, 4th interim report. Florida Department of Agriculture and Consumer Services, Division of Plant Industry. Gainesville, Florida. Report No. 2010-01-LW-04. 20 p.
^Haack, R.A. 2003. Intercepted Scolytidae (Coleoptera) at U.S. ports of entry: 1985–2000. Integrated Pest Management Reviews 6: 253–282 (2001).
^Fraedrich, S. W., T. C. Harrington, R. J. Rabaglia, M. D. Ulyshen, A. E. Mayfield III, J. L. Hanula, J. M. Eickwort, and D. R. Miller. 2008. A fungal symbiont of the redbay ambrosia beetle causes a lethal wilt in redbay and other Lauraceae in the southeastern USA. Plant Dis. 92: 215–224
^Mayfield, AE; Pena, JE; Crane, JH; Smith, JA; Branch, CL; Ottoson, ED; and Hughes, M. 2008. Ability of the redbay ambrosia beetle (Coleoptera: Curculonidae: Scolytinae) to bore into young avocado (Lauraceae) plants and transmit the laurel wilt pathogen (Raffaelea sp.). Florida Entomologist. 91(3): 485 – 487.
Browne, 1961: The observed hosts for this species have been unhealthy or cut trees of almost any size down to a minimum diameter of about 3 cm. The nest penetrates the wood to a depth of only 2-4 cm and the terminal brood chamber is often large in relation to the small size of the beetle, sometimes measuring as much as 2.5 cm square.
The redbay ambrosia beetle is, as the name suggests, a fungus-farming beetle. In its native habitat in Southeast Asia, it is a harmless and relatively rare member of the rain forest beetle community. After its introduction to the US in approximately 2002, it became apparent that the symbiotic fungus vectored by this beetle is highly lethal to North American trees from the family Lauraceae. Since then the beetle spread throughout the eastern seabord, spreading a new tree disease called laurel wilt, and essentially eliminating redbay (the most common lauraceous tree) from local forests. In 2011 the first small population was recorded in Miami-Dade county in the Southern-most tip of Florida. This is bad news, since this county is an important producer of avocado, another lauraceous tree, and also very susceptible to laurel wilt (Mayfield & Thomas, Florida DPI).
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Browne, 1961: The true lewisi is found in Japan, Korea and Formosa, but is also represented in Malaya by a variety to which no separate name has yet been given. The Malayan form, which is a shot hole borer of moderate size and which differs from the Japanese form by having markedly smaller tubercles on the declivity of the elytra, is by no means abundant and infestation of host trees is usually light. Rabaglia et al.2006: The only report of this Asian species in North America is by Hoebeke (1991) in southeastern Pennsylvania. It can be distinguished from other members of the genus in North America by the irregularly biseriate interstrial punctures on the elytral disc. The size is similar to A. tachygraphus, but the tubercules on the declivity are more uniform in size.