Laurel Wilt

Pest Alert - The Redbay Ambrosia Beetle has arrived in Mississippi in Jackson County. (posted 8/12/2009)

Press Release - Disease Killing Redbay Trees Makes First Appearance In Mississippi. (posted 8/12/2009)

Laurel wilt is a deadly disease of redbay (Persea borbonia) and other tree species in the Laurel family (Lauraceae). Laurel wilt has been confirmed in the field on several other Lauraceous hosts including avocado (Persea americana), sassafras (Sassafras albidum), camphor (Cinnamomum camphora), and the endangered species pondberry (Lindera melissifolia) and pondspice (Litsea aestivalis). The disease is caused by a fungus (Raffaelea lauricola) that is introduced into host trees by a non-native insect, the redbay ambrosia beetle (Xyleborus glabratus), that was first detected in the United States near Savannah, Georgia, in 2002. The beetle is believed to have been introduced in wooden crating material imported through the shipment of goods from its native range in southeast Asia. The fungus plugs the water-conducting cells of an affected tree and causes it to wilt. Laurel wilt has caused widespread and severe levels of redbay mortality in the Southeastern coastal plain.

Symptoms: Trees with laurel wilt initially exhibit drooping foliage with a reddish purplish discoloration in a portion of the crown. The symptoms will gradually cover the entire crown and turn brown in color. Wilted leaves may remain on the infected trees for year or more.


Left: Redbay with partially wilted crown. Right: Same tree eight months later (Photos by A. Mayfield, Florida DACS Division of Forestry, Bugwood.org) - Click on picture to enlarge.			String of compacted ambrosia beetle sawdust on redbay. (Photos by A. Mayfield, Florida DACS Division of Forestry, Bugwood.org & James Johnson, Georgia Forestry Commission, Bugwood.org) - Click on picture to enlarge.

In the early stages of the disease, a wilting tree may not show any obvious signs of ambrosia beetle attack. Early attacked are inconspicuous and may happen on branches in the crown or on the stem. As the tree dies from the fungal infection, it is colonized by more ambrosia beetles which produce small dowels or "toothpicks" of sawdust protruding from the stem as they bore into the wood.

Distribution: 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. As of July 2009, laurel wilt has been found in South Carolina, Georgia and Florida.


Distribution of Counties with Laurel Wilt Disease Symptoms, by Year of Initial Detection - Updated July 24, 2009. Click to enlarge picture.	Don't Move Firewood magnet from the Mississippi Forestry Commission. Click to enlarge picture.

Host Trees: In addition to redbay, other hosts of the laurel wilt fungus that have been confirmed from diseased plants in the field include swamp bay, avocado, sassafras, pondspice, pondberry and camphor tree.


Redbay (Persea borbonia (L) A. Sprengel) Click to enlarge picture.	Sassafras (Sassafras albidum (Nutt.) Nees.) Click to enlarge picture.

The Insect: The redbay ambrosia beetle (Xyleborus glabratus) is a very small (about 2 mm in length), dark brown to black, cylinder-shaped beetle, similar to other ambrosia beetles. The larvae are typical of scolytid beetles and are white, c-shaped, legless grubs with an amber colored head capsule. The male beetles are smaller than the females and cannot fly. In contrast, the females are strong flyers. Upon emergence, only the females seek a new host. Attacks are evident by pinhole-sized holes in the bark associated with either pitch flow or light-colored boring dust. Investigation under the bark often reveals galleries. As with other ambrosia beetles, the beetle transmits laurel wilt (Raffaelea lauricola) which serves as a food source for the beetle and also causes infected plants to rapidly wilt and die.


Lateral and dorsal view of the redbay ambrosia beetle. (Photos: Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org).					Florida Department of Agriculture & Consumer Services, Division of Forestry, Forest and Shade Tree Pest, Leaflet Number 13, Published April 2008.