Alabama Forestry Commission confirms first presence in state of redbay ambrosia beetle; insect carries fungus that causes 'laurel wilt,' which kills host trees about two weeks after initial attack

Michelle Rivera

MONTGOMERY, Alabama , November 16, 2010 (press release) – According to forestry officials with the Alabama Forestry Commission, two beetles trapped in Mobile County, just north of Grand Bay, have been confirmed as redbay ambrosia beetles (Xyleborus glabratus). The specimens were collected and identified by Dr. John Riggins from Mississippi State University and confirmed by the USDA Animal and Plant Health Inspection Service (APHIS), Plant Protection and Quarantine (PPQ) Section. This is the first confirmation of the presence of the beetle in Alabama.

The beetle carries a fungus that causes a destructive disease called “laurel wilt.” The fungus moves into the tree, and infects the sapwood. As this fungus spreads, it clogs the vascular system of the tree, causing it to wilt. The infected tree will exhibit wilting foliage that is reddish or purplish in color. Eventually, the entire crown wilts and reddens. In the latter part of the infestation, toothpick-like tubes appear on the trunk of the tree caused by fine sawdust and frass seeping through the entrance holes. If a cross-section of the main stem is viewed, it will show black discoloration of the sapwood. Approximately two weeks after the initial attack, the host tree dies from the disease.

Redbay (Persea borbonia) is the most susceptible tree, but sassafras, camphor and avocado are also known to succumb from laurel wilt disease. Other possible host trees in the Laurel family (Lauraceae) that may die from this disease are pond spice, pondberry, and swamp bay.

In 2002, three redbay ambrosia beetles were found in a trap near Port Wentworth, Georgia. This was the first record of this non-native ambrosia beetle from Asia to be detected in North America. The assumption is that this insect was introduced into the U.S. from solid-wood packing material. Since 2002, the beetle has spread further into Georgia. It has also spread into other states as well and now exists in South Carolina, Florida, and Mississippi.

“As of now, there is no successful control method for laurel wilt disease,” said Dana McReynolds, Forest Health Coordinator for the Alabama Forestry Commission. “The best method right now for inhibiting the spread is to prevent the transportation of infected wood and nursery stock. The US Department of Agriculture and other natural resource agencies will continue to monitor the area for wilting and dying redbay trees.”

The public can help prevent the spread of the redbay ambrosia beetle and laurel wilt disease by following these simple suggestions:

* Become familiar with the signs of laurel wilt disease and redbay ambrosia beetle and be on the lookout for evidence of the pest or disease on your trees.
* Use local firewood only – Redbay firewood should not be transported. Do not transport firewood of any kind from other states because destructive pests and diseases, such as redbay ambrosia beetle and laurel wilt, can hitchhike into Alabama on infested firewood.
* Do not transport host trees (redbay, swamp bay, avocado, sassafras, pond spice, pondberry, and others in the Lauraceae family) unless purchased from a registered nursery.
* Avoid spreading the beetle and pathogen to new areas - Wood or chips from infested trees should not be transported out of the local area where the trees were found. Dead redbay or other Lauraceous tree species cut in residential areas should be chipped and left onsite as mulch, or disposed of as locally as possible.

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