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Laurel Wilt Disease Confirmed on Homestead Avocado Sample

TALLAHASSEE – (FDACS)- Florida Agriculture and Consumer Services Commissioner Charles H. Bronson has announced the confirmation of laurel wilt disease in an avocado sample from Homestead. This find represents the first laurel wilt confirmation in a commercial avocado-growing area.
“This find is alarming for the avocado industry,” Bronson said. “Since laurel wilt disease was first found in North Florida, the department has been working cooperatively with other agriculture agencies to track the spread of this disease and beetle, and retard artificial movement. Despite these efforts this unwanted pest/disease complex has spread rapidly via redbay trees within Florida.”

Laurel wilt is a destructive disease of redbay, avocado and other trees in the laurel family (Lauraceae). The disease is caused by a fungus (Raffaelea
lauricola) that infects the sapwood of host trees, restricting the flow of water, causing the leaves to wilt and the trees to die. The fungus is carried into trees by a non-native insect, the redbay ambrosia beetle (Xyleborus glabratus), that was first detected in the United States near Savannah in 2002 and subsequently found in Jacksonville in September 2007.
Laurel wilt has caused high levels of mortality in redbay trees in South Carolina, Georgia and Florida and has affected several other hosts including sassafras and avocado.

Laurel wilt was discovered in an avocado tree that showed signs of wilt in a commercial grove in southern Miami-Dade County. The tree was found by the grove owner, who thought the tree might be suspect for laurel wilt. A University of Florida Institute of Food and Agricultural Sciences (UF-IFAS) researcher in Miami-Dade County collected the sample. The sample was confirmed using real-time polymerase chain reaction (PCR) testing at a School of Forest Resources and Conservation laboratory at the University of Florida in Gainesville.

Currently, there are four additional suspect samples from three avocado groves in Homestead that have laurel wilt symptoms, but these samples have not yet been confirmed by laboratory diagnosis.

A working group of industry members, agriculture agencies and local agriculture groups was assembled earlier this year to review and chart an effective management strategy to mitigate the potential impact of the redbay ambrosia beetle and laurel wilt on Florida’s avocado industry. This group will continue to pursue research, regulatory and outreach plans. As part of this group, UF-IFAS is currently working on treatment and management recommendations. These recommendations will be available at http://trec.ifas.ufl.edu/.

A multi-agency cooperative systematic survey for the redbay ambrosia beetle and laurel wilt is under way in Miami-Dade County. This survey will cover the avocado-growing area in Miami-Dade County to determine the extent of the disease.

Since June 2007, the Cooperative Agricultural Pest Survey (CAPS) program has monitored traps in eight Florida counties from Pensacola to Miami. The traps are baited with a tree oil that is attractive to the beetles. The traps are checked once a month and processed at Gainesville headquarters of the Florida Department of Agriculture and Consumer Services, Division of Plant Industry (DPI). A distribution map showing counties with laurel wilt disease symptoms can be found at www.doacs.state.fl.us/pi/enpp/pathology/laurel_wilt_disease.html.

CAPS is a combined effort of DPI and the U.S. Department of Agriculture to conduct surveillance, detection and monitoring of exotic plant pests and diseases of agricultural and natural plant resources.

DPI’s plant inspectors are also on the lookout for signs of the redbay ambrosia beetle and laurel wilt during their routine inspections of nurseries and other locations throughout the state.

The Florida Agricultural Statistics Service reports the avocado industry represents a production value of $12.7 million with over 6,500 production acres located in Miami-Dade County with some acreage in Collier County.

The public can help prevent the spread of the redbay ambrosia beetle and laurel wilt 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/disease on your trees.
For photos and information visit
http://www.doacs.state.fl.us/pi/enpp/pathology/laurel_wilt_disease.html.

— Use local firewood only. Do not transport firewood from other states because destructive pests and diseases, such as redbay ambrosia beetle and laurel wilt, can hitchhike into Florida on infested firewood. View firewood video at http://www.doacs.state.fl.us/pi/videos.html.

— Do not transport host trees (redbay, swamp bay, avocado, sassafras, pondspice, pondberry and others in the Lauraceae family) unless purchased from a registered nursery.

— If your Lauraceae-family tree dies, use one of UF/IFAS’s recommended methods of disposal.

If you suspect your trees may be infected with laurel wilt or you think you have found a redbay ambrosia beetle, please contact the DPI helpline at 1-888-397-1517.

For instructions on how to submit a plant or insect sample for analysis, visit http://www.doacs.state.fl.us/pi/enpp/pathology/laurel_wilt_disease.html.

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