Laurel Wilt Disease Confirmed On Avocado Sample

Posted by Paul Rusnak|August 9, 2009

Florida Agriculture and Consumer Services Commissioner Charles H. Bronson announced the confirmation of laurel wilt disease in an avocado sample from Homestead, Florida. This find represents the first laurel wilt confirmation in a commercial avocado-growing area.

“This find is alarming for the avocado industry,” said Bronson. “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,” Bronson added.

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 US near Savannah, GA in 2002 and subsequently found in Jacksonville, Florida 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, 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 the UF-IFAS website http://trec.ifas.ufl.edu/.