The 2012 ASHS Annual Conference

Native and non-native trees in the Lauracae, including the commercially important avocado (Persea americana Mill.) are threatened by laurel wilt (LW), caused by the fungus Raffaelea lauricola.  The redbay ambrosia beetle, Xyloborus glabratus (RAB) is the primary vector of R. lauricola.  During 2002 this exotic beetle was introduced into Port Wentworth, GA, perhaps via infested solid wood packing material.  Since then, LW has spread by the natural dissemination of the vector and anthropogenic  movement of infested wood throughout the southeastern U.S. (Georgia, South and North Carolina, Florida, and Mississippi), eliminating redbay (P. borbonia), swampbay (P. palustris) and other native members of this family.  Research has shown that avocado trees are susceptible to attack by the RAB and susceptible to LW.  In Jan., 2010, the RAB was detected approximately 16 km from the edge of Florida’s primary commercial avocado production area in southeastern Miami–Dade County, and in Feb., 2011, LW was confirmed in dying swampbay trees in the same area.  Swampbay trees continue to die in the area, recently within 7 km of the closest commercial avocado orchard.  Despite intensive research since 2006, no economically viable chemical control measures have been found to combat LW.  Thus, detection and immediate suppression of outbreaks of LW within the avocado production area is viewed as the most appropriate LW management strategy.  Populations of RAB decrease dramatically as populations of host trees are eliminated by LW; therefore, as swampbay is eliminated in Miami-Dade County, disease pressure and vector density would be reduced.  To assess the distribution and spread of LW in Miami–Dade County, helicopter surveys are currently conducted in a 389 km² area that includes 2,914 ha of commercial avocado production.  During these surveys, a hand-held GPS unit is used to locate with long and latitude coordinates of avocado trees with LW symptoms (i.e., wilting, desiccation, and dieback).  With locations that are plotted on Google Earth® suspect trees are ground-truthed with subsequent diagnostic assays for R. lauricola; positive trees or parts thereof are then removed, chipped or otherwise destroyed.  To date, one complete aerial survey of the industry has identified 65 suspect trees, none of which have tested positive for R. lauricola.