Friday, May 8, 2015

Not the avocados! Florida avocado crops under threat from invasive insect-disease duo

The number of avocado recipes seem to have exploded the last few years with the demise of the low-fat diet and the interest in the concept of "healthy fats."  Avocado on toast, eggs baked in avocados, vegan friendly avocado based puddings, and, of course, guacamole are just a few examples of the attention being paid to avocado.  Unfortunately, while the early 2000 were out with the low-fat diets it was also in with the redbay ambrosia beetle.  The redbay ambrosia beetle (Xyleborus glabratus), and it's accompanying fungus laurel wilt (Raffaelea lauricola), came into Georgia likely through infest hardwood pallets or packing material in 2002.  By 2005 it was found to be associated with the rapid decline in redbay (Persea borbonia) and sassafras (Sassafras albidum) in Georgia, Florida, and South Carolina.  So why are we talking about avocados?  Unfortunately, they are all part of the Lauraceae family of trees and once infected, the trees can be dead within six weeks.  While Florida only produces 10% of the avocados in the US, it is still a 64 million dollar industry and is being treated as a urgent threat to the overall crop.

Laurel wilt (Raffaelea lauricola) by R. Scott Cameron, Advanced Forest Protection, Inc.,
 The real concern for growers is that by the time the first signs of infestation by the beetle have shown up, it's already too late.  Finding trees that have been just infested mean that a fungicide can be used to save the tree.  So, what are researchers using to target infested trees?  Drones.  Drones carrying a thermal digital-imaging camera to find stressed trees. Once researchers have identified areas with stressed trees, then they send in the dogs.  Dogs will alert handlers when they find trees that are infested and targeted treatments can be applied.
redbay ambrosia beetle (Xyleborus glabratus) galleries in redbay tree by James Johnson, Georgia Forestry Commission,

As wide as the beetle and fungus have already spread and as there are multiple hosts for this deadly duo, there isn't a practical hope for eradication and there is potential for the disease to spread to other avocado producing states, California being the most concerning.  While the disease can't be controlled in the natural areas of the states, there is the ability to use the tools researchers are coming up with to save avocado orchards.

Laurel wilt (Raffaelea lauricola) EDDMapS. 2015. Early Detection & Distribution Mapping System. The University of Georgia - Center for Invasive Species and Ecosystem Health. Available online at; last accessed May 5, 2015.
For more on the research on detection strategies: Florida turns to drones, dogs in race to save the guacamole
Redbay ambrosia beetle images: Xyleborus glabratus
Laurel wilt images: Raffaelea lauricola