As the laurel wilt pathogen casts a cloud over the $100-million-a-year Florida avocado industry, University of Florida researchers continue to look for clues to prevent the pathogen from spreading.
The main culprit has been the redbay ambrosia beetle, which has infected millions of native redbay and swampbay trees with the laurel wilt pathogen, but it is rarely seen in commercial avocado orchards.
UF/IFAS scientists now know that several other ambrosia beetles are carrying the laurel wilt pathogen; two native ambrosia beetles are capable of carrying it and transmitting the disease to avocados, said Daniel Carrillo, a UF/IFAS assistant professor in tropical fruit entomology.
Scientists at the UF/IFAS Tropical Research and Education Center in Homestead, Florida, are focused on understanding and then disrupting the association between these native beetles and laurel wilt, said Carrillo, a faculty member at the Tropical REC. Just last month, Carrillo detected an outbreak of another ambrosia beetle, the Tea Shot Hole Borer, which can spread another disease of avocados known as fusarium wilt.
“We are planning an industrywide survey to better understand the threat posed by this new ambrosia beetle-pathogen pest complex,” Carrillo said.
For now, they recommend frequent scouting in avocado groves for early detection and immediate removal and destruction of trees with laurel wilt symptoms -- uproot and chip the entire tree -- followed by fungicide infusions to the trees surrounding the removed tree, and ambrosia beetle control with approved chemical treatments to about one acre of trees surrounding the infected tree.
The redbay ambrosia beetle was discovered in the U.S., in Georgia, in 2002. The link between the beetle and the fungal pathogen was made in 2003. The devastating disease has spread rapidly through the natural landscapes along the southeastern seaboard of the U.S. and has begun to affect commercial avocado production in Florida.
“Laurel wilt is spread by ambrosia beetles and among avocado trees through the interconnected roots of avocado trees. The time from infection to tree mortality ranges from four to eight weeks. To prevent spread of the disease, it is important that trees be destroyed as soon as they are affected by the disease,” said Jonathan Crane, a UF/IFAS professor of horticultural sciences and tropical fruit Extension specialist, also at the Tropical REC.
But UF/IFAS researchers are making progress toward detecting laurel wilt early. In November, they published a study in which they found an algorithm to help them find the pathogen by taking photos from a plane over an avocado orchard.
Reza Ehsani, an associate professor of agricultural and biological engineering, said the algorithm finds laurel wilt-infected avocado trees before symptoms are visible to the naked eye. About 500 growers produce Florida’s avocado crop annually, and more than 98 percent of the fruit is grown in Miami-Dade County.