Avocado Scourge Continues Its Spread Through Florida

Last week in this space, Richard Lyons’ Nursery reported more discouraging news concerning citrus greening disease. This week we have received equally ominous information about the disease affecting avocados. The University of Florida has disclosed that the insect responsible for transmitting laurel wilt disease has continued to increase its presence in the state.

Dr. Jonathan Crane of the Tropical Research and Education Center (TREC) in Homestead reports that the ambrosia beetle has distributed the laurel wilt pathogen in 61 of Florida’s 67 counties. Only the Panhandle counties have been spared. Those of you who grow avocado trees at your residence will find Prof. Crane’s advice particularly valuable:

Avocado tree-destroying pathogen now in 61 of 67 Florida counties

A University of Florida Institute of Food and Agricultural Sciences tropical fruit expert is doing his best to help commercial and residential avocado tree owners battle the dangerous laurel wilt pathogen.

With 12,000 commercial avocado trees already destroyed by laurel wilt, growers need a solution, but so do residential homeowners, as the pathogen has now been reported in all but six of Florida’s 67 counties, said Jonathan Crane, a UF/IFAS professor of horticultural sciences and a tropical fruit Extension specialist.

The only counties not to have reported laurel wilt are Escambia, Santa Rosa, Okaloosa, Gulf, Franklin and Wakulla – all in the Panhandle, said Crane, a faculty member at the UF/IFAS Tropical Research and Education Center in Homestead, Florida.

“Eventually, all Florida counties will have laurel wilt,” Crane said.

Though he doesn’t have specific numbers for the residential avocado tree problem, Crane said more and more UF/IFAS Extension faculty members are telling him that their clients are calling about dying avocado trees. Crane is giving tips on how to combat the problem.

Among Crane’s recommendations:

Maintain the health of your avocado tree and other nearby trees. Healthy trees are less attractive to ambrosia beetles. Avocado trees benefit from a good fertilizer program and periodic irrigation.

Report any suspicious redbay, sassafras and avocado trees to the Florida Division of Plant Pathology, 888-397-1517. Look for rapid wilting, dieback and insect boring. Please be sure the tree is a member of the laurel family. You can also call your county’s UF/IFAS Extension office. A list of those offices are here:   http://sfyl.ifas.ufl.edu/map/index.shtml.

Trees affected by laurel wilt or suspected to be positive for laurel wilt disease should not be moved from the infested property unless taken to the local landfill and destroyed or buried. Contact your local waste disposal service for disposal options and procedures. An option is chipping or grinding the entire tree (including the trunk) and tarping the chips for at least one week. The chips may then be used as mulch.

The 12,000 commercial avocado trees destroyed by the laurel wilt pathogen represents about 1.5 percent of avocado trees grown for farming in Florida. More than 98 percent of Florida’s commercial avocados are grown in Miami-Dade County, but avocado trees are popular in residential landscapes.

Laurel wilt is spread by the ambrosia beetle and among avocado trees through the interconnected roots of mature avocado trees. The time from infection to tree mortality ranges from four to eight weeks. The ambrosia beetle was discovered in the U.S., in Georgia, in 2002, and 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.

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