New Disease May Cost Florida’s Avocado Industry Millions, UF Experts Warn

  • By:
    Tom Nordlie – (352) 273-3567
  • Sources:
    Jonathan Crane –, (786) 255-5878
    Edward “Gilly” Evans –, (305) 246-7001 x272

Edward Evans and Jonathan Crane examine avocados
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GAINESVILLE, Fla. — Florida’s avocado industry, the nation’s second-largest, could lose millions of dollars if a new disease reaches the state’s southern tip, according to University of Florida experts.

Laurel wilt disease, caused by a fungus transmitted by the invasive redbay ambrosia beetle, kills avocado and several native trees including redbay, said Jonathan Crane, a professor with UF’s Institute of Food and Agricultural Sciences and co-author of a paper estimating the disease’s financial impact. The paper is expected to be published later this year.

“The scenario is not looking good, if we are right,” said Crane, at UF’s Tropical Research and Education Center in Homestead.

The state’s avocado crop earns about $30 million wholesale each year, said Edward “Gilly” Evans, an agricultural economist at the Homestead center and another co-author. Commercial avocados grow on 7,500 acres, almost exclusively in Miami-Dade County, and account for more than 60 percent of Florida’s tropical fruit production.

Avocado is also an important fruit tree for Florida homeowners – about 60,000 residents have at least one in their yards, he said.

If the disease cuts Florida’s commercial avocado crop in half – something experts say could happen – it could cost the state $27 million in total economic impact and enough lost worker hours to equal 275 full-time jobs, Evans said.

So UF researchers are scrambling to develop damage estimates and management strategies. They’ve evaluated about 30 percent of the 28 avocado varieties grown in Florida; all have been susceptible to the disease, though not all have died, said Jorge Pena, an entomology professor at the Homestead center.

There is no standard method for controlling the fungus or the beetle, but researchers are testing pesticides and repellents, Pena said.

Some redbay trees may be resistant to the disease, said forest pathologist Jason Smith, an assistant professor with UF’s School of Forest Resources and Conservation in Gainesville. Researchers will investigate factors associated with resistance, in the hope that tolerant varieties can be identified and developed.

The disease was unknown to science until 2004. The beetle, first found in the United States in 2002, is native to Asia and may have arrived in wood products, packing materials or pallets.

Laurel wilt is in South Carolina, Georgia and Florida, where it’s reached as far south as Okeechobee County and as far west as Columbia County.

“The disease is moving fairly rapidly, so it’s clear it will arrive (in Miami-Dade County) sooner or later,” said Randy Ploetz, a plant pathologist at the Homestead center.

In Florida, laurel wilt apparently spreads at least two ways, Crane said.

One is via the beetle’s natural reproduction and migration, which expands its range 20 or 30 miles per year. Also, redbay is used as firewood and for outdoor grilling. Because the disease has leapfrogged around the state, researchers believe beetle-infested wood has been sold, he said.

Crane urges Floridians to report laurel wilt symptoms on avocado or redbay trees to the state Division of Plant Industry at 1-888-397-1517. Symptoms include wilted stems and leaves, black streaking in the wood, and strings of compacted sawdust protruding from tree trunks.

DPI and U.S. Department of Agriculture experts are monitoring several counties for redbay ambrosia beetles with traps and inspections, said DPI spokeswoman Denise Feiber.

There’s more at stake for Florida than the avocado industry. Laurel wilt has killed 99 percent of infected redbay trees in many areas, said Smith. Also at risk: sassafras, camphor, silkbay, swampbay, pondspice and an endangered species, pondberry.

Smith developed a test that identifies diseased trees in less than an hour, even if the fungus is present in small amounts. The test will be available to diagnostic labs around the Southeast.

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Posted: January 26, 2009

Category: Agriculture, Crops, Invasive Species, Pests & Disease
Tags: Edward "Gilly" Evans, Jonathan Crane

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