Avocado Industry Under Threat

Avocado Industry Under Threat

Laurel wilt disease, caused by a fungus transmitted by the invasive redbay ambrosia beetle, kills avocado and several native trees including redbay, says Jonathan Crane, a professor with 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,” says Crane, at UF’s Tropical Research and Education Center in Homestead.

The state’s avocado crop earns about $30 million wholesale each year, says 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% of Florida’s tropical fruit production.

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

Economic Impact

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% of the 28 avocado varieties grown in Florida; all have been susceptible to the disease, though not all have died, says Jorge Peña, 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, Peña says.

Some redbay trees may be resistant to the disease, says forest pathologist Jason Smith, an assistant professor with the 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 U.S. in 2002, is native to Asia and may have arrived in wood products, packing materials, or pallets.

Marching South

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,” says Randy Ploetz, a plant pathologist at the Homestead center.

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

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 888-397-1517. Symptoms include wilted stems and leaves, black streaking in the wood, and strings of compacted sawdust protruding from tree trunks.