USDA confirms new disease in Florida citrus

02/01/2011 02:00:00 AM

By Vicky Boyd
Editor

The U.S. Department of Agriculture’s Molecular Diagnostics Laboratory in Beltsville, Md., has confirmed what the Florida Department of Agriculture and Consumer Services is calling a “sweet orange scab-like disease” on three citrus samples from Florida.

Richard Kinney, executive vice president of the Lakeland-based Florida Citrus Packers Inc., says it’s premature to speculate about the impact the disease find would have on fresh citrus exports.

“We’re trying to determine that now,” Kinney says. “The science, to us, is pretty clear that the fruit is not a vector, but you have to look at each market.”

Florida’s agriculture department is calling it sweet orange scab-like because some staff pathologists have found inconsistencies within the disease, says Denise Feiber, spokeswoman for the Florida Division of Plant Industry. Pathologists matched a small portion of the genome from the Florida samples to one taken from Brazil, says Tim Schubert, administrator for DPI’s plant pathology division.

“But the South American [isolate] has symptoms that have not been seen on the citrus fruit and lesions that tested positive here in the U.S.,” he says.

In the United States, SOS fruit lesions appear more like wind scarring than the ugly lesions seen in South America, Schubert says. “It’s so far afield of what we would expect SOS to look like on citrus. It just doesn’t fit cleanly,” he says.

Pathologists plan to conduct further tests to demystify the organism and pinpoint its origin. On Dec. 23, the USDA lab confirmed the SOS-like disease in a grapefruit sample collected from a campground near Lakeland and a bitter orange sample from a residential property in Westin, Broward County, she says. The Broward County homeowner has since removed the tree, she says.

On Jan. 10, the lab confirmed a tangerine collected from a residential property in Sarasota County also was positive for the disease. Owners of the positive sites have been issued emergency action notifications, which prohibit them from moving fruit, leaves or branches off the property, Feiber says.

Inspectors have completed surveys within a 3-mile-radius of each positive site. They plan to expand the survey to a 5-mile radius of each positive site.

Sweet orange scab, caused by the fungus Elsinoe australis, has been confirmed in Louisiana, Mississippi, and Texas, where it has moved into the commercial citrus area. In Arizona, SOS was found in a tangerine grove. In December, USDA issued a regulation that would allow citrus from commercial groves in south Texas to move to citrus-producing states as long as the fruit had undergone approved packinghouse treatment.

Sweet orange scab only affects fruit and is mostly a problem on sweet orange and some tangerine cultivars, according to a University of Florida publication.

Common scab, caused by the fungus Elsinoe fawcetti, infects both fruit and leaves. It is predominately a problem on tangerine hybrids, such as temple, as well as grapefruit and lemon.



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