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Potato farmers, scientists still fighting disease that devastated Ireland

By:
Tom Nordlie (352) 392-0400

Source(s):
Chad Hutchinson cmhutch@ufl.edu, 904-692-1792
Pam Roberts pdr@ufl.edu, 239-658-3400

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GAINESVILLE, Fla. — Each year, the world celebrates St. Patrick for ridding Ireland of snakes, but scientists are still trying to control an ecological menace that strikes the Emerald Isle’s best-known crop, says a University of Florida expert.

Late blight, a fungal-like disease responsible for the infamous Irish potato famine of 1845 to 1849, accounts for up to 10 percent of production costs for U.S. potato growers, said Chad Hutchinson, a UF horticulture associate professor. The disease strikes potato crops in temperate areas around the world.

Monitoring, reporting and preventive use of fungicides are current weapons of choice against the disease, he said. But UF research may offer new options for minimizing damage to potatoes and their close cousin, tomatoes, which are also attacked by late blight.

“It’s a battle every year,” said Hutchinson, who works at the Florida Partnership for Water, Agriculture and Community Sustainability at Hastings. “You don’t want it to show up and if it does show up you don’t want it to spread. That’s why growers are diligent.”

Spores of the pathogen may arrive in fields via the wind or by surviving in debris from the previous season, he said. They can infect northeast Florida potato patches as early as December and January, when seed potatoes are planted. But symptoms of late blight – brown patches and mildew growth on leaves, and dry rot in tubers – often appear months later.

“It’s something you’re not sure is gonna show up,” Hutchinson said.

As a precaution, potato farmers typically spray their plants with fungicide every week, he said. Hutchinson advises farmers on conditions, reported outbreaks and fungicide.

“Late blight can go through a 100- to 200-acre field in 24 to 48 hours and it looks like a blowtorch went through,” he said. “I know people are interested in less pesticide but this is one instance where it’s needed, because this is such a nasty disease.”

The pathogen thrives in wet, cool weather, but despite the recent rains and mild winter temperatures Hutchinson is cautiously optimistic about 2007. No late blight outbreaks have been reported in northeast Florida’s spud-rich tri-county agricultural area, which comprises Flagler, Putnam and St. Johns counties.

“If it hasn’t shown up by about mid-March we’re probably out of danger,” he said.

It’s a different story for farmers in the southwest part of the state, where tomatoes are far more common than potatoes, said Pam Roberts, a plant pathology associate professor in Immokalee.

Since last November, late blight has been found in seven counties, she said. The good news – Roberts and Assistant Researcher Diana Schultz are collaborating with a U.S. Department of Agriculture researcher in Maryland on genotyping research that can distinguish between different strains of late blight.

Their results show the current outbreaks are not caused by the extremely aggressive strain that devastated East Coast tomato crops in 2005. Eventually the work may lead to greater understanding of the reasons outbreaks occur, but for now Roberts plans to focus on developing guidelines for more effective fungicide use.

Several strains of late blight have struck U.S. crops in recent years, she said. Some varieties strike only tomatoes, others stick with potatoes, some infect either crop.

“The late blight populations that strike potatoes tend to be more stable, it’s the ones that affect tomatoes that are more variable,” Roberts said.

Because the pathogen can mutate, new strains sometimes emerge – strains that may be resistant to popular fungicides, Hutchinson said.

“Some chemicals that we used in the past are no longer effective,” he said. “It’s a hot war against this organism. As the technology evolves the genetics improve, so the war changes.”

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