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Fungus a threat to U.S. soybeans

Asian soybean rust has blown into Central Florida, alarming growers nationwide.

By JENNIFER LIBERTO
Published April 16, 2005

OCALA - Armed with a tiny magnifying lens bouncing around his neck, Jim Walker stops and squats in green blankets of kudzu searching for a deadly pest hiding in central Florida.

Walker works as a state plant surveyor - a sentinel in the newest billion-dollar war that threatens the United States' No. 2 cash crop for years to come.

Asian soybean rust, one the world's most virulent and destructive plant diseases, has found a winter home in Pasco, Hernando and Marion counties, thriving in the South's most annoying and fastest-growing vine, kudzu.

New to the United States, Asian soybean rust destroys soybean plants worldwide and is expected to spread northward from Florida to ruin $600,000 to $1.3-billion in U.S. soybean crops this year.

While fungicides and freezes can stymie the pathogen's progress, scientists have not found a way to eradicate Asian soybean rust. U.S. agricultural experts say they expect the disease to retreat each winter to warm roadside patches of kudzu in Central Florida.

"We're going to be a reservoir for soybean rust in this state for many years to come, and it's going to rear its head every year," said Walker, 37, who donned ironed Wranglers, boots and a Navy baseball cap during a daylong scouting trip last week. "But we're going to take the lead and find it."

For years, U.S. agricultural experts have been preparing for the onslaught of Asian soybean rust, a windborne fungus that has assaulted soybeans in Asia for a century.

Scientifically named Phakopsora pachyrhizi (fae-kop-sor-a pack-ee-ry-zee), the plant disease had crossed the Atlantic Ocean to reach South America in 2001, but had yet to reach the continental United States, the world's largest producer of soybeans, an $18-billion industry.

While up to 80 percent of some infected soybean fields withered in Brazil, the world's No. 2 soybean producer, the United States added Asian soybean rust to its list of bioterrorism toxins, fearing a terrorist would intentionally introduce the fungus to U.S. soybeans.

Yet, it was Mother Nature that brought Asian soybean rust to the United States, on the back of Hurricane Ivan in September.

Two months passed before the fungus was detected in a Louisiana university soybean research farm. Weeks later, nine states reported the disease in soybean fields and on kudzu; both are in the same legume plant family vulnerable to the fungus.

Yet, the financial effect was negligible, because the nation's soybeans had been harvested and the approaching winter freeze would kill the disease throughout most of the nation.

Scientists knew the disease would survive the winter somewhere down south. They just didn't know where.

In Florida, home to a mere 10,000 of the 73.9-million soybean acres planted nationwide, the fungus hit bean fields and kudzu as far south as Marion County in 2004 before the freeze arrived.

The freeze didn't reach parts of Pasco and Hernando counties. Soybean rust did.

Plant surveyor Mike Meadows spotted the first sign of the disease on Feb. 23, off Gene Nelson Boulevard in Dade City. The Miami-based surveyor had been scouring Central Florida foliage for weeks.

"It was obvious to us that the infection had been there on these old weathered (kudzu) leaves that had survived the winter," Meadows said.

A few weeks later, Walker spotted the fungus, alive and well, on kudzu leaves under a tree canopy on Hickory Hill Road in Spring Lake, Hernando County. Walker found a third patch in Marion County north of Ocala two weeks ago.

Although the infected kudzu sites were discovered in a northward order, state researchers don't think the sites infected each other.

They estimate Asian soybean rust traveled undetected to Hernando and Pasco counties late last year before the winter freeze struck. The disease survived the winter in each place independently.

Regardless, news that Asian soybean rust had reappeared this year sent a panic through the soybean industry. Farmers and agricultural experts nationwide learned the names and whereabouts of Hernando and Pasco counties and plastered them all over the agricultural trade press.

An Iowa journalist who works for the online agricultural publication DTN.com came to Hernando County last month to check out the Asian soybean rust patch in Spring Lake.

Three times a week, a plant pathogen forecasting center in North Carolina publishes a U.S. map on its Web site with a star on Central Florida sprouting a curvy line that edges northward or eastward, depending on weather patterns for the next few days.

"The way this year's epidemic is going to depend on the weather patterns we get this year," said meteorologist Thomas Keever of the North American Plant Disease Forecast Center at North Carolina State University in Raleigh.

Soybean associations and universities are teaching farmers how to look for and treat the disease as they start to plant soybeans through mid June. The federal government has recently approved a handful of fungicides to treat Asian soybean rust, although the fungicides' long-term effects on soybean food safety are unknown.

"None of us are happy about it, but at least it came at a time of year that gave us a maximum amount of time to prepare for the next year," said Bob Callanan, spokesman for the American Soybean Association in St. Louis.

In the meantime, Florida's team of 10 state surveyors crisscross the state one day each week picking through kudzu forests and small soybean fields for the slightest sign of Asian soybean rust.

The surveyors are experienced scouts because Florida started sending them out looking for Asian soybean rust two years ago while the disease remained in South America.

"It will be important for the foreseeable future to see how soybean rust is going to move north each year, to help plan the timing of applications of fungicides," said Dr. Tim Schubert of the Florida Department of Agriculture and Consumer Service's Bureau of Entomology, Nematology & Plant Pathology.

The disease is difficult to spot in its early stages. Several plant diseases can make a reddish splotch on a kudzu leaf that looks like Asian soybean rust. Surveyors must turn the leave over and look through a lens for the telltale raised bumps.

Walker spent nearly an hour searching a residential block strewn with Kudzu.

He had confirmed Asian soybean rust in the same spot a week earlier. But this time, he couldn't find any.

"It's frustrating sometimes," Walker said.

"You know it's here, and you don't want find it. But it's out there."

[Last modified April 16, 2005, 01:42:20]