Contagious Asian soybean rust lurks as close as Virginia


November 05, 2006|By Ted Shelsby

Asian soybean rust, a contagious fungal disease that has devastated soybean crops in other parts of the world, has come dangerously close to making its way to Maryland for the first time.

The fungus, which can reduce a soybean field's yield by as much as 80 percent if left untreated, was recently spotted as far north as Virginia, according to the U.S. Department of Agriculture.

While an infestation can have a serious economic impact on farming, it poses no threat to humans.

The USDA has been tracking the spread of the plant-killing disease since it was discovered in Japan in 1902. It moved through Asia, Australia and Africa before making its way to Brazil and Argentina in 2000.

It arrived in the United States in 2003, according to agricultural scientists who suspect that the fungus spores caught a ride on the winds of Hurricanes Frances and Ivan.

"It's an airborne disease," said John Bowers, a plant disease specialist with the Maryland Department of Agriculture. "That's the way it travels."

He said Maryland farmers might be thankful that the hurricane season was mild this year.

Maryland agricultural scientists have watched soybean rust spread north state-by-state since it established a foothold in Louisiana three years ago.

The fungus was identified in Virginia about two weeks ago. It was first detected in a field near Chesapeake in the southeast part of the state. At the same time, the fungus was found not far away near Suffolk in a soybean test field operated by Virginia Tech University.

The USDA announced last week that soybean rust was also confirmed in the Virginia counties of Brunswick, James, Mecklenburg and Northampton.

Despite knocking on Maryland's door, the disease does not pose a threat to this year's soybean crop, said Arvydas Grybauskas, an associate professor and plant pathologist at the University of Maryland, College Park.

And a continued progression does not necessarily mean that soybean rust will be a threat to next year's crop, he said.

"It was not a surprise that it came to Virginia, but it came too late to do any damage," Grybauskas said. "The crop was already close to harvest."

The fungus cannot survive Maryland's chilly winter, and it will have to start its northward trek from the Deep South all over again next spring, he said.

"Our best defense is a hard frost," Grybauskas said.

He said that the soybean rust "organisms can only survive on living host tissues or green plants."

To be a major threat here, the fungus would have to arrive during the summer, when the soybean plants are green, flowering and setting pods, said David Clement, director of the University of Maryland's home and garden information center in Ellicott City.

University extension agents have been educating farmers on how to spot the fungus, which shows up as reddish-brown blotches on the plant leaves, he said. It weakens the plants and reduces the amount of beans they produce.

The disease can also affect fields of snap beans and green beans.

Agriculture officials are encouraging farmers to check their fields often for signs of the disease, advising them to part the plants and look at the leaves down near the roots. That's where the first signs of an infestation are apparent.

Maryland Agriculture Secretary Lewis R. Riley said that if farmers wait until they can see signs of an outbreak while driving past their fields in a pickup, it's too late.

"It has gone too far for any remedy," he said.

As part of the Maryland's early warning defense system, Clement said, the university has soybean "sentinel" plots planted around the state designed to detect an infestation.

"During the growing seasons, we go out to the fields on a weekly basis looking for any signs of the disease," he said. "We're trying to give the state as much protection as possible and to provide an early warning if there is a problem."

Nearly one-third of Maryland's 1.6 million acres of cropland are planted in soybeans each year. Soybeans, most of which provide feed for poultry and livestock, accounted for $112 million in farm sales during 2004. Soybeans ranked fifth in total farm sales that year behind poultry, greenhouse/nursery, milk, and corn for grain.

The USDA reports that soybean rust has been found in 214 counties in 15 states this year. The states are Alabama, Florida, South Carolina, Louisiana, Georgia, Texas, Missouri, Mississippi, North Carolina, Kentucky, Illinois, Indiana, Tennessee, Arkansas and Virginia.

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