Published on 09/15/04

Damaging soybean disease headed for United States

By Brad Haire
University of Georgia

A soybean disease has caused major problems for farmers in South America. And U.S. farmers need to be ready to handle it when it arrives here, says a University of Georgia expert.

Asiatic soybean rust attacks a plant and defoliates it, severely reducing yields or killing the plant, said Bob Kemerait, a plant pathologist with the UGA College of Agricultural and Environmental Sciences.

"This rust is an impressive and aggressive disease that infects and produces spores very quickly," Kemerait said. "If it spreads, it could affect a large portion of the soybeans in the United States."

On the move

The disease has been on the radar screen of the agricultural world for some time now. It has hurt soybean production in Asia, Australia and Africa. By 2000, it had jumped the Atlantic Ocean and landed in South America. It cost Brazilian farmers an estimated $1 billion in damage and control measures in 2003.

"It went very quickly from not being a problem to being a major problem in Brazil in about two years," Kemerait said.

Asiatic soybean rust was reported last month to have jumped the equator into Colombia. Models predict it will keep moving north and eventually enter the United States, possibly through Mexico.

A storm like Hurricane Ivan, which skimmed the coast of South America earlier this week, could pick it up and give it a much quicker airlift, he said.

Handle at a cost

No soybean varieties are resistant to this rust. But fungicides can control it, Kemerait said. Soybeans are a higher-value crop in the Midwest. So farmers there protect them with fungicides. Georgia growers usually don't spray fungicides on soybeans. But this would have to change if this disease entered the state.

"There's no doubt we can handle Asiatic soybean rust in America," he said. "The concern is how much additional production cost will it take."

Kemerait, UGA plant pathology department head John Sherwood and Extension Service soybean agronomist Phil Jost met this summer with representatives of the U.S. Department of Agriculture Animal and Plant Health Inspection Service and the Georgia Department of Agriculture to form a first-response plan for Georgia.

UGA Extension Service county agents, along with other farm experts in the state, will train to identify and respond to the disease when it arrives.

Asiatic soybean rust has at least one natural flaw that will help U.S. growers. It's a tropical disease. Freezing temperatures kill it. It could spread in the United States during the summer, but it will have to fall back during winter to places that don't freeze, such as south Florida and Texas.

But once it gets to the United States, it will probably stay. "We won't eradicate this disease when it gets here," Kemerait said. "We'll just have to contain and control it."

Other major Georgia crops aren't at risk to the disease. But one of Georgia's most infamous plants, kudzu, could be in trouble. The disease attacks and defoliates kudzu much as it does soybeans, Kemerait said.

Georgia farmers grew about 250,000 acres of soybeans this year, about 60,000 more than in 2003.

Brad Haire is the former news editor with the University of Georgia College of Agricultural and Environmental Sciences.