By Brad Haire
University of Georgia
The disease wasn’t as bad as they expected. But they will likely have to deal with it annually, says a University of Georgia expert.
Asiatic soybean rust has damaged soybeans in Asia, Australia and Africa. It annually costs Brazilian farmers about $1 billion in damage and control measures, said Bob Kemerait, a plant pathologist with the UGA Cooperative Extension.
“If left untreated, it can cause near 100 percent damage to soybean fields in Brazil,” Kemerait said.
The disease was first reported in the United States in November 2004 in Louisiana. Tropical storms that fall are believed to have carried it from South America to Gulf Coast states. It arrived too late to cause damage to the ‘04 crop. In Georgia, soybeans are planted in April and May and harvested in October.
Freezing temperatures kill this tropical disease. In addition to soybean, kudzu, a notorious Southern weed, is a good host. It was learned this year that Florida beggar weed, a plant as common as kudzu, is also a host, Kemerait said.
“We knew that it would probably overwinter in the warm regions of Florida,” he said, “and that it would likely be reintroduced into the state this year.”
The disease was detected in Seminole County in southwest Georgia in April. By July, it had spread to other southwest Georgia counties. By November, 35 counties across the state had reported the disease.
Asiatic soybean rust can be devastating. But it wasn’t in Georgia this year. It showed up later and traveled much slower than expected, moving an estimated 60 miles per week, Kemerait said. The disease is reported to move as fast as 300 miles per day in Brazil.
Also, about 60 percent to 70 percent of Georgia farmers sprayed fungicides to combat the disease this year. They usually don’t spray because doing so costs about $12 per acre. Farmers in Midwest states like Iowa, where about 10 million acres are grown and the crop is higher-valued, routinely spray.
Georgia farmers this year planted about 170,000 acres, about 100,000 acres less than last year, according to the Georgia Agricultural Statistics Service.
It isn’t certain now what damage the disease caused farmers this year.
Research at the UGA Attapulgus Research and Education Center in Decatur County, near the Florida line, showed that fungicide sprays helped soybeans there.
Infected plots sprayed with fungicides yielded about 57 bushels per acre. Untreated infected plots yielded 38 bushels.
The disease was detected in other Gulf Coast states like Mississippi, Texas and Alabama, too. It traveled as far north as Kentucky and the Carolinas before winter freezes stopped it.
Farmers in Georgia and other Southeastern states will likely see Asiatic Soybean Rust again next year. And Georgia could likely see it first.
Scientists from across the country will focus on Georgia this winter and next spring because of its boundary with Florida, Kemerait said. The time of year it shows up in Georgia will give experts a better idea of when or if the disease could reach Midwest fields to the north.