By Brad Haire
University of Georgia
Georgia farmers knew that a new deadly soybean disease was
poised to attack their crop this year. But they were ready.
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.
