By Brad Haire
University of Georgia

University of Georgia scientists learned recently that Asiatic
soybean rust, a deadly tropical soybean disease, can survive
Georgia’s winter weather. This raises concerns that it could
spread earlier and stronger this year.

Other than soybeans, the disease thrives on Florida beggarweed
and kudzu, an Asian vine that’s notorious in the South.

It was found growing on live kudzu in Grady County Jan. 30 and
Thomas County Feb. 10, said Bob Kemerait, a UGA Cooperative
Extension plant pathologist. It has been confirmed on kudzu in
two counties in south Alabama, too, and 11 counties in Florida
so far this year, he said.

Kudzu, Florida beggarweed and any soybeans left from the
previous year’s harvest are usually killed by freezing
temperatures each year in Georgia. But nothing is guaranteed.

“These sites answer the question, can Asiatic soybean rust
overwinter in Georgia?” Kemerait said. “The answer is yes.”

The infected kudzu in Grady County was found protected from the
cold weather by a building in downtown Cairo, Ga. The infected
kudzu in Thomas County was protected by a concrete culvert.

The living kudzu from the two sites was taken to the UGA Plant
Disease Diagnostics Laboratory in Tifton, Ga., Feb. 17 to be
studied. It will be destroyed, Kemerait said.

The disease is in Georgia now, he said. There are probably other
south Georgia sites similar to those in Grady and Thomas
counties where the disease and kudzu are protected from freezing
weather.

Georgia farmers who choose to plant soybeans this year need to
budget an extra $20 to $30 per acre to protect the crop with
fungicides. Before the threat of the disease, Georgia farmers
rarely needed to spray fungicides on soybeans.

Because of the threat the disease poses to Georgia and the rest
of the country, Kemerait and UGA Extension agents in south
Georgia monitored the state for it this winter. A U.S.
Department of Agriculture grant has helped in the search.

Asiatic soybean rust first appeared in the United States in
November 2004 on the Gulf Coast. Scientists believe it blew in
on tropical storms that skirted South America, where the disease
has already cost soybean farmers billions of dollars in
damage.

Kemerait and other scientists with the UGA College of
Agricultural and Environmental Sciences will conduct fungicide
spray trials this year to determine the optimal time to spray
for the disease and the best fungicides to use.

Georgia is not considered a major soybean-growing state. Georgia
farmers grew about 170,000 acres in 2005. The crop is worth $30
million to $40 million annually.

Asiatic soybean rust is here to stay, Kemerait said.

When it first shows up and how fast it travels will determine
how much of a threat it will be for the Midwest, where most U.S.
soybeans are grown. The U.S. is the world’s leading soybean
producer. The crop is worth about $18 billion annually.