Plant samples from Tennessee are being tested for the highly contagious Asian soyabean rust, a withering disease that has rapidly marched throughout the US South, the US Agriculture Department said on Tuesday. If confirmed, Tennessee would be the seventh state infected with the fungus since its initial discovery in the mainland United States two weeks ago. The yield-slashing fungus has already been found in Louisiana, Mississippi, Florida, Alabama, Georgia and Arkansas.
Claude Knighten, spokesman for USDA's Animal and Plant Health Inspection Service, said the Tennessee test results were expected on Wednesday.
The suspect field is in Cannon County, about 50 miles south-east of Nashville, according to the Tennessee Agriculture Department. Tennessee is a relatively small producer of soyabeans and harvested about 47.2 million bushels this year.
Farmers fear the fungus will spread by next growing season to big soyabean states such as Iowa and Illinois, which together harvested about 989 million bushels or one-third of this year's US crop.
Worries about the rapidly spreading disease have sent US soyabean futures prices more than 50 cents a bushel higher since the first report of soyarust was confirmed on November 10.
Soyabean futures at the Chicago Board of Trade rose again on Tuesday, with the January delivery contract settling at $5.61-1/4 per bushel, up 6-3/4 cents.
The USDA believes the disease was blown from South America into the US Gulf Coast by Hurricane Ivan in mid-September.
The fungus destroyed 4.5 million tonnes out of Brazil's last soyabean crop of just over 50 million tonnes, and showed signs it could survive freezing temperatures, according to plant pathologist Ricardo Balardin with the Santa Maria Federal University.
Temperatures of around 32 degrees Fahrenheit (zero Celsius) failed to kill the fungus, which was found on winter grasses such as alfalfa and clover in the southern cone of Brazil, Balardin said in an interview.
The disease is characterised by reddish brown lesions on soyabean plants that make them shed their leaves. It spread from Asia to Africa and Latin America, devastating crops in many countries.
The United States is the world's biggest soyabean producer, followed by Brazil.