By Tom Polansek
CHICAGO (Reuters) - A tropical storm could have carried the corn disease tar spot into the heart of the U.S. farm belt for the first time, as winds and rain blew in from Latin America, researchers told Reuters.
The U.S. Department of Agriculture has confirmed cases of tar spot in at least four locations in Indiana and three in Illinois. The fungal disease has been a problem for years in Mexico and in Central and South America, with farmers fighting infections that can lower yields.
Tropical Storm Bill, which brought rain to the central United States in June after spinning through the Gulf of Mexico, may have transported the disease, said Bill Dolezal, a research fellow for seed company DuPont Pioneer.
"It looks like it came up out of that area," Dolezal said.
The USDA is working with experts in Indiana and Illinois to determine how tar spot entered the country.
Kiersten Wise, extension specialist for field crop diseases at Purdue University in Indiana, said she was studying weather records for a potential link to U.S. infections.
Tar spot arrived too late in the growing season to have much affect on crops this year, Wise said. Harvests have already begun in Indiana and Illinois.
For next year, the disease will likely need to arrive anew from Latin America to be a problem for farmers, said Suzanne Bissonnette, director of the Plant Diagnostic Clinic at the University of Illinois. It probably will not be able to withstand the cold Midwestern winter because tar spot needs to survive on living tissue, such as corn plants, she said.
A number of different corn varieties have been found to be susceptible to the disease, which appears as black spots, Bissonnette said.
"It really does look like somebody dripped tar on the leaf," she said.
In 2004, an active hurricane season is thought to have brought a soybean disease called Asian soybean rust into the United States from South America for the first time.
Recently, farm animals have suffered more than crops from new diseases entering the country from abroad. This year, the United States suffered its worst animal-disease emergency ever in poultry from a strain of bird flu that originated in Asia.
In 2013, a pig virus never before seen in the United States was found. Previously seen in Europe and Asia, it has since killed millions of baby piglets. It's still unclear exactly how the virus arrived.
(Reporting by Tom Polansek)