Illinois agriculture officials say a new disease is affecting corn in the state.

The Illinois Department of Agriculture said Monday that the disease tar spot has been confirmed in Illinois' Bureau, DeKalb and LaSalle counties. Agriculture director Philip Nelson doesn't anticipate an impact on yields this late in the season but he says farmers should report any suspected findings to prevent spreading.

Plant pathologists at Purdue University confirmed the Illinois cases. Their confirmation of tar spot in Indiana last week was the first in the U.S. The disease previously was found in Mexico, Central America and South America.

Illinois corn farmers should look for brown lesions on leaves followed by black, spore-producing structures that make leaves feel rough or bumpy. Farmers should contact University of Illinois Extension with suspected cases.