Tar spot on corn has been confirmed in 12 eastern Iowa counties, according to Iowa State University (ISU) Extension agronomists.

The disease has been found in Jones, Jackson, Johnson, Muscatine, Fayette, Clayton, Black Hawk, Buchanan, Delaware, Dubuque, Clinton and Scott counties.

Agronomists also have seen the disease “take off”  in northern Illinois, southern Wisconsin, Michigan and parts of Indiana, says Nathan Kleczewski, University of Illinois Extension field crop pathologist.

“Some fields ...