Tar Spot was identified in Indiana and Illinois last fall on samples submitted to the respective Plant Diagnostic labs, with confirming diagnosis from the USDA Animal Plant Health Inspection Service, which has the national fungal identifier lab in Beltsville, Maryland. These are the first cases of Tar Spot ever reported in the United Sates, and samples were found in corn fields in 13 counties in Illinois and 7 counties in Indiana.
Tech_271 - Tar Spot
Don’t worry! Tar spot is not expected to overwinter in corn residue in the Midwest. The expectation for reintroduction from South America is negligible; given this is the first year the disease has ever been detected in the United States. The key point of this article is to alert producers that the disease had been found this past year, to allow producers to more effectively scout fields next season, and to submit any suspect samples to plant diagnostic labs for testing of this previously unrecognized fungal disease.