13 of 18 Top Corn-Growing States Confirm Tar Spot Infected Crops

According to the latest Crop Protection Network map, positive cases of tar spot have been reported in 13 of the top 18 corn growing states. Additional cases have been reported in Georgia, Maryland, and New York.

First reported in the Corn Belt in 2015, 18 U.S. states have a history of the disease.

So far this season, Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Nebraska, Ohio, Pennsylvania, South Dakota, and Wisconsin have confirmed infected crops.

Illinois

As of Aug. 1, 19 Illinois counties have reported cases of tar spot. There are only 11 counties in the southern part of the state that have no history of the disease.

Wyffels agronomist Ryan Gentle ranked “late disease pressure,” including tar, spot the second biggest yield thread to corn in his territory behind tight tassel wrap.

USDA rated the state’s corn crop 4% very poor, 5% poor, 22% fair, 52% good, and 17% excellent the week ended Aug. 3.

Indiana

In Indiana, 32 counties have reported cases of tar spot, as of Aug. 4.

USDA rated the state’s corn crop 3% very poor, 8% poor, 27% fair, 51% good, 11% excellent the week ended Aug. 3.

Iowa

As of Aug. 4, more than one third of Iowa’s counties confirmed cases of tar spot. The Crop Protection Network noted cases in 37 counties.

Wyffels agronomist Eric Wilson noted foliar disease and late season nitrogen loss are the biggest threats to corn yield in his Iowa territory.

USDA rated the Iowa corn crop 1% very poor, 2% poor, 12% fair, 57% good, and 28% excellent the week ended Aug. 3.

Kansas

Kansas reported positive tar spot cases in 8 northeast counties, as of Aug. 4.

USDA rated Kansas corn 2% very poor, 7% poor, 25% fair, 45% good, and 21% excellent the week ended Aug. 3.

Kentucky

Four Kentucky counties along the border with Indiana reported cases of tar spot, as of Aug. 4.

In the latest Crop Progress report, USDA rated Kentucky corn 2% very poor, 7% poor, 28% fair, 55% good, 8% excellent.

Michigan

In Michigan, 16 counties have corn crops infected with tar spot.

USDA rated the state’s corn crop 1% very poor, 8% poor, 35% fair, 40% good, and 16% excellent the week ended Aug. 3.

Minnesota

Nine Minnesota counties reported cases of tar spot, according to the latest Crop Protection Network maps.

USDA rated Minnesota corn 2% very poor, 5% poor, 18% fair, 51% good, and 24% excellent in the latest Crop Progress report.

Missouri

In Missouri, 23 counties reported corn crops infected with tar spot.

USDA rated Missouri corn 1% very poor, 4% poor, 16% fair, 58% good, and 21% excellent.

Nebraska

In Nebraska, 31 counties reported cases of tar spot.

Behind weather, Syngenta agronomist Travis Gustafson sees diseases such as southern rust and tar spot threatening corn yields in the state.

In the latest Crop Progress report, Nebraska corn was rated 1% very poor, 3% poor, 17% fair, 55% good, and 24% excellent.

Ohio

As of Aug. 4, 6 Ohio counties reported cases of tar spot.

USDA rated Ohio corn 1% very poor, 5% poor, 35% fair, 52% good, and 7% excellent for the week ended Aug. 3.

Pennsylvania

Eight Pennsylvania counties have reported cases of tar spot so far this season.

In the latest Crop Progress report, Pennsylvania corn was rated 1% very poor, 5% poor, 17% fair, 55% good, and 22% excellent.

South Dakota

Two counties in southeast South Dakota have reported cases of tar spot.

USDA rated South Dakota corn 1% very poor, 4% poor, 18% fair, 52% good, and 25% excellent for the week ended Aug. 3.

Wisconsin

In Wisconsin, 18 counties have reported cases of tar spot.

Syngenta agronomist Nick Groth told Successful Farming, “Late season diseases such as tar spot, northern corn leaf blight, and southern rust are probably the biggest remaining threat to the Wisconsin corn crop.”

USDA rated the state’s corn crop 1% very poor, 3% poor, 15% fair, 57% good, and 24% excellent for the week ended Aug. 3.