Disease assaults Wisconsin corn fields

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Corn along Stroupe Road northeast of Whitewater, Wisconsin, shows the effects of tar spot disease. The green field on the right was sprayed with fungicide at tasseling time; it has only a mild case of tar spot disease. The brown field on the left was not sprayed with fungicide and is severely infected with the disease.

Mary Hookham/For Agri-View

Researchers are studying tar spot disease, an invasive fungus affecting Wisconsin corn fields this growing season. Many farmers are concerned about lost yields as harvest season approaches. "We don't know a lot about this disease yet," said Doug Rebout of Janesville, president of the Wisconsin Corn Growers Association. "We are watching our crops and need to begin making decisions about when to harvest to get the best yields. We've heard this is variety-specific, not brand-specific."

Mary Hookham/For Agri-View

Jack Hass drives alongside a chopper, getting a load of corn silage at Hass Acres of Evansville, Wisconsin. The Hass family's corn is severely infected with tar spot disease this year, a fungus affecting corn fields all across the state.

Mary Hookham/For Agri-View

A corn leaf on a stalk in a field owned by Casey Kelleher of Whitewater, Wisconsin, has only the beginning stages of tar spot disease -- a fungus caused by high humidity and cool nights. Farmers across the state are dealing with fields of infected corn and hoping yield loss is minimal.

Mary Hookham/For Agri-View

A cornfield infected by tar spot disease reflects the disease's damage -- stalks turn brown and the crop dries down as though it's late in the harvest season rather than early fall. Farmer Casey Kelleher is hoping his yield is still good.

Mary Hookham/For Agri-View

An Asian beetle walks on a corn leaf that has a mild infection of tar spot disease in a field near Footville, Wisconsin. Farmers Steve and Liz Case decided to spray their corn at tasseling time with fungicide after their son, Craig, suggested it earlier this year. The family believes the fungicide has lessened the severity of tar spot disease infection on all their corn fields this year.

Mary Hookham/For Agri-View

Farmer Jack Hass unloads corn silage on his family's farm near Evansville, Wisconsin.

Mary Hookham/For Agri-View

A mild case of tar spot disease affects a corn leaf in a field at Pineview Farm near Footville, Wisconsin. The fungus can cause soft kernels and cobs as well as premature plant death. It's another challenge farmers are facing in an already-difficult agricultural economy this year.

Mary Hookham/For Agri-View

A severe case of tar spot disease is reflected on a corn leaf at Hass Acres of Evansville, Wisconsin. Farmer Aaron Hass is harvesting this field for corn silage for his dairy herd.

Mary Hookham/For Agri-View

Jack Hass, a farmer near Evansville, Wisconsin, unloads a load of corn silage. Hass and his son, Aaron, run their dairy farm together. They say they are disappointed in the invasion of tar spot disease on their corn crop this year. Farmers across the state are concerned about yield loss as a result of this fungus this season.

Mary Hookham/For Agri-View

Tar spot disease first shows as small black tar-like spots often described as 'fish eyes.' As the fungus progresses tan circles appear around the black spots as shown on a corn leaf in a field at Toberman Farms west of Footville, Wisconsin. 'Unfortunately the weather this year has been ideal for fungal diseases, including tar spot,' farmer Colleen Toberman said. 'Hopefully our experience this year will prepare us for if it comes again.'

Mary Hookham/For Agri-View

A severe case of tar spot disease attacks a cornfield near Evansville, Wisconsin.

Mary Hookham/For Agri-View

Mary Hookham For Agri-View

Tar spot disease has invaded Wisconsin corn fields, causing yet another concern in an already-difficult agricultural market. Agronomists, researchers and farmers are worried about the coming harvest and the yield impact of the fungal disease – all while trying to learn as much as possible about it.

Mary Hookham is a freelance agricultural journalist and photographer from Janesville, Wisconsin. She grew up near Footville on a 140-acre beef and chicken farm and went to high school in Orfordville. She graduated from University of Wisconsin-Whitewater with a bachelor of arts degree in print journalism and a minor in English for writers.