Wisconsin farmers deal with fungal disease ‘tar spot’ during harvest time

Published: Oct. 12, 2021 at 6:28 PM CDT|Updated: Oct. 12, 2021 at 7:03 PM CDT
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SAUK CITY, Wis. (WMTV) - Many Wisconsin farmers are dealing with a fungal disease called ‘tar spot’ popping up on their feed corn crops in the fall of 2021.

Feed corn is different than sweet corn. Feed corn is typically used to feed cattle and can be turned into other byproducts like corn oil and renewable fuel, like ethanol.

Farmers have been dealing with tar spot for the last six years, watching it spread from parts of southern Midwest up toward the Madison area.

“Holy cow, look at this one,” Mitch Breunig, farmer, and owner of Mystic Valley Dairy LLC., in Sauk City said as he picked a black speckled yellow leaf off the ground.

In July, Breunig spotted the fungal plant disease on some of his feed corn crops.

“You could be driving past the same field, every day, all summer long and then one day you drive by and you go, ‘whoa, that corn is turning yellow and looks like it’s dying,’ and within a week, it’s dead,” Breunig said.

Damon Smith, a UW-Madison Plant Pathologist, has been closely studying the fungus in Wisconsin for the last five years.

“Based on some of our work in 2018, we’re anticipating 30–50-bushel losses in corn this year,” Smith said.

Smith says tar spot is causing more issues, throwing off harvest timing, and cost.

“We’re all going to be impacted,” Smith said. “Obviously the farmer is going to be most directly impacted because they’re going to have an ongoing and recurring challenge here,” Smith said.

“I think it’s important because this is an agriculture community, and we need our farmers to thrive,” Breunig said. “If farmer crops are failing it affects our community economics and affects really our whole state.”

Farmers can salvage their crops by using a treatment called “fungicide.” Breunig anticipates he was able to save much of his 80-acre crop. However, at $30 an acre, that can add up over time.

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