A "serious disease" is killing corn across the Midwest

JOPLIN, Mo. — "Tar spot" is moving across the Midwest and Great Plains, according to a report from researchers at Kansas State University.

The disease first appeared in Indiana and Illinois in 2015. Since then, it has spread to surrounding states. Farmers spotted it in Nebraska for the first time in 2021, and in Missouri, Kansas, and South Dakota last growing season.

"It's a very aggressive disease compared to some of the other diseases we deal with like southern rust, or gray leaf spot, or northern corn leaf flight. It moves very, very quickly. I've seen pictures from the Midwest where the infection begins, and seven days later that field is completely shut down," said Southwest Missouri agronomist, Brian Bunt.

The fungal disease attacks leaf tissue in corn and can rapidly deteriorate the plant. According to the Crop Protection Network, it's estimated that tar spot caused farmers to lose around $3 billion in the United States from 2018 to 2021, and has the potential to be more destructive in states that are just now seeing cases.

"This could continue to spread west and spread south, from where we first saw it in the northern parts of the Great Plains, so there's definitely a risk it could move into our immediate area," said Bunt.

Since it’s still early, farmers will have to wait to see how much of an effect tar spot will have in states where it’s just appearing. The disease prefers relatively cool temperatures and humidity to develop and spread.

"It's definitely a challenge for the growers that are facing it. It's probably one of the most aggressive diseases that farmers have ever seen. But we're already doing a good job as an industry, when it comes to finding things we can do both culturally and chemically, to help mitigate this disease," said Bunt.

Farmers are encouraged to report any sightings to their local extension office and to save the leaves so that the extension can confirm the disease. There is also a website called Corn ipmPIPE where farmers can report tar spot and get identification from extension specialists.