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Corn tar spot spreads to western Missouri

Corn tar spot has expanded its footprint to northwest Missouri this season.

University of Missouri Integrated Pest Management Coordinator Mandy Bish tells Brownfield in previous years tar spot had been found in the northeast quarter of the state, but earlier this month it was confirmed further west in Holt County, with another report in Carroll County.   

“It wasn’t necessarily surprising because we knew it has been confirmed in Nebraska. I think it is important when we talk about tar spot to know that we are not at the epicenter just yet. We see it, just not at high level yet, but I anticipate that is going to change.”

Bish says, “We had such a dry summer that it didn’t really show up until recently. Right now we’ve already passed the point where kernels have formed in the corn and are filling out. So, this year it is about monitoring where the disease is for future planning purposes.”

She says while cases have been mild so far, it is important to keep in mind the impacts of tar spot in other areas of the corn belt.

“In 2018 there was a severe outbreak in the Indiana/Illinois region with an estimated 25%-30% yield loss. We have not seen that yet in Missouri, but again, the pathogen is relatively new to our state.”

She encourages farmers who see permanent black lesions on corn leaves to submit samples to the MU plant diagnostic clinic.

“Now that the pathogen is in the state, it is not going to leave. It can overwinter in Missouri. So, we really want to know where it is for the sake of planning in the future.”

And she says farmers noticing tar spot symptoms in other states should also consider sending samples to a lab to help track how far the disease has spread this season.