Corn Tar Spot Identified in Northwest Missouri

Infected leaf with symptoms of corn tar spot. Red arrows point to characteristic black, raised stroma that cannot be scraped off the leaf. Photo by University of Missouri Integrated Pest Management.

Samples from at least one Northwest Missouri county have tested positive for the presence of corn tar spot, highlighting the continued spread of the fungal infection that can suppress yields. The discovery last month in Holt County follows new cases in several of the nine counties in Northeast Missouri where the fungus has already been spotted. Doctor Mandy Bish, director of the University of Missouri’s Integrated Pest Management program, says the discovery in Northwest Missouri highlights one of the ways that corn tar spot can be spread.

Bish notes that the pest has also been detected in eastern Nebraska and can overwinter in the stubble from the previous fall’s harvest. She explains some of the signs of infection.

University of Missouri Integrated Pest Management director Mandy Bish adds that the university’s Plant Diagnostic Center is also investigating a possible case of corn tar spot in Carroll County. She says scouting fields now for signs of the fungus can help with management decisions for next year, including whether to apply fungicide.

Additional details are available on the MU Integrated Pest Management website.