b'Seed Innovation is Fighting Back a Growing Threat in CornTar spot is a significant challenge for corn, but seed companies and agronomists are stepping up with solutions. By Peter Scharpe, Seed World ContributorFOR NEARLY A DECADE,corn seed developers have been addressing the rise of a new disease threatening the Midwests corn yields. Tar spot, a fungal disease caused by Phyllachora maydis, has emerged as one of the most significant challenges for corn production, presenting both risks and oppor-tunities for seed companies to innovate and provide solutions.First detected in the United States in 2015, tar spot has rapidly gained a foothold, thriving under the right environmental condi-tions and causing significant yield losses.The Yield-Loss RealityIve been able to see tar spot firsthand for the last four straight seasons in central Iowa, says Matt Vandehaar, field agronomist with Pioneer. Most farmers in my geography now definitely know what tar spot looks like; however, some dont quite know the full economic impacts if it gets a lot of pressure.The disease manifests as small, black lesionstar-like spotson corn leaves. These lesions can coalesce, reducing pho-tosynthetic capacity and causing premature plant death. The economic implications are staggering. In 2021 alone, tar spot was responsible for an estimated reduction of 231.3 million bushels in U.S. corn yields, equating to nearly $1.25 billion in losses. For seed companies, this underscores the urgency of developing hybrids with robust tolerance.Tar spot can shut down that corn plant early, and even if youve made a fungicide application, it can still cause significant damage, Vandehaar explains. Weve seen areas with a lot of pressure where yields are hit hard.The spread and severity of tar spot are heavily influenced by weather. Cool, wet conditions, particularly in late summer, create the perfect environment for the disease to thrive. However, these conditions have not been consistent across the Midwest.The Weather WildcardWeve lacked a cooler-than-average, wetter-than-average August for the past few years, Vandehaar says. But even so,Tar spot is a big challenge for corn.PHOTO BY MATT VANDEHAAR, PIONEER FIELD AGRONOMIST.38/ SEEDWORLD.COMJUNE 2025'