b'there have been pocketsin Indiana, Illinois, Wisconsin, Northern Iowa, and Southern Minnesotathat have experienced signifi-cant tar spot outbreaks.Tar spot seems to be a bit of a wildcard in the field. At this point, the fungi itself is prevalent in fields and crop residue. Early scouting is likely to reveal tar spot stroma on leaves. Now, if the weather conditions do not favor tar spot growth, that is where the disease will stay, as a stroma.Should the weather patterns shift and favor tar spot growth, then it can really take off and shut down corn plants before grain fill has completed. Were aiming to release hybrids with even The Race to Develop Resistant Hybrids higher scores for tolerance, so farmers For seed developers, the goal is clear: create hybrids that offer improved tolerance to tar spot. Pioneer and other companies arehave better tools to manage this disease. making strides in this area.We dont have genes that completely defend against it,Matt VandehaaarVandehaar admits. But we do have hybrids that show very strong tolerance. These hybrids have excellent yield potential, the agronomics farmers need, and the ability to handle tar spot pressure.One key trait in these hybrids is stay-green, a measure of a plants ability to maintain healthy, photosynthetic tissue late into the season.Stay-green correlates highly with tar spot tolerance in our lineup, he says. These plants remain healthy despite significant tar spot pressure, allowing them to maintain yields.To meet the evolving needs of the market, seed companiesVandehaar notes, Just because the tar spot stroma is present are intensifying their efforts to screen hybrids and identify thosedoesnt mean it will become an issue. Monitoring weather condi-with superior performance against tar spot. This requires robusttions is crucial to determine the right time for fungicide applica-field trials, data analysis, and the integration of genetic insights. tion. Sometimes, two applications during grain fill are necessary Each year, we screen hybrids to identify the ones thatto hold back significant pressure.perform best against tar spot, Vandehaar emphasizes. Were aiming to release hybrids with even higher scores for tolerance,Innovations to Combat the Diseaseso farmers have better tools to manage this disease. For seed developers, the challenge is balancing the introduction of hybrids with high tolerance against tar spot while support-Fungicides: A Tool, Not a Silver Bullet ing integrated management practices. This includes educating In addition to genetic improvements, understanding tar spotsfarmers on the importance of field monitoring, fungicide use, lifecycle is critical for seed companies when educating theirand maintaining overall plant health through good fertility and customers. The fungus survives on corn residue and spreadsresidue management.via wind and rain splash. Early scouting often reveals tar spotAs tar spot continues to spread, its impact on the Midwest stroma on leaves. While this stage does not always lead to sig- corn belt likely will grow. For seed companies, and Vandehaar nificant outbreaks, weather shifts toward cool and wet condi- says this presents an opportunity for the seed industry to lead tions can trigger rapid disease progression, impacting grain fillthe charge in providing innovative, resilient hybrids. By staying and yield potential. ahead of this disease through advanced breeding strategies and Fungicides play a complementary role in managing tar spot,customer education, the industry can help secure the future of but their success depends on application timing. corn production in the face of this evolving threat.SW40/ SEEDWORLD.COMJUNE 2025'