Tar Spot on the Rise Across the Corn Belt

As corn nears reproduction, growers are facing a daunting challenge. Tar spot has quickly made its way into the Midwest, and is not slowing down. As this fast-acting pathogen spreads, there are things to look for and ways to help manage your corn crop and maintain yield potential.

Tar spots on corn are a product of the fungus Phyllachora maydis. It was first confirmed in the United States in 2015. It can be identified along the plant as small black raised circles. These fungal structures are called stromata. When looking at the plant, tar spot can be found on tissue of the husks, stalks and leaves.

Leaf wetness has a direct correlation to tar spot. Extended periods of leaf wetness (greater than 6 hours) creates an environment for tar spot to flourish. Wind-driven rain, high levels of humidity and storms can also promote disease development and infection.

Ben Wilson, Helena Agri-Enterprises Agronomist based in Michigan, suggest growers make their first fungicide application during tassel and see what the weather provides in the weeks to follow. Typically, a second pass is needed three weeks later if conditions are favorable. The two-pass strategy of premium fungicides will help control the pathogen, starting the first pass with Odyssey® and the second with Miravis® Neo, Veltyma™, Delaro® Complete, or Avaris® 2XS.

Disease management is an essential part of a comprehensive Corn Wise program. Being Corn Wise means putting the right tools in place at the right time to maximize your corn crop, and ultimately, your ROI. To create your plan and learn more about tar spot and how it may be affecting your area, contact your local Helena representative.

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