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POSTERS: New and emerging diseases

Tar Spot of Corn: Hybrid Reaction and Susceptibility
Mariama Brown - Purdue University. Richard Raid- University of Florida, Martin Chilvers- Michigan State University, Diane Plewa- University of Illinois, Nathan Kleczewski- University of Illinois, Darcy Telenko- Purdue University, Pierce Paul- The Ohio State University, Damon Smith- Univers

An unforeseen epidemic of tar spot of corn, caused by Phyllachora maydis, had a significant yield impact on corn production in the upper Midwest during 2018. Tar spot was first observed in 2015 in both Illinois and Indiana, and has since been confirmed in Florida, Iowa, Michigan, Ohio, and Wisconsin. The 2018 tar spot epidemic was the first time yield losses were documented in the U.S. Prior to this epidemic, no field research had been done in North American to screen corn germplasm for resistance to tar spot. Preliminary data from state hybrid trials in Indiana, Illinois, Michigan and Wisconsin demonstrated a range in hybrid susceptibility and reaction to tar spot and it is estimated that a 0.4 – 0.8 bu/A loss occurred per 1% increase in tar spot. Tar spot was observed on all hybrids assessed, although some hybrids showed lower tar spot severity and the crop canopy remained greener for a longer duration. All hybrids evaluated across the upper Midwest are considered susceptible based on data collected from this epidemic, consequently farmers in areas with a history of tar spot are urged to scout their fields during the growing season to ascertain if the disease is present. Although fungicides are available to manage the disease, hybrid and germplasm screening for susceptibility will be an important component of tar spot IPM in the future.