Tar Spot of Corn: Management Options Once Detected On Your Farm
2022
- Department of Botany and Plant Pathology, Purdue University
Project Media
Tar spot of corn, caused by Phyllachora maydis, has become a major disease issue in corn production in northern Indiana. The annual impact of this emerging disease will be a function of the weather, hybrid and when the disease epidemic initiates, earlier vs. later in the season. Our research has found that some hybrids are more resistant than others, but strong hybrid resistance can be overcome by a favorable disease environment. Fungicide application can reduce tar spot severity, but product and timing are important. Fungicide application needs to occur close to the onset of the epidemic and the number of applications and optimal timing are going to vary year by year. In 2019 and 2020 in uniform fungicide trials, fungicides significantly reduced tar spot and protected yield by 1.5 to 7.9% over the non-treated controls. Products that had two or three modes of action (MOAs) decreased tar spot severity over not treating and products with one MOA. Three MOAs significantly increased yield over not treating with a fungicide or using a single MOA group. A summary of our research in Indiana will be presented as we continue to improve our understanding of tar spot disease management options to mitigate yield loss.