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​Fungicides on our Corn Fields: Case Study Part A

Sally O. Mallowa1, Edward J. Braun1, Alison E. Robertson1, and Paul D. Esker2

1 Department of Plant Pathology and Microbiology, Iowa State University
2 Escuela de Agronomía, Universidad de Costa Rica

Mallowa, S.O., E.J. Braun, A.E. Robertson, and P.D. Esker. 2016. Fungicides on our Corn Fields: A Case Study on Foliar Fungicide use Decisions in the U. S. Corn Belt. The Plant Health Instructor. DOI: 10.1094/PHI-T-2016-0607-01


The Markus family owns an 800-acre farm in Iowa on which they grow hybrid corn.  Brad hoped to work as an extension specialist before joining his father and brother full time on the farm. Brad did several field trials investigating foliar disease management in corn and his findings influenced his perspective on disease management. He witnessed first-hand that positive results from fungicide use were best when diseases were present and severe. In addition, he acknowledges that research results on yield response and calculations on profitability from fungicide trials are not always easy for growers to use when making a decision. Brad is a typical millennial; he cares about the environment and social causes more than just making a profit.

Brad had a conversation with his father once planting was over. Mr. Markus said, “Brad, you remember this season we considered Pablo’s suggestion and planted a susceptible hybrid for the higher yield potential? He also made arrangements last November for fungicide application in mid-July when the corn is tasseling. Do you think we should go ahead with those plans?” Brad responded, “Dad, I have been telling you about my research for three years. If we go ahead with the decision we made in advance and it later turns out we didn’t need to spray, isn’t that a loss for us, and adds unnecessary chemicals to the environment? I suggest we scout, consider the weather, and only spray if disease is present or there is a risk.”

“This is such a hard decision to make based on your research and the fungicide commercials I hear on the radio” Mr. Markus said. “We have to look at the dynamics season by season and make several decisions, not just on foliar fungicides but about the whole system. Why don’t you visit with Dr. Matthews regarding your perspective and find out what the consensus is from the fungicide trials he has done. I will ask Pablo to call up SalSal Ag Agency for more information, since they are passionate about the plant health benefits of using fungicides. We can all prepare for a family meeting in about two weeks, to try and figure out how best to manage foliar diseases on our farm.”

Mr. Markus later talked to Pablo who was also agreeable to the idea. To prepare, both boys began to consult with the experts. What would they find out?