Agronomy Talk

E. Indiana & W. Ohio - Brent Minett, CCA

Fungicide: To Spray or Not To Spray

Published on Monday, July 20, 2015

Every year at this time farmers make the decision “to spray or not spray” their corn fields with fungicide. Understanding all the factors that need to be evaluated before full tassel helps eliminate confusion and hand wringing when the planes are ready and available. 


Fungicide Response Ratings – We rate all our corn hybrids for the likelihood of an economic return on investment from a VT application of fungicide. A high rating means a positive return on investment is very likely and you should budget to spray that hybrid. A medium rating means an economic response is a toss-up and thorough scouting should be done during and after pollination to evaluate disease pressure. A low rating means an economic response is unlikely even when some disease is present in the field. 


Scouting – All fields should be scouted before, during, and after pollination for fungal diseases. I look at the two leaves right below the ear leaf to evaluate what might happen in the future. Rule of thumb: if 50 percent or more of the plants have lesions on those leaves, that can’t be covered by a quarter if they were all together, it’s time to make a fungicide application. The goal is to protect that ear leaf and the leaves above it as they are doing the heavy lifting from pollination to physiological maturity.

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Brent Minett

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