The question Kiersten Wise gets most often sounds simple: Are fungicides warranted on corn? The Purdue University Extension disease specialist says the question is not as simple as it sounds.

Here’s how she answered this and other questions recently at Purdue’s first-ever Corn Showcase.

Are fungicides needed on corn?

FUNGICIDE QUESTIONS: Kiersten Wise answers questions about fungicide use in a relatively low disease pressure year like 2016 at the first-ever Purdue Corn Showcase at the Agronomy Center for Research and Education.

Wise: There are really three parts to this question. First, what is the hybrid rating for fungal disease? Second, how much disease is present when you intend to apply the fungicide? Third, how can you make a fungicide application profitable? Since corn prices have dropped significantly compared to a few years ago, it takes more bushels per acre on treated corn just to pay for the fungicide and application cost.

If you are going to use a fungicide, why is timing so important?

Wise: Over the last several years, we've continued to see some recommendations that fungicides shouldn’t be applied until brown silk. Apparently there was concern about impact on pollination and final yield. 

We believed that [brown silk stage] was too late to capture maximum gain from the fungicide. Research shows disease may not have as great an impact on yield after brown silk. Two years ago we started research funded by the Indiana Corn Marketing Council. We applied fungicides at different stages of corn development.

What do the results show?

Wise: During the first two years of the study, yield response dropped as we waited longer to apply the fungicide. Based on these studies, we recommend that if you’re going to apply fungicide, apply it at the tasseling and silking stage. If you’re concerned about pollination issues, apply when silks are pollinated, but before they turn brown. You can carefully pull back husks and do the shake test to determine when pollination is complete. If silks fall off, they have been pollinated.

What are you doing this year?

Wise: We again applied fungicide at a series of different timings, and we will look at the effect of timing on severity, yield and stalk health. We inoculate our trials with the fungus that causes northern corn leaf blight, but 2016 is not a good year for the disease. It prefers cooler temperatures than what we’ve seen this summer. Overall, disease pressure has been relatively low across most of Indiana this summer.

What do you expect in a year like 2016 in terms of yield response?

Wise: In 2016, you need 6 to 10 bushels per acre of extra yield to cover the cost of fungicide and application. Your best chance of seeing that return if you applied a fungicide was if it was applied at the tasseling and silking stage. In years with low disease, if you’re not seeing some disease by tasseling and silking, you may not need the fungicide application.

Do differences in hybrids become a factor?

Wise: Yes. In years with more disease pressure, hybrids that are more susceptible may be more likely candidates to benefit from a fungicide. Talk with your seed rep now about disease resistance in the hybrids you select for next year so you know what fields to monitor for disease in 2017.