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Should You Apply A Corn Fungicide

Soggy conditions in much of the corn belt this spring delayed planting. This could also mean delayed harvest in the fall, which sets up a risk for fungal diseases. Northern corn leaf blight, gray leaf spot, tar spot, and others could affect yields. Before you spray fungicides, there are several factors to consider such as environmental conditions and where the diseases are showing up.

Daren Mueller is an extension plant pathologist at Iowa State University. He says you can get a good indication of disease pressure without walking into the field. A lot of your scouting can be done from the computer.

"One of the things you could be doing is reading newsletters from seed companies or extension services not just from your state, but the states around you. Looking at Twitter or whatever social media that you are on and just look for the chatter," says Mueller. "So, if tar spot’s blowing up in the same areas you’re going to hear about it. Once you start seeing that pattern, you should be walking out in the field and making sure that what they’re seeing would be reflected on what’s going on locally."

Know the foliar disease resistance of the hybrid you’re growing. On intermediate and moderately resistant hybrids, any yield benefit would not cover the costs of the fungicide application.

"My encouragement would be to be using a fungicide when a fungicide’s needed," he says. "And so, try to not look at yield response when you’re considering a fungicide and that’s hard to do, but really, that yield response will happen if you’re applying the fungicide to manage a fungus at a high enough level that would warrant a fungicide."

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