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Weather Providing Increased Risk for Disease in Indiana Corn


Recent rains and increased humidity across Indiana have increased the risk for foliar diseases to develop in both corn and soybeans. Purdue Field Crop Extension Plant Pathologist Darcy Telenko joined us on the latest Purdue Crop Chat Podcast to discuss what she’s seeing in corn.

“I think it’s time to get out and start looking in the lower canopy of your corn. Gray leaf spot is active throughout the state, so I think if you get out there, you’ll begin to see it depending on your hybrid. Whether there was a resistance package or not, that’s going to determine how much gray leaf spot is developing and then watching it to see if it’s moving up into that upper canopy. Our goal with our fungicides is we want to protect that ear leaf and above so we can fill out that ear.”

Telenko says if you have a history of northern corn leaf blight in your field, that is starting to be active around the state. They’re also keeping a close on southern rust emerging in Indiana’s southern counties with one confirmed report in Gibson County, though Telenko suspects it’s in other southern counties as well.

Another disease cropping up around northern Indiana is tar spot, which was first discovered in Indiana in 2015. She says tar spot thrives on moisture. To protect against it, “Getting a fungicide out there now at VTR1 is a good timing, but this disease does come on later and it kicks up later in the season, so we need to monitor it,” says Telenko.

“Your fungicide is going to provide a nice window, two to three weeks of protection, the idea is to protect that ear leaf. But if we go on and 3 weeks after you’ve put a fungicide out and the weather conditions are still conducive, then we need to think about if a second fungicide would be beneficial for that disease in particular. For our standard diseases, gray leaf spot, northern corn leaf blight, generally that VTR1 application is showing the most efficacy against controlling those diseases.”

And for those more standard diseases, Telenko believes one fungicide application is enough. She says resistance is developing and we need to be cautious and protect the tools that we have.

“Most of the work that we’ve looked at when you combine this metadata from multiple trials across the different states, that one application seems to work just as well as putting out two or three applications. You’re really not getting the return on investment in the disease management side of things. So, in my mind, I would want us to hold on to our fungicides and use them as needed.”

Hear much more from Telenko in the Purdue Crop Chat Podcast found below: