Doug Jardine, Extension Row Crop Pathologist for K-State

(Doug Jardine) I am Doug Jardine and I am the Extension Row Crop Pathologist for Kansas State University. This winter while we were out talking to farmers there were a few diseases that were significant in the 2016 cropping season that we were discussing with them. The three most important ones, the first one is a disease called Southern Rust, that is a disease that has been around Kansas for a long time, but for reasons we are not quite sure about, we think perhaps weather-related, the last two years it has been especially severe and we have been actually able to go into some replicated hybrid test plots and show yield losses with an average of about 10% in certain really susceptible hybrids – maybe as high as 25%. So you can see if you have 150 or 200-bushel corn that would be a significant amount. Fortunately, we do have hybrids that are pretty resistant to it and there are also fungicides available that can be used. As we were talking to the growers this winter we discussed some of those management options for them. The second disease we have been talking a lot about again is one that’s been around for a long time. It is an ear rot disease called Diplodia, and if you look hard enough you can find Diplodia somewhere in Kansas pretty much every year. But this year because of specific weather conditions it was an epidemic. It’s been the worst that I’ve seen in my 32 years in Kansas. Those specific conditions were in areas of the state where we got a lot of rainfall at silking and then extended out for about two weeks after silking. This particular fungus enters the ear through the silks, it likes really wet weather. Where we have heavy rains just after silking, if the fungus is present at some level in the field we can get significant infections. That’s what happened this year. Two particularly hard hit areas of the state were south central Kansas and the Kansas River Valley. Diplodia, on the good side, doesn’t produce any mycotoxins so it’s not a danger to cattle for feeding. But because it penetrates the cob it causes the cob to shatter as it goes through the combine and you get a lot of foreign material in the load and when you take that to the elevator you can get a significant dockage. That’s been the main concern with growers, not necessarily the actual yield loss but the dockage from foreign material at the elevator. The final disease is a bacterial disease which is brand new not only to Kansas but also to the United States. We are calling it Bacterial Streak. We’ve simply been showing producers pictures of what the disease looks like so that they can become familiar with it and maybe begin to look at it in the upcoming 2017 season. The main thing we’re emphasizing is it looks a lot like Gray Leaf Spot, most common leaf disease of corn. We’re trying to give them some keys where they can separate out, “Do I have Gray Leaf Spot or do I have Bacterial Streak?” Because if it’s Gray Leaf Spot then they can go ahead and apply a fungicide management. If it’s Bacterial Streak there’s really not much they can do at this point. We are trying to avoid people putting fungicides on the bacterial disease because it’s not going to work. Those are the main issues that we’re addressing at our winter school this year.

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