Corn Disease Issue

(Doug) I’m Doug Jardine and I’m the Row Crops Extension Specialist for Crop Diseases for K-State. And we’re here at today’s Corn Production School to talk about some of the corn disease issues that we had in 2015, what were some of the root causes, what they could’ve or should’ve done about it and maybe then translate that to what might happen in the 2016 season. The disease out there that is probably going to be highlighted today is one called Gray Leaf Spot. It’s a disease that’s been in Kansas since 1989, but because of weather conditions particularly all the rain that many parts of the eastern part of the state got in May and June caused that disease to develop early and at higher levels than we’ve ever seen. So, this was the worst year we’ve had for Gray Leaf Spot. And to put that into a context, we’ve estimated that on a statewide basis we had about a three percent yield loss in Kansas to this single disease. And if we do the math on that, that would be about four and a half bushels per acre of corn grown in Kansas and that’s about four million acres. So, again about 17 million bushels at current prices would have been about 68 million dollars lost. So, one of the things we’ll do with them today is review the management principles for Gray Leaf Spot. It’s going to start with hybrid selection. Some hybrids are very resistant and some are very susceptible, but this is also a disease that can be fairly easily treated with a fungicide. But they have to understand what the thresholds are for application because if the disease hasn’t developed then they don’t need to be spending the money and putting the particular pesticide out in the environment. But if the disease is there at the right level, then it’s definitely economical to go ahead and treat. The second disease we’re going to visit about is one called Southern Rust. Again, this is a disease that appears every year in Kansas, but most years it’s not an issue. It moves up into Kansas usually from southern Texas. It normally gets here in late July or early August and if we get our corn planted on time, the corn is so far along in crop development that the disease really has minimal effect on the crop. However this year, and some people may not remember this, but in mid-June there was a tropical storm in the Gulf Coast called Tropical Storm Bill, that kind of slammed into Texas and Louisiana and caused a lot of flooding down there. But what that storm also did was push these rust spores into Kansas at least a month prematurely. And again, because of the rains we had this spring, we had a lot of corn that didn’t get planted til June. So, the early arriving disease combined with the late planted corn, proved to be fairly disastrous in a number of fields. During the summer we tried to alert people to that and hopefully some of the fields were sprayed. But we’ll talk more about that this afternoon. And then the last disease we’re going to cover is one called Goss’s Leaf Blight. For the last several years it’s been a very significant disease in Kansas. In 2015 for reasons we’re trying to understand, it pretty much disappeared. And so that’s a good thing, but we’re going to try and review the principles of that disease with the growers and maybe we can make 2016 another good year for not getting that particular disease. Well there’s a number of places they can get information. I would say for those that are social media users, we have a K-State Crop Diseases web page, which they might want to find and like and we provide a lot of this information through there. But also through the K-State Research and Extension website, they can find their way to the Plant Pathology Department web page and within that on our Extension section, we have links to all of the publications that deal with not only the corn diseases, but wheat, soybeans, grain sorghum as well.

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