Where Is All the Disease in Corn?

Dry start to season hijacked it ... so far.

Airplanes are flying over Indiana. If you see one dipping low as you drive down the road, heading over a cornfield, then smell a chemical as you drive by, he's either applying an insecticide to stop silk-cutting in corn, or he's applying a fungicide. Many of the crop duster runs this summer across Indiana have been to apply a fungicide. Apparently farmers saw results from many tests last year and decided it was a good investment, especially with the high price prospects for corn.

But what are field scouts, farmers and agronomists see far in fields this year? So far, it may not be a big goose egg, but it's close. It just hasn't been a season over most of Indiana that favors disease development.

It's not just lack of rain in many areas. It's also low humidity levels. Last week humidity levels on the weather monitoring station at the Corn Illustrated plots near Edinburgh read below 40% at noon. For mid-July in Indiana, that's unusual, to say the least.

"There's one hybrid in our plot that's a high-yielder, but it is somewhat susceptible to gray leaf spot," says Dave Nanda, Bird Hybrids, Tiffin, Ohio. "If gray leaf spot was going to show up anywhere, it should show up there, but so far, that hybrid in the plot is squeaky clean. We haven't found the first indication of gray leaf spot yet."

A Pioneer field rep who works with seed growers reports similar findings. He notes that in '06 many seed fields were sprayed twice for disease. Inbreds, especially certain inbreds, tend to be susceptible to diseases. Nut so far, they're not seeing disease in seed fields. With pollination winding down in many of their irrigated field production, there could be fields where no fungicides are applied this year, he notes.

A plant pathologist checking seed corn last week reported finding nothing but a small amount of rust in a field in central Indiana, and it was miniscule. Purdue University conducts fungicide trials of various known and experimental products, and is again this year. They put the trials out whether disease pressure is there or not. They also do trials in commercial hybrid corn and in soybeans. But they typically don't see big yield differences if diseases aren't present when fungicides are applied.

It's not too late for weather conditions to change and favor disease development. But the later in the season that a disease gets a foothold, especially in corn, the less likely that it will cause significant economical damage.

Stay tuned, just in case.

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