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This Could Be Decision Week for Fungicides

Answer not as clear-cut this year.

The hot topic for the Corn Illustrated plots near Edinburgh, Ind., again this week is whether or not they should be sprayed with fungicide. It’s also the hot topic in many areas of the Corn Belt, based upon what we’re hearing form seed dealers, fertilizer and chemical dealers and farmers.

One year ago excitement ran high and many people lined up to spray for fungicides, not waiting to see fi there were diseases symptoms or not. Results were spotty, and depended somewhat upon which hybrid was planted and how resistant or susceptible it was to various diseases. In many parts of the Corn Belt a year ago, disease symptoms were all but non-existent early in the season, due to dry weather. Later, some diseases did come in in areas where rains fell and humidity and hot weather combined to favor various foliar diseases, including gray leaf spot.

What seedsmen report so far is that they are finding rust, but not much else in some fields. Yet the corn is tasseling, and farmers, dealers and custom applicators, mostly aerial applicators, are pushing for a commitment. Here’s what one central Indiana seed dealer is doing: if it’s a hybrid that isn’t as resistant as some, he’s suggesting spraying it. And if he’s already finding rust, especially on leaves up in the canopy near the ear leaf, he’s suggesting spraying it, even though he’s not seeing as many symptoms of other foliar diseases as he expected to see at this point.

There are two problems inherent in scouting and waiting to apply fungicide. First, the pathogen itself can spread quickly once conditions are right. The inoculum is likely present in most cases. All that it’s waiting for are the conditions that encourage it to grow. Once those develop, you can go from very little symptoms to enough to cause economic loss in a relatively short time, sometimes a shorter time frame than you can react and treat the field.

That’s the second problem- dealers need adequate time to get their hands on enough fungicide. And there are only so many aerial applicators available. Some may elect to go with high-clearance sprayers, but it’s an even slower process in terms of covering acreage.

At the Corn Illustrated Plots, Dave Nanda, president of Bird Hybrids, LLC., Tiffin, Ohio and consultant for the Corn Illustrated project, says the high-yield plots should be sprayed. He’s just waiting for the later-planted plots to tassel and pollinate before spraying. Last year there were cases of injury reported when certain products were sprayed too early, before tasseling and silking.

Nanda has inspected the populations study; planted earlier, on May 5, and so far, does not see the need for fungicides there. Those plots were clean as of just a few days ago. Even bottom leaves were showing few if any symptoms.

On the row spacing plot, with twin rows, 15-inch rows, varying populations and starter vs. no-starter, there was probably more symptoms of foliar diseases present earlier than anywhere else. Nanda found symptoms of several foliar diseases when plants were only kneep0-high.

However, the CI staff has elected not to spray those plots. The concern is that it will be another complicating factor, especially if only part of the plots are sprayed in an effort to get comparison data between treating and not treating,. The plots were replicated, but enough replication wasn’t provided to add in another factor. Instead, all pots will be handled the same- and not treated. So comparisons for yield and other factors, including stalk lodging, at the end of the year will be on an equal footing.

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