One of Dave Nanda's customers started the ball rolling. He normally grows non-GMO corn and sells it at a premium at a river terminal in southeast Indiana. As the rains continued and planting date loomed farther out, he began hearing about neighbors pressured to make sure they had corn with Bt corn borer protection since the risk of corn borers would be up. He came to Nanda for advice.
Nanda, a frequent columnist here and in Indiana Prairie Farmer magazine, is a crops consultant and also director of genetics and technology for Seed Consultants, Inc., Washington Courthouse, Ohio. Seed Consultants provides seed to farmers in several states, including an increased presence in Indiana.
Common wisdom is that late plantings of corn are typically more subject to corn borer infestation than if corn is planted earlier. Bob Nieslen, Purdue University corn specialist, confirmed that for Nanda However, the most vulnerable fields are those planted late when everything else around them is planted earlier. Then the late-planted field acts as a sink, attaching and catching moths looking for green corn in the stage it likes, with nowhere else to go.
The other factor that impinges on this decision is how often corn borer is an economic factor in the first place. While it's a factor almost every year in Iowa and the western Corn Belt, it's a major factor only two to three years out of 15 in Indiana, agronomists say. The trick is knowing when those two or three years are. The risk of corn borer pressure would be higher this year due to alter planting of all corn, but risk is relative. It's difficult to get a handle on and quantify.
One way to approach the problem for this grower is that if he has a non-GMO contract for a premium on non-GMO corn, and this non-GMO hybrids typically yield as well as GMO hybrids, then he may choose to stick with the non-GMO hybrid. However, he might want to be prepared to harvest early if stalk integrity becomes an issue. It could become an issue either because of feeding by corn borers directly, or because corn borer feeding, if it occurs, would open up the stalk to secondary infections. Often the secondary infections are what cause stalk rot and a higher potential for lodging.
For someone without a non-GMO contract, considering switching to a GMO hybrid with corn borer protection, if available and if you can find one at the same yield level that fits your climate and soils, might be worthwhile insurance.