Two years ago problems with corn rootworm control in parts of Iowa and Minnesota made headlines. It was primarily on one trait and much worse in continuous corn. This past summer the University of Illinois confirmed severe rootworm damage on some rotation corn fields in east-central Illinois. That's according to Jeff Nagel, an Indiana Certified Crop Adviser and agronomist for Ceres Solutions, based in Lafayette.
The problem in Illinois, according to reports, was confined to hybrids that exhibited a single rootworm protein, Cry3Bb1. Larval damage and beetle populations were both reported to very high, Nagel says.
In contrast, performance of all traited hybrids in Indiana has still been good, he says. Yet he notes that the problem in Illinois, not that far away, is concerning.
Nagel suggests a five-pronged, integrated approach to manage rootworms in Indiana. First, use crop rotation when possible. There is a variant that can lay eggs in soybeans. And it's more prevalent in northwest and northern Indiana, but does show up in pockets elsewhere.
Second, control any volunteer corn in soybeans if the previous corn crop contained a rootworm protecting trait.
Third, plant the required refuge. If you're using the refuge in a bag concept, then you take care of the refuge issue by planting the seed with a second, non-traited hybrid mixed in.
Fourth, where historical rootworm pressure has been higher, such as in northwest Indiana, plant hybrids that contain two Bt proteins effective against rootworms. Nagel especially recommends this in corn and soybean rotations.
Fifth, last but not least, consider using a soil insecticide for continuous corn fields. This would only apply if you're planting a hybrid that only has a single Bt event for corn rootworm control.
Having a strategy will hopefully help delay any problems that could occur here if producers don't follow good procedures.