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Options to protect corn from rootworm

You’ve got options today when it comes to protecting against corn rootworm. Each option has its pluses and minuses. There is no such thing as a silver bullet or foolproof remedy for rootworm control. But compared to days gone by, there are alternatives that allow you more flexibility.

Key Points

Where you live will affect rootworm pressure.

Rootworm is always a threat in corn after corn.

Options: Bt-rootworm hybrid from another company, or high rate of seed insecticide.

Here’s an example from a farmer that illustrates the point. The Indiana Certified Crop Advisers panel members explain how they would handle the situation.

My seed company had to substitute another hybrid, and I’m going to end up with two fields of corn that don’t have built-in rootworm protection. One is corn after corn, the other is corn after beans. I hate to calibrate and mess with soil insecticide for two fields. What would you recommend?

Greg Kneubuhler, G & K Concepts, Harlan: You can’t afford to plant corn after corn without rootworm protection. We have proven consistent returns in our consulting business in corn on corn, with either soil-applied or built-in protection. Either re-adjust your hybrids to allow for rootworm protection in corn on corn, or don’t plant corn there.

With the corn-after-bean field, the decision may come down to where you live. On the east side of Indiana, rootworm pressure has appeared to diminish. The full rate of seed-applied insecticide may provide enough protection there. See if your company can supply you with seed with the full rate of seed-applied insecticide.

Overall, the answer can depend greatly on your area’s rootworm pressure. This is a potentially costly decision. Confer with a local agronomist about rootworm pressure in your area.

Jesse Grogan, LG Seeds, Lafayette: Economic corn rootworm larval damage is more frequent in fertile silty clay loam soils. Corn rootworm is less of a threat in sandy soils; tight, poorly drained clays with low organic matter; and mucks. A seed treatment insecticide is an option. Seed companies utilize products such as Cruiser Extreme 1250 or Poncho 1250 for corn rootworm control. These products are considered most effective at low to moderate levels of rootworm pressure. Rootworm pressure is usually greater in corn following soybeans north of Interstate 70. If high pressure is anticipated, rig up and calibrate soil insecticide applicators, or find another company to supply a rootworm-resistant hybrid.

Darrell Shemwell, Posey County Co-op, Poseyville: One option is to buy a proven hybrid that has corn rootworm protection from another company. Or ask your dealer for Poncho 1250 instead of Poncho 250 seed treatment. This would be the easiest way to get partial rootworm control.

Another option would be a liquid insecticide labeled for corn, such as Regent 4SC, Capture LFR or Bifenthrin 2E. They can be applied in-furrow and provide partial control. On the corn-after-beans field, I wouldn’t be very concerned unless you have a history of extreme rootworm pressure, or know you have a problem with the western corn rootworm variant. If so, treat the first-year cornfield the same as for corn after corn.

Photo courtesy of Purdue University

This article published in the March, 2011 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.