Resistance Reality: Run a Rotation

July 29, 2012 09:07 PM

Part 5 of our "Resistance Reality" story, featured in the Farm Journal 2012 Seed Guide. Click here to start reading from the beginning.

That’s what Daly did after encountering western corn rootworm resistance in a 40-acre field in Iowa four years ago.

"I knew something was wrong; that corn goosenecked pretty bad," recalls Daly, who uses a rotation of four years of continuous corn followed by a year of soybeans.

Today, he rotates hybrids with different Bt toxins in his fields, uses a soil-applied insecticide at planting and then scouts for the pests and conducts root digs during the growing season. For additional support and education, he relies heavily on his seed retailer and co-op agronomist.

Scientists are divided on the topic of insecticide use in conjunction with Bt hybrids. The entomologists who wrote to EPA say, "In general, treatment of rootworm protected transgenic corn with insecticides is not a recommended control strategy. It elevates production costs, reduces profits, selects for resistance to the insecticides and masks the geographic extent and
in-field severity of Cry3Bb1 resistance."

Gray says the $20 to $25 farmers spend per acre on an insecticide is perceived as cheap insurance to protect a valuable corn crop.

This spring, so many farmers wanted to use insecticides at planting that product was hard to come by. At the same time, some planter companies sold out of insecticide boxes.

"Part of the reason was fear; people didn’t want to gamble with their crop," explains Farm Journal Field Agronomist Ken Ferrie.

Another reason farmers are opting for more insecticide use at planting, Ferrie adds, is that the insecticide Furadan was banned by EPA several years ago as a rootworm rescue treatment in-season.

Without Furadan, Ferrie says, "there’s no way to clean up a rootworm problem now if one occurs."

"Since there is no rescue option, you have to be more aware of the rootworm pressure you have in the field, so you can manage for it effectively next year," adds Rick Kesler, national business services manager for FMC Corporation, which made Furadan.

Syngenta’s Araba advises farmers to consider making an aerial application of Warrior insecticide if they see high numbers of adult rootworm. "That would address beetle populations at pollination and minimize egg laying for the next year," he says.


Continue: "Few Non-Bt Options" >>


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