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Iowa Farmers Rotate Through Corn Rootworm Pressure

Posted on November 7, 2013 at 7:30 AM by Iowa Corn

Scout for beetles, monitor for damage, treat and repeat. The corn rootworm is a devastating insect that has caused an estimated $1 billion worth of damage in past years, and it seems like a never-ending battle to keep up with it. But many Iowa farmers seem to have gotten ahead of the pest and broken the corn rootworm cycle, and they’re doing it through rotation and more rotation.

“When we’ve run continuous corn in the past, we’ve experienced some downed plants in some areas of our fields,” says Chris Edgington, a corn and soybean farmer from Mitchell County, Iowa. “Our research showed it was due to root feeding from corn rootworms.”
With the entire state of Iowa typically in the “high risk” zone for corn rootworm pressure each year, Edgington is one of hundreds of farmers on the front lines waging war on the yield-busting pest. He says the best deterrent has been rotation – rotating crops as well as rotating to Bt products with different and multiple modes of action. But it all depends on what you’re seeing on your own individual fields.

“This past year, we’ve rotated some corn with beans to minimize any potential corn rootworm pressure. That seems to help since corn rootworms don’t feed on beans,” says Edgington.  
But with the demand for corn, it’s not economically viable or practical for Edgington to rotate crops on all of his fields, so he also plants corn on corn. To help combat the pest and ultimately help ensure it doesn’t build up a resistance to one particular technology, Edgington alternates the Bt traits and modes of action that he uses on his corn-on-corn acres.
The Agricultural Biotechnology Stewardship Technical Committee (ABSTC), a consortium of agricultural biotechnology companies and associations, agrees with Edgington and has suggested some corn rootworm best management practices.

“This year we continued to see heavy corn rootworm pressure in the upper Midwest in states like Minnesota, Iowa, Illinois, Nebraska, South Dakota and Indiana,” says Mike Smith, ABSTC IRM Stewardship Subcommittee Chair. “So we’ve come together as an industry to offer ways these farmers can manage corn rootworm populations.”

To help break the corn rootworm cycle, ABSTC recommends rotating crops from corn to a non-host crop that rootworms won’t feed on (i.e., soybeans).

If farmers prefer to plant corn on corn, ABSTC recommends they at least use Bt products with multiple modes of action. For example, if a Bt trait with a single mode of action is used one year, select a trait that uses a dual or pyramided mode of action the following year. By doing this, farmers are safeguarding against corn rootworms becoming resistant to one particular mode of action, while providing effective below ground protection.


“Ultimately you’ve got to walk your fields and know every area. Then take the time to analyze and determine which approach – whether it’s rotating crops or choosing a multiple mode of action – will work best for you,” says Edgington. “These best management practices work.”

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