Weld, Colo. Crop Rotations Help Avoid Widespread Rootworm Problem In Corn

The diversity of crops grown in Weld County has helped most local farmers avoid a problem that's been making national headlines recently.

Reports in the Wall Street Journal and other media outlets have described many farmers nationally returning to chemicals to control corn rootworm, corn's No. 1 pest, because the insect in recent years has developed a resistance to the genetically modified seeds engineered specifically to kill it.

Some parts of Colorado experienced a "major" rootworm resurgence a couple years ago, but that's not been the case in Weld County, many local farmers say, and it's largely due to rotating a variety crops on their fields.

Rotating crops is the best way to break the rootworm cycle, said Bruce Bosley, Colorado State University Extension crop specialist.

And in Weld County -- where many irrigated farmers grow a cocktail of corn, onions, sugar beets, dry beans, alfalfa and wheat -- rotating is already the "norm."

Hudson-area farmer Dave Dechant said he's never planted genetically modified corn on his fields, and still -- because he seldom plants corn on the same ground in consecutive years -- he's rarely had any issues with rootworm.

"Going back about 20 years, when we were planting corn on our fields every year, we saw some issues with rootworm. But ever since we stopped that, we've been fine," Dechant said.

It's widely known that crop rotations are ideal for avoiding pests like rootworm.

But Bosley said high corn prices in recent years led many farmers across the U.S. to plant corn on the same fields year in and year out, looking to take advantage of the opportunity, and they depended on genetically modified seeds to help them do so.

Those modified seeds -- containing a rootworm-targeting gene known as Bt -- were first introduced in 2003 and proved to be largely effective against the corn rootworm. According to the U.S. Department of Agriculture, two-thirds of all corn grown in the U.S. now includes Bt.

But as farmers in many corners of the U.S. grew corn on the same fields each year, rootworm evolved and developed a resistance to Bt corn varieties.

It hasn't been a major issue in Weld County, though.

A dozen local farmers who recently spoke with The Tribune -- some who plant genetically modified corn varieties, and others who don't -- said they've avoided rootworm in recent years, and all attributed that success to their constant crop rotations.

With snowmelt in the mountains nearby to fill irrigation ditches, Weld County has historically grown crops like sugar beets, potatoes, onions and other vegetables. Because of that, packing sheds and other facilities needed for such production remain in place, giving local farmers incentive to continue growing crops beside corn, regardless of commodity prices.

That's not the case in the Midwest's Corn Belt.

Because there hasn't been as much crop rotation in the Midwest, the rootworm resurgence has taken place there.

Parts of Colorado, too, have fallen victim, according to Bosley.

"If we'd been doing here what they've been doing in the Midwest and elsewhere, we'd probably have the same problem," Dechant said. "But that's not how we do things."

Bosley said he and other CSU Extension specialists have surveyed about 200 fields across the state where rootworm issues were reported in 2011.

He said the problem overall in Colorado has improved during the past couple years, thanks to newer varieties of Bt corn seeds, farmers doing more crop rotating, and others simply spraying more insecticides on their fields.

According to recent reports, insecticide sales have been surging after years of decline, as farmers have planted more corn and Bt seed varieties have lost their effectiveness.

As more farmers switched to the modified seeds, the share of corn acreage treated with insecticide fell to 9 percent in 2010, the most recent year for which data are available, from 25 percent in 2005, according to the USDA.

Also driving insecticide use is the rising share of farmland planted to corn, as farmers seek to take advantage of the corn prices that are about double their historic norms. U.S. farmers planted 97 million acres of corn last year, the most since the 1930s.

According to the Wall Street Journal's report, Syngenta, one of the world's largest pesticide makers, reported that sales of its major soil insecticide for corn, which is applied at planting time, more than doubled in 2012.

According to a report from Harvest Public Media, a survey of Illinois farmers showed as many as half are now supplementing Bt corn with insecticide, and one-fourth are returning to chemicals as a precaution, whether they've seen the bugs or not.

But Weld County pesticide distributors and applicators say they haven't noticed any uptick in activity, since the rootworm resurgence hasn't been a factor locally.


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