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Why Western corn rootworm is so tough to controlWhy Western corn rootworm is so tough to control

This native insect is so well adapted and genetically wired to overcome Bt that it will make you pay if you cut corners on refuges or rotations.

Curt Arens

April 16, 2015

2 Min Read

While Bt hybrids have worked well in controlling European corn borer, they have failed to consistently control Western corn rootworm.

Related: This iPad app helps you prep for corn rootworm risks

Tom Hoegemeyer, retired University of Nebraska agronomy professor and a corn breeder with Hoegemeyer Hybrids, lists a number of the reasons why:

•WCR is a native insect that is well adapted with a huge genetic pool of variability, compared to the less variable ECB that was transplanted to the U.S.

•Refuges of non-Bt corn haven't worked as effectively, partly because too few farmers plant refuges or the plant the required number of acres of refuges.


•Two to 20% of the insects that get a dose of Bt don't die

•There's a lot of continuous corn planted in the Western Cornbelt. This increases the WCR population.

•Mating between resistant and susceptible WCR isn't completely random because not enough susceptible beetles get into Bt corn fields.

•Resistance to Bt toxins is not a recessive genes. "It actually might be partially dominant," Hoegemeyer says. "We're seeing this at a scary rate."

•There isn't a significant "fitness cost" incurred by resistant insects, causing them to have a lower survival rate and fewer offspring than susceptible beetles. "Actually, they have a higher survival rate on Bt corn and do better on Bt corn than on non-Bt corn," Hoegemeyer says. Also, resistant WCR beetles are not more susceptible to natural enemies such as fungi or nematodes.

Crop rotation is the most effective tactic to use to control WCR beetles Hoegemeyer says.

"Rotate your crops and rotate your chemistries."

He also suggests planting Bt hybrids with a single, effective protein or a pyramid of multiple proteins. Scout corn and use a liquid or granular insecticide at planting time for larval control and post emergence treatments for larval and adult control when necessary. Follow protocol for non-Bt refuge plantings and other management tools.

"We will never control WCR with a single trait or insecticide," Hoegemeyer says. "Multiple tactics are the key to slowing down WCR."

About the Author(s)

Curt Arens

Editor, Nebraska Farmer

Curt Arens began writing about Nebraska’s farm families when he was in high school. Before joining Farm Progress as a field editor in April 2010, he had worked as a freelance farm writer for 27 years, first for newspapers and then for farm magazines, including Nebraska Farmer.

His real full-time career, however, during that same period was farming his family’s fourth generation land in northeast Nebraska. He also operated his Christmas tree farm and grew black oil sunflowers for wild birdseed. Curt continues to raise corn, soybeans and alfalfa and runs a cow-calf herd.

Curt and his wife Donna have four children, Lauren, Taylor, Zachary and Benjamin. They are active in their church and St. Rose School in Crofton, where Donna teaches and their children attend classes.

Previously, the 1986 University of Nebraska animal science graduate wrote a weekly rural life column, developed a farm radio program and wrote books about farm direct marketing and farmers markets. He received media honors from the Nebraska Forest Service, Center for Rural Affairs and Northeast Nebraska Experimental Farm Association.

He wrote about the spiritual side of farming in his 2008 book, “Down to Earth: Celebrating a Blessed Life on the Land,” garnering a Catholic Press Association award.

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