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2013 Farm Poll: Farmers Concerned About Bt-Resistant Corn Rootworm

Iowa farmers are well aware that populations of Bt-resistant corn rootworm have been found in the state, and more than half are concerned that the pest will become a major problem here, according to the 2013 Iowa Farm and Rural Life Poll.

“We wanted to better understand farmers’ perspectives on the threat of Bt-resistant corn rootworms and various management practices,” said J. Gordon Arbuckle Jr., a sociologist with Iowa State University Extension and Outreach. Arbuckle co-directs the annual poll with Paul Lasley, also an ISU Extension and Outreach sociologist.

The questions were developed in partnership with the ISU Department of Entomology. Only farmers who planted corn, soybeans or other row crops in 2012 were asked these questions, Arbuckle said. The survey data were collected in February and March of 2013.

“Corn rootworm is becoming a more prominent issue for Iowa corn growers. We’ve seen performance problems with Bt traits in continuous cornfields since 2009,” said Erin Hodgson, an associate professor and extension entomologist who was part of the research team.

Bt corn has been genetically modified to express genes from Bacillus thuringiensis (Bt). Farmers plant this type of corn to prevent injury by larvae of the western corn rootworm in the Midwest. However, western corn rootworm populations that have evolved resistance to these transgenic technologies have been found in Iowa and other Corn Belt states.

Sixty-nine percent of farmers responding to the 2013 Iowa Farm and Rural Life Poll indicated that they were aware that populations of Bt-resistant corn rootworm had been found in Iowa. Fifty-three percent were concerned that Bt-resistant corn rootworm would become a major problem in the state, Arbuckle said.

Thirty-eight percent of farmers said they had changed their approach to rootworm management during the past five years, and 77 percent of those who planned to plant corn in 2013 reported that they would use a rootworm-resistant variety, Arbuckle said.

One method for maintaining rootworm susceptibility to Bt toxins is to establish “refuge” areas of corn plants that do not express Bt genes. If farmers do not follow the refuge recommendations, rootworms can rapidly evolve resistance to Bt.

“We asked farmers whether other farmers in their area generally comply with refuge requirements. Sixty-three percent reported that farmers in their area comply, seven percent indicated that they don’t comply, and 31 percent indicated they didn’t know,” Arbuckle said.

“We also asked farmers whether they had used particular practices to reduce the risk of corn rootworm larvae damage to corn plants, and how effective the practices were,” Arbuckle said.

Ninety-three percent of farmers said they rotated corn and soybeans, and 86 percent planted rootworm-resistant corn. These two most commonly used strategies for preventing injury to corn by rootworm larvae were also rated as either effective or very effective by more than 80 percent of farmers, Arbuckle said.

“The single most effective thing farmers can do to manage corn rootworm is to rotate away from corn. Planting soybeans, alfalfa or any other crop will starve corn rootworm larvae,” entomologist Erin Hodgson said. “We strongly encourage farmers to assess root injury in every cornfield, every year. Looking for rootworm feeding is an important step in evaluating Bt efficacy.”

About the Iowa Farm and Rural Life Poll

Arbuckle said 1,209 farmers participated in the 2013 Farm Poll and on average they were 65 years old. Because the Farm Poll is a panel survey, in which the same farmers participate in multiple years, participants are somewhat older on average than the general farmer population. Fifty-two percent earned more than half of their income from farming, while an additional 17 percent earned between 26 and 50 percent of their household income from the farm operation.

In addition to Bt-resistant corn rootworm, the 2013 Iowa Farm and Rural Life Poll asked for farmers’ opinions on climate change, rented land, herbicide resistant weeds, and soil health and compaction.

The 2013 Iowa Farm and Rural Life Poll summary report (PM 3061) and previous Iowa Farm and Rural Life Poll summary and topical reports are available to download from the ISU Extension and Outreach Online Store,, and Extension Sociology,  

Conducted every year since its establishment in 1982, the Iowa Farm and Rural Life Poll is the longest-running survey of its kind in the nation. ISU Extension and Outreach, the Iowa Agriculture and Home Economics Experiment Station, the Iowa Department of Agriculture and Land Stewardship, and the Iowa Agricultural Statistics Service are all partners in the Farm Poll effort.

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