New government data show that farmers’ violation of rules governing the planting of genetically engineered (GE) pest-resistant corn is more widespread than previously thought. According to the nonprofit Center for Science in the Public Interest (CSPI), overplanting of Bt corn threatens the long-term effectiveness of the crop by increasing the likelihood that insects would gradually become resistant to the natural insecticide that Bt corn contains.

At issue is whether farmers are planting required amounts of non-genetically engineered corn alongside plantings of GE corn. Those "refuges" are planted so that any insects that do develop resistance to Bt corn are likely to mate with those insects that haven’t--resulting in offspring that will continue to be susceptible. And while a recent CSPI report showed that farmers in three Corn Belt states weren’t planting sufficient refuges, the new data from the U.S. Department of Agriculture (USDA) show that fully 20 percent of farms in ten major agricultural states are not complying with the requirement.

"It is distressing to see that a relatively easy requirement is being ignored by so many farmers," said CSPI biotechnology project director Gregory Jaffe. "Clearly farmers, the seed industry, and the government are not doing an adequate job of safeguarding the environmental benefits of agricultural biotechnology."

4.2 million acres of Bt corn were planted without the required refuges of 20 percent non-Bt corn, according to the latest data. Previous government data only indicated the number of noncompliant farms, not the overall acreage. 80 percent of the noncompliant acres were planted by large farms.

"When huge corn farms don’t plant enough of a refuge, it becomes more likely that insects will breed resistance to Bt corn," Jaffe said.

Bt corn is engineered with a gene from a bacterium, Bacillus thuringiensis, which produces a toxin that kills European Corn Borer pests. Because of its pesticidal properties, Bt corn is regulated by the Environmental Protection Agency, rather than the USDA or the Food and Drug Administration.