University study reveals pest now resistant to genetically modified corn

Rootworms have become resistant to a common strain of genetically engineered corn, according to a University study.

Genetically modified corn that produce a toxin called Bacillus thuringiensis, or Bt, was designed to damage pests’ intestines if they ingested the corn.

University entomology professor Mike Gray’s research confirmed a previous Iowa State University study indicating that rootworms, which are considered corn’s worst pest, have become resistant to a breed of Monsanto-produced genetically engineered corn.

Gray’s research involved analyzing adult rootworms from Illinois in Iowa State University labs and comparing the results to the previous study.

“It’s an unfortunate consequence of the overuse of good technology,” Gray said.

Gray related the overuse of the corn strain Cry3Bb1 to the overuse of antibiotics in medical practices. When an antibiotic is used too often, the infection will develop a resistance to it. Now, with the results of his research study back from the Iowa State University lab, the genetically engineered corn has proved to be analogous to the overuse of antibiotics.

According to the USDA’s study on the adoption of genetically engineered crops in the United States, 88 percent of farmers in Illinois use genetically engineered corn; of the 88 percent, 50 percent use Cry3Bb1.

Gray said farmers should talk to their seed salesmen to see what they recommend to control the rootworm resistance. However, he said that because the rootworm problem began after farmers started growing corn or year after year in the same field, they could try alternating between planting corn and soybeans each year to deter pests.

“Rather than rely on the same protein hybrid and same cropping pattern, mix it up in order to prevent resistance,” Gray said.

Monsanto issued a statement in response to Gray’s research. According to the release, Monsanto had no data supporting Gray’s findings, but they did have new techniques “to better assist farmers who reported unexpected damage to us in 2011.”

Jorge Fernandez-Cornejo, USDA agricultural economist in the Resource and Rural Economics Division, offered a different solution for farmers who would like to continue using genetically modified corn.

“You need to separate part of the land without Bt corn, and there will be less resistance because of the refuge,” he said. “It’s what a lot of experts are suggesting.”

Gray said there will be new technologies invented to control the problem. In the meantime he said, “I hope farmers are listening and taking advice from other entomologists in the state.”

_The reporter can be reached at

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