Bt corn, the most popular type of genetically modified maize, is designed to express one or more proteins poisonous to a variety of insect pests. It has been one of biggest success stories of bio-engineered crops, and accounts for roughly three-quarters of all corn grown in the U.S.
But new research offers evidence that one of those pests, rootworms, has quickly evolved to resist the Bt proteins and feast on swaths of the modified corn in a variety of Iowa fields.
"Unless management practices change, it’s only going to get worse," Aaron Gassmann, an Iowa State University entomologist who has studied the rootworm's resistance to Bt, told Wired. “There needs to be a fundamental change in how the technology is used.”
Gassmann and fellow entomologists at Iowa State recently published a paper on the rootworm's lightning-fast evolution in the latest edition of the journal of the National Academy of Sciences.
If the Bt resistant rootworms continue to reproduce and spread, the U.S.'s corn crop could be vulnerable to serious losses.
Rootworms and corn borers used to cause billions of dollars a year in damages to corn crops. But the wide adoption of Bt corn has helped diminish the populations of these pest insects, as well as minimized the necessity of large amounts of pesticides on corn crops.
But ever since Bt corn began being planted in 1996, scientists have warned that without careful management, pests could evolve a resistance and reproduce in even greater numbers -- free to roam the vast monoculture fields now void of the insects' predators.
Entomologists suggested that farmers plant non-engineered varieties of maize in fields adjacent to the Bt corn -- refuge fields. That way any insects that might develop a resistance would continue to mate with non-resistant pests, slowing down any possible evolution of a Bt-resistant worm.
Pest-experts also pointed out that crop rotations would help slow new pests. But most farms continue to grow corn in the same fields, year after year, making the evolution of Bt-resistant pests even more likely.
The Environmental Protection Agency, farmers, and the Bt seed industry mostly ignored these concerns and strategic suggestions. Now, farmers -- and grocery shoppers -- could pay the price.
Entomologist Elson Shields of Cornell University is one of many scientists who has been warning of dangers of insect resistance.
Even if rootworms make a comeback, farmers are likely keep using Bt corn, as it continues to resist a number of other pests. But they will be forced to use more pesticides, raising production costs and negating the environmental benefits of modified corn. At least until bio-engineers invent a new kind of corn.
But as Shields told Wired, the adoption of the next pest-resistant corn variety will likely follow the same path towards vulnerability, unless famers are made to use the agricultural technology more prudently. “[It] will fall under the same pressure,” she said, “and the insect will win. Always bet on the insect if there is not a smart deployment of the trait.”
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