Corn-eating worm evolves to feed on GMO corn designed to kill it

A voracious crop-destroying pest has evolved to feed upon the very GMO product that was designed to eliminate it. Wired.com reported that the triumph over corn rootworms was one of biotech's great success stories, saving billions of dollars in crops each year.

So-called Bt corn -- named for the Bacillus thuringiensis gene, which killed rootworms, corn borers and other pests -- currently makes up more than three quarters of the total corn grown in the U.S., a lack of crop diversity that could spell disaster if the resistant cornworms spread.

The crop itself is not to blame, say scientists, but rather mismanagement by farmers, corporations and lawmakers that has led to the squandering of whatever benefits had been gained by the use of the genetically modified crop.

Aaron Gassman, Iowa State University scientists and lead author of the study "Field-evolved resistance by western corn rootworm to multiple Bacillus thuringiensis toxins in transgenic maize," which was published in the March 17 PNAS journal, told Wired, "Unless management practices change, it’s only going to get worse. There needs to be a fundamental change in how the technology is used.”

Bt corn was first introduced to the market in 1996. Since then it has proven to be enormously popular and populations of corn rootworms and borers have plummeted in the Midwest where the Bt corn is grown. However, scientists were warning more than a decade ago that problems were looming.

In order to keep the rootworms from developing a resistance to the Bt corn toxin, farmers were told to keep "refuges" of non-Bt corn so that rootworms could grow there unaffected. Those worms were meant to be mated with worms in Bt fields in order to keep the worms from developing an immunity to the GMO corn.

Scientists proposed to the EPA that farms should consist of at least half non-Bt corn, but these regulations were opposed by the seed companies peddling the GMO corn. Eventually, the EPA set voluntary guidelines of 5 to 10 percent of land left for non-Bt corn.

Many farmers didn't even follow that recommendation.

Now, rootworms are back, returning in 2009 to cornfields in northeastern Iowa. Those worms had become resistant to one species of the three available Bt corn types. More reports followed from Illinois, Minnesota, Nebraska and South Dakota.

Farmers are going to have to return to the pesticides they abandoned in order to fight the rootworms. They will most likely to continue to use the Bt corn because it repels other pests, but the reintroduction of pesticides promises to undo the environmental benefits that GMO crops were supposed to produce.

Scientists wrote to the EPA in 2012 about this problem, saying, "When insecticides overlay transgenic technology, the economic and environmental advantages of rootworm-­protected corn quickly disappear.”

[Image: "Girl Eating Corn" via Shutterstock]