Meet the Mutant Worm That's Stronger Than Pesticides

Fields of genetically modified corn are being destroyed by insects that have evolved to resist the toxins contained in the plants.

Western corn rootworm. (Photo: Ellmist/Wikimedia Creative Commons)

Mar 31, 2014· 3 MIN READ
Steve Holt is a regular contributor to TakePart. He writes about food for Edible Boston, Boston Magazine, The Boston Globe, and other publications.

This is a story about bugs and food, but even deeper than that, it’s a cautionary tale about a food system owned by big agribusiness companies and how they have steamrolled regulators to increase the borders of their empires.

Like other genetically engineered seeds before it, the Bacillus thuringiensis, or Bt, corn seed was touted by the biotech companies that created it as an antidote to the corn rootworm, which has the potential to devastate a maize field. The idea was that farmers wouldn’t need to spray herbicides and pesticides on the cornstalks because the toxin Bt was built right into the genetic makeup of the seed.

In a recent study published by Proceedings in the National Academy of Sciences, entomologists reported that rootworms are becoming resistant to a second class of Bt corn, something first observed in 2009. Corn growers have known this for years, though, and many are resorting to spraying their Bt corn fields with chemicals to double down on the invasive pest. Prior to the 2013 planting season, University of Illinois entomologist Michael Gray surveyed Illinois corn and soybean growers, nearly half of whom said they planned to plant Bt corn seeds and apply insecticide to their crops. Prior to the availability of Bt corn, only about 20 percent of corn fields were sprayed for corn rootworm, says Bill Freese, Washington, D.C.–based policy analyst with the Center for Food Safety.

That’s right: The introduction of a seed that was supposed to eliminate the need for insecticides may be increasing their use. And as corn growers double up on their pest protection and insecticide sales continue to rise, you’ll never guess who’s laughing all the way to the bank. OK, maybe you will: Monsanto.

Since Monsanto started selling it in 2003, Bt corn has been fairly effective at staving off the rootworm—whose nickname is the “billion-dollar pest” because of the harm it inflicts on North American corn crops—and as a result become enormously popular among farmers. Bt corn is not, however, without its critics, who say that the strain is associated with elevated risk for allergies and other conditions and should be labeled. Still, today, three-quarters of the 97 million acres of corn planted in the United States is injected with the Bt toxin, according to the United States Department of Agriculture Economic Research Service. By 2009, scientists had observed that the pest had “gotten smart,” evolving to resist the toxin in Bt corn—in just six years.

This all could have been prevented, Freese says, if the Environmental Protection Agency—which approves and regulates genetically modified seeds—had listened back then to its scientists calling for a requirement that farmers plant half their fields with conventional, or non-Bt, corn as “refuges.” Pests from the conventional cornfield would mate with those from the Bt cornfield, diluting out the resistance genes in the corn rootworms. The idea had worked with corn engineered to repel the European corn borer: Farmers planted a minimum of 20 percent of their fields with conventional corn as a refuge.

But in the lead-up to the 2003 EPA approval of Monsanto’s rootworm-fighting Bt corn, scientists warned that because the pest feeds on the roots of corn, the rootworm is capable of even more damage than the European corn borer—and requires a larger refuge requirement of 50 percent. Not wanting to relinquish up to 30 percent of fields not planted with its G.E. corn, Monsanto lobbied the EPA hard to cap the refuge at 20 percent, which it did.

“From the very start, the EPA was not doing its job,” Freese says. “It let Monsanto influence it, and that’s one of the main reasons we have resistance today.”

In 2012, after discovering resistance in rootworms for the first time in 2009, the two leading entomologists on the subject of Bt corn—Bruce Tabashnik and Fred Gould—again called on the EPA to raise refuge to 50 percent. In addition to increasing refuge percentage, Gould and Tabashnik recommended a return to a concept known as integrated pest management, which fights off critters using a multifaceted approach not wholly reliant on Bt seeds.

“Key IPM recommendations for corn rootworms include crop rotation, rotation of Bt corn hybrids producing different toxins…and judicious use of insecticides,” the authors wrote in the paper, which was published in the Journal of Economic Entomology.

However, the EPA has shown no desire to do what it should to protect corn from rootworms, and Freese says things will get worse before they get better. Farmers in 11 states are now complaining that Bt corn is not controlling corn rootworm, and Freese predicts “resistance is going to skyrocket very quickly.”

Absent the federal government, the biotech companies, which Freese says are tasked with testing fields for signs of resistance to corn rootworm, have little incentive to take the steps to curb or stop the pest. Not wanting to diminish the acreage that is planted with their own Bt corn, he says, companies will likely never get behind a plan that raises the refuge percentage. Maybe this is the price we pay for the rapid industrialization of a now largely corporate-controlled agriculture system, he says.

“We took a real wrong turn when we allowed our seed supply to fall into the hands of the pesticide companies,” he says. “Monsanto, Dupont, Syngenta, Dow—they pretty much call the shots now.”