When crops were first introduced that had been engineered to withstand the herbicide glyphosate — better known by the trade name Roundup — the agricultural industry said it would confer a terrific environmental advantage. Glyphosate is a relatively benign herbicide, after all, and the industry claimed it would be able to use less of it to get rid of weeds, without harming the corn or soy.
At first, farmers did spray less glyphosate. But resistant versions of the weeds soon cropped up. That meant heavier, repeated spraying, which in turn meant more resistant weeds.
No problem, agribusiness said. We'll just make new crops genetically engineered to resist other herbicides.
But that's not a solution. Just as the nation must stop overusing antibiotics if it hopes to slow the emergence of resistant infections, it must do the same with herbicides and genetically modified crops. The way to deal with so-called superweeds isn't by escalating the arms race against them.
A new generation of herbicide-resistant crops is wending its way through the federal approval process. A division of Dow Chemical recently won the approval of the U.S. Department of Agriculture for corn and soy that have been bioengineered to withstand spraying with both glyphosate and 2,4-D, a more toxic weed-killer that some critics say is dangerous to the environment and to people. Why both? About 18 weeds have developed resistance to 2,4-D over the more than 50 years it has been in use. So the idea is to use both herbicides, with each one eradicating the weeds that the other one can't.
But first, the Environmental Protection Agency would have to approve the special blending of the two herbicides developed by Dow. Called Enlist Duo, the mix has been formulated not to drift over large areas as 2,4-D commonly does. It would thus reduce the risk of killing crops miles away. According to USDA estimates, the introduction of the new crops would mean the spraying of five to 13 times as much 2,4-D by the year 2020.
Meanwhile, Monsanto, the developer of Roundup Ready corn, is developing its own new generation of herbicide-resistant crops able to withstand a third weed killer.
The USDA considers only whether the genetically engineered seeds represent a hazard to other crops; the EPA is responsible for overseeing the safety of herbicides used in agriculture. No agency looks at the bigger policy question of whether the nation is embarking on a potentially dangerous path toward creating ever-more-resistant weeds and spraying them and crops with larger and larger doses of stronger herbicides. That question should be answered before the country escalates the war out in the fields.
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