Roundup-resistant weeds are a rapidly emerging threat that puts U.S. agriculture in a terribly precarious position. The threat has evolved from farmers’ heavy use of the herbicide glyphosate, (aka Roundup, a Monsanto product) to control weeds, and farmers’ simultaneous reliance on crop varieties (also Monsanto products) that are genetically modified to resist Roundup. Despite a New York Times  article last year, this topic has received far less attention than it deserves, as the potential for Roundup-resistant weeds to raise food prices and threaten U.S. food security is severe.

The latest issue of peer-reviewed Weed Science contains a number of articles on the rising threat of herbicide-resistant weeds, with 21 weeds now confirmed as resistant to Monsanto’s Roundup, as reported by Fast Company. An article by University of Georgia scientists reported that Palmer Amaranth, a problematic weed found in cotton, corn, and soybean crops, which can impede harvesting, is now resistant to Roundup as well as another herbicide.  

Ideally, “Roundup Ready” crops work by allowing Roundup applications to kill competing weeds, leaving the Roundup-tolerant crops unaffected. This form of chemical weed suppression has long been touted as an important way to reduce soil erosion, as plowing is generally unnecessary using this method of chemical weed control. However, there have been unintended consequences of this system. Farmers have become entirely dependent on specific herbicide-tolerant varieties, especially Monsanto’s “Roundup Ready” corn, soybean, and, approved just earlier this year, alfalfa. As Figure 1 (below) shows, 90, 78, and 70 percent of the U.S. soybean, cotton and corn crops, respectively, are now planted with herbicide-tolerant varieties. This places American agriculture in a risky situation—as Roundup-resistance in weed species continues to spread, farmers have few resources in their arsenal to deal with problematic weeds, which could lead some farmers to revert to mechanical weed management (and consequent erosion problems) or over-application of herbicides in an effort to combat weeds (with negative consequences for the environment and human health).

What should be done? First, instead of continuing to rely on specific herbicide-tolerant crop varieties, we should be exploring diversified weed management systems that will remain effective in the long term. Second, the USDA should re-evaluate the approval and use of these crops before the scenario turns catastrophic in the coming years.