St. Louis, Missouri, USA
June 16, 2011
Resistant horseweed flourishes after herbicide application. Courtesy of Luke Samuel, Phillips Co, via Monsanto collaborator
As everyone knows, the pharmaceutical industry is struggling to deal with bacteria that have become resistant to common antibiotics. Less well known is the similar struggle in agribusiness to deal with weeds that have become resistant to a herbicide that is widely used in farming practice.
The herbicide, first introduced in 1974, is glyphosate, the active ingredient in Monsanto’s Roundup products and also in herbicides produced by other manufacturers. The first case of glyphosate resistance was documented in 1997, and today more than 20 weed species globally are reported to be resistant. (For more on the history of the herbicide read "The Back Story" here.)
Recently a team of scientists from Washington University in St. Louis and Monsanto, the St. Louis-based company that makes Roundup herbicides, were able to follow molecules of glyphosate as they entered a resistant variant of horseweed to discover exactly how the plant disarms the herbicide. Their work was published in Pest Management Science last year.
In a second paper published in April 2011, also in Pest Management Science, they describe herbicide application conditions that can be used to overcome the resistance mechanism they had discovered.
This is not the end of the story, the scientists say, because some weed species are resistant to the herbicide in ways different from horseweed. Still the scientists are glad to have won this round even if they know the contest will be prolonged.
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