In 2004, farmers in Georgia discovered a weed that was resistant to glyphosate, the active ingredient in Monsanto’s Round Up herbicide. The weed, palmer amaranth, quickly became the “poster child for the potentially devastating impacts of herbicide-resistant weeds,” writes Andrew Kniss, Associate Professor of weed biology and ecology at the University of Wyoming. National news outlets immediately coined the term “superweed,” and some said it threatened the sustainability of cotton production in the southeastern US.
However, Kniss writes, according to the US Department of Agriculture’s National Agriculture Statistics Service, the average cotton yields since 1938 have increased by an average of 7.9 lbs/acre/year. Since 2004, when ‘superweeds’ were discovered, national cotton yields have actually been higher than the long-term trend. The same trend was found in Georgia, Arkansas and North Carolina, where palmer amaranth has been said to be devastating farmers’ fields.
Farmers have had to use additional weed-control methods, such as tillage, cover crops and other herbicides to fight the ‘superweeds,’ Kniss writes, which may contribute to their reduced net economic gains. But “it is important to note that these herbicide-resistant weeds have not had the devastating effects on crop yields…that is often implied by the sensational coverage of this topic.”
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