Are genetically engineered crops really the main culprit?
Today genetically engineered, glyphosate-resistant crops are often singled out as a major contributor in the evolution of herbicide-resistant weeds. But a new data analysis featured in the journal Weed Science shows it may be time to revisit that common assumption.
When you look at area sprayed, the evolution of new glyphosate-resistant weed species is relatively low compared to other herbicides. In addition, the overall rate of newly confirmed herbicide-resistant weed species in the U.S. has actually slowed over the past two decades.
At the crop level, the data shows farmers adopting genetically engineered corn continued to use a diverse group of herbicides – making it unlikely that glyphosate increased selection pressure for herbicide-resistant weeds. Farmers adopting genetically engineered cotton and soybean crops took the opposite approach and relied almost solely on glyphosate. But the herbicides they displaced were more likely than glyphosate to select for herbicide-resistant weeds.
What does all this mean for growers? While herbicide diversity is important, it clearly won’t be enough to mitigate the problem of herbicide-resistant weeds. It’s time to take a broader view of weed management that includes robotics and other new nonchemical technologies, as well as long-proven practices like tillage and crop rotation.
To find out more, read the article “Genetically Engineered Herbicide-Resistant Crops and Herbicide-Resistant Weed Evolution in the United States” in Weed Science Vol. 66, Issue 2.
*Images show herbicide use and diversity of herbicide sites of action in major row crops in the United States. Image by Andrew Kniss.