Genetically engineered crops increased pesticide use

Herbicide resistant genes driving greater use

Dr. Charles Benbrook of Washington State University.

Dr. Charles Benbrook of Washington State University.

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A study conducted by Dr. Charles Benbrook of Washington State University concluded that pesticide use has increased by approximately 7 percent over the past 15 years. Using data from the US Department of Agriculture’s National Agricultural Statistical Service (NASS) on pesticide use on corn, cotton and soybeans planted in the US from 1996 to 2011, Benbrook’s study, published in the open access peer-reviewed scientific journal Environmental Sciences Europe, showed that planting of herbicide tolerant crops increased herbicide use.  The herbicide showing the greatest increase is glyphosate, marketed under the trade name Roundup.  Approximately 95 percent of soybean and cotton acres, and over 85 percent of corn planted in the US are genetically modified herbicide resistant varieties.

One of the drivers of the increase in herbicide use is the selection of glyphosate-resistant weeds, which require greater volume and more toxic herbicides to kill.

"Resistant weeds have become a major problem for many farmers reliant on GE crops, and are now driving up the volume of herbicide needed each year by about 25 percent," Benbrook said.

The annual increase in the herbicides required to deal with tougher-to-control weeds on cropland planted to GE cultivars has grown from 1.5 million pounds in 1999 to about 90 million pounds in 2011.

Herbicide-tolerant crops were effective shortly after introduction and adoption, Benbrook’s analysis shows, but over-reliance on glyphosate appear to have selected for weed communities more difficult to manage with herbicides and farmers have increased glyphosate and other herbicide application rates, spray more often, and add new herbicides that work through an alternate mode of action into their spray programs to kill glyphosate resistant weeds.

While the planting of crops that express toxins produced by the microorganism Bacillus thuringiensis reduced pesticide use, the Bt itself is a pesticide and planting the crop has led to the selection of Bt resistant insects tobacco budworm, European corn borer and Western corn rootworm. Continuation of the trend of selection of Bt resistant insects is likely to diminish the pesticide reductions achieved by Bt crops.

More information

Citation

Benbrook, Charles M.: Impacts of genetically engineered crops on pesticide use in the U.S. - the first sixteen years. Environmental Sciences Europe 2012, 24:24 doi:10.1186/2190-4715-24-24. Published: 28 September 2012. Available at http://www.enveurope.com/content/24/1/24/abstract

Correspondence

Charles M Benbrook cbenbrook(at)wsu.edu

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