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Agricultural Biotechnology and the Use of Herbicides in US Agriculture

December 1, 2013

An interesting response to an earlier post on the limited consumer benefits of agricultural biotechnology led me in search of data on the application of herbicides and pesticides to genetically engineered crops. What I found paints a pretty bleak picture. The technology was developed with an environmental benefit in mind—by developing crops that were resistant to the application of wide-spectrum herbicides like Round Up, the total amount of herbicides applied to any crop would be reduced. Similarly, the development of insect resistant varieties—like Bt cultivars—would reduce the need to apply various insecticides throughout the growing season, thereby reducing the total volume applied.

Early in their lifecycles, the genetically engineered varieties seemed to be living up to their promise. A study by Food and Water Watch, for example, finds that “Herbicide use on corn, soybeans and cotton did fall in the early years of GE crop adoption, dropping by 42 million pounds (15 percent) between 1998 and 2001. But as weeds developed resistance to glyphosate, farmers applied more herbicides, and total herbicide use increased by 81.2 million pounds (26 percent) between 2001 and 2010.”

They also noted that “The total volume of glyphosate applied to the three biggest GE crops — corn, cotton and soybeans — increased 10-fold from 15 million pounds in 1996 to 159 million pounds in 2012,” as reflected in the table below.

HerbicideVolumebyYear

The study by Food and Water Watch echoes an earlier study by study by Charles Benbrook of Washington State University which concluded that “[Herbicide tolerant (HT)] crops have increased herbicide use by 527 million pounds over the 16-year period (1996-2011). The incremental increase per year has grown steadily from 1.5 million pounds in 1999, to 18 million five years later in 2003, and 79 million pounds in 2009. In 2011, about 90 million more pounds of herbicides were applied than likely in the absence of HT, or about 24% of total herbicide use on the three crops in 2011.” He argues that the increased application of herbicides is connected to an expansion of herbicide tolerance among weeds, observing that “There are now two-dozen weeds resistant to glyphosate, the major herbicide used on HT crops, and many of these are spreading rapidly. Millions of acres are infested with more than one glyphosate-resistant weed. The presence of resistant weeds drives up herbicide use by 25% to 50%, and increases farmer-weed control costs by at least as much.”

The most widespread glyphosate-resistant weeds include waterhemp, palmer amaranth, and ragweed, and as the map by WeedSceience.com and cited in the Food and Water Watch study shows, they have spread as the use of glyphosate has increased.

The Expansion of Glyphosate Resistant Weeds in the United States

The Expansion of Glyphosate Resistant Weeds in the United States

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3 Comments
  1. Reblogged this on Science on the Land and commented:
    argylesock says… US agriculture has become dependent on genetically modified (GM, genetically engineered, GE) crops. Some of those crops have been engineered to resist the very popular weedkiller (herbicide) Roundup (glyphosate). But oops! Weeds evolve. Roundup Ready crops have paved the way for Roundup Ready weeds. Then farmers have to spray more herbicide. You can scroll down the article I reblog here to see maps of Roundup Ready weeds spreading across the US,

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