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Assessment & Impacts » Ecological

Title: Herbicide-tolerant GE Crops Create Resistant Weed Problems in the US
Publication date: July 15, 2013
Posting date: July 15, 2013


Dear friends and colleagues

Re: Herbicide-tolerant GE Crops Create Resistant Weed Problems in the US

The US is the biggest global adopter of genetically engineered (GE) crops, of which the bulk comprises Monsanto’s Roundup Ready (RR) varieties that are tolerant to glyphosate. A recent study on herbicide-tolerant GE crops in the US examined US Department of Agriculture (USDA) and US Environmental Protection Agency (EPA) data, and has revealed that herbicide use has increased substantially since the latter half of the 90s. Alongside this, RR crops have given rise to a serious negative externality called ‘superweeds’ which are resistant to glyphosate and which cost farmers as much as USD12-50 per acre to get rid of.

Although initially dropping from 1998-2001, herbicide use in the US subsequently increased by 81.2 million pounds (26%) from 2001-2010 as farmers applied more herbicides to overcome glyphosate-resistant weeds. The total volume of glyphosate applied to GE corn, cotton and soy increased ten-fold from 15 million pounds in 1996 to 159 million pounds in 2012.

Glyphosate-resistant superweeds are appearing in more states across the country covering as much as 61.2 million acres. As of 2012, gyphosate-resistant waterhemp, Palmer amaranth and horseweed were found in 8, 12 and 21 states, up from 5, 8 and 12 states, respectively, 4-8 years earlier. In addition, the International Survey of Herbicide Resistant Weeds found three times as many multiple herbicide-resistant weed infestations in 2011 compared to a decade earlier.  

The emergence of the resistant weeds has paved the way for the introduction of 2,4-D tolerant corn and dicamba-tolerant soybean. The application of these two herbicides is expected to increase dramatically in coming years. 2,4-D is a known endocrine disruptor and dicamba is a carcinogenic herbicide.

The study makes several recommendations, which include proper health evaluations of GE crops, better data collection, and the adoption of non-chemical best management practices to prevent weed resistance and control weeds on a long-term basis.

The full study by Food & Water Watch can be downloaded from:‎. The Executive Summary is reproduced below.

With best wishes,

Third World Network

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Executive Summary

Genetically engineered (GE) crops were first approved in the United States in the 1990s, and since then the United States has been the biggest global adopter of this technology. GE crops were supposed to improve yields, lower costs for farmers and reduce agriculture’s environmental impact. Yet nearly 20 years after their introduction, genetically engineered crops have not provided the benefits promised by the companies that patented them. Food & Water Watch examined U.S. Department of Agriculture (USDA) and U.S. Environmental Protection Agency (EPA) data to document the increased use of herbicides that has accompanied the adoption of herbicide-tolerant GE crops. Our analysis looks at the rapid proliferation of GE crops and affiliated pesticides in the United States and points out the interdependent relationship between these two industries that also fuels the crisis of weed resistance. Food & Water Watch evaluated data from the International Survey of Herbicide Resistant Weeds that reveal burgeoning herbicide-resistant weeds caused by the over-reliance on glyphosate for broad control of weeds. These data make it clear that the problem of herbicide-resistant weeds will not be solved with the intensified use of older, more toxic herbicides like 2,4-D and dicamba.

Some of Food & Water Watch’s findings include:

• 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.

• 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.

• Total 2,4-D use declined after glyphosate was widely adopted, but its use has increased since glyphosate-resistant crops became widespread, growing 90 percent between 2000 and 2012. 2,4-D application on corn could easily increase by nearly three-fifths within two years of 2,4-D-tolerant corn’s introduction. And if just a million dicamba-tolerant soybean acres are planted, it would increase dicamba use 17 times.

• Reports of weeds developing glyphosate resistance are popping up in more and more states. In 2008, glyphosate-resistant waterhemp was reported in five states, but by 2012 it was reported in 12 states. Glyphosate-resistant Palmer amaranth was reported in eight states in 2008 but 17 by 2012. Resistant horseweed spread from 12 states in 2004 to 21 in 2012.

• The International Survey of Herbicide Resistant Weeds found only about one weed infestation per year that was resistant to multiple herbicides between 1997 and 2001, but a decade after GE crops were introduced (2007 to 2011), there were three times as many multiple herbicide-resistant weed infestations.

• Herbicide-resistant weeds’ costs to farmers can range from $12 to $50 an acre, or as much as $12,000 for an average-sized corn or soybean farm or $28,000 for an average cotton farm.

More biotech industry-led solutions will only perpetuate agriculture’s reliance on chemicals as the end-all-be-all solution to weed and insect management. But this approach drives the rise of superweeds, poses risks to human health and threatens critical habitat for wildlife in the process.

Food & Water Watch recommends that:

• The USDA, EPA and Food and Drug Administration (FDA) must work together to thoroughly evaluate the potentially harmful effects of GE crops and linked chemicals before commercialization, to ensure the safety of humans and the environment.

• The USDA should support and encourage cultivation best management practices to prevent weed resistance in the first place.

• The USDA should educate and encourage farmers to adopt non-chemical strategies for long-term weed control. The USDA must dedicate research dollars to developing alternatives for sustainable management of herbicide-resistant weeds.

• The U.S. government must improve the collection and distribution of weed resistance and agricultural pesticide application data.

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