A study published this week by Charles Benbrook of Washington State University finds that the use of herbicides in the production of three genetically modified herbicide-tolerant crops (cotton, soybeans, and corn) has actually increased over the last sixteen years. Benbrook writes that there is a strong correlation between the emergence and spread of glyphosate-resistant weeds and the upward trajectory in herbicide use.
We are particularly keen to hear your comments on these findings. How well do you think the study was designed? How do these findings compare to other studies in other regions of the world?
Abstract:
Genetically engineered, herbicide-resistant and insect-resistant crops have been remarkable commercial successes in the United States. Few independent studies have calculated their impacts on pesticide use per hectare or overall pesticide use, or taken into account the impact of rapidly spreading glyphosate-resistant weeds. A model was developed to quantify by crop and year the impacts of six major transgenic pest-management traits on pesticide use in the U.S. over the 16-year period, 1996–2011: herbicide-resistant corn, soybeans, and cotton; Bacillus thuringiensis (Bt) corn targeting the European corn borer; Bt corn for corn rootworms; and Bt cotton for Lepidopteron insects.
Results:
Herbicide-resistant crop technology has led to a 239 million kilograms (527 million pounds) increase in herbicide use in the United States between 1996 and 2011, while Bt crops have reduced insecticide applications by 56 million kilograms (123 million pounds). Overall, pesticide use increased by an estimated 183 million kilograms (404 million pounds), or about 7%.
Conclusions:
Regulators in the U.S. have thus far done little to prevent the emergence and spread of resistant weeds, while several resistance-management interventions have been imposed as part of the approval of Bt crops. In addressing weed resistance, the hands-off regulatory posture in the U.S. reflects, in part, the basic authorities granted to the EPA and USDA in federal law. Both agencies regard weed resistance as an efficacy-economics challenge that can best be addressed by the private sector consistent with market forces. The need for novel policy interventions will grow in step with the emergence and spread of resistance weeds and evidence of adverse economic, environmental, and public health consequences triggered by markedly increasing reliance on older, higher-risk herbicides.
The citation from the study is as follows:
Benbrook, C. (2012) 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
The full study can be found here.
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