A report has found that farmers are using more herbicides on genetically engineered soybeans, corn, and cotton because of resistant weeds.
A report released by the Organic Center found that the amount of herbicides used on genetically engineered crops has increased in the past 10 years, not decreased as might be expected. Since many genetically engineered crops were modified so that farmers could spray Roundup, or Glyphosate, to kill the weeds in their fields but not the crops themselves, the expectation was that less herbicide would be required. But the new report found that this is not what happened.
The authors of the report, entitled “Impacts of Genetically Engineered Crops on Pesticide Use,” used US Department of Agriculture data to look at America’s three largest genetically engineered crops – soybeans, corn, and cotton. They found that the amount of herbicides used on them has increased from 1996 to 2008 by approximately 7 or 8 percent, with a particularly sharp increase from 2005 on.
In particular, the amount of Roundup that is used on genetically engineered crops has multiplied several times during the time period, says the report’s main author, Charles Benbrook, who's the chief scientist at the Organic Center.
“This big increase in herbicide is driven largely by the emergence of Roundup-resistant weeds,” Dr. Benbrook says. But “industry is still saying to the public that genetic engineering [has] reduced herbicide use.”
Benbrook found that Roundup-resistant weeds have become a particularly big problem in soybeans. Roundup originally killed all weeds, leaving only soybeans in the fields, but after a few years, farmers had to use more Roundup as well as the older, more toxic chemicals to kill the weeds, according to the authors of the report.
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