Genetically engineered (GM) crop technologies are triggering a rise of “superweeds” and hard-to-kill insects that are forcing farmers to use larger amounts of hazardous pesticides, according to a new study reported on by Carey Gillam of Reuters.The study, titled “Impacts of genetically engineered crops on pesticide use in the U.S. – the first sixteen years,” found that pesticide use has increased by 404 million pounds from the time GM crops were introduced in 1996 through 2011.
In 1996 Monsanto introduced herbicide-tolerant or “Roundup Ready” soybeans and then rolled out GM corn, cotton and other crops. Roundup Ready and other herbicide-tolerant crops now account for about 95 per cent of soybean and cotton acres as well as over 85 per cent of corn.
The crops immediately became popular with farmers who found that they could easily kill weed populations without damaging their crops. But over time more than two dozen weed species have become resistant to glyphosate, Roundup’s chief ingredient, causing farmers to increase amounts of glyphosate and other weed-killing chemicals to combat the “superweeds.”
The paper’s author, Washington State University research professor Charles Benbrook, found that the amount of herbicides required to deal with superweeds near GM crops has grown from 1.5 million pounds in 1999 to about 90 million pounds in 2011.
“Resistant weeds have become a major problem for many farmers reliant on [genetically-engineered] crops, and are now driving up the volume of herbicide needed each year by about 25 per cent,” Benbrook said in a press release.
Benbrook’s analysis, published in the peer-reviewed journal Environmental Sciences Europe, is thought to be the first published estimate of the impacts of genetically engineered, herbicide-resistant crops on pesticide use.
Its conclusion is that the findings undermine oft-repeated claims that today’s genetically-engineered crops reduce pesticide use.
Monsanto spokesman Thomas Helscher told Reuters that the company is “looking at this. Our experts haven’t been able to access the supporting data as yet.”
Science writer Carl Zimmer tweeted that the study requires scrutiny, citing an article on BIOfortified that said Benbrook failed to “distinguish between different pesticides” and failed to “consider non-biotech traits that could increase pesticide use.”
Benbrook also found that “Bt” corn and cotton—crops engineered to be toxic to certain insects—has led to a recent rise of insects resistant to the crop toxin so even though insecticide dropped 28 per cent from 1996 to 2011, it is now on the rise.
“Things are getting worse, fast,” said Benbrook told Reuters. “In order to deal with rapidly spreading resistant weeds, farmers are being forced to expand use of older, higher-risk herbicides. To stop corn and cotton insects from developing resistance to Bt, farmers planting Bt crops are being asked to spray the insecticides that Bt corn and cotton were designed to displace.”
This study doesn’t touch on the toxicity of pesticides, only that pesticide use has gone up. The toxicity question was recently explored in a widely-debated study of rats.
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