Skip to: Content
Skip to: Site Navigation
Skip to: Search


More herbicide use reported on genetically modified crops

A report has found that farmers are using more herbicides on genetically engineered soybeans, corn, and cotton because of resistant weeds.

By Julie MasisContributor to the Christian Science Monitor / December 21, 2009

A farmer harvests genetically engineered corn at his farm in Dixon, Calif. Some farmers say they like GE corn because there are fewer weeds and the crops are protected from worms that eat the roots.

NEWSCOM

Enlarge

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.

Skip to next paragraph

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.

Troy Roush, a farmer in Indiana, says resistant weeds became such a big problem that this year he decided to switch back to conventional soybeans.

“The only advantage a genetically modified soybean has over the value of (conventional soy) is diminished,” Mr. Roush says. “We might as well not pay for the technology and use conventional seeds.”

His fields of genetically engineered soybean became infested with “mare’s tail”, a bushy weed that looks like the tail of a horse, and with genetically-engineered corn, he says. Because Roush rotates corn and soybeans on the same field, the Roundup-resistant corn actually became a weed when it went to seed the following year.

Because of these problems, Roush is now back at growing soybeans the old way and using a more toxic 2,4-D herbicide. He is saving money on seeds (genetically engineered seeds cost five times more than the seeds a farmer saves himself), and he can make more from selling his crop to customers in the European Union and Japan, who prefer non-genetically modified soy.

The authors of the report also found that the amount of insecticide used on genetically modified crops decreased during the same time period (although by a smaller amount). According to the report, herbicide use grew by 383 million pounds from 1996 to 2008, while insecticide use decreased by 64 million pounds due to the adoption of crops that are engineered to resist insects.

Permissions