Last month, listeners to this program heard about a weed-killer called RoundUp that is sprayed on genetically modified corn and soybean crops across the U.S.
Over the last 15 years, scientists say, this herbicide has contributed to a 90 percent decline in the monarch butterfly population by poisoning the milkweed plants that are the only food for monarch caterpillars.
After that radio program aired, the U.S. Environmental Protection Agency on October 15 approved a new herbicide to replace Roundup in farm fields. The new chemical, Enlist Duo, is an even more powerful weed-killer, because it combines RoundUp’s main ingredient-- glyphosate --with a second herbicide, called 2, 4 D.
The herbicide 2,4 D is an older weed killer, invented in the 1940’s and used as an ingredient the herbicide Agent Orange during the Vietnam War (although it was not the primary chemical blamed for illnesses in American soldiers.) 2,4 D mimics plant growth hormone, making stems grow so abnormally fast they curl over and die.
Modern corn and soybeans are not harmed by 2, 4 D or glyphosate – because 2,4 D was designed to attack other plants, and corn and soybeans have been genetically engineered to tolerate glyphosate. It is the wildflowers, weeds and milkweed around farm fields that die – and with them, monarch butterflies.
Now, why would farmers – just a decade or so after adopting a new herbicide, RoundUp – have to switch to a new and more deadly double-whammy of weed killers?
“What happens is that you kill 99.9 percent of all those weeds, but .1 percent are not killed, and so they are going to survive and produce weeds that are resistant to the herbicide," said Lincoln Brower, a Professor of Biology at Sweet Briar College in Virginia.
Brower said several weeds, including giant ragweed and hairy feabane, quickly evolved resistance to Roundup and became hardy superweeds. (Sadly for the monarchs, milkweed did not._
“And that’s happening in this whole industry across the world -- spraying like crazy with herbicide A, developing resistance in the weeds, and the weeds taking over again," Brower said. "So it’s a race between technology and the evolution of the plants to develop resistance. And basically, it’s a never-ending race.”
In response to EPA’s approval of the new herbicide, the Natural Resources Defense Council (NRDC) sued the federal agency in an attempt to block the new herbicide mixture.
Kristen Pullen, staff scientist at the NRDC, said that while 2,4 D has been legal for decades, use of the herbicide could multiply six fold or more if it is sprayed on corn and soybeans as part of the Enlist Duo.
"The potential health impacts of 2,4 D mostly have been studied in farm workers," Pullen said. " And some of the health impact that we’ve seen in these populations are increased birth defects, decreased fertility, as well as an increase in hypothyroidism, and so we know that the thyroid is really potentially being impacted by the use of 2,4 D.”
Abnormalities in the thyroid gland, she explained, can damage the developing brains of infants.
Both the manufacturer of the chemical, Dow AgroSciences, and EPA say the new herbicide mixture is safe.
In an emailed statement, Dow Agro Science spokeswoman Kenda Resler Friend wrote: "The Enlist Weed Control System was developed to address farmers’ needs as they struggle to control weeds that impact the food supply, while respecting the well being of both people and the environment."
EPA issued a statement that reads in part: "For the pesticide licensing decision regarding the pesticide, Enlist Duo, EPA had robust science -- a large body of scientific information to support a decision. The decision protects everyone, including agricultural workers. ...Data does not support a cause and effect connection between exposure to 2,4-D and these diseases."
Dr. Lynn Goldman, an expert on pesticides and Dean of George Washington University's School of Public Health, said the jury is still out on the question of whether 2,4 D poses a risk to human health. But she said it is clear that the herbicide's partner in the new mix – glyphosate -- damages the ecosystem by killing native plant and insect species.
“In general, I think we are headed in the wrong direction, with this continuing to escalate the war on weeds in a way that is putting more and more weed killer, more herbicides, into the environment," Dr. Goldman said.
The monarch butterfly and wildflowers are the most recent victims of this ramped-up chemical warfare on America’s farms.
People can voice their protests against this war by writing to EPA, and by buying organic produce.
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To send a comment to EPA, visit: http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2014-0195-2418
Photo: David R. Alamy / Frazier