Jenny Mennenga farms corn and soybean with her husband between Le Roy and Farmer City in central Illinois. This past harvest brought Mennenga’s farm record corn production, though soybean yields were just “fairly average.”

The mediocre soybean yields, she said, were largely related to her farm’s ongoing struggle with “super weeds,” tough weeds that have grown resistant to the herbicides used to kill them.

“The biggest challenge that I’ve got on my farm is glyphosate-tolerant weeds,” Mennenga said. “The two biggest ones that I deal with yearly are waterhemp and marestail.”

Farmers everywhere are fighting a similar battle.

An international survey funded by government, academic and industry groups identified more than 400 different herbicide-resistant weeds globally. In addition to water hemp and marestail, Palmer Amaranth, nightshade, prickly lettuce and clover are all prominent weeds that have gained resistance to herbicides.

And controlling those weeds can be costly.

Mennenga said she spent $40 an acre last year on control efforts for the weed waterhemp alone.

“Controlling weeds in a soybean crop or in even a corn crop is not much different than controlling weeds in a lawn,” Mennenga said. “You let one dandelion go in your lawn, and it’s going to populate the rest of your lawn.”

Similar to the weeds on Mennenga’s farm, most super weeds are resistant to glyphosate, the herbicide used with Monsanto’s genetically engineered Roundup Ready crops from the 1990s. To kill the weeds that have grown immune to glyphosate, Monsanto is working on a next generation of genetically engineered seeds designed to also be used with a different, older herbicide formulated from dicamba.

Farmer Jenny Mennenga holds soybean seeds at her family farm in central Illinois on Jan. 26, 2015.
Farmer Jenny Mennenga holds soybean seeds at her family farm in central Illinois on Jan. 26, 2015.

The U.S. Department of Agriculture deregulated two of those next generation varieties – soybean and cotton – in January.

“As a farmer, I am very supportive of the dicamba soybeans,” Mennenga said.

The soybean and cotton will be part of Monsanto’s Roundup Ready Xtend brand projected to go to market in 2016. Before the soybean and cotton can be commercialized, the Environmental Protection Agency must sign off on their related herbicide use.

“For some time now, we have been hearing from farmers across the country that they need new tools to control tough-to-manage and glyphosate-resistant weeds,” said Miriam Paris, Xtend system launch manager for Monsanto. “These weeds can rob farmers’ crops of nutrients, water and sunlight.”

Brian Diers is a professor in the crop sciences department at the University of Illinois. In the future, he said, it is likely companies will continue pumping out genetically engineered crops designed to withstand multiple herbicides.

“What we’re probably going to be seeing in the future is more crops coming out with additional genes that give resistance to other herbicides,” said Diers, who specializes in soybean breeding and genetics.


Marestail infests a cotton field. Marestail is just one of hundreds of weeds that have become resistant to popular herbicides.
Marestail infests a cotton field. Marestail is just one of hundreds of weeds that have become resistant to popular herbicides.

The ‘super weed’ cycle

Larry McClendon is a fourth-generation cotton grower who farms anywhere from 5,000 to 10,000 acres a year in eastern Arkansas. He voiced his support for the recently deregulated Monsanto cotton during a USDA public meeting in September.

“As a farmer, I can say with a lot of confidence that growers need new weed management technologies,” he said, according to transcripts from the meeting.

Document: read the GMO meeting transcripts

Bruce Tiffany is a soybean, corn, sweet corn, cattle and sheep farmer in Minnesota. He, too, expressed support for the Monsanto technology. Under a special permit granted by the Animal and Plant Health Inspection Service, Tiffany is one of the select few U.S. farmers who has been able to grow Monsanto’s dicamba-resistant soybean before commercialization.

“My experience is the weed control system is effective, economical, safe for the operator and environmentally responsible,” Tiffany said, according to transcripts.

But while Mennenga, McClendon, Tiffany and other farmers applaud the new Monsanto soybean and cotton, critics argue the move is shortsighted and will only lead to the further reliance on herbicide.

Most soybean acres are planted with a genetically modified seed, such as the ones shown here, according to the USDA.
Most soybean acres are planted with a genetically modified seed, such as the ones shown here, according to the USDA.

“One of the biggest problems with these crops is that they completely changed the way we control weeds and the way we use herbicide,” said Doug Gurian-Sherman, a senior scientist for the Center for Food Safety. “They essentially encouraged practices of weed control and overuse of these herbicides that has led to an epidemic of weeds that are resistant to those herbicides.”

If Monsanto’s genetically engineered cotton and soybean became commercially available, farmers would widely replace their old Roundup Ready, glyphosate-tolerant seeds with the new dicamba-tolerant ones, Gurian-Sherman said. As a result, they would begin the same cycle that produced the glyphosate-tolerant weeds originally.

The Center for Food Safety, a national nonprofit and public interest organization, projects that the majority of all cotton and soybean crops would become dicamba-resistant.

Instead of turning to a different herbicide to kill the resilient weeds, Gurian-Sherman said farmers should use alternative methods.

However, according to studies cited in a USDA analysis, those methods would lead to steep financial losses for farmers. If growers decreased herbicide use by shifting to more hand weeding and tillage, U.S. crop production would decline by 20 percent with a $16 billion loss in value.

Researchers estimate weeds cause about 37 percent of the world’s soybean production loss.

And – even if farmers shifted to methods outside of genetically modified crops and herbicides – it’s likely the weeds would still find a way to adapt and continue to bother farmers.

“The problem is that, in any of these kinds of situations, nature is eventually going to win,” Diers said.

Type of work:

Creative Commons License

Republish our articles for free, online or in print.

Join the Conversation

9 Comments

  1. It would be awesome if, instead of lawsuits, CFS would fund research into the “alternative methods” Doug claims are available. If they were cost- and labor-effective I’m sure farmers would be open to them. C’mon Doug–show ’em.

  2. Instead of turning to a different herbicide to kill the resilient weeds, Gurian-Sherman said farmers should use alternative methods.

    What are these so called alternative methods?

  3. And people always seem to forget that most crops are planted by machines, and it is really tough to weed them without trampling the crops.
    When i was just a kid, Gramps paid us to kill the thistles in his Canola, we most likely killed far more Canola than the weeds would have done. I am sure he just wanted us out of the house.

  4. “One of the biggest problems with these crops is that they completely changed the way we control weeds and the way we use herbicide,”

    That is not really true. Prior to the introduction of RR soybeans, most farmers used sulfonyurea herbicides to control these weeds and there was plenty of sulfonylurea resistance around then.

    What is actually needed is a longer term approach that diminishes weed seed banks. This may mean a change in the rotation to be able to use other weed control tactics as part of the strategy, rather than relying on a single herbicide.

    Farmers need more options available for weed control, rather then fewer options. There also needs to be work conducted on how to get the best out of those options.

  5. Thank you for reading the story and sharing your comments. As
    the story mentions, those alternative methods do include hand weeding and
    tillage. As a comment in the main story pointed out, alternative methods that
    still use herbicide would include “stacked” herbicide use. While reporting on
    this story, it is clear from the farmers I spoke with that they want more options.
    As Jenny Mennenga said, farmers need more tools in their tools box. It’s also
    important to note that, as Brian Diers said, nature is going to win and weeds
    are always going to find a way to adapt.

  6. Nobody asked for GMO crops and the saturated poisons that go along with them. This is a disaster in many ways than one can imagine!

  7. There are two main GE crops….One is BT toxin which is an unnatural form ovaccf a naturally occurring bacteria which is far more toxic than its natural counterpart, this unnatural bacterium has been genetically engineered into the seed, so this toxin is then expressed in every cell of the plant, so then our corn for example becomes a registered pesticide with the EPA…yummy….then there are Roundup Ready crops that have been genetically engineered to withstand heavy doses of Roundup without dying, so mothers get to feed their babies Glyphosate ridden breast milk and the rest of us get to process it though our kidneys and out in our urine…..Not to mention the active retro virus called the cauliflower mosaic virus that is used to turn the desired trait on and then the antibiotic marker used to ascertain if the desired trait is being expressed… antibiotic resistance anyone? There were never any independent, long-term, minimum of 3 mammalian species, preferably multi-generational studies done to deduce toxicology in human beings concerning the consumption of GMOs…. it’s criminal that they were allowed into our food supply….PERIOD!

Leave a comment

Your email address will not be published. Required fields are marked *