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Beyond the Rows is a Monsanto Company blog focused on one of the world’s most important industries, agriculture. Monsanto employees write about Monsanto’s business, the agriculture industry, and the farmer.
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Roundup-Resistant "Superweeds" In the News

It's a bird, it's a plane, no, it's SUPERWEED!

There was a story today in the New York Times (“Farmers Cope with Roundup-Resistant Weeds”) about glyphosate-resistant weeds, or as the headline states – Roundup-resistant weeds. (Glyphosate is the active ingredient in Roundup. Its success has made the two interchangeable similar to the case of facial tissue and the brand name Kleenex).

This is the second story in recent weeks about “superweeds,” as the mainstream media has sensationally dubbed the weed resistance issue.

Overall the NYT story talks about the positive contributions of biotechnology on weed control—increase in no-till, the switch from alternative herbicides to Roundup, reduced soil erosion, less herbicides/fertilizer runoff into waterways, and an easier management system for farmers – but also warns that farmers are having to resort to some of the old ways of killing weeds because of weed resistance.

These articles seem a bit late to the game since we’ve been dealing with glyphosate-resistant weeds for 10 years now. The first resistant weed –horseweed – was discovered in Delaware in 2000. But, I guess the mainstream media has decided weed resistance is now in vogue.

A few notes about resistance:

  • After four decades of use, there are 18 weeds that have become resistant (10 in the U.S.) Glyphosate is the most widely used herbicide, and still controls more than 300 different types of weeds. Not a bad track record.
  • Weed resistance is not unique to glyphosate and is a potential issue with any herbicide. Herbicide-resistant weeds have been around since the 1950s. For an exhaustive list of different herbicides and their resistant weeds, check out the International Survey of Herbicide-Resistant Weeds. The survey also includes dates when the resistance was identified as well as location by country and state/region.
  • Overuse of a glyphosate is often stated as one of the key reasons behind resistance. In actuality, it’s over reliance, which is different. Over reliance on a single herbicide increases the selection pressure.* As does growing a single crop with no rotation (ex. corn over and over again on the same field).
  • Underuse of the herbicide can also be a contributing factor. If farmers reduce application rates to save money, that also increases the selection pressure. It’s similar to what happens when your doctor tells you to take the prescribed antibiotics for 10 days, and you only do it for 5. You’re increasing the risk for your body to become resistant to the antibiotic.
  • And finally, what the heck is a superweed? Seriously, this term gets thrown around a lot, primarily in non-agriculture venues. I imagine pigweed standing tall with a red cape, refusing to die. Glyphosate may no longer be able to kill these weeds, but that by itself doesn’t make them “superweeds.” There was a time when glyphosate wasn’t around, and guess what? These weeds existed.

Palmer amaranth, or pigweed, a weed that has received a lot of attention as a glyphosate-resistant weed.

We know resistant weeds are a concern for our customers. Over the past 10 years, we’ve worked with farmers, weed scientists and public institutions to monitor and research the issue and to provide recommendations on managing resistant weeds as well as prevention for further resistance. These best management practices have evolved over time as we have learned more.

Today, those practices include proper application rates, the use of other herbicides as necessary, rotation of crops and tillage. We work to broadly encourage those practices among farmers via communications on our product labels, in our technology use guides, print literature, and via professional websites to growers, retailers and farm consultants.

*What is selection pressure? Well, imagine that you have a whole population of pigweed in a field. Some of those pigweeds can naturally resist the effects of a particular herbicide. You spray the herbicide, and if you leave these weeds alive in the field, they can come back the next year and are harder to control.

For more information on weed resistance, check out these links:

WeedTool.com – (includes fairly comprehensive list of resources: university weed science departments, industry organization learning modules,

Herbicide Resistance Action Committee

Weed Resistance and Benefits of Diversified Weed Management Programs (Monsanto)

For the Record – Science – Weed Resistance (Monsanto)

Weed Resistance Risk Assessment (Monsanto)

6 Responses to "Roundup-Resistant "Superweeds" In the News"

  1. I would note that it’s not accurate to speak of resistance as only being something that pertains to herbicides. There is for instance barnyardgrass that avoids hand weeding by mimicing rice until it is too late to hand weed it.

    Anything that works will have resistance.

    And so it’s no surprise, at least it wasn’t outside Monsanto when resistance to Roundup started to show up.

    Partly it was such news because of the Monsanto Representatives who would stand in front of groups and with a straight face deliver the line that plants would never develop resistance to Roundup. Even upon closer examination they seemed to actually believe that.

    I can’t excuse the media for coming up with terms like superweeds or such, they aren’t they just happen to be resistant to something. Always seeems like there is a bias to make something bigger news than it really is by juicing up the language.

    No question there was and continues to be overreliance on the product Roundup on more than a few farms. It’s an easy thing to do whereas other weed management strategies are certainly more complex and often more costly in the short term monetarily.

    All in all, I have to say the NY Times article mentioned was one of the better ones I’ve seen. So many articles just pure propaganda by the religious fanatics of organic or some other false school of philosophy, which are designed to instill beliefs on others, not report news.

    Anyway, thanks for making Roundup and Roundup resistant crops. They don’t solve anything, but I would miss them as production tools. Hopefully your company can find another horse to ride along with Roundup to give us even more tools.

    • @Marv – Thanks for your comments and for providing more context on weed resistance.

      Since the time I’ve been at Monsanto (5 years), we have talked about prevention methods including multiple modes of action and crop rotation, but I’ve heard stories similar to yours of how the company handled this topic early on.

  2. Holy mother of Jesus–are you serious? Could you perhaps be a little less snide? And your links–can you provide some outside links, rather than Roundup and Monsanto glossyphalia? I’m guessing that this blog is sorta like the Chinese online media; this post won’t be posted.

    • @Lee – I believe the chart you pulled off the weedscience.org home page is for all resistant weeds to all classes of herbicides. There are more than 300 resistant weeds. That graph shows that herbicide-resistant weeds are not new.

      What may be more helpful is this chart from the same website: http://www.weedscience.org/ChronMOA.GIF.

      This graph lists the number of resistant weeds by the type of herbicide. You’ll note that the blue line represents glycines, which is the category of herbicide that glyphosate-based chemicals (including Roundup) fall into. This category includes less than 20 weeds. The majority of the weeds in the graph you linked to earlier are resistant to other classes. So, there are around 280 resistant weeds to other herbicides.


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