Skip to content
for a responsible, fair & sustainable food system

RR Crops to Raise the White Flag?

Immediate release (19 Oct 2011)

Calls to: Pete Riley 07903 341 065

Superweed spreading “exponentially” in GM cotton – Monsanto tells farmers they are on their own

Herbicide resistant weeds are winning the pesticide “arms race” in US Roundup Ready crops, and Monsanto has no intention of shouldering responsibility for rising weed control costs, according to a new briefing by GM Freeze published today. [1]

The briefing reports that in the 2010/11 season so far, two new weed species have become resitant to glyphosate (the active ingredient in Monsanto’s herbicide Roundup used on RR soya maize and cotton), bringing the global total to 21.

Infestations of superweeds now cover 4.5 million hectares in the US alone. The noxious weed Palmer Amaranth is spreading “exponentially” in RR cotton according to Robert Nichols of Cotton Incorporated [2], and once it has reached a certain size it can only be controlled by hand pulling.

GM Freeze also reports that Monsanto’s warranty [3] on the weedkiller does not cover the failure of the product to control weeds that are now resistant to it:

Growers must be aware of and proactively manage for glyphosate-resistant weeds in planning their weed control program. When a weed is known to be resistant to glyphosate, then a resistant population of that weed is by definition no longer controlled with labelled rates of glyphosate. Roundup agricultural herbicide warranties will not cover the failure to control glyphosate-resistant weed populations.

The severity of glyphosate resistance has forced Monsanto to sign agreements with other pesticide companies to provide other herbicides to be used in combination with Roundup. The new approach includes [3]:

  • Weedkillers that act in the soil to kill off resistant weeds as soon as they germinate.
  • Roundup and 2,4-D mixtures to burn off weeds in stubble after harvest.
  • “Stacked” GM herbicide tolerance genes in seeds to allow spraying with both Roundup and Dicamba to try to kill resistant weeds in the growing crop. [4]

Dicamba and 2,4-D have been approved for many years, but their overall safety for people and the environment has been challenged. [5]

RR crops were once marketed as a cheap and simple way to manage weeds in cotton, soya and maize. Now the rise in glyphosate resistance is cited by at least one investment adviser in its recommendation to sell Monanto shares.

One US soyabean farmer said recently, “Just spraying Roundup was so easy…There is no ease anymore.”

Other biotech companies, such as Dow and Bayer, are rushing to get their GM herbicide tolerant crops, using different weedkillers, onto the market to rotate with them with RR crops to try to prevent or slow the development of weed resistance.

However growing the same crops with several different herbicide tolerances runs the risk that the wrong weedkiller could be used and kill the crops as well as the weeds. To ensure the correct herbicide is used on the right crop, Bayer suggest marking glyphosate resistant crops with white flags, and others with green and red flags.

The new industry approaches to controlling weeds in soya, maize and cotton mean that dependence on glyphosate looks set to continue despite mounting scientific evidence about its safety for farmers, people, wildlife, the soil and water supplies. [6]

Commenting Pete Riley of GM Freeze said:

There is clear evidence that resistant weeds are rampant and winning in RR crops, and the white flag has been raised on glyphosate!

The biotech industry seems intent on using more and more chemicals in untested cocktails to try to control superweeds. The days of cheap and simple weed control in GM crops are long gone. All farmers are being offered now is more weedkillers to combine with Roundup or hand pulling. It is clear that Monsanto has no intention of shouldering any responsibility for the extra costs of the current weed crisis in their GM crops, and farmers are now paying the price.

UK farmers should take careful note of what it happening in the US and reflect on the fact that we would be in a similar position if public opposition to GM crops had not slowed their introduction. Thankfully we have labels on food to help us avoid GM, unlike the US where they reject GM but can’t always tell what they are eating.

What we need in is a different approach to weed control, one we know will work over time based on longer rotations, crop breaks and crop diversity to avoid weeds becoming a major problem.



[1] See GM Freeze briefing Weed Resistance in RR Crops – An update (summary available)

[2] Nichol R, 2011. “Pigweed Resistance: How much? To what? And where?”, presentation to the Pig Posium organised by the University of Arkansas.

[3] Monsanto (undated), “Glyphosate Resistant Weed Biotypes”.

[4] Stacked GM crops contained several GM traits either for different herbicide tolerant or insect resistance traits. Stacked herbicide tolerant gens enable mixtures of two or more herbicide to be applied without killing the crop or for herbicide use to be rotated.

[5] Herbicides are approved individually based on evidence submitted by companies. Approvals to spray mixtures are based on the individual assessment, not on data on the toxicology of the whole mixture. Dicamba and 2,4-D are similar chemicals and were first approved in 1967 and 1940s respectively. Their approval on safety for health and the environment grounds has been challenged. See for Dicamba and for 2,4-D.

[6] See GM Freeze/Greenpeace International briefing Herbicide Tolerance and GM Crops – Why the world should be ready to round up glyphosate