Roundup Ready Crops

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Roundup Ready Crops (RR Crops) are genetically engineered crops that have had their DNA altered to allow them to withstand the herbicide glyphosate (the active ingredient of Monsanto's herbicide Roundup). They are also known as "glyphosate tolerant crops." RR crops deregulated in the U.S. include: corn, soybeans, canola, cotton, sugarbeets, and alfalfa. When planting Glyphosate Tolerant crops, a farmer can spray the entire crop with glyphosate, killing only the weeds and leaving the crop alive. However, one concern with the heavy use of glyphosate on RR crops is that it will lead to the development of glyphosate resistant weeds (sometimes referred to as "superweeds").[1] One variety of RR Corn, NK603, was linked to tumors in rats by a 2012 study.[2]


For more detailed information, see the article on the History of Roundup Ready Crops.


  • 1982: Monsanto and Calgene are already working on creating RR crops.[3]
  • 1985: Monsanto succeeds in creating petunia plants tolerant of small amounts of Roundup.[4] Calgene also has some success, which it publishes in Nature.[5]
  • 1989: Monsanto has a breakthrough in creating the first Roundup Ready crops.[6] It begins work with Agracetus and Asgrow (then owned by Upjohn and later acquired by Monsanto) to create Roundup Ready Soybeans.





Some of the many controversies related to the use of Roundup Ready (RR) crops are illustrated by the testimony of Troy Roush, an Indiana farmer, before Congress in 2010: [23]

"I have been using genetically engineered (GE) soybeans since 2000, when a lawsuit for patent infringement against my family was dismissed by Monsanto. After having endured two years of costly litigation that took its toll on my family, we decided that, in order to protect ourselves from future baseless lawsuits, we would make the conversion to biotech crops and began using Roundup Ready (RR) varieties for our non-organic crops.
"During the first few years we were able to rely exclusively on RR technology for weed management, applying glyphosate for burndown and again to eliminate weed pressure after the crop emerge. However, due to problems with glyphosate tolerant weeds, the skyrocketing costs of RR seeds and the price premiums being paid for non-GE soybeans, we have since returned to using conventional varieties on approximately half of our 2,600 soybean acres. The diminishing effectiveness of glyphosate, as demonstrated in the dramatic increase in glyphosate tolerant weeds, destroyed any benefit from the technology.
"Fortunately, Indiana enacted Farmer Protection laws in 2002 after my lawsuit with Monsanto to prohibit patent infringement cases where small amounts of GE content is detected in crops and fields. Without those protections, our return to conventional soybean production would have brought with it the potential of significant risk of patent infringement liability.
"In 2005, we first began to encounter problems with glyphosate resistance in marestail and lambsquarter in both our soybean and corn crops. Since there had been considerable discussion in the agricultural press about weeds developing resistance or tolerance to Roundup, I contacted a Monsanto weed scientist to discuss the problems I was experiencing on the farm and what could be done to eradicate the problematic weeds. Despite well documented proof that glyphosate tolerant weeds were becoming a significant problem, the Monsanto scientist denied that resistance existed and instructed me to increase my application rates.
"The increase in application rates proved ineffectual, and I was forced to turn to alternative methods for weed management including the use of tillage and other chemistry. In 2007, the weed problems had gotten so severe that we turned to an ALS inhibitor marketed as Canopy to alleviate the problem in our preplant, burndown herbicide application. In 2008, we were forced to include the use of 2,4D and an ALS residual, to our herbicide programs. Like most farmers, we are very sensitive to environmental issues and we were very reluctant to return to using tillage and more toxic herbicides for weed control. However, no other solutions were then or are now readily available to eradicate the weed problems caused by development of glyphosate resistance....
"As I mentioned earlier, I have now returned to the use of conventional soybean varieties for about 1/2 of my total acreage. That proportion of acreage will increase if supply of quality conventional seed varieties increases. While conventional soybean varieties have been very difficult to find, a number of small, independent seed companies are now beginning to respond to the demand. This year, I was able to find convention seeds from a small seed company that sources germplasm from an Ohio breeding program that allowed me to increase acreage in conventional varieties."

This testimony highlights: 1) intimidation and legal threats by Monsanto against farmers 2) lack of availability of high quality non-GMO seeds 3) the problem of glyphosate resistant weeds resulting from the use of RR crops and the resulting overuse of Roundup and 4) questions over the claim that use of RR crops reduces or eliminates the use of more toxic herbicides.

Study Links RR Corn to Tumors in Rats

On September 19, 2012, a team led by Gilles-Eric Séralini of the University of Caen published a study called "Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize" in the journal Food and Chemical Toxicology.[2] The study ran for two years, studying the effects of Monsanto's Roundup Ready corn variety NK603 and/or Roundup herbicide on 200 rats. Only 30% of males and 20% of females in the control group died during the experiment, compared to much higher rates of mortality among treated rats.

"Up to 14 months, no animals in the control groups showed any signs of tumors whilst 10–30% of treated females per group developed tumors, with the exception of one group (33% GMO + R). By the beginning of the 24th month, 50–80% of female animals had developed tumors in all treated groups, with up to 3 tumors per animal, whereas only 30% of controls were affected. The R [Roundup] treatment groups showed the greatest rates of tumor incidence with 80% of animals affected with up to 3 tumors for one female, in each group."[2]

The study found that the first large detectable tumors occurred "at 4 and 7 months into the study in males and females respectively, underlining the inadequacy of the standard 90 day feeding trials for evaluating GM crop and food toxicity (Séralini et al., 2011)." (emphasis added)

Elsevier retracted the study from the journal on November 28, 2013.[24] The retraction met with controversy and criticism.

For more information on this study, see the article on the NK603 variety of corn.

The Safety of Roundup

One of the arguments in favor of using RR crops is the claim that Roundup is an extremely safe, environmentally friendly herbicide. For example, Dr. Michael D. Owen testified before Congress, saying: "Because it binds to the soil rapidly, is biodegraded by soil bacteria, and has a very low toxicity to mammals, birds, and fish, glyphosate kills most plants without substantial adverse environmental effects on animals or soil or water quality. The widespread adoption of glyphosate-resistant crops has therefore reduced the use of more toxic (albeit EPA-registered) herbicides in soybean, cotton, and corn fields."[25] However, some question the claim that Roundup is "safe" and/or "environmentally friendly." For more information, see the article on glyphosate.

This is a particularly important issue because the use of Roundup has increased dramatically with the adoption of Roundup Ready crops. (Between 1996 and 2006, the amount of glyphosate applied per planted acre of soybeans in the U.S. increased from less than 0.2 to about 1.2 pounds, a six-fold increase.[25])

Increase in Herbicide Use

Predictably, the introduction of Roundup Ready crops resulted in an increase of glyphosate (Roundup) use.

"USDA NASS data show that since 1996, the glyphosate rate of application per crop year has tripled on cotton farms, doubled in the case of soybeans, and risen 39% on corn. The average annual increase in the pounds of glyphosate applied to cotton, soybeans, and corn has been 18.2%, 9.8%, and 4.3%, respectively, since HT [herbicide tolerant] crops were introduced.[26]

Simultaneously, as glyphosate resistant weeds began to emerge as a result of over-reliance on glyphosate, farmers began using other - often more toxic - herbicides on crops:

"Growing reliance on older, higher-risk herbicides for management of resistant weeds on HT crop acres is now inevitable in the foreseeable future and will markedly deepen the environmental and public health footprint of weed management on over 100 million acres of U.S. cropland."[26]

Intimidation and Suing of Farmers by Biotech Companies

The Emergence of Superweeds

For more information, see the article on glyphosate resistant weeds.

Lack of Independent Research

Articles and resources

Related SourceWatch articles


  1. William Neuman and Andrew Pollack, "Farmers Cope With Roundup-Resistant Weeds," New York Times, May 3, 2010, Accessed February 18, 2011.
  2. 2.0 2.1 2.2 Gilles-Eric Séralini, Emilie Clair, Robin Mesnage, Steeve Gress, Nicolas Defarge, Manuela Malatesta, Didier Hennequin, Joël Spiroux de Vendômois, "Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize," Food and Chemical Toxicology, Available online September 19, 2012.
  3. Daniel Charles, Lords of the Harvest: Biotech, Big Money, and the Future of Food, p. 63.
  4. Daniel Charles, Lords of the Harvest: Biotech, Big Money, and the Future of Food, p. 65-66.
  5. Daniel Charles, Lords of the Harvest: Biotech, Big Money, and the Future of Food, p. 67.
  6. Daniel Charles, Lords of the Harvest: Biotech, Big Money, and the Future of Food, p. 68-69.
  7. Daniel Charles, Lords of the Harvest: Biotech, Big Money, and the Future of Food, p. 120.
  8. Federal Register, Vol. 59, No. 99, May 24, 1994.
  9. Novel Food Decisions - Approved Products, Health Canada, Accessed August 17, 2012.
  10. Daniel Charles, Lords of the Harvest: Biotech, Big Money, and the Future of Food, p. 163-164.
  11. 11.0 11.1 Monsanto - Company History, Accessed August 1, 2012.
  12. Herbicide Resistant Weeds: Horseweed, Accessed August 17, 2012.
  13. Herbicide Resistant Weeds: Giant Ragweed, Accessed August 17, 2012.
  14. Geertson Seed Farms v. Johanns, Ninth Circuit Court of Appeals.
  15. Tadlock Cowan and Kristina Alexander, "Deregulating Genetically Engineered Alfalfa and Sugar Beets," Congressional Research Service, January 25, 2012.
  16. Herbicide Resistant Weeds: Palmer Amaranth, Accessed August 17, 2012.
  17. Herbicide Resistant Weeds: Common Waterhemp, Accessed August 17, 2012.
  18. Herbicide Resistant Weeds: Palmer Amaranth, Accessed August 17, 2012.
  19. Monsanto Company History, Accessed August 14, 2012.
  20. Federal Register, Vol. 73, No. 143, July 24, 2008.
  21. Federal Register, Vol. 76, No. 242, December 16, 2011.
  22. Petitions for Nonregulated Status Pending, USDA, Accessed August 9, 2012.
  23. Testimony of Troy Roush, "Are ‘Superweeds’ an Outgrowth of USDA Biotech Policy? (Part I)," Hearing, Committee on Oversight and Government Reform, U.S. House of Representatives, July 28, 2010.
  24. Elsevier Announces Article Retraction from Journal Food and Chemical Toxicology - See more at:, Accessed Dec 9, 2013.
  25. 25.0 25.1 Testimony of Michael Owen, "Are ‘Superweeds’ an Outgrowth of USDA Biotech Policy? (Part I)," Hearing, Committee on Oversight and Government Reform, U.S. House of Representatives, July 28, 2010.
  26. 26.0 26.1 Charles Benbrook, "Impacts of Genetically Engineered Crops on Pesticide Use: The First Thirteen Years" and Supplemental Tables, The Organic Center, 2009.

External resources

External articles