Over 80% of all GM crops are engineered to tolerate one or more herbicides.Herbicide-tolerant soybeans are the most widely grown GM crop, going from 17% percent of US soybean acreage in 1997 to 93% in 2013.2

The most widely grown GM crop is Roundup Ready (RR) soy,1 which is engineered to tolerate Roundup herbicide, the presumed “active ingredient” of which is glyphosate. The RR gene enables farmers to spray the field liberally with herbicide. All plant life is killed except the crop.

The widespread adoption of GM RR soy in North and South America has led to substantial increases in the use of Roundup and other glyphosate herbicides.3,4

GM RR crops do not break down glyphosate herbicide, but absorb it into their tissues. Some of the glyphosate is broken down (metabolized) into a substance called aminomethylphosphonic acid (AMPA). Both glyphosate and AMPA remain in the plant and are eaten by people and animals. As documented below, both are toxic.

As well as being used on GM RR crops, Roundup is increasingly used as a desiccant on grain crops to dry them before harvest, making the grains easier to harvest and store without rotting. The herbicide is also widely used by municipal authorities on roads, railway lines, parks, and other public places, and by home gardeners.


  1. James C. Global status of commercialized biotech/GM crops: 2012. ISAAA; 2012. Available at: http://www.isaaa.org/resources/publications/briefs/44/download/isaaa-brief-44-2012.pdf.
  2. USDA Economic Research Service. Recent trends in GE adoption. 2013. Available at: http://www.ers.usda.gov/data-products/adoption-of-genetically-engineered-crops-in-the-us/recent-trends-in-ge-adoption.aspx#.UzgPocfc26w.
  3. Benbrook C. Impacts of genetically engineered crops on pesticide use in the US – The first sixteen years. Environ Sci Eur. 2012;24.
  4. Binimelis R, Pengue W, Monterroso I. Transgenic treadmill: Responses to the emergence and spread of glyphosate-resistant johnsongrass in Argentina. Geoforum. 2009;40:623–633.