Glyphosate

Glyphosate (N-(phosphonomethyl)glycine) is a broad-spectrum systemic herbicide used to kill weeds, especially annual broadleaf weeds and grasses known to compete with commercial crops grown around the globe. It was discovered to be a herbicide by Monsanto chemist John E. Franz in 1970. Monsanto brought it to market in the 1970s under the tradename Roundup, and Monsanto's last commercially relevant US patent expired in 2000.

Called by experts in herbicides "virtually ideal" due to its broad spectrum and low toxicity compared with other herbicides, glyphosate was quickly adopted by farmers. Use increased even more when Monsanto introduced glyphosate-resistant crops, enabling farmers to kill weeds without killing their crops. In 2007 glyphosate was the most used herbicide in the US agricultural sector, with 180 to 185 million pounds (82,000 to 84,000 tonnes) applied, and the second most used in home and garden market where users applied 5 to 8 million pounds (2,300 to 3,600 tonnes); additionally industry, commerce and government applied 13 to 15 million pounds (5,900 to 6,800 tonnes). While glyphosate has been approved by regulatory bodies worldwide and is widely used, concerns about is effects on humans and the environment persist.

Glyphosate's mode of action is to inhibit an enzyme involved in the synthesis of the aromatic amino acids: tyrosine, tryptophan and phenylalanine. It is absorbed through foliage and translocated to growing points. Because of this mode of action, it is only effective on actively growing plants; it is not effective as a pre-emergence herbicide.

Some crops have been genetically engineered to be resistant to it (i.e. Roundup Ready, also created by Monsanto Company). Such crops allow farmers to use glyphosate as a post-emergence herbicide against both broadleaf and cereal weeds, but the development of similar resistance in some weed species is emerging as a costly problem. Soy was the first Roundup Ready crop.