Adoption and impacts at farm level in the USA
The GM field crop revolution started in the USA in 1996 as the first GM-corn, soybean and cotton varieties became available to farmers. Soybean, corn, and cotton varieties became available with genetically engineered herbicide tolerance (HT), and cotton and corn varieties became available that were engineered for insect resistance (IR) (Fernandez-Cornejo and McBride 2000, NRC 2010). Second generation GM traits of herbicide tolerance and insect resistance became available by 2000 for cotton, and for corn shortly thereafter. Third generation GM corn varieties became available to some farmers in 2010, and Monsanto has an eight transgene variety—three genes for above ground insect resistance, three for below ground insect resistance, and two for herbicide tolerance. IR varieties provide a biological alternative to chemical insecticide applications and provide a reduced pesticide load on the environment and lower risks to human health (NRC 2010). HT soybean, corn, and cotton provide more effective weed control than with earlier herbicides. The key herbicide in this process is Roundup, which is environmentally and human health friendly relative to earlier chemical herbicides used for weed control (NRC 2010). In contrast, GM-wheat varieties are not available to farmers. The primary reason is the negative image that GM wheat has in the export market.