Bt cotton is a genetically modified version of the plant that contains genes for an insecticide. The cotton plants include Bacillus thuringiensis (Bt), a spore-forming bacteria that produces cry proteins. When insects eat these cotton plants, the cry proteins bond to cells inside the insect, disturbing the flow of potassium through the insect, eventually killing it. Bt cotton is produced by Monsanto and grown in India.
The family of Bt bacteria contains 200 proteins that are harmful to many insects, especially beetles, butterfly larvae, cotton boll worms, flies and moth larvae. In areas where these pests are the key threat to cotton, use of Bt cotton reduces the need to use broad-spectrum insecticides on the crops. However, Bt is ineffective against other pests, including aphids and stink bugs. In some areas of China, insecticide use has been increased to pre-Bt levels in cotton fields because of the need to fight these Bt-resistant pests.
In the United States, use of Bt cotton yielded approximately 5 percent more per acre than standard cotton between 1996 and 1998.
Bt cotton is in widespread use in India, the second largest producing nation in the world. However, because Monsanto's Bt cotton seeds are expensive and do not last well past one generation, Indian agriculturalists have developed their own variety that has reusable seeds. Although the use of Bt cotton is controversial in India, 83 percent of the country's cotton comes from it as of 2012.