Bt cotton is a genetically modified variety of cotton producing an insecticide. It was 1^st developed by Monsanto and supplied in India’s Maharashtra state by the agri-biotechnology company, Mahyco.

“Bt” stands for bacterium Bacillus thuringiensis (Bt). It is a family of proteins that are harmful for selective insects mostly moths and butterflies. The gene coding for Bt toxin, when inserted into cotton, cause cotton to produce this natural insecticide in its tissues.

The quality of insecticidal gene of Bt is expressed during the growth cycle of cotton. The gene encoding toxin crystals are added to the “Cry” group of endotoxin. The activated Cry molecules attach to the specific locations in the bodies of the organisms. This hinders the regulation of K⁺ ions resulting in the death of the epithelial cells of the organism which in turn creates gaps. These gaps allow the Bt spores to enter the body of the organism causing its death.

The main pest in commercial cotton lepidopteran larva is killed by Bt Toxins. Bt cotton, though highly resistant towards pests, may be ineffective against cotton pests such as plant bugs, stink bugs, and aphids.

Bt Cotton accounts for 90% growth of cotton in India. But the seeds are expensive and they lose their vigor after one growth. So the farmers have to buy new stock every year. Another trend that has been put forward by few experts is that the pest against which Bt toxin was most effective is developing resistance against the same.