So far, the only successful approach to engineering crops for insect tolerance has been the addition of the Bt toxins, a family of toxins originally derived from soil bacteria, Bacillus thuringiensis. These toxins are effective against a variety of economically important crop pests but pose no hazard to nontarget organisms like mammals and fish.
Monocultured cotton requires intensive pesticide use to combat numerous pests.
Over the past 40 years, many of those pests have developed resistance to pesticides. Resistance means that increasing numbers of applications are required for control until, finally, the pesticide performs so poorly that farmers turn to the next pesticide. When a new pesticide comes along to which pests are not yet resistant, farmers can reduce the number of pesticide applications for a while, saving both money and the environment. But eventually resistance develops and the number of applications increases again until the new pesticide, too, becomes useless. In the past, this cycle, often referred as a pesticide treadmill, was the way of doing business in the pesticide industry.