Some of the most popular GM (genetically modified, also called genetically engineered, GE) crops are called Bt crops. That means they make an insecticide (Bt toxin) in the plant’s own tissues. So the farmer doesn’t need to spray insecticide. At least, that’s the aim. The not-for-profit International Service for the Acquisition of Agri-biotech Applications (ISAAA) explains how Bt crops work. Scroll down that page if you want to see what Bt crops are being grown.
How well does this work in practice? How soon do insect pests evolve resistance to the toxin? What can farmers do to get the best out of Bt crops? Another not-for-profit, Plantwise, tells us about insects evolving resistance to Bt toxin and farmers’ responses to that.
In practice, some farmers increase their use of insecticide spray when they’re growing Bt crops. That’s not the aim of making or growing these crops. But sometimes, it’s what happens.
[Edit] My fellow blogger Daniela at The Noah Project tells us about the Western corn rootworm (Diabrotica virgifera virgifera) evolving resistance to Bt toxin. A gene called Cry 3Bb was inserted into these corn (maize, Zea mays) plants, so that they make Bt toxin. But the canny little rootworms fought back.