Resistance to Bt crops emerges

Some caterpillars are cottoning to transgenic cotton.

Genetically engineered cotton and corn produce a toxin that kills caterpillar larvae and other pests, but a new study shows that resistance to this toxin could be spreading among one species of caterpillar.

Farmers worldwide plant more than 400 million acres of these transgenic crops each year. A bacterial gene inserted into the plants’ DNA enables the crops—called Bt crops—to kill insects without sprayed pesticides.