In a world that each year loses up to 40 percent of its crops to insects, some form of pest control is desperately needed. But chemical pesticides have backfired. Pesticide-resistant insects frequently develop, and previously harmless insects have be... (more)come devastating infestations. Farmers have found themselves trapped on a "pesticide treadmill"—the more they spray, the more they have to spray. NOVA examines several alternatives for pest control.