Farmers in Arizona increasingly are growing cotton that has been genetically modified to combat the pink bollworm, a pest that's the most lethal enemy of the state's cotton. The hybrid cotton has been genetically modified to produce Bt toxin, a naturally occurring insecticide that kills the bollworm. Bt cotton has been planted in Arizona since 1996 and now accounts for nearly 70 percent of the crop.
Environmentalists have criticized cotton production because of its relatively heavy use of pesticides. The University of Arizona has been conducting research showing promising results on how Bt cotton is leading to significant reductions in the use of broad-spectrum pesticides in Arizona with no decrease to yields.
Bt cotton controls only one of Arizona's three major cotton pests. Growers still must use broad-spectrum insecticides to control the sweet potato whitefly and the Western tarnished plant bug.