Transgenic Bt crops and resistance: Broadscale use of pest-killing plants to be true test

More than 10 million acres of transgenic insect-resistant crops, including cotton, corn and potatoes, were planted in the United States in 1998 — and growers are on the verge of much more extensive plantings. Genetically engineered to produce insecticidal proteins of the bacterium Bacillus thuringiensis, these plants provide effective, environmentally safe pest control. However, current transgenic crops may lead to insect resistance, partly because they have been engineered to produce only single Bt insecticidal proteins, and partly because plant senescence can result in lower production of Bt proteins as crop plants age. Australia cotton growers, for instance, found they had good control for the first half of the season in 1997, but required insecticide treatments in the latter half. Resistance avoidance strategies and crop varieties in the pipeline that produce two or more insecticidal proteins are planned to provide long-term resistance management. This is crucial not only to growers using the transformed crops, but to organic growers who rely on traditional Bt insecticides. If successful, this new technology promises high crop yields as well as benefits to most nontarget arthropods and biological control insects by reducing the use of broad-spectrum chemical insecticides.