About 98 million acres of GE crops were cultivated worldwide in 1999, a 43-percent increase over acreage in 1998, and U.S. acreage accounts for 72 percent of this. However, actual benefits in terms of costs, yields, and pesticide use vary with the crop and engineered trait. Crops carrying herbicide-tolerant genes were developed to survive certain herbicides that previously would have destroyed the crop along with the targeted weeds.
Farmers thus can choose from a broader variety of herbicides to control weeds.
Glyphosate tolerance has been incorporated into cotton, corn, soybeans, and canola. HT cotton expanded from 10 percent of surveyed acreage in 1997 to 26 percent in 1998 and 46 percent in 2000. The bacteria produce a protein that is toxic when ingested by certain lepidopteran insects, such as butterflies and moths. Crops containing the Bt gene are able to produce this toxin, thereby providing protection against lepidopteran insects throughout the entire plant. Bt has been built into several crops, the most important being corn and cotton.