Herbicide-tolerant (HT) crops, developed to survive application of specific herbicides that previously would have destroyed the crop along with the targeted weeds, provide farmers with a broader variety of options for effective weed control. Based on USDA survey data, HT soybeans expanded from 17 percent of U.S. soybean acreage in 1997 to 68 percent in 2001 and 81 percent in 2003. Plantings of HT cotton expanded from 10 percent of U.S. acreage in 1997 to 56 percent in 2001 and 59 percent in 2003.The adoption of HT corn, however, has been much slower, reaching 15 percent of U.S. corn acreage in 2003.

Insect-resistant crops containing the gene from the soil bacterium Bt (Bacillus thuringiensis) have been available for corn and cotton since 1996. These bacteria produce a protein that is toxic to certain lepidopteran insects (insects that go through a caterpillar stage), protecting the plant over its entire life. Plantings of Bt corn grew from 8 percent of U.S. corn acreage in 1997 to 26 percent in 1999, then fell to 19 percent in 2000 and 2001, before climbing to 29 percent in 2003. Plantings of Bt cotton expanded more rapidly, from 15 percent of U.S. cotton acreage in 1997 to 37 percent in 2001, but adoption appears to be leveling off as U.S. farmers planted 41 percent in 2003.

Use of Bt corn will likely continue to fluctuate over time, based on expected infestation levels of European corn borer (ECB), which is the main pest targeted by the Bt corn. Similarly, adoption of Bt cotton depends on the expected infestation of Bt target pests, such as the tobacco budworm, the bollworm, and the pink bollworm. Adoption appears to have reached the low-growth phase, as adoption has already occurred on acreage where Bt protection is needed most. Insects have not posed major problems for soybeans, so insect-resistant varieties have not been developed.

These figures include adoption of “stacked” varieties of cotton and corn, which have both HT and Bt traits. Stacked cotton reached 27 percent of cotton plantings in 2003. Plantings of stacked corn are much lower, making up only 4 percent of corn acres in 2003.

Adoption of all GE cotton, taking into account the acreage with either or both HT and Bt traits, reached 73 percent in 2003, versus 81 percent for soybeans. In contrast, adoption of all biotech corn was 40 percent.

page updated: September 10, 2003