Posted on August 7, 2013 at 10:00 AM by Iowa Corn
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 went from 17 percent of U.S. soybean acreage in 1997 to 68 percent in 2001 and 93 percent in 2013 (the same as the previous year). Plantings of HT cotton expanded from about 10 percent of U.S. acreage in 1997 to 56 percent in 2001 and 82 percent in 2013. The adoption of HT corn, which had been slower in previous years, has accelerated, reaching 85 percent of U.S. corn acreage in 2013.
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 specific insects, protecting the plant over its entire life. Plantings of Bt corn grew from about 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 and 76 percent in 2013. The increases in acreage share in recent years may be largely due to the commercial introduction of new Bt corn varieties resistant to the corn rootworm and the corn earworm, in addition to the European corn borer, which was previously the only pest targeted by Bt corn. Plantings of Bt cotton also expanded rapidly, from 15 percent of U.S. cotton acreage in 1997 to 37 percent in 2001, peaked at 77 percent in 2012 and stood at 75 percent in 2013.
Use of Bt corn will likely continue to fluctuate over time, based on expected infestation levels of European corn borer (ECB), and the corn rootworm which are the main pests targeted by 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. Adoption of stacked varieties has accelerated in recent years. Stacked cotton reached 67 percent of cotton plantings in 2013. Plantings of stacked corn made up 71 percent of corn acres in 2013.
Adoption of all GE cotton, taking into account the acreage with either or both HT and Bt traits, reached 90 percent of cotton acreage in 2013, versus 93 percent for soybeans (soybeans have only HT varieties). Adoption of all biotech corn accounted for 90 percent of corn acreage in 2013.