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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 91 percent in 2007. Plantings of HT cotton expanded from 10 percent of U.S. acreage in 1997 to 56 percent in 2001 and 70 percent in 2007. The adoption of HT corn, which had been slower in previous years, has accelerated, reaching 52 percent of U.S. corn acreage in 2007.
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
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 49 percent in 2007. The recent increases
in acreage share may be largely due to the commercial introduction
in 2003/04 of a new Bt corn variety that is resistant to the
corn rootworm, a pest that may be more destructive to corn yield
than the European corn borer, which was previously the only pest
targeted by Bt corn. Plantings of Bt cotton expanded more rapidly,
from 15 percent of U.S. cotton acreage in 1997 to 37 percent
in 2001 and 59 percent in 2007.
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 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 42 percent of cotton plantings in 2007. Plantings
of stacked corn made up 28 percent of corn acres in 2007.
Adoption of all GE cotton, taking into account the acreage with
either or both HT and Bt traits, reached 87 percent in 2007,
versus 91 percent for soybeans. In contrast, adoption of all biotech
corn was 73 percent.
See details about data sources...
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