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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 92 percent
in 2008. Plantings of HT cotton expanded from about 10
percent of U.S. acreage in 1997 to 56 percent in 2001 and
68 percent in 2008. The adoption of HT corn, which had
been slower in previous years, has accelerated, reaching
63 percent of U.S. corn acreage in 2008.
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 57 percent in 2008. 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 63 percent in 2008.
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. Adoption
of stacked varieties has accelerated. Stacked cotton reached 45
percent of cotton plantings in 2008. Plantings of stacked corn
made up 40 percent of corn acres in 2008.
Adoption of all GE cotton, taking into account the acreage with
either or both HT and Bt traits, reached 86 percent in 2008,
versus 92 percent for soybeans (soybeans have only Ht varieties).
Adoption of all biotech corn was 80 percent in 2008.
See details about data sources...
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