Joint study shows genetically modified cotton less profitable in China
26/7/2006 17:10
A genetically modified (GM) cotton capable of resisting bollworms has
caused Chinese farmers to lose money after a seven-year trial because other
pests have thrived, according to a joint study by Chinese and US
researchers.
The study, the first to look at the longer-term economic impact
of GM cotton, was conducted by the Center for Chinese Agricultural Policy, the
Chinese Academy of Sciences, and Cornell University in the United
States.
Scientists reported their findings on Tuesday at a meeting of the
American Agricultural Economics Association in Long Beach, California.
The
findings were likely to be controversial, said the researchers, because it
suggested that the Bt cotton, named for the Bacillus thuringiensis bacterial
gene it contains, didn't live up to the agricultural success story predicted by
some earlier studies.
"These results should send a very strong signal to
researchers and governments that they need to come up with remedial actions for
the Bt-cotton farmers. Otherwise, these farmers will stop using Bt cotton, and
that would be very unfortunate," said Per Pinstrup-Andersen, a Cornell professor
who led the study.
The Bt gene inserted into the cotton seeds can produce
toxins that are lethal to the leaf-eating bollworm, a major pest in cotton
fields.
In the seven-year survey, the researchers found that by year three
cotton farmers who had planted Bt cotton had cut pesticide use by more than 70
percent and had earnings 36 percent higher than farmers planting conventional
cotton.
But by 2004, they had to spray just as much as conventional farmers,
which resulted in a net average income of 8 percent less than conventional
cotton farmers, because Bt seed is triple the cost of conventional
seed.
After seven years, populations of other insects such as mirids have
increased so much that farmers are now having to spray their crops up to 20
times a growing season to control them, according to the study of 481 Chinese
cotton farmers.
"The problem in China is not due to the bollworm developing
resistance to Bt cotton, but is due to secondary pests that are not targeted by
the Bt cotton and which previously have been controlled by the broad-spectrum
pesticides used to control bollworms," said Pinstrup-Andersen.
He indicated
that researchers, farmers and policy-makers now needed to find ways to control
the secondary pests by, for example, introducing natural predators of the
mirids, or engineering a second generation of Bt cotton that kills the other
pests.
Another idea is to use refuges, which are small pockets of land used
to grow conventional cotton alongside Bt cotton. The land can maintain a
population of insects not exposed to the Bt toxin and help prevent the
development of toxin-resistant insects, according to the
researchers.
Xinhua
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