Healthy soil and sustainable growing

["TradingPostPaul" <tradingpost@riseup.net>]

25 July 2006; | doi:10.1038/news060724-5

Transgenic cotton drives insect boom
Secondary pests could undermine initial benefits of Bt cotton.
entire article at
http://www.nature.com/news/2006/060724/full/060724-5.html


After 7 years of planting cotton genetically engineered to kill bollworms,
other insects have boomed so much on Chinese farms that their owners are
losing money.

The new finding, from a study of nearly 500 cotton farmers, is likely to
be controversial because it suggests that the genetically modified (GM) Bt
cotton, named for the Bacillus thuringiensis bacterial gene it contains,
doesn't live up to the agricultural success story suggested by some
earlier studies.

China was the second country after the United States to adopt Bt cotton,
in 1997. After 2 or 3 years of use, studies showed that the cotton had
dramatically boosted yield and helped farmers to cut their use of
insecticides by as much as 70%, saving money and protecting both people
and the environment from the toxic chemicals.

The new study, conducted 7 years after the cotton's introduction, paints a
gloomier picture of the crop's economic impact. Per Pinstrup-Andersen and
his colleagues at Cornell University in Ithaca, New York, worked with
Chinese agricultural researchers to interview cotton farmers about their
finances and insecticide use in 2004.

The researchers found that populations of other cotton pests, particularly
ones called mirids, have blossomed. These were once killed by the same
broad-spectrum pesticides used to control the bollworm. Now, farmers are
spending almost as much on pesticides to control these secondary pests as
those farmers growing regular cotton.

Because Bt seed is more expensive, this means that the Bt cotton farmers
have a net average income that is 8% lower than farmers growing
conventional cotton. "It's kind of a shock," says team member Shenghui
Wang, who presented the results today at the American Agricultural
Economics Association Annual Meeting in Long Beach, California.