A study in northern China indicates that genetically modified cotton, altered to express the insecticide, Bt, not only reduces pest populations among those crops, but also reduces pests among other nearby crops that have not been modified with Bt. These findings could offer promising new ideas for controlling pests and maximizing crop yields in the future.
The report will be published by the journal Science on Friday, 19 September. Science is the journal of AAAS, the nonprofit science society.
Dr. Kong-Ming Wu from the Chinese Academy of Agricultural Sciences in Beijing and colleagues analyzed data from 1997 to 2007 about the agriculture of Bt cotton in six provinces in northern China, covering 38 million hectares of farmland cultivated by 10 million resource-poor farmers. They compared that information with data on pest populations in the region, focusing on the cotton bollworm, a serious pest for Chinese farmers.
The researchers' results show that populations of the cotton bollworm were dramatically reduced with the introduction of Bt cotton, especially during the period from 2002 to 2006. They considered the contribution of temperature and rainfall along with the introduction of the genetically modified cotton, and confirmed that Bt cotton was responsible for the long-term suppression of the pests in the cotton and a host of other un-modified crops after 10 years. Dr. Wu and colleagues suggest that this may be because cotton is the main host for bollworm eggs, and reducing larval populations in the cotton consequently reduces the entire population and protects other crops.
Bt is an insecticide derived from the spores and toxic crystals of the bacteria Bacillus thuringiensis, and has been sold commercially since 1960. It is considered non-toxic to humans, animals, fish, plants, micro-organisms, and most insects. However, it is highly selective and lethal to caterpillars of moths and butterflies. Bt is curr
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