EXTRACT: "It's not surprising that the number of target pests has fallen – the GM cotton contains a toxin poisonous to them.

"This study tells us nothing about the wider ecological impacts of growing Bt cotton, such as the impact on non-target species. It also fails to identify the impact on crop yields and the overall level of pesticide-use.

"This limited study must not be used to justify the cultivation of GM cotton or any other GM crop." - Clare Oxborrow

NOTE: What this limited study also ignores is the whole problem of secondary pests emerging, as identified by the Cornell multi-year study of Bt cotton cultivation in China.

That study showed that while farmers were spraying less for the bollworm, over time they were having to spray an awful lot more for other pests. This was so much the case that their overall pesticide use was not really reduced - and nor were the farmers' costs (even though they had to pay more for the Bt seed in the first place)! This is an issue the present study fails to address.

The bollworm improvement that the new study focuses on is also, of course, entirely dependent on the bollworm not developing resistance - something that the researchers admit is so far more down to luck than design. This means reliance on Bt cotton cannot be an option for the long term.
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GM cotton grown in China has wider impact on insects than intended crop
By Roger Highfield, Science Editor
Daily Telegraph, 18 September 2008

Genetically-modified cotton which has been altered to include an insecticide can help cut pests in neighbouring fields of ordinary crops.

Cotton grown in China that has been genetically modified to produce the insecticide, Bt, had a wider impact on insect pests than the target crop, a discovery which is welcomed by the agriculture lobby and criticised by environmentalists.

Drs Kongming Wu and colleagues analysed data from 1997, when the GM cotton was commercialised, to 2007 about the agriculture of Bt cotton in northern China, and compared them to data on pest populations in the region.

The use of Bt cotton reduced the populations of cotton bollworms, a problematic pest for Chinese farmers, cutting the need for pesticides by around half, and reduced the insects on neighbouring crops.

The insect usually moves between crops, after first invading cotton.

"Bt cotton kills most of the larvae of the second generation and accordingly works as a dead-end trap crop for cotton bollworm population," said Dr Wu.

"This case study for Bt cotton also implies that other Bt crops such as Bt rice may have a great potential value for agricultural practices in China," he added.

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 lethal to caterpillars of moths and butterflies. However, major challenge to the success of Bt cotton in China remains the potential for insects to evolve resistance to it.

Dr Wu and colleagues recommend that Bt cotton should be considered only one component in the overall management of pests. Environmentalists will argue that the study shows GM crops could disrupt neighbouring ecosystems but Dr Wu said: "There are two kinds of ecological balances, one is balance for all wild species, another is for agricultural production.

"Bt cotton is good for ecological balance in an agricultural system. If environmentalists want to get an ecological balance for all wild species, this means we need to protect wild ecology and risk food shortages."

Cotton bollworm is one of the most important insect pests of cotton, corn, soybean, peanut and vegetables. In 1992, this pest cut China's cotton yield by almost one third. The outbreaks resulted in overuse of chemical insecticides which increased cost, polluted environmental, and bring a series of economic, ecological and social issues.

Dr. Jian-Zhou Zhao, a co-author, also highlights the health benefits of using Bt cotton.

"Poisoning from other insecticides, and even death, was a big problem for cotton farmers in the 1990s. Most farmers did not have proper protective clothes while applying insecticides with small backpack sprayers. This may be another reason that many farmers refused to plant cotton before Bt was available - it was too dangerous and scary."

Commenting on the study, Friends of the Earth’s GM campaigner, Clare Oxborrow said: "It's not surprising that the number of target pests has fallen - the GM cotton contains a toxin poisonous to them.

"This study tells us nothing about the wider ecological impacts of growing Bt cotton, such as the impact on non-target species. It also fails to identify the impact on crop yields and the overall level of pesticide-use.

"This limited study must not be used to justify the cultivation of GM cotton or any other GM crop."