Pests infesting GM cotton fields in China

One of the problems with genetically modified crops is that they create unintended consequences. Scientists cannot foresee how a GM plant will interact once it is in a complex ecosystem. A case in point: A new study published in the journal Science says that the use of GM cotton in China has led to a widespread increase of another insect pest that is damaging cotton and other crops.

Chinese farmers have been planting GM cotton, which is engineered to contain the Bt bacterium that kills bollworm, since 1997. Today more than 4 million hectares (9.8 million acres) of GM cotton are grown in China.

Since GM cotton was approved, a team led by Kongming Wu, an entomologist at the Chinese Academy of Agricultural Sciences in Beijing, has monitored pest populations in cotton fields. Wu and his team have found that numbers of mirid bugs, which were previously only a minor pest in northern China, have increased 12-fold since 1997.

"Entire swathes of agricultural land that never had any problem with this pest are facing a major problem," says Wu. "Their rise in abundance is associated with the scale of Bt cotton cultivation.

The increase in mirids is forcing Chinese farmers back to using more pesticides. They are currently using about two-thirds as much as they did before Bt cotton was introduced. As mirids develop resistance to the pesticides, Wu says the farmers will soon spray as much as they ever did.

Two years ago, a study led by David Just, an economist at Cornell University found that the economic benefits of Bt cotton in China had eroded due to increased pesticide use on secondary pests.

Wu's findings confirm Just's study, says David Andow, an entomologist at the University of Minnesota in St Paul.

"The finding reminds us yet again that genetically modified crops are not a magic bullet for pest control," Andow says. "They have to be part of an integrated pest-management system to retain long-term benefits."

Environmental groups seized on the study as further evidence that GM crops are not benefitting the environment as biotech companies have claimed.

"This is a massive issue in terms of the environment, but also in terms of costs for the farmer. The plan with GM crops was to reduce costs and environmental impact, but neither of these things seem to be happening," said Kirtana Chandrasekaran, a food campaigner at Friends of the Earth.

(Source: The Guardian, UK)

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