Crop researchers have voiced scepticism over claims that genetically modified (GM) rice needs less pesticide than conventional varieties.
Jikun Huang of the Beijing-based Center for Chinese Agricultural Policy and colleagues published a paper in Science this April saying that farmers growing GM rice used 80 per cent less pesticide than those growing non-GM rice (see GM rice 'good for Chinese farmers' health and wealth').
Huang's team concluded that opting for GM rice would not only reduce pesticide use and save the lives of hundreds of Chinese farmers who die each year from exposure to the chemicals, but would also save the farmers money.
But in this week's issue of Science, three groups of researchers raise concerns over the findings, questioning the study's reliability, legality and financial implications.
K. L. Heong, from the International Rice Research Institute in the Philippines, and colleagues say farmers might have been using less pesticide for their GM rice crops because they had decided beforehand that they would need fewer chemicals, not because they saw fewer insects.
Farmers tend to spray more insecticide than is needed to ensure all insect pests are wiped out, say Heong's team. Indeed, other research has shown that pesticide use can be reduced without reducing yields, and without the need for GM rice (see Bangladeshi farmers banish insecticides).
Also writing in Science, Pang Cheung Sze and Janet Cotter of Greenpeace China, point out that it is still illegal to grow and sell GM rice in China, but that at least one of the varieties in Huang's study was found in Chinese markets earlier this year.
Finally, David Cleveland and Daniela Soleri of the University of California at Santa Barbara, United States, express concerns that the Huang's team did not discuss the costs of genetically modifying rice. "One estimate of the cost to develop a GM variety is 50 times that of a conventional variety," they write.
They note that there are cheaper ways to reduce plant disease and boost yields, such as growing more than one crop in a field.
Huang and colleagues have responded to all three concerns.
They say that although pesticide use could be reduced for conventional crops, the reduction would still only be a quarter of that achievable with GM rice.
They maintain that contrary to Greenpeace China's allegations, the GM strain they used had been approved by the Chinese government's biosafety committee.
Finally, they agree with Cleveland and Soleri that China needs other methods alongside GM crops to tackle hunger and poverty.
However, they say their study's purpose was to look at one aspect of GM crops, without providing an overall assessment of the advantages and disadvantages of commercialising them.