Crops genetically modified with the Bt bacteria could be an effective way of controlling pests and maximizing the country's harvests in the coming years, a report by a group of Chinese researchers has shown.

The report, to be published in the academic journal Science on Friday, is based on a 10-year study led by Wu Kongming from the Chinese Academy of Agricultural Sciences.

The country started commercial use of the Bt bacteria on cotton plantations in 1997.

Bt is used as an insecticide derived from the spores and toxic crystals of the bacteria Bacillus thuringiensis. Sold since 1960, it is considered to be non-toxic to humans, animals, fish, plants, micro organisms and most insects. It is also said to be safe for groundwater because it degrades rapidly.

Wu and his colleagues analyzed data from 1997 to 2007 on the use of Bt on cotton farming in six of the country's northern province. Their research covered 38 million hectares of farmland cultivated by 10 million farmers.

The researchers then compared the information with data on pest populations in the region, focusing on the cotton bollworm, a serious pest to Chinese farmers.

Also known as the corn earworm or tomato grub, the cotton bollworm ranks as one of the world's most polyphagous and widespread pests, reportedly causing an annual damage of US$5 billion globally.

The bug is resistant to nearly every class of chemical pesticide so far except Bt, which can be developed as an insecticide through genetic modification.

The research by Wu and his colleagues showed that populations of the cotton bollworm were dramatically reduced with the introduction of cotton applied with Bt, especially during the period from 2002 to 2006.

They considered 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 crop and a host of other unmodified crops, after a decade.

"Cotton bollworms like to lay eggs in the flower buds of host crops, with cotton being their favorite they have no idea that the cotton will soon kill them all with the toxin expressed by Bt," Wu said.

Bt technology will give China a new tool for pest control and all farmers using it can experience the benefits, the researcher added.

Its successful application could be used throughout the country to benefit the agricultural sector, Wu said.

"The results are easily transferable to food crops since the type of pest damage they would sustain would be the same," he said.

(China Daily September 19, 2008)