India will screen genetically modified (GM) cotton hybrids on sale in the country to identify the varieties that are resistant to whitefly, a pest that recently caused extensive damages to crops in two northern states, a government official said.

The whitefly attack on the Bt cotton variety in Punjab and Haryana was the first major infestation since India adopted transgenic cotton in 2002. It has stoked worries over the vulnerability of the GM seeds that yield nearly all of the cotton in the world's top producer.

The federal agriculture ministry does not want to take any chances as the pest could thrive and affect nearby farms growing vegetables, said P.K. Chakrabarty, an assistant director general of the Indian Council of Agricultural Research.

"Out of the 1,128 hybrids, we have asked to see which have an inherent tolerance to whitefly," Chakrabarty told Reuters on Thursday. "The government will screen the available hybrids and then put up a list. That will sensitise private producers to select suitable hybrids only."

A joint venture of Monsanto with Maharashtra Hybrid Seeds Co Pvt Ltd, Kaveri Seeds and Bayer Bioscience Pvt Ltd are among companies allowed to sell GM cotton hybrids in India. (bit.ly/1QfaRRf)

Bt cotton was tweaked by scientists at Monsanto to produce its own insecticide to kill bollworms. But two years of drought in India have encouraged the spread of whitefly against which the strain has no resistance.

The government now plans to educate farmers to use only those hybrids that are less vulnerable to whitefly, Chakrabarty said. There is no plan, however, to take any punitive action against the seed companies over the pest attacks.