New Delhi: At a time when several counties across the world, including India, are looking towards adopting genetically modified (GM) crops to ensure food safety by lowering use of harmful pesticides, a latest study has revealed that there is a “surge in insect resistance to transgenic crops".

The study done by researchers at US-based University of Arizona was published in the journal Nature Biotechnology on Tuesday.

The study is significant for India as the government is contemplating large-scale adoption of GM crops, including food crops for ensuring food safety of its 1.2 billion population. India, however, is also witnessing strong resistance against commercialisation of GM crops.

The researchers analysed published data for 36 cases representing responses of 15 pest species in 10 countries on every continent except Antarctica. They discovered resistance that substantially reduced the efficacy of the Bt crops in the field in 16 cases as of 2016, compared with only three such cases by 2005.

“In these 16 cases, pests evolved resistance in an average time of just over five years," the study said.

In the study, the researchers looked into concerns that “why pests adapted quickly in some cases but not others".

“When Bt crops were first introduced in 1996, no one knew how quickly the pests would adapt. Now we have a cumulative total of over two billion acres of these crops planted during the past two decades and extensive monitoring data, so we can build a scientific understanding of how fast the pests evolve resistance and why," said Bruce E. Tabashnik, who is head of the Department of Entomology of university of Arizona.

“A silver lining is that in 17 other cases, pests have not evolved resistance to Bt crops. Some crops continue to remain effective after 20 years," he added.

The study highlighted that, in 2016, farmers worldwide planted more than 240 million acres (98 million hectares) of genetically modified corn, cotton and soybeans that produce insect-killing proteins. These Bt proteins kill some voracious caterpillar and beetle pests, but are harmless to people and considered environmentally friendly.

“While organic farmers have used Bt proteins in sprays successfully for more than half a century, some scientists feared that widespread use of Bt proteins in genetically engineered crops would spur rapid evolution of resistance in pests," it added.

Bt cotton, which in 2002 received regulatory approval for commercial cultivation, helped India turn from a net importer to a large exporter, but pest attacks have been frequent in recent years.

In March last year, India’s agriculture ministry slashed royalty fees payable to technology developers on grounds that Bt cotton’s ability to resist pink bollworm pests have declined over the years.

Since last month several farmers have died in Maharashtra’s Yavatmal district after they inhaled poisonous pesticide fog sprayed on Bt cotton plots to control a surge in pest attacks.

In India, at present, only GM cotton is allowed for commercial production. But there has been a fierce debate around GM mustard food crop which has received all regulatory approvals but is waiting for a final nod from India’s environment ministry.

There is among strong opposition from environmentalists who feel GM crops are harmful to environment and human health. A case regarding the issue is pending in the Supreme court of India.

If GM mustard is allowed it will become India’s first transgenic food crop. Few years ago, Bt Brinjal also got regulatory approval, but was stalked after countrywide protests.