How GM can bring cash benefits to non-GM crops

A new study has shown for the first time that farmers can save money on traditional crops grown near GM fields thanks to the knock-on effects of resistance to pests. The US research is the first time such a cash saving has been demonstrated.

Researchers studied crops in five different US states, where about two-thirds of the maize crop is now grown from genetically modified stock. The plants are resistant to the European corn borer, a widespread maize pest in the US.

The GM plants have been modified in the lab so that they contain a gene taken from the bacterium Bacillus thuringiensis (Bt). The gene creates a toxin within the plants' leaves that kills corn borers.

Farmers are legally required to grow a quota of non-GM crop alongside their pest-resistant strains, in the hope that it will stop the insects from developing, through natural selection, resistance to the toxin contained in the Bt variety. And it was these conventional crops which formed the basis of the new study.

It's not the first time scientists have documented these knock-on benefits. The decline in the corn borer population effected by the Bt variety also benefits the nearby conventional crops: fewer corn borers is good news for all maize plants, GM or not.

What is new in the latest study is the calculation of a cash saving to farmers brought about by the use of GM: and it turns out the biggest saving is actually in neighbouring, non-GM fields.

The study shows that, over 14 years, use of Bt varieties improved profits by about $3.2bn in Illinois, Minnesota and Wisconsin, with $2.4bn of that profit made on conventional crops. This unexpected result is a factor of the relative cheapness of non-GM seed, compared to Bt seed.

But the use of GM crops still remains controversial in the US and around the world. Bill Freese, a US opponent of GM, told the BBC: "Organic farmers use a lot of cultural techniques to combat insects, such as crop rotation, and that's very beneficial."

"But in most of these mid-western farms there is hardly any crop rotation - the most you might get is corn-soy-corn - so these cultural methods are being forgotten, and I think that's a shame." ·