Letter: GM hysteria

Sir: Your report on the effects on Monarch butterflies of Bt toxin from GM maize (20 May) failed to mention a twist in the tale. Because Bt toxin is derived from a soil bacterium, Bacillus thuringiensis, it is regarded as a "natural product" and widely applied as an insecticide by organic farmers, who use commercially available spray or dust preparations.

Of course it would be ludicrous to use this fact to call for a five-year moratorium on organic farming, but this is the logic that Friends of the Earth are applying when they call for a five-year ban on GM crops.

GM crops, like all other issues in agriculture, need to be carefully considered on a case-by-case basis, and not be subject to a blanket ban.

The reason that populations of Monarch butterflies have been declining is because their over-wintering habitat in Mexico is being destroyed by deforestation. One way to reduce the pressure that the demand for land for crops is placing on our remaining natural environment is to improve yields from existing agricultural land. Application of GM technology to improvements in agricultural efficiency, and reduced dependence on chemicals, thus have the clear potential to reduce environmental damage. It would be more valuable for environmental groups to be campaigning for GM technology to be applied in such beneficial ways, rather spreading needless public alarm by the calling for poorly thought-out bans and moratoria.

Dr SEAN MUNRO

Cambridge