Insects thrive on GM Bt pest-killing crops

Independent on Sunday (London)
March 30, 2003

By Geoffrey Lean, Environment Editor

Genetically modified crops specially engineered to kill pests in fact nourish them, startling new research has revealed. The research - which has taken even the most ardent opponents of GM crops by surprise - radically undermines one of the key benefits claimed for them. And it suggests that they may be an even greater threat to organic farming than has been envisaged. It strikes at the heart of one of the main lines of current genetic engineering in agriculture: breeding crops that come equipped with their own pesticide.

Drawbacks have already emerged, with pests becoming resistant to the toxin. Environmentalists say that resistance develops all the faster because the insects are constantly exposed to it in the plants, rather than being subject to occasional spraying.

But the new research - by scientists at Imperial College London and the Universidad Simon Rodrigues in Caracas, Venezuela - adds an alarming new twist, suggesting that pests can actually use the poison as a food and that the crops, rather than automatically controlling them, can actually help them to thrive.

They fed resistant larvae of the diamondback moth - an increasingly troublesome pest in the southern US and in the tropics - on normal cabbage leaves and ones that had been treated with a Bt toxin. The larvae eating the treated leaves grew much faster and bigger - with a 56 per cent higher growth rate.