Thursday, August 26, 1999 Published at 08:26 GMT 09:26 UK
'GM crop can help environment'
A wasp lays its eggs in moth larvae - and seems impervious to GM effects (Photo IACR-Rothamsted)
By Environment Correspondent Alex Kirby
Some crops which have been genetically-modified (GM) to produce pesticides may have an "environmental advantage" over sprays, because they do not harm useful insects, according to UK researchers.
Nor did the crop prevent the parasitic wasp finding the moth's larvae.
The scientists conclude that the GM rape, which allows the wasps to continue killing the moths, may therefore be better for the environment than insecticide sprays, which kill both the moths and the wasps.
The IACR researchers, led by Dr Guy Poppy, believe their work shows that the behaviour of non-target insects can be as important as toxicity in determining the impact of GM plants.
The new evidence is published in the science journal Nature.
The laboratory-based experiment involved GM oilseed rape, the diamondback moth (Plutella xylostella) that damages the crop, and the parasitic wasp (Cotesia plutellae), which kills the moths' caterpillars by laying its eggs in them.
The rape was modified to produce the same Bt (Bacillus thuringiensis) toxin used in the Cornell study. The diamondback moth has gained notoriety for being the first insect pest to evolve resistance to Bt sprays in the field.
The authors say: "The presence of Bt toxin had no direct effect on wasp survival."
The parasitic wasps only find their host moths thanks to a chemical "alarm bell" released by the plant when its leaves are damaged. So in another experiment the team used a wind tunnel to see if the wasps would make a distinction between Bt rape and wild rape.
Overall, when the damage to the two sorts of rape was equivalent, the wasps showed no significant preference for either sort of leaf.
"Our results highlight the need to consider behavioural as well as toxicological aspects when looking at possible side effects of transgenic crops on non-target organisms."
The UK Government's official wildlife advisory body English Nature, which has raised concerns about GM technology, welcomed the research. "I think it is a very interested piece of research because it gives us pointers to the sorts of things that we need to take outside from these laboratory trials into the filed trials," says Chief executive Dr Keith Duff.
"It is only by looking in the field that we will really see what the effect of these modifications is on wildlife."