GENETICALLY MODIFIED winter oilseed rape cultivation leaves fewer broad-leaved weeds – which are important to many insects and birds – than conventional winter oilseed rape.

This is the conclusion from the Farm Scale Evaluations of GM crop management in the UK, the final results of which were published by the Royal Society on Monday (Mar 21).

“In the GM crop, there was more grass weed, but fewer broad-leaved weeds than in the conventional crop. The significance of this is that broad-leaved weeds are important to farmland wildlife,” said Les Firbank, of the Centre for Ecology and Hydrology in Lancaster, who has been co-ordinator of the FSE trials.

At harvest time, in the GM crop, the amount of broad-leaved flowering weeds and the number of their seeds were one-third of those in the conventional variety.

The trial results also showed that the GM crop areas had half the number of bees and two-thirds the number of butterflies found foraging in the fields with conventional crops.

Bird numbers were not studied, but broad-leaved weeds such as chickweed feature strongly in the diet of farmland birds such as bullfinch, skylark and tree sparrow.

“It is hard to see that this is beneficial for birds,” said David Gibbons, the RSPB”s representative on the scientific steering committee for the trials.

As for grass weeds, three times as many of these and five times as many of their seeds were found in the GM as in the conventional crops.

The reason, according to David Bohan of Rothamstead Research, one of the authors of the paper published by the Royal Society, was “relatively poor control of the grass weeds by late-applied glufosinate-ammonium to the GMHT crops compared with herbicides applied much earlier in the conventional”.

The results for the GM herbicide-tolerant winter-sown oilseed rape were broadly consistent with those for spring rape and sugar beet reported last year.

There were more weeds to provide food and shelter for insects such as butterflies and bees in the conventional crop.

But the researchers were keen to stress that all the differences found in the trials were not a result of the way in which the GM crops have been genetically modified. The differences were all down to the different herbicide regimes used.

The results on winter oilseed rape will now be passed to the Advisory Committee on Releases to the Environment to advise on the environmental implications for commercial growing of the GM oilseed rape involved and the wider implications of the results for sustainable agriculture. There are currently no applications, however, from any biotech company to grow GM winter oilseed rape in the UK or in the EU.

paul.andersen@rbi.co.uk