Oilseed rape plants resistant to three or more herbicides are 鈥渘ot uncommon鈥� in Canada, says a report commissioned by English Nature, the UK government鈥檚 advisory body on conservation.
The so-called 鈥榮uperweeds鈥� result from accidental crosses between neighbouring crops that have been genetically modified to resist different herbicides. Farmers are often forced to resort to older stronger herbicides to remove them.
Brian Johnson, at English Nature is alarmed by the speed of the process: 鈥淭his has happened in three or four years,鈥� he says. The report predicts that, in the UK, plants with multiple herbicide resistance will be 鈥渁lmost impossible to prevent unless the crops are very widely dispersed.鈥�
Advertisement
Adrian Bebb, of Friends of the Earth claims the research leaves a stark choice: 鈥淓ither we keep the current separation distances between GM and non-GM crops, in which case contamination and gene stacking looks certain. Or we can have an effective separation distance 鈥� of at least three miles 鈥� in which case GM crops have no commercial future in the UK. There is no third way.鈥�
However, Paul Rylott of biotech company Aventis argues many herbicide tolerant crops are created through conventional breeding, 鈥淕M crops are no different.鈥�
He suggests that crossing between conventional varieties could have the same result. But Johnson notes that resistance bred into plant varieties tends to be much weaker and there is no evidence of 鈥榮uperweeds鈥� having been created in this way.
Multiple resistance
Oil seed rape, or canola, is typically alternated on a two-yearly cycle with a cereal crop such as wheat. Multiple resistant oil seed rape appears as a weed in the following year鈥檚 crop, especially around field margins where seeds spilled during harvest can gather.
The Canadian study found that these plants contained resistance genes from up to three GM varieties 鈥� so-called gene stacking. Farmers were forced to resort to a different and much more persistent herbicide, 2,4-D, to control them.
Multiple resistant 鈥榮uperweeds鈥� would not be capable of taking over the countryside says Johnson. 鈥淭hey would only have an advantage in agricultural fields,鈥� he says. 鈥淏ut agricultural land is very important for biodiversity in Britain.鈥� So widespread use of persistent herbicides to remove the 鈥榮uperweeds鈥� could be disastrous.
The biotechnology industry has admitted being slow to engage in the public debate over GM crops. 鈥淲e haven鈥檛 done a brilliant job in the past of selling the benefits of GM,鈥� says Tony Combes of Monsanto, 鈥淪upport for GM is dependent on people being able to weigh the benefits against their concerns.鈥�
An opinion poll commissioned by the industry and released on Tuesday suggests that two thirds of people feel they do not know enough about GM and that many would be more favourable to the technology if environmental or health benefits could be demonstrated.