Australia should be looking to Canada, not the United States, as a model for management of genetically modified (GM) crops if it wants to avoid increa

Warning on GM herbicide resistance
MATTHEW CAWOOD
10/04/2008 11:08:00 AM
Australia should be looking to Canada, not the United States, as a model for management of genetically modified (GM) crops if it wants to avoid increased herbicide resistance in weeds, a herbicide expert says.

Dr Chris Preston of the Cooperative Research Centre for Australian Weed Management (Weeds CRC) notes that farmers will also have to manage their paddocks to work around the longevity of canola seed, which a recent Swedish study discovered to be viable in the soil for up to 10 years.

This winter will see the beginning of the end for the long GM debate, with 180 growers in Victoria and NSW becoming the first to experience Monsanto’s Roundup Ready technology in a limited GM canola sowing of 50-150 hectares each.

(Bayer CropScience’s InVigor canola, engineered for resistance to glufosinate, won’t be ready for release in 2008.)

Dr Preston said that of all the dangers attributed to GM crops, herbicide resistance is the problem most likely to materialise if GM varieties with the same traits are over-used.

He says this as the case in the US, where Roundup Ready varieties account for 91 per cent of US soybean sowings, 70 per cent of cotton and 52 per cent of corn plantings.

As a result, glyphosate resistance has appeared in eight US crop weed species, including pigweed, one of the country’s main weed families.

By contrast, Dr Preston said, across the border in Canada farmers have been rotating between GM varieties engineered for resistance to three different herbicide families, only one of them glyphosate.

By rotating their GM crops according to herbicide category, Dr Preston said, the Canadians have avoided increasing herbicide resistance under GM cropping systems over the 12 years that herbicide-resistant GM crops have been used there.

Monsanto spokesperson Anna Hall said that all growers wanting to sow GM canola must undergo an accreditation process that has avoidance of herbicide resistance as a key objective.

About 400 agronomists and farmers have already undertaken the accreditation, despite the limited availability of seed for 2008.

Australian farmers will also need to manage for the longevity of canola seeds, which will have implications for successive crops.

A Swedish study has found viable GM canola seed persisted for up to 10 years under European conditions, but Dr Preston said Australian research had found canola seed persisted only for 3.5 years under local conditions.

This still presents challenges for farmers wanting to switch in and out of the GM/non-GM markets by sowing alternate crops, Dr Preston said.

If a farmer wants to sow non-GM canola following a GM canola crop, they will need to wait up to four years to be assured of not getting GM contamination.