By Matthew Cawood
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.


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