Weed management's coexistence challenge

GroundCover Live and online, stay up to date with daily grains industry news online, click here to read more

Zero per cent tolerance levels of GM grain in Australian organic crops makes our growers uncompetitive, Nuffield scholar says

Photo of woman

Western Australian grower and Nuffield Scholar Jemma Sadler sees GM varieties having an increasing role in weed management around the world, but notes the need for further education and communication to ensure a workable coexistence with non-GM growers.

PHOTO: Nicole Baxter

Western Australian grower Jemma Sadler describes the 6000-hectare property she farms with her brother and father in Wongan Hills as located within “the herbicide resistance capital of the world”.

In a landscape resistant to Group A and B herbicides, and increasingly to the phenoxy group and Treflan® (trifluralin), the Sadlers employ a range of weed management options for cropping wheat, barley, canola and lupins and running Merino and cross-breed sheep.

“We used to windrow everything and burn it, but for the past two years we’ve used a chaff cart,” Jemma says. “We have the sheep with the pasture phase to achieve full control, and try as much as we can to rotate the new chemicals – Sakura® (pyroxasulfone, a Group K herbicide) and Boxer Gold® (which contains prosulfocarb, a Group J herbicide and active S-metolachlor, Group K).”

Integrated weed management has been one of Jemma’s key interests since she completed a thesis on herbicide-resistant ryegrass as part of her Bachelor of Agricultural Science degree at the University of Western Australia. With GM canola becoming an important weed management tool for growers in New South Wales, Victoria and WA, including for the Sadlers, she is also concerned about the implications for coexistence with neighbours who wish to remain GM free.

These dual concerns of weed management and coexistence were the basis of the Nuffield Scholarship that Jemma completed in 2013. Her travels confirmed to her that Australian growers are world leaders in integrated weed management. But she is now concerned that the zero per cent tolerance levels for the presence of GM grain in organic-certified product in Australia is out of step with other countries and will gradually undermine Australian growers’ competitiveness.

In the European Union the tolerance for the presence of GM grain in most countries is 0.9 per cent, while in the US the emphasis is on the integrity of the production systems: “As long as the producer adheres to the standards of organic production and takes all necessary steps to avoid the presence of GM in their organic produce, any adventitious GM in the end product itself will not affect the farm’s non-GM status.”

For example, Jemma visited a farm in North Dakota, in the US, that produces non-GM soybeans, even though 95 per cent of North Dakota’s soybeans are GM. “Buffer zones of 30 centimetres [in effect, no buffer] are maintained between GM and non-GM soybeans and other GM crops, and strict farm hygiene is adhered to in all farm machinery and storage facilities,” Jemma wrote in her Nuffield report. “For their market there is a 0.1 per cent tolerance to GM contamination in their crops.”

Jemma expects the next big pressure on farming coexistence in Australia to be GM glyphosate-tolerant wheat, and given the dominance of wheat in Australian cropping, this will pose a far greater segregation challenge than canola.

She is also conscious of the risk of over-reliance on glyphosate, particularly having witnessed widespread resistance to this herbicide in the US. From her own family’s experience she says adherence by growers to good stewardship plans will continue to be crucial to limiting herbicide resistance.

In terms of the GM tool, Jemma’s observations of coexistence in other countries have emphasised to her the importance of education about how to use GM crops wisely and to communicate, especially with neighbours.

More information:

Jemma Sadler,
0408 721 029,



Crop roots push deeper after lime


Experiments fine-tune early sowing strategies

GRDC Project Code NUF00010

Region National, West