Mrs Marshall said that contaminated canola seed had fallen from trucks alongside the Riverina Highway where she lived, leading to an issue with GM canola volunteers this season.

She began testing canola volunteers for the presence of GM after noticing the plants.

"The tests have proved these are GM canola volunteers," she said.

Mrs Marshall said first-hand from Canadian farmers their experiences since the introduction of GM had been a sobering account on the removal of choice.

"We wish to market our canola as GM-free, as that is what the market wants, and I object to have that right taken away," she said.

"They say GM is supposed to be about choice, so what about our choice to stay GM-free?"

Mrs Marshall said she had grave concerns about increasing corporate control into farming.

"By agreeing to the GM licensing agreement, you give Monsanto the right to come onto your farm whenever they like and to dictate the herbicide regime farmers will use.

"It is effectively like losing control of your land – and that loss of control was one of the big messages I got from the Canadian farmers."

Mrs Marshall stressed she was not against the technology per se, rather the way it was being used to infiltrate Australian agriculture without any protection for GM-free farmers.

"I am not an activist; this is about the GM industry taking responsibility for the control of their patent seed."

She claimed the usefulness of the Roundup Ready canola has yet to be publicly demonstrated and said it possessed neither a yield advantage nor a strong agronomic benefit.

"In the dry seasons we are having, the advantages of an early glyphosate application aren’t that significant.

"I think the costs of the technology will outweigh any of the so-called benefits."

And she is positive the decision to embrace GM will hurt Australian growers at the marketplace.

The pro- and anti-GM lobbies have argued furiously over the implication of growing GM on marketing, but Mrs Marshall said her research indicated it would cut down on market access for Australian growers, both at home and internationally.

In relation to the volunteer weeds, Mrs Marshall said they would soon be past the stage where they could be effectively controlled with herbicide and needed to be removed shortly before their seeds matured.

She called on the state minister to ensure the eradication of these GM plants.