The Organic Agriculture Association is urging dairy farmers to oppose the lifting of a moratorium on genetically modified canola.
The State Government is conducting a review on the moratorium due to be lifted early next year.
The Organic Association’s Robin Grant says once the ban is lifted no-one will be able to stop the G-M crops spreading to non-GM properties.
And she says the invading crops will be resistant to conventional weed killers.
She says evidence of canola spread can be seen along railway lines in Victoria’s cropping belt.
"The amount of canola that is along those railway lines if you go there in October when it’s flowering you’ll just see that they can’t control these crops," she said.
"The agricultural weeds that are on our roadsides now, they just can’t control it, they won’t be able to control it."