Cropwatch and Network of Concerned Farmers member Jessica Harrison will test GM canola roadside plants and crops in the Wimmera for GM contamination after the coming GM canola harvest.

Ms Harrison was in the Wimmera yesterday to alert Wimmera growers to the availability of a GM test kit.

Speaking from near the Lubeck silo, a GM canola receival point, Ms Harrison said she was worried about GM crop contamination.

The Lubeck silo will receive GM canola and conventional crops but no conventional canola.

Ms Harrison said she was worried spills during GM crop transit could spread GM canola.

"What's spilt in this harvest could easily come up in the next year," Ms Harrison said.

"All they need is a little bit of rain and next year's roadside could be a GM crop."

Ms Harrison said American and Canadian farmers used a test kit to verify crops were GM free.

She said the test kit could determine GM presence through the seed or leaf of a canola plant.

She said testing plant material involved macerating the plant material and placing a sensitive testing trip into the matter.

If a Roundup Ready crop was detected the crop indicated two lines and if a Roundup Ready crop was not detected the strip showed one line.

She said the sensitive strips cost $8 each and could be purchased online in lots of 100.

"In the future farmers might have to prove crops are GM free," she said.

"That's the problem with GM, if it is windy like today the seed will spread."

Ms Harrison said it was important trucks transferring GM canola to receival points were water-tight.

She said if a truck could not hold water, without leaks, there was a chance canola could spill onto roadsides.

She said signs of GM contamination included plants that survived Roundup application.

"It is a worrying time for farmers who want to stay GM free and get the premium price for Australian canola," she said.

"As someone who's buying food, I've never demanded GM."