MONSANTO has dismissed reports of genetically modified canola contamination along the Riverina Highway near Berrigan.

Monsanto spokeswoman Honi McNaughton said a few plants found outside a paddock "did not equate to "rogue weeds or contamination" but was a normal, agriculture occurrence.

This followed claims by Berrigan farmer Gai Marshall that GM canola weeds were found on the highway near her farm.

She said tests showed the weeds were GM.

She called on the Road Traffic Authority to clean up the weeds and prevent contamination to her canola crops.

She said the seeds must have escaped from a truck as no neighbours grew GM canola.