ABOUT 120 Queensland and NSW sorghum growers will head into court-ordered mediation in Brisbane next week, seeking compensation for their farm businesses affected by the weed shattercane.
If a settlement cannot be reached during the formal talks on December 17 and 18, the growers are set to appear in court at the end of March for up to four weeks.
Advanta Seeds spokesman Barry Croker said the company and its legal team was "vigorously" defending against the allegations, "none of which have been proven".
Growers claim MR43 Elite seed supplied by Advanta Seeds (formerly Pacific Seeds) and planted in 2010 was contaminated with the pernicious weed seed.
Advanta, an Indian-owned company that supplies up to 80 per cent of the sorghum seed planted in Australia, is defending the claims on a range of grounds.
"In following court protocol, we cannot speculate on the evidence to be presented as part of the action, nor an outcome, but we're confident in our stance," Mr Croker said.
"We maintain confidence in our stringent quality controls and the consistent application of these across our seed breeding and supply practices."
Quirindi grower Bernie Perkins, part of the class action along with brother Kevin, said the weed had prevented the farm from being able to exclusively produce summer crops.
"The introduction of shattercane in 2010 meant we were forced to start growing winter crops in an attempt to control the weed, which made our operation less productive."
Mr Perkins said it was not until February 2012 they picked up the shattercane problem.
"We thought it was just sorghum talls in the crop," Mr Perkins said.
"Advanta did not warn there was a problem in 2011 and, because of that, the in-paddock weed seed population was allowed to develop in the subsequent crop.
"It's a problem we're still dealing with today."
Toowoomba-based solicitor Dan Creevey from Creevey and Russell Lawyers, who is representing the growers, said it was not too late for other farmers to join the class action.
"Under Australian law, people are eligible to be part of a class action unless they opt out," Mr Creevey said.
It is understood up to 400 growers could have farms affected by shattercane.
About 70 growers are thought to have already opted out of the class action.
In addition to being expensive to control, growers argue shattercane has stopped them from growing optimally profitable sorghum in crop rotations.
They say it out-competes sorghum and, as a grass similar to sorghum, is impossible to control in growing crops.