Weeds scientists in northern New South Wales (NSW) and Queensland will "piggyback" computer models developed by their counterparts elsewhere in Australia to look at ways of minimising the development and spread of glyphosate resistance.

By adapting models used in southern and Western Australia, they believe they can study the many different patterns of glyphosate use on northern region grain farms and identify options for reducing the resistance risk.

The Grains Research and Development Corporation (GRDC) is negotiating the new project with the same team of scientists that identified sowthistle and summer grasses as the northern region weeds at most risk of developing resistance to group M herbicides (glyphosate).

Team leader, Toowoomba QDPI&F weeds specialist Steve Walker, says glyphosate is an essential herbicide for managing weeds in Australian cropping systems, as it is world wide.

"Loss of glyphosate due to herbicide resistance would have a major impact on the viability and sustainability of conservation cropping systems in Queensland and northern NSW," Dr Walker said.

"Yet the threat of weeds developing glyphosate resistance is very real for conservation cropping in the north, a fact highlighted at the GRDC initiated workshop last year on sustainable glyphosate use.

"In our current research on integrated weed management, our team has been devising and testing on-farm a number of preventive strategies for glyphosate resistance, and we have trials evaluating the effectiveness of components of these strategies in weed control.

"However it¹s not possible to field test these strategies for their potential to reduce the resistance risk over the long term, and the most practical option is to simulate their impact using a model developed specifically for the different cropping systems and weeds of the northern region.

"We plan to adapt models developed to predict the evolution of glyphosate resistance in ryegrass in the broadacre farming systems of southern and Western Australia, and possibly one being developed for use in irrigated cotton."

Dr Walker said the weeds team expected to begin work on the project early in 2005, starting by adapting the most appropriate computer model for key northern weeds ­ nominally barnyard grass and sowthistle ­ for the different cropping systems of Queensland and northern NSW.

After identifying any deficiencies in the model, and generating any necessary additional data with field research, they would simulate the long term impacts of different management strategies on the evolution of glyphosate resistance in northern weeds.

"The project calls for wide communication to the industry of the best management practices we develop, and the model will be a very convincing extension tool to motivate growers and their agronomists to adopt preventive strategies," Dr Walker said.

"It will be able to predict for growers how far they are down the track leading to glyphosate resistance."