Herbicide resistance testing remains an under-used tool by Western Australia graingrowers.

A recent study showed that although 60 per cent of growers had used some testing, only 10 per cent of cropping land had ever been tested. 

Surprised that Western Australia growers didn't make greater use of herbicide resistance testing services, University of Western Australia (UWA) Honours graduate Tracy Gillam looked for answers.

In her research project with the Grains Research and Development Corporation (GRDC) funded Western Australia Herbicide Resistance Initiative (WAHRI), Ms Gillam examined grower use of testing and whether there was a need for greater use of testing services.

The study, supported by growers and the Federal Government through the GRDC, involved more than 120 growers in resistance-prone areas and confirmed the potential for more active testing. 

Testing of ryegrass populations found that while most growers were aware if their ryegrass was resistant or not, up to 15 per cent incorrectly perceived that their ryegrass was susceptible to the Group A fop herbicides.

It was also found that, for a number of reasons, it was difficult for growers to accurately predict when resistance would develop. For example, other management strategies used by individual growers could contribute to altering the onset of resistance and the efficacy of herbicides varied.

"Grower knowledge of herbicide use history was not a strong predictor of the development of herbicide resistance, which further highlights a need for growers to use herbicide resistance testing to gain an accurate idea of their resistance status," Ms Gillam explained.

Project supervisor, Rick Llewellyn, said that although several growers were concerned about the reliability of some test results, growers generally did not consider resistance testing to be too costly or time consuming.

Past WAHRI research, conducted by Mechelle Owen, confirmed some variability in the results produced by seed testing services in different states.
 
"The establishment of a reliable local Western Australia testing service should help farmers make the most of resistance testing as a management tool," Mr Llewellyn predicted.