Growers not applying scientific approach to ryegrass war

WAHRI Graduate Research Officer Mechelle Owen, pictured at UWA with ryegrass plants being tested for resistance in a GRDC-suppurted research project.

HOW TO gauge the scope and scale of a problem Testing is, a good step in the right direction. Yet herbicide-resistance testing remains an under-used tool by WA graingrowers.

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

Surprised that WA 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 GRDC supported WA Herbicide Resistance Initiative (WAHRI), Ms Gillam surveyed 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 predict accurately 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.

Varying test results

Past WAHRI research, conducted by Mechelle Owen, confirmed some variability in the results produced by seed testing services in different states.

Mr Llewellyn said the establishment of a reliable local WA testing service should help farmers make the most of resistance testing as a management tool.

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Contact: Mr Rick Llewellyn, UWA 0893803419