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In a season critical for barley powdery mildew control, Western Australian growers are urged to report cases of the disease on varieties rated moderately susceptible (MS) or better, and where cultivars have been sprayed with fungicides that have so far remained effective.

Barley powdery mildew

Professor Richard Oliver, from the Grains Research and Development Corporation (GRDC) supported Australian Centre for Necrotrophic Fungal Pathogens (ACNFP), said the vigilance of growers would help determine whether powdery mildew would be brought under control in the next couple of seasons.

“Barley powdery mildew caused productivity losses of up to $100 million in WA last year,” he said.

“Two factors combined to produce this perfect storm – the use of very susceptible varieties such as Baudin on the majority of the area planted to barley, and the failure of tebuconazole and triadimefon-based fungicides to control mutant strains of the fungus.”

Professor Oliver said the area planted to barley cultivars with good levels of resistance was expected to be much higher this season and new cultivars with genetic resistance would soon to be released.

“While this will undoubtedly reduce disease losses, the larger area planted to resistant varieties increases the chance that the powdery mildew population will evolve to overcome their resistance genes,” he said.

Professor Oliver said GRDC-supported trials over the last three years indicated that 100 per cent of the WA powdery mildew population had evolved resistance to the DMI fungicides tebuconazole (including Folicur® and Hornet®) and triadimefon (including Triad® and Slingshot®), but other DMIs remained effective.

“However, research from Europe indicates that resistance to the newer DMIs is acquired with a combination of mutations, on top on the ones we have already detected,” he said.

“The presence of the mutant powdery mildew populations in WA therefore threatens the efficacy of the newer DMIs.

“New fungicides are being trialled but may be some years away from on-farm use.”

Professor Oliver said the ACNFP was concerned that the powdery mildew population in WA could evolve virulence on barley cultivars with levels of resistance, and that the pathogen could evolve resistance to DMI fungicides that had so far remained effective.

“To guard against these scenarios, we need up to date information on the spread of the disease,” he said.

“We are therefore asking growers to report to us cases of powdery mildew on the following barley cultivars: Buloke, Barque, Capstan, Dash, Fleet, Oxford, Scope and Yagan.

“We are also asking for reports of powdery mildew disease on any cultivars that were sprayed prior to noticeable disease levels with the following fungicides: Opus®, Opera®, Amistar Xtra®, Tilt Xtra®, Prosaro®.

Growers can contact the ACNFP at Curtin University via e-mail on Richard.oliver@curtin.edu.au or phone (08) 9266 7872.

The ACNFP will then arrange to collect the pathogen and analyse samples for fungicide resistance and pathotype.

In recognition of the problem posed by barley powdery mildew to growers, the GRDC is planning additional research investments including trials of new fungicides.

ENDS

GRDC project code: CUR00015, CUR00016

Media releases can be found at www.grdc.com.au/media

Contact: Natalie Lee
Cox Inall Communications
08 9864 2034; 0427 189 827