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Choosing resistant barley varieties is vital

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Barley powdery mildew has fired a shot across the bows of the grains industry, warning growers, breeders and chemical companies to change their ways or face potential resistance issues.

Almost 100 per cent of barley powdery mildew tested in Western Australia across the past three years has been found to be resistant to commonly used fungicides.

The research has been conducted by the Australian Research Centre for Necrotrophic Fungal Pathogens (ACNFP) and funded by the Grains Research and Development Corporation (GRDC).

ACNFP director and GRDC western panel deputy chairman Richard Oliver will be presenting the results at next month’s 2011 Agribusiness Crop Updates, which are coordinated by the Grains Industry Association of Western Australia (GIWA) on behalf of the WA Department of Agriculture and Food (DAFWA) and the GRDC.

Professor Oliver says growers planning their 2011 barley crop should take note and very carefully consider what varieties to plant.

“Barley powdery mildew costs growers in WA around $39 million a year in lost yield, particularly in the medium to high rainfall zones which experience high humidity,” Professor Oliver said.

“The fungus has abundant wind-borne spores, so all you need is the right conditions to be affected.

“Unfortunately, most of the malt barley and many feed grade varieties available are susceptible, which has created a lot of pressure in disease prone areas.

“Many growers have used fungicides with the same mode of action several times a year, including seed treatments – a perfect recipe for the situation we’re now facing.”

Using genetic testing, Professor Oliver’s team has found mutations in the barley powdery mildew collected over the past three years that make it resistant to fungicides, including tebuconazole and propiconazole – the active ingredients in Folicur and Tilt respectively.

Triadimefon has also been compromised, while there is suspicion over fluquinconazole (in Jockey) as well.

Professor Oliver says growers in mildew prone areas should avoid susceptible varieties, using the varieties guide put out every year to review their options.

It is also critical to eliminate barley volunteers prior to sowing to reduce the early disease pressure.

Growers should also avoid the use of compromised fungicides in favour of newer triazole fungicides and fungicides with alternative modes of action. These include Amistar Xtra (a mixture of triazole and azoxystrobin); Prosaro (including prothioconazole); and Opus (epoxiconazole).

“2010 was a tough year for barley and its diseases, so chances are only the toughest – and likely resistant – strains of the fungus have survived,” Professor Oliver said.

“We can deal with the issue by changing our fungicides resistance management practices, and longer term looking for new disease resistance varieties, not just for barley and powdery mildew but right across the grains industry.”

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