Australia
August 12, 2010
Barley growers are urged to use newer fungicides for disease control following confirmation of triazole resistance in the damaging barley disease – powdery mildew.
The resistant strain, identified by Grains Research and Development Corporation (GRDC) research, is Australia’s first confirmed case of a broadacre crop pathogen resistant to fungicide.
The resistant strain of the barley powdery mildew pathogen – Blumeria graminis hordei (Bgh) – came from Western Australia’s Great Southern region.
Barley powdery mildew causes annual losses of $39 million to Australia’s barley crops, with most losses incurred in WA.
GRDC western panel deputy chairman and Australian Research Centre for Necrotrophic Fungal Pathogens (ACNFP) director, Richard Oliver (photo), said the resistant pathogen was one of a number of strains found to be significantly less sensitive in laboratory tests to tebuconazole.
Tebuconazole is from the triazole group of fungicides and is the active ingredient in Folicur®. Cross resistance to triadimefon, propiconazole and flutriafol fungicides is also very likely.
“One of the resistant strains was analysed by DNA sequencing and a genetic mutation associated with strong resistance to triazole fungicides was found,” Professor Oliver said.
“This is the first time triazole resistance has been confirmed in Australia, and the country’s first confirmed case of fungicide resistance in broadacre crop pathogens.”
Professor Oliver said the discovery is not surprising given the widespread use of triazoles in Australia.
“Similar genetic mutations in pathogens are frequent in Europe and, according to some barley growers in WA’s southern grainbelt, the performance of the older triazole fungicides against powdery mildew has been disappointing in recent years,” he said.
Professor Oliver said WA growers who have planted barley varieties susceptible to barley powdery mildew in areas commonly affected by the disease may expect poor levels of disease control with some commonly used triazole fungicides.
“It is not yet known how widespread the resistant strains are,” he said.
“Growers must take steps to protect barley crops from barley powdery mildew and help limit the spread of resistant barley powdery mildew strains.”
These steps include:
- Considering the use 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).
- Minimising the number of triazole applications in a season, particularly fungicides with poor performance, to prevent the spread of resistant barley powdery mildew strains.
- If possible, avoid sowing barley varieties susceptible to barley powdery mildew in coming seasons.
Professor Oliver invites growers with suspected cases of fungicide resistance in their crops to contact him on 0414 305 999.
The GRDC recently recontracted research work with the ACNFP, led by Professor Oliver, with the Curtin University of Technology.
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