Australia
May 13, 2013
Monitoring of all Western Australian barley crops for powdery mildew disease and careful fungicidal management including the use of seed dressings will reduce the risk of yield losses this season, with commonly grown varieties found to have an increased susceptibility to the disease.
Recent rainfall could favour the development of powdery mildew, which has already been observed in barley regrowth at a number of sites across barley growing regions in WA’s central and southern grain growing regions.
Australian Centre for Necrotrophic Fungal Pathogens (ACNFP) investigator Simon Ellwood said producers who were growing barley in areas prone to powdery mildew should not rely on previous years’ resistance levels being present.
“If 2013 is wet, growers will need to monitor all barley crops closely for changes in mildew response, particularly those rated moderately resistant to moderately susceptible,” he said.
“In 2012, with support from the Grains Research and Development Corporation (GRDC), we extensively sampled powdery mildew isolates from disease prone regions of WA and found that virulence exists against the bulk of major resistance genes in WA barley cultivars.
“This means that at some stage in the future, more of the mildew could infect varieties carrying those genes.
“The research found that virulent powdery mildew isolates exist to the commonly grown varieties Buloke (rated moderately resistant) and Yagan (moderately resistant to moderately susceptible).
“These isolates were not widespread, but these varieties have a greater risk of infection than previously thought.
“The ACNFP found that only Dash and Oxford remain fully resistant, along with newly introduced varieties that contain the durable resistance gene mlo (Grange , Henley and Westminster ) and are awaiting Barley Australia Classification.”
Department of Agriculture and Food (DAFWA) plant pathologist Kith Jayasena said he had observed powdery mildew and leaf rust on regrowth of susceptible barley varieties in the South Stirlings in recent weeks, and there had also been reports of powdery mildew at other sites.
“Spore traps in the South Stirlings have also shown that reasonable levels of spores are present for these diseases,” he said.
Dr Jayasena said growers should monitor barley regrowth and emerging crops; select barley varieties with levels of resistance; and use fungicide seed dressings when growing very susceptible to susceptible varieties in high risk environments.
“Use protective fluquinconazole-based seed dressings such as Jockey®, Stayer®, CropCare Jockey® and Maxiflo®,” he said.
Dr Jayasena said growers selecting foliar fungicides should avoid using compromised triazoles (DMI).
Several triazole products were still highly effective and products containing strobilurin were also effective.
In addition, a permit has been issued in WA for the use of Prosper 500 EC, containing the active ingredient spiroxamine, for the control of powdery mildew in barley.
Where powdery mildew occurs, samples should be sent to the ACNFP for testing (contact Dr Ellwood at srellwood@gmail.com).
More information is available in the GRDC Barley Powdery Mildew Fact Sheet at www.grdc.com.au/GRDC-FS-BarleyPowderyMildew or in a DAFWA AgMemo and fact sheet at www.agric.wa.gov.au/PC_95575.html
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