A mix of favourable conditions and extensive plantings of susceptible varieties are the key reasons growers may be experiencing unprecedented levels of powdery mildew on wheat, according to Centre for Crop and Disease Management (CCDM) researchers.
Fran Lopez-Ruiz, Fungicide Resistance Group leader of the co-funded Grains Research and Development Corporation (GRDC) and Curtin University centre, also said the difficulties experienced by growers in controlling the disease were unlikely to be the result of fungicide resistance at this time.
“We are currently experiencing perfect seasonal conditions for disease outbreaks,” he said.
“The recent cold weather, paired with humid conditions in thick crop canopies, has seen powdery mildew thrive in wheat paddocks throughout the State’s central and northern grainbelt.”
Dr Lopez-Ruiz said that in some cases where the crops were not so advanced, a second application of fungicide might be effective, but growers should always use the recommended label dose rate.
“Always opt for a fungicide mixture where possible, such as a DMI (DeMethylation Inhibitor) and QoI (strobilurin) fungicide mixture to help prevent the development of fungicide resistance,” he said.
“If this is not available, then mixtures containing different DMI fungicides are always better than just using a solo product,” he said.
Dr Lopez-Ruiz said the CCDM conducted genetic tests on disease samples submitted by growers and advisers to determine if there were any unusual changes within disease populations.
He said none of the samples submitted so far from different areas in the State had mutations responsible for fungicide resistance.
“The methodologies developed by our research group allow us to stay on top of any fungicide resistant disease populations and help growers act quickly before a disease can get out of hand,” Dr Lopez-Ruiz said.
“So far, we have not seen any signs of resistance development in wheat powdery mildew.
“However, as we saw in barley powdery mildew in 2009 and given that wheat and barley powdery mildews are very close genetically, it is highly possible that mutations endowing fungicide resistance could quickly occur in wheat powdery mildew under the right pressures.
“Growers therefore need to be mindful of how they use fungicides, and stick to integrated disease management strategies that do not depend solely on fungicides.
“Pressures that encourage the development of fungicide resistance arise from excessive and repeated use of chemistry from the same mode of action over an extended period of time.”
Dr Lopez-Ruiz encouraged growers who suspected fungicide resistance issues, to contact CCDM’s Fungicide Resistance Group for testing and advice click here.
He said that to avoid wheat powdery mildew in future growers should:
- Use fungicide mixtures that contain different modes of action including cyproconazole and azoxystrobin; epoxiconazole and azoxystrobin; and epoxiconazole and pyraclostrobin
- Always spray fungicides at the first sight of symptoms and control the disease as early as practical
- Always use recommended fungicide label rates
- Rotate wheat crops with non-host crops such as canola, barley or legumes
- Keep crops healthy, but avoid over application of nitrogen. Excess nitrogen levels contribute to the development of mildew
The CCDM was set up at Curtin University in 2014 to conduct cutting-edge crop disease research into genetics, breeding and fungicides, and to improve agronomy and farm management practices.
The GRDC has committed $30 million over five years to the $100 million CCDM as part of its long-term bilateral agreement with Curtin University signed in April 2014. Discoveries and innovations from the centre are expected to be delivering savings of $400 million a year to the grains industry by 2020.
Fran Lopez-Ruiz, CCDM
08 9266 3061,
Megan Meates, CCDM
08 9266 4818, 0437 538 541
Natalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827
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