Western Australian growers are encouraged to carefully check wheat crops for signs of powdery mildew following initial reports of the disease this season.
Until 2015, wheat powdery mildew had not caused significant widespread damage to the State’s wheat crops since the late 1990s and early 2000s.
But high levels of summer and autumn rain during 2015, followed by a humid and moist growing season, resulted in the disease persisting and spreading - especially in central, northern and south-eastern grainbelt regions.
A Grains Research and Development Corporation (GRDC) analysis estimates that, in conducive seasons, powdery mildew has the potential to cut yields by up to 0.4 tonnes per hectare in WA.
DAFWA plant pathologist Ciara Beard says 2015 wheat powdery mildew trials found that timely application of foliar fungicide, as soon as possible after the disease is seen moving up the crop canopy, is more important than product choice. Photo by DAFWA.
Department of Agriculture and Food (DAFWA) plant pathologist Ciara Beard said wheat powdery mildew had developed rapidly in recent weeks at a Geraldton trial site and the DAFWA service PestFax had received some reports of wheat powdery mildew from central and northern cropping regions.
Ms Beard, who is leading GRDC-funded wheat powdery mildew trial work, said growers monitoring paddocks should pay special attention to early sown, susceptible varieties; wheat crops grown on wheat stubble, especially where powdery mildew was present last year; and areas where there had been a green bridge carry-over.
“The disease is favoured by moist soil and a humid environment and it is important to check under the crop canopy, as infection often starts on the lower leaves or at the base of the stem,” she said.
“Initial symptoms are fluffy, white powdery growths of fungal spores on the leaf surface.
“Under severe disease pressure, the fluffy, white powdery growth can also affect stems and heads as the season progresses.”
GRDC-supported trials led by DAFWA in 2015 – combined with outcomes from research funded and conducted by Landmark, Imtrade, Liebe Group and Northampton Agri Services – found that timely application of foliar fungicide, as soon as possible after the disease was seen moving up the crop canopy, was more important than product choice.
Under severe disease pressure the white powdery growth of wheat powdery mildew can spread to stems and heads as the season progresses. Photo by Evan Collis Photography.
“A registered fungicide is recommended when the disease is observed moving up the canopy and the outlook is for continuing humid moist conditions and temperatures between 15° and 22°C that favour the disease,” Ms Beard said.
She said a range of fungicide actives, when applied at registered rates on susceptible wheat varieties, reduced disease impact on yield at four out of the six WA field trial sites in 2015.
“Further fungicide trials, led by DAFWA, are taking place throughout the grainbelt this season and are investigating the effectiveness of a wide range of fungicide options,” Ms Beard said.
“Currently no in-furrow or seed dressing fungicides are registered for powdery mildew control in wheat but a wide range of fungicides are registered as in-season foliar sprays.”
Researchers from the Centre for Crop and Disease Management (CCDM) have not yet seen any signs of fungicide resistance in wheat powdery mildew in WA, but have detected the first signs of mutations in NSW and Tasmania which could lead to disease control issues.
Growers who suspect fungicide resistance issues are encouraged to contact CCDM’s Fungicide Resistance Group for testing and advice via email here.
To slow down resistance mutations arising in wheat powdery mildew, growers are advised to be mindful of how they use fungicides and stick to integrated disease management (IDM) strategies that do not depend solely on fungicides – such as using resistant crop varieties, crop rotations and green bridge control.
More information about managing wheat powdery mildew in WA is available in the GRDC Hot Topic Managing powdery mildew in wheat (western region) via this link.
Ciara Beard, DAFWA
08 9956 8504
Natalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827
GRDC Project Code