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Protect Barley Crops From Powdery Mildew

11 August 2011

AUSTRALIA - Western Australian barley growers are urged to monitor crops now for signs of powdery mildew and apply effective fungicide protection. The advice comes following reports that barley crops, particularly the susceptible variety Baudin, are being significantly affected by powdery mildew in parts of the grainbelt.

Professor Richard Oliver, from the Grains Research and Development Corporation (GRDC) supported Australian Centre for Necrotrophic Fungal Pathogens (ACNFP), said barley crops in the Esperance region, parts of the Great Southern, Corrigin and as far north as Jurien Bay were affected by powdery mildew.

Professor Oliver said the high disease levels had been caused by weather conditions, farmers growing barley varieties susceptible to powdery mildew, and the disease having developed resistance to triazole fungicides.

Professor Oliver said growers should use newer fungicides to protect their crops because it appeared that powdery mildew across the entire WA grainbelt had now developed resistance to the older triazole group of fungicides.

“Spraying an old triazole fungicide such as propiconazole, tebuconazole or flutriafol will have no impact on the disease and may even increase the chance of resistance developing in newer fungicides,” he said.

“However, newer products including Prosaro®, Opus®, Opera® and Amistar Xtra® are performing reasonably well.

“All these products are more effective when used to protect crops than to eradicate disease, so growers cannot be expected to clean up crops which are already infected.


ACNFP director Professor Richard Oliver.

“But these products applied to uninfected crops will provide protection for up to five weeks.

“If you don’t spray you could have yield losses of about 25 per cent and downgraded grain quality.”

Professor Oliver said that with large populations of the powdery mildew pathogen present in the grainbelt, the risk of resistance developing to the four remaining effective fungicides was relatively high.

“Growers should be vigilant for cases of failure of these fungicides and report them to us,” he said.

“Fungicides should always be used according to label instructions and in cases of severe disease pressure, full rates should be used.

“Growers should also avoid applying too much nitrogen as powdery mildew thrives on overfed crops.”

Professor Oliver said that to minimise the risk of powdery mildew damaging barley crops next season, growers should avoid growing varieties susceptible to the disease, and use recommended newer fungicides.

 

TheCropSite News Desk



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