Powdery Mildew of Barley
Erysiphe graminis f.sp. hordei
Cream to white powdery spores surrounded by a yellow to brown halo mainly on the top of the leaves, sheaths and occasionally on stems an heads. On the underside of the leaf opposite spore masses is a yellow to brown area. The infected area turns a dull grey with a yellow brown margin with age and may have spherical black fruiting bodies. Severely infected plants may be stunted and fail to produce a head.
Biology:More common in humid conditions (85-100% RH) caused by the weather or density of the crop and at temperatures o 15-220C.
More common in high nitrogen conditions.
Survives from one season to the next on Barley residues and green volunteer Barley and Barley Grass.
The black spores from fruiting bodies on dry residues and the white spores from green plants are both infectious and spread the disease.
The disease evolves rapidly and quickly overcomes varietal tolerance.
Life Cycle:Origin and History:
Usually fairly evenly distributed through the crop.
Significance:In WA, this is the disease that causes the greatest economic losses in Barley. It varies from year to year but is significant in most seasons and preventative measures are usually recommended.
Early infections cause the greatest yield losses.
(Murray and Brennan, 2009) estimated the potential yield loss to be 13%.
Management and Control:Use resistant varieties. See HYPERLINK \l "_Disease_Susceptibility_of_Barley Va" Disease Susceptibility of Barley Varieties. Note that this disease quickly evolves to overcome varietal tolerance so use a variety of techniques to reduce this disease and note any breakdown of tolerance.
Seed treatments or flutriafol (Impact®) on fertilizer in furrow should be used on nearly all crops to control early infections. Seed treatments with fluquinconazole (Jockey®) and flutriafol (Impact®) or triadimefon in furrow usually provide control for about 8 weeks after planting.
Foliar treatments need to be applied before the first signs of disease.
Strains that are partially tolerant to tebuconazole are becoming common. The strobilurin (azoxystrobin e.g. Amistar and pyraclostrobin e.g. Opera) and the newer generation DMI's (epoxiconazole e.g. Opus and prothioconazole e.g. Prosaro) are still effective.
For susceptible varieties use a product like Jockey on the seed then a spray of 150 mL/ha Prosaro at Z31 (jointing) and 150 mL/ha Prosaro (or 400 mL Amistar Xtra) at Z42 (boot) for good levels of control. (Jayasena 2011)
Related and Similar Species:References:
Collated by HerbiGuide. Phone 08 98444064 or www.HerbiGuide.com.au for more information.