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Management of foliar diseases in oats using resistant varieties and fungicides in south-eastern Australia

Management of foliar diseases in grain and hay oats can improve yield and quality during favourable seasons. Surveys during 2018 identified red leather leaf (Fig. 1.) (caused by the fungus Spermospora avenae) and bacterial blight (Fig. 2) (caused by the bacteria Pseudomonas syringae) as the most common foliar diseases in oats in south-eastern Australia. 

 Red leather leaf symptoms in oat               red leather leaf of oat symptoms 

Figure 1. Red leather leaf symptoms in oats. 

Field experiments at Horsham in Victoria found that red leather leaf caused up to 0.5 t/ha (13%) of grain yield loss in the commonly grown variety Bannister, despite the dry season. 

Foliar fungicides provided suppression of red leather leaf and were most effective when applied at mid tillering (Z25) and early stem elongation (Z31). However, they did not provide complete control.

Avoiding sowing oats into stubble residue by having at least 2 years break between oat crops is recommended.  

 bacterial blight symptoms               bacterial blight symptoms

Figure 2. Bacterial blight symptoms in oats. 

Background

Oats are commonly grown throughout south-eastern Australia to produce grain for human consumption and as stock feed  (grain, grazing and hay production). The demand for milling grade oats and fodder has recently increased, providing opportunity for improved returns to growers through disease management. Agriculture Victoria, in collaboration with the Department of Primary Industries and Regional Development (DPIRD) in Western Australia, are investigating the distribution and importance of foliar diseases of oats and strategies for their management. Target diseases are Red leather leaf (caused by the fungus Spermospora avenae) and Septoria blotch (caused by the fungus Parastagonospora avenaria f.sp. avenaria). This work is through investment from the Agrifutures “National oaten hay agronomy” and the Grains Research and Development Corporation’s “Integrated disease management strategies for southern region cereal and pulse growers” projects.  

Findings

Survey

Red leather leaf and bacterial blight were the most common foliar diseases of oats in south-eastern Australia during 2018. Both diseases were found in all crops, with the severity of each varying depending on the variety grown and local seasonal conditions. Disease severity was greatest in susceptible varieties and in the high rainfall zone. Septoria blotch and ring spot were found to be uncommon and at low levels, and don’t appear to be as important in south-eastern Australia. 

Losses

Field experiments showed that red leather leaf severity was greatest in susceptible rated varieties and significantly less in moderately resistant varieties. Growers can get variety ratings from a current Cereal Disease Guide. Red leather leaf caused up-to 0.5 t/ha (13%) of grain yield loss in var. Bannister, demonstrating that foliar diseases should be managed in moderately susceptible or susceptible rated varieties during favourable seasons to avoid losses in milling oat crops. Losses are likely to be greatest during wetter seasons as infection occurs during rainfall events. Agriculture Victoria are investigating the effects of red leather leaf in other grain and hay oat varieties during 2019-20.  

Fungicides

Foliar fungicide application was most effective in suppressing red leather leaf when applied at mid tillering (Z25) and early stem elongation (Z31). The most effective strategy combined both Z25 and Z31 applications which reduced infection by 5-10%. Fungicides did not provide total control, showing that they can be used as a tool to help manage red leather leaf but should not be relied on. There are several products registered for oats which can be used which is listed on the product labels.  

Crop rotation

Red leather leaf is carried over from one season to the next on infected stubble. It is important to allow stubble to break down for 2-3 years before re-sowing oats. 

Acknowledgements

Research of grain yield and quality loss in milling oats was done using investment from the Grains Research and Development Corporation (GRDC) and Agriculture Victoria. Survey of foliar diseases and hay yield loss was done with investment from Agrifutures. 

Geoff Thomas, Department of Primary Industries and Regional Development (DPIRD)

Grant Hollaway, Agriculture Victoria

Further information

You can view our article which lists the Cereal Disease guides across the country for the latest variety ratings for 2019.

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