Blackleg – New Seed Treatment, Stubble Management And Fungicide Resistance

GRDC - Steve Marcroft (Marcroft Grains Pathology, Horsham, Vic), Angela van de Wouw (School of BioSciences, University of Melbourne, Vic)and Susie Sprague (CSIRO Agriculture & Food, Canberra, ACT).

Type: Research Paper
Knowledge level: Advanced

Farm Table says:

The authors of this paper note in the conclusion: "If UCI occurs, it has been shown that fungicides that are used to control Sclerotinia will also reduce UCI severity and yield losses. Application of Prosaro®/Aviator® Xpro for Sclerotinia control around 30% bloom can also provide protection from blackleg infection during early flowering. The 30% bloom spray may control flower, peduncle, stem and branch infections but is unlikely to provide pod protection. There are currently no control strategies for pod infection. High levels of pod infection tend to occur in seasons with frequent late rainfall events (such as 2016) or where there is physical damage to the pods from hail (such as 2018). In 2019, fungicide applications gave excellent control of UCI but did not control pod lesions. Although UCI was controlled it did not always result in yield returns from fungicides." Please access the full paper via the link below if this research interests you.

The take home messages from this GRDC funded research are below. Please access the full paper via the link below for methodology, references, acknowledgements and discussion.

Take home messages from the paper include:

  • Blackleg crown canker results from infection during early seedling growth. Prior to sowing, use the BlacklegCM decision support tool to identify high risk paddocks and explore management strategies to reduce yield loss.
  • New succinate dehydrogenase inhibitor (SDHI) seed treatment fungicides have higher efficacy, increased longevity and improved seed safety.
  • The improved efficacy of SDHI fungicide may result in a reduced need for early foliar application of fungicide (4-10 leaf applications).
  • Modern farming systems that enable earlier sowing/germination may result in reduced damage from blackleg crown cankers.
  • Blackleg pathogen populations with resistance to the triazole fungicides fluquinconazole, flutriafol and a tebuconazole + prothioconazole mixture have been detected. No resistance has been detected for new SDHI and quinine-outside inhibitor (QoI) chemistries.
  • Blackleg upper canopy infection (UCI) is the collective term for flower, peduncle, pod, main stem and branch infection, but does not include crown canker.
  • UCI can cause yield losses of up to 30%. Yield loss is reduced by selecting cultivars with effective major gene resistance and using crop management strategies to delay the commencement of flowering to later in the growing season, especially in high disease risk areas.
  • Fungicide applications at 30% bloom often controls UCI but does not always result in yield gains. Thirty per cent bloom fungicide application is unlikely to control pod infection.

2020 - Australia - GRDC - Steve Marcroft (Marcroft Grains Pathology, Horsham, Vic), Angela van de Wouw (School of BioSciences, University of Melbourne, Vic)and Susie Sprague (CSIRO Agriculture & Food, Canberra, ACT).
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