Abstract
New disease symptoms were observed on canola (Brassica napus) crops late in the 2019 and 2020 growing seasons in Western Australia. Cladosporium macrocarpum was isolated from infected material, and the fungus responsible for the symptoms was demonstrated by fulfilling Koch’s postulates. One strain exhibited relatively high tolerance to prothioconazole and tebuconazole fungicides compared to other canola pathogens Sclerotinia sclerotiorum and Leptosphaeria maculans. In a 2019 field trial in a commercial canola crop, symptom incidence caused by Cladosporium was only significantly reduced by a double application of a foliar fungicide (active ingredients prothioconazole and tebuconazole) registered in canola for other diseases, while single applications gave no significant response. This new disease, caused by a ubiquitous fungal species, may be a consequence of changes to farm management strategies to reduce other fungal diseases of canola.
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Acknowledgements
This research was supported by the University of Melbourne, Australian Research Council (ARC grant LP170100548), Department of Primary Industries and Regional Development (DPIRD) and the Grains Research and Development Corporation (GRDC and DPIRD co-funded projects DAW1907-002RTX and DAW1810-007RTX). We thank Jacky Edwards (Agriculture Victoria) and Vincent Lanoiselet (DPIRD) for advice on disease reporting procedures and C. macrocarpum incidence in Australia, and for accessioning strains and diseased material. We also thank the growers who hosted the field trials, Bayer for providing the fungicide used in the trials and Syngenta for providing fungicides for in vitro, David Nicholson and Debra Donovan (DPIRD) for their assistance in season at Dale, and DPIRD research support units at Geraldton and Northam who harvested the Alma and Dale trials, respectively.
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Through ARC linkage project LP170100548 A.I. receives funding for research from Syngenta Australia. Any use of registered trade names is for the purpose of research transparency, and constitutes neither an endorsement nor a recommendation against products or services by the authors, their institutions, or their funding bodies.
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Idnurm, A., Beard, C., Smith, A. et al. Emergence of Cladosporium macrocarpum disease in canola (Brassica napus). Australasian Plant Pathol. 50, 687–694 (2021). https://doi.org/10.1007/s13313-021-00819-8
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DOI: https://doi.org/10.1007/s13313-021-00819-8