Sensitivity of Leptosphaeria maculans isolates to pyraclostrobin and assessment of fungicide efficacy in the management of blackleg of canola

  • Author / Creator
    Fraser, Michelle C.
  • Blackleg (Leptosphaeria maculans) disease is endemic to canola (Brassica napus) worldwide. With shortened canola rotations and increasing levels of blackleg in Alberta, Canada, growers may look to fungicides as an attractive disease management tool. However, the improper or intensive use of fungicides can result in insensitivity to these products in pathogen populations. Pyraclostrobin is a strobilurin fungicide that was first registered on canola for blackleg control in 2010. The objective of this thesis project was to determine the pyraclostrobin sensitivity of L. maculans populations in Alberta, and examine the efficacy of seed and foliar fungicides in managing blackleg. A group of 113 single-spore L. maculans isolates from Alberta were evaluated for pyraclostrobin sensitivity in a growth plate assay, and no insensitive isolates were found. These results were confirmed when a subset of 41 isolates were further evaluated for sensitivity in a microtiter assay. Various seed and foliar fungicide treatments, some of which contained pyraclostrobin, were tested on blackleg-susceptible and moderately resistant canola cultivars under greenhouse and field conditions. A combination of the experimental seed treatment BAS 720 F and the foliar treatment Priaxor, both of which contain fluxapyroxad and pyraclostrobin, often decreased blackleg levels and improved seed yield, especially in the susceptible cultivar under high disease pressure. Pyraclostrobin may represent an effective and sustainable blackleg management tool for canola growers in Alberta, as long as fungicide stewardship is practiced and included as a component of an integrated pest management plan.

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  • Degree
    Master of Science
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    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.