title: Blackleg (Leptosphaeria maculans) Severity and Yield Loss in Canola in Alberta, Canada.
abstract: Blackleg, caused by Leptosphaeria maculans, is an important disease of oilseed rape (Brassica napus L.) in Canada and throughout the world. Severe epidemics of blackleg can result in significant yield losses. Understanding disease-yield relationships is a prerequisite for measuring the agronomic efficacy and economic benefits of control methods. Field experiments were conducted in 2013, 2014, and 2015 to determine the relationship between blackleg disease severity and yield in a susceptible cultivar and in moderately resistant to resistant canola hybrids. Disease severity was lower, and seed yield was 120%-128% greater, in the moderately resistant to resistant hybrids compared with the susceptible cultivar. Regression analysis showed that pod number and seed yield declined linearly as blackleg severity increased. Seed yield per plant decreased by 1.8 g for each unit increase in disease severity, corresponding to a decline in yield of 17.2% for each unit increase in disease severity. Pyraclostrobin fungicide reduced disease severity in all site-years and increased yield. These results show that the reduction of blackleg in canola crops substantially improves yields.
authors.affiliation: Crop Diversification Centre North, Alberta Agriculture and Forestry, Edmonton, AB T5Y 6H3, Canada. sheau-fang.hwang@gov.ab.ca.
authors.forename: Sheau-Fang
authors.initials: SF
authors.lastname: Hwang
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada. stephen.strelkov@ualberta.ca.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Strelkov
authors.affiliation: Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, Saskatoon, SK S7N 0X2, Canada. gary.peng@agr.gc.ca.
authors.forename: Gary
authors.initials: G
authors.lastname: Peng
authors.affiliation: Crop Diversification Centre North, Alberta Agriculture and Forestry, Edmonton, AB T5Y 6H3, Canada. hafiz.ahmed@gov.ab.ca.
authors.forename: Hafiz
authors.initials: H
authors.lastname: Ahmed
authors.affiliation: Crop Diversification Centre North, Alberta Agriculture and Forestry, Edmonton, AB T5Y 6H3, Canada. qixing.zhou@gov.ab.ca.
authors.forename: Qixing
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: Crop Diversification Centre North, Alberta Agriculture and Forestry, Edmonton, AB T5Y 6H3, Canada. george.turnbull@gov.ab.ca.
authors.forename: George
authors.initials: G
authors.lastname: Turnbull
keywords: Leptosphaeria maculans; blackleg; canola; yield loss model