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Effects of cultivar resistance and fungicide application on stem canker of oilseed rape ( Brassica napus ) and potential interseasonal transmission of Leptosphaeria spp. inoculum
Author(s) -
Fortune James A.,
Qi Aiming,
Ritchie Faye,
Karandeni Dewage Chinthani S.,
Fitt Bruce D. L.,
Huang YongJu
Publication year - 2021
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/ppa.13453
Subject(s) - biology , canker , leptosphaeria maculans , cultivar , fungicide , phoma , agronomy , brassica , stem rot , horticulture
Phoma stem canker is a damaging disease of oilseed rape ( Brassica napus ) that causes annual yield losses to UK oilseed rape growers worth approximately £100 million, despite the use of fungicides. In the UK, oilseed rape is sown in August/September and harvested in the following July. The disease epidemics are initiated by ascospores released from Leptosphaeria spp. pseudothecia (ascocarps) on stem stubble in the autumn/winter. Control of this disease is reliant on the use of cultivars with “field resistance” and azole fungicides. This study investigated the effects of cultivar resistance and application of the fungicide prothioconazole on the severity of stem canker before harvest and the subsequent production of pseudothecia on the infected stubble under natural conditions in the 2017/2018, 2018/2019, and 2019/2020 cropping seasons. The application of prothioconazole and cultivar resistance decreased the severity of phoma stem canker before harvest, and the subsequent production of Leptosphaeria spp. pseudothecia on stubble in terms of pseudothecial density. Results showed that stems with less severe stem cankers produced fewer mature pseudothecia of Leptosphaeria spp. on the infected stubble. This investigation suggests that the most sustainable and effective integrated control strategy for phoma stem canker in seasons with low quantities of inoculum is to use cultivars with medium or good field resistance and apply only one spray of prothioconazole when required.