Effects of cultivar resistance and fungicide application on stem canker of oilseed rape (Brassica napus) and potential interseasonal transmission of Leptosphaeria spp. inoculum. (28th August 2021)

• Record Type: Journal Article
• Authors: Fortune, James A.; Qi, Aiming; Ritchie, Faye; Karandeni Dewage, Chinthani S.; Fitt, Bruce D. L.; Huang, Yong‐Ju
• Is Part Of: Plant pathology. Volume 70:Number 9(2021)
• Page Start: 2115
• Page End: 2124
• Publication Date: 2021-08-28
• Subjects: blackleg -- Brassica napus -- disease control -- integrated pest management -- Leptosphaeria maculans -- oilseed rape; Agricultural pests -- Periodicals; Plant diseases -- Periodicals; 632
• DOI: 10.1111/ppa.13453
• Languages: English
• ISSNs: 0032-0862

Abstract

Abstract: 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. Abstract : Deployment of phoma stem canker resistant cultivars combined with accurate fungicide applications resulted in fewer ascospores able to infect new oilseed rape crops in the following season.