Effects of cultivar resistance and fungicide application on stem canker of oilseed rape ( <i>Brassica napus</i> ) and potential interseasonal transmission of <i>Leptosphaeria</i> spp. inoculum

Phoma stem canker is a damaging disease of oilseed rape (Brassica napus) that causes annual yield losses to UK growers worth approximately £100 million, despite the use fungicides. In UK, sown in August/September and harvested following July. The epidemics are initiated by ascospores released from Leptosphaeria spp. pseudothecia (ascocarps) on stubble autumn/winter. Control this reliant cultivars with “field resistance” azole This study investigated effects cultivar resistance application fungicide prothioconazole severity before harvest subsequent production infected under natural conditions 2017/2018, 2018/2019, 2019/2020 cropping seasons. decreased phoma harvest, terms pseudothecial density. Results showed stems less severe cankers produced fewer mature stubble. investigation suggests most sustainable effective integrated control strategy for seasons low quantities inoculum medium or good field apply only one spray when required.