Occurrence of SDHI-fungicide-resistant strains of <i>Mycovellosiella nattrassii</i> isolates from eggplants in Osaka Prefecture, Japan

In this study, we evaluated the efficacy of penthiopyrad, isopyrazam and pyraziflumid against Mycovellosiella nattrassii isolates. These isolates, collected from eggplants in Osaka Prefecture, Japan, in 2024, had previously shown reduced sensitivity to succinate dehydrogenase inhibitors (SDHI) in culture medium tests (Yasumatsuya et al., 2025). Three strains (N8, N9 and N10) were tested. N8 and N10 demonstrated low sensitivity to penthiopyrad, isopyrazam and pyraziflumid on culture medium, were resistant to these SDHI on plant body. N9, which was sensitive to pyraziflumid and resistant to penthiopyrad, isopyrazam on culture medium, was sensitive to pyraziflumid and resistant to penthiopyrad, isopyrazam on plant body.