Author(s): Sushmita Kalika-Singh, Luis Del Rio Mendoza and Mohamed Khan

Abstract: Cercospora leaf spot (CLS), caused by Cercospora beticola, is a major foliar disease of sugar beet (Beta vulgaris L.) that can significantly reduce yield and quality. Fungicides, particularly demethylation inhibitors (DMIs) and quinone outside inhibitors (QoIs), are central to disease management, yet resistance to both classes has been reported across multiple sugar beet growing regions. This study represents one of the first systematic evaluations of the in vitro activity of a DMI-QoI fungicide combination against C. beticola isolates. The sensitivity of 40 isolates to a mixture of prothioconazole (DMI) and pyraclostrobin (QoI) was assessed across concentrations of 10-800 µg/mL. The mean EC₅₀ for the combination was 111 µg/mL, with isolate-specific values ranging from 9 to 214 µg/mL. These findings demonstrate substantial inhibition of mycelial growth, suggesting additive or synergistic effects of the mixture, while also highlighting that some isolates retain reduced sensitivity. The results provide valuable insights for developing integrated CLS management strategies and underscore the need for ongoing resistance monitoring.

DOI: 10.22271/27893065.2025.v5.i2b.150

Pages: 109-111 | Views: 81 | Downloads: 21

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