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POSTERS: Chemical control

Sensitivity of Colletotrichum acutatum, causal agent of anthracnose fruit rot of strawberry to fungicides alternative to quinone-outside inhibitors
Carolina Rebello - Gulf Coast Research and Education Center, University of Florida. Bruna Forcelini- Corteva Agriscience, Natalia Peres- University of Florida - Gulf Coast Research and Education Center, James Mertely- Gulf Coast Research and Education Center, University of Florida, Juliana Baggio- Gulf Coast Research and Education Center

Colletotrichum nymphaeae and C. fioriniae belong to the C. acutatum species complex and cause anthracnose fruit rot (AFR) of strawberry. Quinone-outside inhibitor fungicides were frequently used for AFR management, however resistant populations were recently reported in Florida strawberry fields. Therefore, alternative modes of action, such as the succinate dehydrogenase inhibitors (SDHIs) and uncouplers of oxidative phosphorylation (OxPhos), were investigated to provide tools for disease management. Isolates collected from diverse strawberry fields in the U.S. were challenged with discriminatory doses of the SDHIs fluopyram, fluxapyroxad, isofetamid, penthiopyrad, and benzovindiflupyr, and the OxPhos fluazinam. Mycelial growth inhibition for each fungicide was evaluated using the spiral gradient dilution (SGD) method. Mean EC50 values for C. nymphaeae (n=90) were 0.14 µg/ml, 34.3 µg/ml and 0.20 µg/ml for benzovindiflupyr, penthiopyrad, and fluazinam, respectively. Mean EC50 values for C. fioriniae (n=12) were 0.86 µg/ml, 3.42 µg/ml and 0.06 µg/ml for benzovindiflupyr, penthiopyrad and fluazinam, respectively. Disease incidence was reduced on detached fruit inoculated and treated with these fungicides, as well as in field trials, indicating that the products are effective in controlling AFR. The SDHI benzovindiflupyr may be used as an alternative for disease management in strawberry fields while OxPhos fluazinam may be used in nurseries, upon registration.