Efficacy and Baseline Sensitivity of Succinate-Dehydrogenase-Inhibitor Fungicides for Management of Colletotrichum Crown Rot of Strawberry

The current management of Colletotrichum crown rot (CCR) of strawberry, caused by Colletotrichum gloeosporioides sensu lato, relies on the use of a few fungicide classes, particularly QoI fungicides. Since resistance to QoI fungicides has recently been detected, alternative fungicide groups are needed to control this disease. Our objective was to evaluate the efficacy of succinate-dehydrogenase-inhibitor (SDHI) fungicides in managing CCR. Five SDHI fungicides, fluopyram, isofetamid, penthiopyrad, fluxapyroxad, and benzovindiflupyr, were applied 2 days before or 1 day after inoculation of cultivar Strawberry Festival. SDHI treatments were compared with the most common fungicides used for CCR management, i.e., thiophanate-methyl, pyraclostrobin, and captan. Benzovindiflupyr applied 1 day after inoculation was effective in reducing plant mortality and disease development. The baseline sensitivity of C. gloeosporioides isolates was determined in vitro using a spiral gradient dilution assay. The EC₅₀ for benzovindiflupyr and penthiopyrad varied from 0.08 to 1.11 and 0.45 to 3.17 µg/ml, respectively, whereas the other SDHI fungicides did not inhibit fungal growth. If registered, benzovindiflupyr could serve as an alternative to manage CCR in Florida.

Keywords: chemical; disease management; fungi; small fruits.