Quantifying Control Efficacy of Fungicides Commonly Applied for Potato Early Blight Management.

Early blight is an economically important foliar disease of potato in the United States. Because of the lack of resistant potato cultivars, fungicides are applied extensively to obtain adequate control. To manage early blight, standard protectant fungicides and single-site mode-of-action "specialty" fungicides are applied either alone or incorporated into a fungicide rotation program. Control efficacy at two crop growth stages (tuber initiation/early bulking and late bulking/tuber maturation) and the overall tuber yield response to standard and specialty fungicides were assessed using network metaanalytic models. Control efficacy of fungicides ranged from moderate to very high (>30 to 75%) compared with the nontreated control. For both potato growth stages, specialty fungicides performed better than standard protectant fungicides. Furthermore, control efficacy of both fungicides was higher (3 to 9%) at late bulking and tuber maturation when compared with early bulking crop growth stage. Specialty fungicide programs increased overall tuber yields by 4 and 9% over standard fungicides and nontreated control, respectively. Based on the results, more precise fungicide use recommendations and fungicide programs can be developed for early blight management.