Individual Participant Data Meta-Analysis of Foliar Fungicides Applied for Potato Early Blight Management

Foliar fungicides continue to be the primary means of early blight management on potato in the United States. Both premium-priced, single-site mode-of-action "specialty" fungicides and standard protectant multisite fungicides are applied, either alone or incorporated into fungicide rotation programs to combat early blight. Individual participant data meta-analysis was conducted to compare overall fungicide efficacy against early blight on potato, quantify tuber yields, and identify the most efficacious timing for fungicide applications. In this study, the specialty fungicide-based applications were compared against the standard fungicides chlorothalonil and mancozeb applied alone. Type 3 fixed effects indicated that there was a significant difference (P < 0.0001) in overall efficacy and yield among the treatments applied to manage early blight in potato. There was a significant difference (P < 0.0001) among treatments in early blight development during the growing season. Applications incorporating specialty fungicides, when compared with standard fungicides, significantly affected disease severity from vegetative growth initiation (P = 0.0139) to tuber maturation (P = 0.0009). Results demonstrate that the higher cost, specialty-fungicide-based applications were most effective for early blight management in North Dakota and Minnesota.