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Efficacy and Cost-Benefit Analysis of Fungicide Combinations against Soybean Rust and Cercospora Leaf Blight in Paraguay
Abstract
This study evaluated the efficacy, seed yield and economic returns of nine fungicide mixtures for the integrated management of Asian soybean rust (Phakopsora pachyrhizi) and Cercospora leaf blight (Cercospora kikuchii) under field conditions in Canindeyú, Paraguay, during the 2023/24 and 2024/25 seasons. Trials were arranged in a randomized complete‐block design with four replicates, comparing premixes of QoI, DMI, SDHI and multisite actives. Disease severity was monitored over time to calculate the area under the disease progress curve (AUDPC) and control efficacy. Grain yield, thousand‐seed weight, gross return, treatment cost and benefit–cost ratio (B/C) were also determined. In both seasons, mixtures combining systemic actives (QoI + DMI ± SDHI) achieved the greatest disease suppression, reducing AUDPC values by > 80 % relative to the untreated control and exceeding 95 % control efficacy under higher disease pressure. These treatments outyielded the control by 700–1 000 kg ha⁻¹ and increased thousand‐seed weight by up to 4 g. Although multisite fungicides (mancozeb, chlorothalonil) delivered moderate disease control (50–70 %), their low cost yielded the highest B/C ratios (> 16). Overall net benefits ranged from USD 770 to USD 1 150 ha⁻¹. We conclude that locally validated systemic–multisite fungicide mixtures provide robust, economically viable control of late-season soybean foliar diseases in Paraguay and support sustainable disease management under variable epidemic conditions.
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References
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DOI: 10.33687/phytopath.015.01.5718
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Copyright (c) 2026 Marcos Javier Mendoza-Duarte, Milciades Ariel Melgarejo-Arrua, Andrea Celeste Zarza-Cabrera, Nery Rubén Villasboa-Cardozo, Marta Alicia Fernandez-Gamarra, Marco Maidana-Ojeda, Andrea Alejandra Arrua, Guillermo Andrés Enciso-Maldonado
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