Quantifying <scp>ENSO</scp> ‐Mediated Shifts in Soybean Rust Impact: Yield Loss Dynamics and Management Implications in Brazil

ABSTRACT Soybean rust (SBR), caused by the fungal pathogen Phakopsora pachyrhizi , severely threatens soybean production in Brazil, with outbreak dynamics tightly linked to climatic variability. This study evaluates how El Niño Southern Oscillation (ENSO) phases modulate SBR severity and associated yield losses, employing a meta‐analysis of 417 field trials across 73 Brazilian locations from 2005 to 2020. We quantified disease damage coefficients (yield loss per percentage point of disease severity) and the efficacy of management practices in protecting yields during warm (El Niño), neutral and cold (La Niña) ENSO phases. Results revealed that damage coefficients were significantly higher during El Niño, causing disproportionately greater yield losses at equivalent disease severity levels compared to neutral and La Niña phases. Notably, disease control scenarios provided the highest yield protection during El Niño but were least effective during La Niña. These findings highlight the critical role of ENSO‐driven climatic variability in shaping SBR dynamics, influencing disease pressure and altering the effectiveness of management strategies. The study underscores the potential of integrating ENSO‐based forecasts into pre‐season disease outlooks to enhance resource allocation, optimise fungicide applications and improve profitability under varying climatic conditions.