Forecasting the Rising Threat: How Climate Change Could Amplify Rice Brown Spot in Côte d'Ivoire

ABSTRACT Rice brown spot (RBS), mainly caused by Bipolaris oryzae , is an emerging threat to rice production across Africa, particularly within lowland rice ecosystems that dominate the region. Despite its growing impact, knowledge of the environmental factors influencing RBS occurrence remains limited. This study aimed to elucidate the influence of meteorological variables on RBS prevalence in Côte d'Ivoire, spanning three major agro‐ecological zones. Field surveys were conducted in 99 farmer‐managed fields during both the rainy and dry seasons from 2021 to 2022, and average RBS severity was calculated across different stands within each field. Parameters assessed included air temperature, relative humidity, wind speed, soil moisture, solar radiation, and rainfall. Linear regression analyses were used to identify main drivers, and regression models were developed to project future risk maps under SSP2‐4.5 (moderate) and SSP5‐8.5 (high) climate scenarios. Key drivers were identified: air temperatures above 27°C and wind speeds exceeding 1 m/s were associated with decreased disease prevalence, whereas relative humidity above 80%, wet bulb and dew point temperatures between 23°C and 27°C, and soil moisture and wetness in the range of 0.4–0.7 significantly promoted RBS development. Results revealed a yearly increase in RBS severity, ranging from 2.47 to 3.46 (on a 0–5 scale), with consistently higher prevalence during the rainy seasons. Predictive modelling based on these variables suggests a likely expansion and intensification of RBS risk for the future. Under a high‐emission scenario, RBS severity could reach 4.9 by the late 21st century, while the moderate scenario projects a peak severity of 4.33 between 2060 and 2080. These findings underscore the pivotal role of climate in shaping RBS risk and highlight the urgent need for climate‐adaptive disease management strategies to sustain rice production in Africa.