Climatic drivers of coffee disease dynamics: insights from a decadal study on Hemileia vastatrix and emerging fungal pathogens in southern India

Abstract

Climate change–driven variations in rainfall pattern and temperature are increasingly influencing disease dynamics in India’s coffee plantations. Erratic and prolonged rainfall has led to persistent canopy wetness, favoring outbreaks of black rot, stalk rot, leaf spot, and berry infections, which cause severe defoliation and fruit drop. Among these, coffee leaf rust (CLR) caused by Hemileia vastatrix remains the most destructive disease of Coffea arabica , capable of causing up to 30% crop loss without effective control. A long-term study (2015–16 to 2024–25) at the Central Coffee Research Institute, Chikkamagaluru, Karnataka, assessed the influence of weather variables on CLR development using the susceptible cultivar Sln.3. Fortnightly disease observations and daily weather data (temperature, relative humidity, and rainfall) were analyzed. Results showed that CLR epidemics are strongly regulated by minimum temperature (Tmin) and vapor pressure deficit (VPD). CLR incidence consistently peaked during the post-monsoon period. Spline regression modelling demonstrated superior performance of VPD-based models (AIC = −83.03, R 2 adj = 0.99, RMSE = 0.73) compared to RH-based models (AIC = −73.01, R 2 adj = 0.96, RMSE = 1.42). Lagged Tmin and VPD variables effectively represented the pathogen’s latent period, improving model realism and prediction. Emerging pathogens such as Paramyrothecium roridum , Neopestalotiopsis clavispora , and Agroathelia rolfsii also showed increasing incidence. The study underscores that temperature and rainfall distributions critically influence coffee disease outbreaks, emphasizing the need for integrated climate-responsive management strategies.