The impact of climate, local habitat, surrounding landscape and management on coffee wilt disease and Armillaria root rot on Arabica coffee in its native range

• Coffee wilt disease increased with mean soil temperature, while Armillaria root rot decreased • Soil moisture had a positive impact on the incidence of both coffee wilt disease and Armillaria root rot • Canopy cover affected the two diseases through opposing direct and indirect pathways, resulting in non-significant total effects • Neither Armillaria root rot nor coffee wilt disease were affected by the coffee structure index (e.g., reflecting pruning), the proportion of coffee cultivars or each other’s presence Climate change is predicted to lower yields through increased disease pressure. Yet, we often lack insights into how climate affects disease dynamics, and how we can manage the environment to reduce the impact of climate change. This knowledge gap is especially prominent for stem and root diseases that concern smallholder farmers in low-income countries. To provide insights into the patterns and drivers of stem and root diseases, and how they will be affected by climate change, we surveyed the prevalence and incidence of a major stem (coffee wilt disease; Gibberella xylarioides ) and root disease (Armillaria root rot; Armillaria mellea ) attacking Arabica coffee in 58 sites in southwestern Ethiopia, and simultaneously recorded climatic, habitat, spatial and management variables. Coffee wilt disease was found in all but four sites, and the incidence of coffee wilt disease was positively affected by temperature and soil moisture, negatively affected by coffee density and lower in sites with a more forest-like shade tree species composition. Armillaria root rot was found in 29 out of 58 sites. While none of the factors explained the prevalence of Armillaria root rot, Armillaria root rot incidence was, in contrast to coffee wilt disease, negatively affected by temperature. Armillaria root rot was positively affected by soil moisture and surrounding forest cover. Canopy cover affected the two diseases through opposing direct and indirect pathways, resulting in non-significant total effects. Neither of the two diseases was affected by coffee structure index (reflecting e.g. pruning), the proportion of coffee berry disease resistant cultivars, or each other’s presence. Overall, our findings shed light on the patterns and drivers of stem and root diseases, and provide management guidelines to reduce the devastating impact of these diseases for smallholder farmers.