The <i>Coffea arabica</i> Fungal Pathosystem in New Caledonia: Interactions at Two Different Spatial Scales

Abstract

Abstract The simultaneous analysis of epidemiological and environmental variables could contribute to the determination of the main factors which govern the epidemic dynamics of diseases (i.e. rust, anthracnose and Cercospora leaf spot) in Coffea arabica. With this in mind, the condition of previously marked leaves in 29 plots. which were grouped in 11 different sites in New Caledonia. were surveyed monthly. In the same period, the environmental characteristics of the plots (soil type, climate, etc.)were determined. Statistical analysis of these data revealed significant correlations between pathology and the environment. at the sites’ level (analysis of the mean site values) as well as at the plots' level (analysis of the deviations with the mean site value). The site effects predominated: at those sites in which rust was the major disease, leaf and branch mortality were more pronounced than at sites in which anthracnose or Cercospora leaf spot predominated. Rust was generally associated with soil pH values that were favourable for coffee tree development. with poor soil structure and with large temperature ranges. Within a site. plot exposure to sun and wind could enhance anthracnose and Cercospora leaf spot. Finally, in New Caledonia the three variables soil pH, soil structure and temperature range allow a simple and satisfactory estimation of the epidemiological risks in a given plot.