THE COFFEA-ARABICA FUNGAL PATHOSYSTEM IN NEW-CALEDONIA - INTERACTIONSAT 2 DIFFERENT SPATIAL SCALES

The simultaneous analysis of epidemiological and environmental variabl es could contribute to the determination of the main factors which gov ern the epidemic dynamics of diseases (i.e. rust, anthracnose and Cerc ospora leaf spot) in Coffea arabica. With this in mind, the condition of previously marked leaves in 29 plots, which were grouped in 11 diff erent sites in New Caledonia, were surveyed monthly. In the same perio d, the environmental characteristics of the plots (sail type, climate, etc.) were determined. Statistical analysis of these data revealed si gnificant correlations between pathology and the environment, at the s ites' level (analysis of the mean site values) as well as at the plots ' level (analysis of the deviations with the mean site value). The sit e effects predominated: at those sites in which rust was the major dis ease, leaf and branch mortality were more pronounced than at sites in which anthracnose or Cercospora leaf spot predominated. Rust was gener ally associated with soil pH values that were favourable for coffee tr ee development, with poor soil structure and with large temperature ra nges. Within a site, plot exposure to sun and wind could enhance anthr acnose and Cercospora leaf spot. Finally, in New Caledonia the three v ariables soil pH, soil structure and temperature range allow a simple and satisfactory estimation of the epidemiological risks in a given pl ot.