Temporal and spatial dynamics of coffee leaf scorch caused by Xylella fastidiosa
Field experiments were conducted at a commercial coffee (Coffea arabica) field in the counties of Sao Gotardo and Ervalia in the state of Minas Gerais, Brazil, to study the spatial and temporal dynamics of coffee leaf scorch (CLS) by assessing the incidence and severity of the disease. The spatial distribution of CLS were analysed using ordinary runs on rows and across rows, analyses of the dynamics and structure of foci, as well as analysis using modified Taylor's law. The temporal distribution of CLS was analysed using the real and cumulative incidence of the disease, and the data were used to calculate the rate of the disease progress. Diseased plants were aggregated according to modified Taylor's law and by the analysis of ordinary runs and structure of foci. Dissemination of the disease occurred mainly in plant rows. Diseased plants occurred at the beginning in isolated foci, and with an increase in disease incidence they later became more aggregated. The maximum values for CLS incidence occurred in December, when the rate of disease progress was 0.18 plants/month, whereas in the winter months the CLS rate of progress was close to zero.