Spatio-temporal dynamics of arabica coffee berry disease Caused by Colletotrichum kahawae on a plot scale

Coffee berry disease (CBD) is caused by Colletotrichum kahawae. This pathogen only attacks green berries; it causes cherry rot and premature fruit fall. The disease leads to major harvest losses in the western highland region of Cameroon. The origin of the primary inoculum and the beginning of epidemics are unknown. The interactions between the pathogen and its host were studied at locations where CBD was known to cause severe disease. The disease was monitored weekly in uniform plots of adjacent coffee trees at Santa (1,750 m) in 2003 and 2004 and Bafou (1,820 m) in 2004 and 2005. The logistic model provided good fit of the epidemic's temporal dynamics. The spatial distribution of CBD over time indicated that plants in a plot were contaminated stepwise from the first infected coffee tree. An analysis of semi-variograms and the disease dispersal maps obtained by kriging revealed primary infection foci at both sites. They were observed from the 8th to the 10th week after flowering at Bafou and from the 11th to the 13th week at Santa. CBD affected the entire plots 3 weeks after the foci first appeared. These results suggest that inoculum from previous epidemics survives at points in the initial foci in a coffee plantation. (Résumé d'auteur