Water-borne spore dispersal in coffee berry disease and its relation to control

Devices are described which were used to catch rain-dispersed Colletotrichum conidia within and between coffee trees infected with coffee berry disease (CBD). The amount of CBD inoculum dispersed was related to the number of diseased and sporulating berries but not to the sporulating capacity of the fungus in maturing bark. Wet conditions encouraged spore production and dispersal, and spraying with fungicides prolonged sporulation of diseased berries. The amount of pathogenic inoculum, subsequent disease development and crop losses were greatly increased by the presence of only a few diseased berries during growth of the young crop. Spore concentrations were greatest close to diseased berries, but most spores within trees were dispersed downwards through the canopy. Some spores were dispersed between trees by wind-driven rain-splash and vectors such as pickers. Inoculum sources in tree tops are most important during CBD epidemics and disease can be restricted by removing or spraying the tops of multiple-stem trees. Fungicide applied to tree tops effectively controls CBD, because spores dispersed during rain are accompanied by redistributed fungicide