The fungus infects all stages of the crop from flowers to ripe fruits and occasionally leaves, but maximum crop losses occurs following infection of green berries with the formation of dark sunken lesions with sporulation, causing their premature dropping and mummification.
CBD is a very severe disease that may destroy up to 80% of the coffee berries if no control measures are taken.
“First colonies from sporulating lesions densely floccose, grey to dark olivaceous grey, dark greenish in reverse, on 2% malt extract agar at 25 oC attaining 14—28 mm in diameter in seven days. With successive transfer cultures becoming variable, often paler or brownish. Acervular conidiomata not formed, conidia produced from simple hyphae. Conidia straight, cylindrical, aseptate, invariably guttulate, obtuse at the apex, 12.5—19 x 4 µm. Appressoria moderately abundant, pale to medium brown, circular or slightly irregular, 8—9.5 x 5.5—6.5 µm, often becoming complex. Unable to metabolize citrate and tartrate as sole carbon sources. Pathogenic to young green berries and seedling hypocotyls of Coffea arabica causing dark sunken anthracnose lesions” (Waller et al. 1993).
The initially white mycelium of C. kahawae changes after 4-6 days to grey and eventually to dark olive brown. Conidia are produced at the tips of hyhae or in acervuli; their shape and size are variable. The perfect state, Glomerella cingulata (Stonem.) Spauld. & Schrenk, has never been observed (Hindorf 1970, Rodrigues Jr. et al. 1991).
The conidia of C. kahawae germinate and differentiate melanised appressoria both "in vitro" and "in vivo" and the penetration of different coffee organs (hypocotyls, leaves and green berries) occurs directly through the epidermal cell walls. This fungus is a hemibiotroph, as it exhibits a transient post-penetrative asymptomatic biotrophy that is rapidly succeeded by a phase of destructive necrotrophy culminating in the appearance of symptoms of disease and pathogen reproduction. During the symptomless biotrophic phase, the pathogen invades host cells without killing them and feeds on living cells. Subsequently, the pathogen switches to a necrotrophic mode of nutrition, feeding on dead host tissues (Várzea et al. 2002, Silva et al. 2006).
Three species of Colletotrichum have been isolate from coffee berries, leaves and branches: C. kahawae (the only parasitic species of green berries, originally designated as C. coffeanum), C. gloeosporioides Penz and C. acutatum Simmond (Hindorf 1970, Masaba and Waller 1992, Waller et al. 1993).