Anthracnose (Colletotrichum cereale)

Anthracnose: biology

Anthracnose is a fungal disease affecting edible beans; it is mainly seed borne but may also be found in crop stubble. Rainy weather favours this disease, as spores are splashed from diseased areas and carried in windborne water droplets or by surface water throughout the field by machinery. Infected seed produces seedlings with diseased cotyledons, where sporulation occurs. Yield losses result from loss of foliage, pod shriveling and seed shrinkage. Seed discolouration and pitting results in downgrading.

Symptoms of anthracnose appear as brown to red-brown lesions along veins on the lower leaf surface and on leaf stalks and stems; the lesions on pods are circular with a brown centre and raised dark brown margin. Black specks in the pod lesions contain spores of the anthracnose fungus. Additionally, infected seed may appear as discoloured and pitted.