Cercospora is caused by the fungal pathogen Cercospora zonata. This disease can cause problems in some years. The disease often occurs when plants are grown in wet patches, particularly where free water remains on the soil surface.
Dark irregular lesions which may be difficult to distinguish from ascochyta blight. However, lesions of cercospora tend to be darker and their shape is more irregular. Within the spots a concentric ring pattern can often be seen, (Figure 6.10).
Figure 6.10 Cercospora leaf spots tend to be darker than those of chocolate spot with irregular shaped edges. A ring pattern may also develop. Unlike ascochyta, no pycnidia are produced.
This disease has not been well studied. Cercospora is thought to survive on bean trash and its spores are probably spread by rainsplash. It is not known to be seed borne, (Figure 6.11).
Figure 6.11 Disease cycle of cercospora on faba beans. (Illustration by Kylie Fowler)
ALTERNARIA LEAF SPOT OF FABA BEANS
RUST OF FABA BEANS