CERCOSPORA LEAF SPOT OF FABA BEANS

Introduction

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.

What to Look For

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.

Disease Cycle

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)

Management

Cercospora leaf spot is often confused with ascochyta blight and chocolate spot. Fungicide control may be warranted in some years.

ALTERNARIA LEAF SPOT OF FABA BEANS

RUST OF FABA BEANS