Alternaria leaf spot is caused by the fungal pathogen Alternaria alternata. This is a minor disease of faba beans occurring late in the season and is often confused with chocolate spot.
Dark brown leaf spots which often have a zoned pattern of concentric brown rings with dark margins, (Figure 6.9). Symptoms can be confused with chocolate spot.
Figure 6.9 Alternaria lesions have concentric rings within lesions. However no black fruiting bodies are produced as does ascochyta
Alternaria is a weak pathogen of many hosts and is usually a secondary pathogen that only attacks following damage by other fungi or insects. Alternaria leaf spot develops late in the season as the plants start to mature. The fungus probably survives on crop residues and on other hosts.
ASCOCHYTA BLIGHT OF FABA BEANS
CERCOSPORA LEAF SPOT OF FABA BEANS