Fungal diseases are important contributors to the relatively large yield fluctuations in faba bean cultivation in central and northern Europe. In particular, rust (caused by Uromyces viciae-fabae) and chocolate spot disease (caused by Botrytis fabae) can cause significant yield reductions. Both diseases reduce the photosynthetically active crop canopy by attacking the leaves. This results in a reduced formation of assimilates, which in turn reduces the formation of seeds and thus the generation of crop yield. Early death of the entire plant can occur in severe cases. In addition, chocolate spot can cause sudden loss of flowers and young pods presenting a very significant risk to yield. Several other pathogenic fungi cause diseases on faba bean, but these two are the most widespread on spring-sown crops where they often occur together.