Abstract
Detailed observations and cultural studies led to the conclusions that the causal fungus of black leaf blight of Allium fistulosum does not have any anamorph, and that the hitherto described anamorphs belonging to the causal fungus in Japan were incorrect. These anamorphs were different fungi, causing other diseases of welsh onion, or often occurring together with black leaf blight. Through comparative morphological studies, the causal fungus of Allium black leaf blight disease was identified as Mycosphaerella allicina (Fries: Fries) Vestergren having no anamorph. M. schoenoprasi (Auerswald) Schröter, which had long been known as the causal fungus in Japan, was treated as a synonym of M. allicina.
