Abstract
Leaf sheath rot of rakkyo plants (Allium chinense G. Don) has been observed in Chiba Prefecture since 1990. Lerf blades became reddish and underground parts of leaf sheaths rotted. A Fusarium species was isolated from the diseased leaf sheaths and typical symptoms observed in nature were reproduced by inoculation. The casual agent was identified as Fusarium avenaceum (Fries) Saccardo.