Yellow spot of white lace flower caused by Pleospora herbarum in Japan

Yellow spots on leaves of white lace flower, Ammi majus, were found in Chiba Prefecture, Japan, in October 2006. The symptoms later developed into large brown spots. Brown lesions were also observed on the lower stem, and stem rot followed. A fungus was frequently isolated from the lesions, and the symptoms were reproduced after artificial inoculation. The causal fungus was identified as Pleospora herbarum based on morphology and molecular analysis. We named the new disease “yellow spot” (“ouhan-byo” in Japanese).