A new disease of edible burdock (Arctium lappa L.) was observed in Okayama Prefecture in 2002. The fungus consistently isolated from symptomatic roots was identified as Phoma exigua Desm. var. exigua on the basis of morphological characteristics of the fungus, color reaction with 1 N-NaOH on malt agar and pathogenicity on roots of edible burdock. Phoma black spot (Ne kokuhan-byo in Japanese) of edible burdock (Arctium lappa L.) is proposed for the new disease name.
