Abstract
A description is provided for Rhytisma umbonatum. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Tarspot disease of willows. Compared with Rhytisma salicinum (IMI Description 1339) very little information is available about the time of fruiting of this species, though it is probably rather similar. HOSTS: Leaves of Salix caspica, Salix exigua, Salix fluviatilis, Salix longifolia, Salix purpurea, Salix viminalis, Salix sp. Rhytisma umbonatum seems to occur mostly on the rather narrow-leaved willows. GEOGRAPHICAL DISTRIBUTION: Austria, Czech Republic, Republic of Georgia, Germany, Hungary, India (Himachal Pradesh), Italy, Latvia, Rumania, Russia (Orenburg Oblast), USA (Washington. Wyoming), Ukraine. Altitude records exist up to 2700m (India) and 2200m (USA). TRANSMISSION: By air-borne ascospores in humid conditions.
