Didymascella thujina. [Descriptions of Fungi and Bacteria].
Abstract A description is provided for Didymascella thujina. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: 'Keithia disease' or 'cedar leaf blight'. HOSTS: Leaves of Thuja occidentalis, T. plicata. Occurring on T. plicata throughout its range in western North America, and widespread in North America on T. occidentalis, apparently confined to these two hosts, fide Pawsey (1958). GEOGRAPHICAL DISTRIBUTION: Austria, Belgium, Canada (Alberta, British Columbia, New Brunswick, Northwest Territories, Ontario, Prince Edward Island, Quebec), Denmark, Eire, Netherlands, Norway, UK (England, Scotland, Wales), USA (Alaska, Idaho, Oregon, Vermont, Washington, Wisconsin). Unsuccessful searches on introduced plants in Chile and Ukraine. With the introduction of resistant varieties of its host, this fungus is becoming less common in planted forests and on hedge trees, though it is still generally abundant in natural stands of its hosts. TRANSMISSION: By air-borne ascospores in humid conditions.