Septocyta ruborum . [Descriptions of Fungi and Bacteria

Abstract

Abstract A description is provided for Septocyta ruborum . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Rubus laciniatus, R. nessensis, R. procerus and wild blackberry ( R. fruticosus agg.). DISEASE: Purple blotch or stem spot disease (8, 288) or sometimes referred to as dieback of blackberries (32, 572). First symptoms appear in the summer on the basal portions of the shoots as intense dark green spots, the size of a pin's head, reddening after a few weeks and enlarging to a diameter of about 2 cm. Later the centres turn brown, the margin remaining red. The pathogen remains inactive during winter but at the end of February and beginning of March infection recommences, progressing rapidly upwards to a distance of 2.5-3 m from the root stock. The attack results in metabolic disturbances, the leaves and flowers or fruit rudiments becoming discoloured and sooner or later fading and shrivelling. In Switzerland the disease is widely distributed throughout the country on the cultivated variety, Theodor Reimers ( Rubus procerus ). GEOGRAPHICAL DISTRIBUTION: Europe (Britain, Czechoslovakia, France, Germany, Italy, Netherlands, Norway); North America (USA). TRANSMISSION: By conidia liberated from pycnidia in wet weather. Infection can also be spread from old branches to young shoots. In the Netherlands, in spore trapping experiments, conidia were caught daily from the beginning of April until the end of August with a sharp peak of over 4, 000 per sq. cm. daily at the end of June and beginning of July. No conidia were trapped in dry weather (32, 572). On blackberry shoots conidia on germination were observed to produce germ tubes which grew in the direction of the stomata and penetrated them (31, 561).