Fungi occurring on aerial constituents of cultivated blackberry (Rubus fruticosus L.) in Norway.

Cultivated blackberry (Rubus fruticosus) was recently introduced in Norway, and most plantings were established in the 1990's. Many of these plantings died back or had severe damage on leaves and stems. Plant pathogens incombination with frost injury were suspected to be the cause of the damage. In 1998-99, field and greenhouse plantings of blackberry were surveyed for the occurrence of plant pathogenic and saprophytic fungi. A total of 33 different fungi were identified in 18 cultivars from 23 plantings (19 field and 4 greenhouse). Of these, 12 were pathogenic fungi, while 21 were non-pathogenic, secondary invaders. The most important pathogens on the canes were (common name in parenthesis) Septocyta ruborum (Purple blotch), Gnomonia rubi (Gnomonia canker) and Sydowiella depressula (Sydowiella canker). Pathogenic fungi of less importance on the canes were Elsinoe veneta (Anthracnose) and Coniothyrium fuckelii (Cane blight). Peronospora sparsa (Downy mildew) was the most important fungus attacking leaves. On fruits Botrytis cinerea (Grey mould) was the most prevalent pathogen. Cladosporium spp. (Cladosporium rot) and Penicillium spp. (Blue mould) were frequently observed on fruits, but did not seem to be of significant importance. Other minor fruit rots were due to Colletotrichum gloeosporioides (Bitter rot) and Mucor sp. (Mucor rot). Phragmidium violaceum (Blackberry rust) was found on canes and leaves, but was of minor importance. G. rubi and S. depressula caused damage mostly in the thornless cultivars, and P. sparsa was found almost exclusively in the thornless cultivar 'Loch Ness'. Both thorny and thornless cultivars were damaged by S. ruborum. In greenhouses the major fungal problem was B. cinerea.