On the occurrence of root, root collar and stalk rot of oilseed rape and on the inciting fungi of these diseases

Results about a survey at the time of full flowering (growth stage (EC 64)), at swashing (EC 85) and after harvest (EC 92) on rape diseases are presented, in which the roots, the root collar and stalk were included. During flowering or at swashing, fairly extended grey flecks in the cortex of the roots were caused by Rhizoctonia solani. Brown corky strips found at same time at shallow depth at the roots yielded mainly Phoma lingam. From the roots less fungus species were isolated than from the root collar. In both plant parts P. lingam was the dominating fungus, accompanied by Fusarium tabacinum. In the root collar Alternaria spp., Fusarium avenaceum and other Fusarium species were present at moderate share. In the roots, however, R. solani, Chaetomium- and Cylindrocarpon spp. were more present. The fungus spectrum changed from GS 85 to harvest, but this changing seems to be influenced by the weather conditions as changes were not the same each year. Specific symptoms in which no pycnidia of P. lingam or microsclerotia of Verticillium dahliae were present, had in many cases a specific fungus spectrum. - From the blueback to black discolourations on the roots and the root collar, P. lingam was present as nearly the sole fungus. Grey spots at the root cylinder yielded F. tabacinum, P. lingam and R. solani and whitish to yellow discolourations had the same fungi, but P. lingam was more present than R. solani. Discolourations inside the main root and the root collar yielded mainly P. lingam and only few accompanying fungi. - A discoloured pith contained mainly P. lingam. Even from streaky discolourations alongside the stalks, in which no microsclerotia or pycnidia were present, and which are said to be caused mainly by V. dahliae, yielded mainly F. tabacinum and P. lingam. - V. dahliae and Cylindrosporium concentricum were less present in 1987. Based on these investigations, some symptoms can be related to certain fungi, others not