Risk-factors for the occurrence of Verticillium longisporum in winter oilseed rape in Germany

摘要

In a two-year monitoring the occurrence of Verticillium-wilt in oilseed rape could be confirmed for all surveyed regions in Germany. However, there are some regional differences in the infestation frequency. In North- and Northeast- Germany, where traditionally oilseed rape is cultivated intensively, the disease is more frequently diagnosed. The obtained data show a clear effect of the percentge of oilseed rape in the crop rotation on the occurrence of infections by the pathogen V. longisporum. By performing the oilseed rape crop rotation in longer intervals (more than three years) and an additional growing of non-host plants in close cereal/oilseed rape crop rotations, the risk of an infestation by this pathogen could be reduced. In addition, a longer cultivation interval of oilseed rape had a positive effect on its yield. The influence of the sowing time became clear, too. The earlier the sowing/the longer the growing-period in autumn, the higher the risk of an infection by V. longisporum. The influence of the tillage on the occurrence of the disease cannot be assessed from the monitoring data. For this statement, long-term studies of a soil-cultivation field trial were consulted. The results of the studies point out the importance of the cultivation method. The influence of the harvesting machines could also be determined as the most important source of spreading the pathogen. For the evaluation of the influence of the variety characteristics on the occurrence of the pathogen and on the resulting measure of harm,data were consulted from additional trials, too. During several years, tolerances of certain varieties could be determined. The effect of organic nitrogenous fertilizer could not be assessed finally. These investigations showed also no effect of the factors soil type,pH-value and the application of fungicides on the occurrence of Verticillium-wilt disease.