Gegenwärtige Verbreitung, Ausbreitungs- und Begrenzungsfaktoren der Phytophthora-Erkrankung an Erle im Spreewald

2003

S. 251-255

17 Lit. Ang.

Unselbständiges Werk

200099704

Since its first identification in the biosphere reserve Spreewald Forest in 1998, the new alder disease has already far spread in this region. Therefore, since 2001 the causes of its distribution have been sought within the scope of a research project, to develop measures for limiting or controlling the hazard. Stand survey in 15 representative stands has shown the average proportion of infected trees in the study area accounting for approx. 15 %, with the younger trees (= 50 year-old) being slightly more damaged. The alder Phytophthora could be identified as the most frequent agent causing this disease. Moreover, fruit bodies of 8 different white-rot agents were ascertained in ca. 10 % of trees primarily suffering from Phytophthora spp., which contribute to an acceleration of the diseases process. Based on a continuous sampling, statements can be deduced of the seasonal activity of the alder Phytophthora. Consequently, the development of the pathogen over the frostly months December through March seems to be largely stopped, thus wintry flooding does not cause the disease to progress. High degrees of the infection develop especially after inundations during the growing season in low-height stands and riparian zones. The alders planted on sufficiently high borders or hills are not or almost not affected. By means of a laboratory experiment it could be shown that pH values continuously measured in the water streets provide favourable preconditions for a vegetative reproduction and spreading of the alder Phytophthora. In vitro an optimal production of the sporangia was obtained in pH range from 6 to 7. Testing of the susceptibility of the seed material to alder Phytophthora revealed that the pathogen, though it could not be isolated from fruits of the wintry water harvest, was verified, however, by an inoculation experiment. But several incubation conditions showed that survival is possible but limited and for a short period only.