Occurrence and distribution of Phytophthora spp. : affecting European beech (Fagus sylvatica) within Söderåsen National Park

Abstract: There has been an increase of damage on beech in Europe since the 1990s, especially in central Europe and Germany. The first report on beech in Sweden was in 2010 in Malmö and since then there have been additional observations of symptomatic beech trees at multiple locations, among which Söderåsens national park is one such location. The aim of this thesis was to investigate which Phytophthora species are present at Söderåsen and to confirm previous observations of symptomatic trees within the park. Through tissue plating and environmental sequencing the presence of Phytophthora at Söderåsen was confirmed, specifically Phytophthora plurivora and Phytophthora cambivora, of which P. plurivora is a newly confirmed species. The main spreading pathway of Phytophthora in Europe is thought to be via nursery stocks. Between 2002 and 2006 many trees were planted at Söderåsen, grown at nursery stocks in Germany and Poland. This is one possible spreading pathway through which Phytophthora may have become established at Söderåsen. Finally, this thesis gives further suggestions for management strategies within the park, of which monitoring of new symptomatic trees is the most pressing one. The success of sampling Phytophthora is heavily dependent on the freshness of the sampled lesions. For further research it is of importance to sample symptomatic trees soon after discovery for best chance of isolation success. These results give further understanding of the Phytophthora situation at Söderåsen, however there is still a lot to understand about these pathogens and how they interact with their surroundings. Further monitoring and management strategies will be needed for the future ensuring of Söderåsen as a hotspot for nature conservation in Sweden and Scandinavia.