Control of marsh ragwort in conservation grassland

Recent modification of grassland cultivation led to severe changes in the vegetation structure. One of these changes was that undesired species became dominant. One of these problematic species is marsh ragwort (Senecio aquaticus). This species has always been quite common in the wet grasslands of Central Europe, however, coverage was usually low. Now, a substantial increase and a local formation of dominance stands are reported from Austria, Southern Bavaria, Upper Suevia and Switzerland. As all parts of the plant contain pyrrolizidine alkaloids which are poisonous to livestock and men, this development is highly problematic. Currently, the most effective methods to control marsh ragwort are pulling the plants out or applying herbicides (Suter&Lüscher 2008, 2012; Gehring&Thyssen 2016). The disadvantage of these methods is that they are economically unviable and that they are not allowed at conservation sites. Knowledge on the control of this species on extensively managed areas which are relevant for nature conservation is still poor. The objective of the present study is therefore to develop management concepts which achieve adequate control of marsh ragwort by strengthening the competition of the associated plant assemblage and by preventing seed shedding.

One of the approaches followed here is shading where the competitive ability of the plant assemblage associated with S. aquaticus is supported by a reduced mowing frequency. This shall suppress the development of the light demanding and low competitive marsh ragwort by reducing biomass- and seed production. This approach is implemented in five different variants at six sites with a low productivity in the Bavarian and Suevian part of the Allgäu, Germany. At seven more productive sites cutting regimes are additionally tested which target to reduce reproduction by cutting before the flower heads develop ripe seeds. The objective of this study is to derive recommendations for a sustainable regulation of marsh ragwort. A second important aim of these field experiments is that the impact of the recommended methods on the species diversity is as low as possible. Studies under controlled conditions in glasshouse focusing the light demand, the competitive ability and the sensitivity to cutting of marsh ragwort shall complement the knowledge acquired in the field investigations.

This project is based on a cooperation with the Bayerischen Landesamt für Umwelt (LfU), the Landesanstalt für Umwelt Baden-Württemberg (LUBW), the Landschaftserhaltungsverbands (LEV) Ravensburg, the Landwirtschaftlichen Zentrums Baden-Württemberg (LAZBW), the “Allgäuer Moorallianz“ and the city of Kempten. The project is also closely collaborating with the complementary project “Effective management of marsh ragwort in Bavarian pastures”. It is financial supported by the Bayerisches Landesamt für Umwelt in Augsburg (LfU) and the Landesanstalt für Umwelt Baden-Württemberg (LUBW).

The project is managed by MSc biol. Marie-Therese Bleicher who writes her doctoral thesis on this project. Senior project manager and supervisor of the thesis is Dr. Harald Albrecht.