Senecio aquaticus – Can the occurrence be influenced by management pratice?

Senecio aquaticus Hill (marsh ragwort) is a poisonous weed in grasslands of various countries (e.g. Great Britain and Central European states); its further spread into farmland must be prevented. This study provides information on habitat preferences of S. aquaticus and reveals how management practice can influence the occurrence of the species. In a survey conducted in the northern and central part of Switzerland, botanical assessments were carried out on grassland plots containing S. aquaticus and on neighbouring plots without S. aquaticus. On all plots, we analysed the soil nutrients and the details of management practice, such as type and intensity of management and fertiliser application. The most important factors influencing S. aquaticus were related to management practice. There was a high risk for occurrence of the species with low nitrogen fertilisation, with a decrease of management intensity in the preceding 15 years, high inclination, and gaps in the sward. The change of vegetation composition caused by the decrease in management intensity most probably provided gaps in the sward, which were colonised by S. aquaticus. For long-term control of S. aquaticus, we suggest promoting dense swards, preventing sward damage as much as possible, and controlling the species when it first arrives on a parcel.