Background: Senecio aquaticus is an esteemed wetland species, but it is also a poisonous species in grasslands for forage production of various countries (e.g. Great Britain and Central European states), and its further spread onto farmland must be prevented. To reveal links between management practice and the occurrence of S. aquaticus, a survey was carried out on agricultural grassland in the summer of 2005.

Location: The mountain region in the northern and central part of Switzerland.

Methods: Botanical assessments were carried out on management units (parcels) where S. aquaticus occurred and on neighbouring parcels without occurrence. For all parcels, we analysed the soil nutrients and the details of management such as intensity of fertilisation and defoliation frequency.

Results: There was a high risk of S. aquaticus occurrence in parcels with low nitrogen fertilisation, a change of management intensity in the preceding 15 years, high inclination, and gaps in the sward. The change in the vegetation composition caused by altering the management intensity most probably provided gaps in the sward, which were then colonised by S. aquaticus. A novel finding is that, despite its preference for low-nutrient sites, the species was also persistent at sites with a moderate to high management intensity.

Conclusion: A long-term control of S. aquaticus on agricultural grasslands can best be achieved by avoiding sward damage and by promoting dense and stable swards. The management should be adjusted to the local environmental conditions and the requirements of the favourable plant species. This could prevent the spread of S. aquaticus from the protected wetlands onto agricultural grasslands, where the species would threaten animal health.

Nomenclature: Lauber & Wagner (2007).