Common ragweed (Ambrosia artemisiifolia L.): breaking the plant life cycle in order to exhaust the seed bank. 1. Optimisation and efficacy of various mowing schemes

Common Ragweed is becoming an increasing source of concern in Switzerland, notably because of the allergenic nature of its pollen. As a result, the control of this species is not simply targeted at arable land but indeed at every single invaded site. Thus, it is necessary to develop techniques that break the life cycle of this plant in order to stop any further seed production. This article describes and discusses results from experiments using mowing solely. This approach is particularly suitable for sites where the application of herbicides is not to be desired, like road verges, gravel pits, nature reserves, and river banks. While for certain years a single mowing at the beginning of September was sufficient to break the life cycle of the plant, for others it was not efficient enough. Thus, a single mowing strategy clearly proves to be inefficient if aiming at the long term clearing of invades sites. Actually, even the implementation of two mowings cannot guarantee a totally successful break of the plant life cycle; however, it considerablely reduces the seed production. On the basis of the best results obtained, it is recommended to carry out a first intervention mid-August, followed by a second mowing end of September.