Jimsonweed (Datura stramonium L.) is an invasive weed that produces highly toxic alkaloids, posing a threat to both human and livestock health by infecting crops. The aim of my project is to identify biosolution using fungi (and oomycetes) and/or plant extracts for managing this plant in agricultural fields. 195 fungi and oomycetes were isolated from jimsonweed plants showing collar pinching, wilting, yellowing, and root necrosis symptoms. Symptomatic plants were collected either directly from field or from bioassays in growth chambers using soils from crop fields with varying degrees of jimsonweed infestation. The isolates were purified by successive subculturing and cultivated on potato dextrose agar and carnation leaf agar for morphological characterisation. Most of them showed characteristics similar to those of Fusarium spp., Alternaria spp., Rhizoctonia spp. and Pythium spp.. The pathogenicity of different isolates was evaluated through their necrotic activity towards the germ tube and rootlets of germinating jimsonweed seeds, and their ability to cause damping-off on seedlings. Two experiments were conducted. First, pregerminated jimsonweed seeds were placed on pleated germination paper in a Caubère box and hydrated with 50mL of propagule suspension. The rate of necrosis on germ tubes and rootlets was evaluated. The second experiment consisted in transplanting pregerminated jimsonweed seeds into disinfected and non-disinfected substrates (soil/perlite, 70/30, v/v), which were inoculated with propagule suspension to assess the damping-off ability of each isolate. The most efficient isolates were characterised and their specificity evaluated. Two of them, including one that had never been described anywhere and one described only in the US, turned out to be pathogenic to jimsonweed and constitute promising candidates for the control of this weed. The second approach based on the use of substances of plant origin was carried out by spraying a panel of essential oils previously selected via a bibliographic analysis. Eight essential oils (Orange, Eucalyptus, Lavender, Lavandin, Thyme, Savoury, Clove, and Oregano) were sprayed at different concentrations (0.1, 1, 5, 10, 15%) on jimsonweeds at the 2-3 leaf stage. Two essential oils performed very well. A bioguided fractionation of these essential oils is being carried out, in interaction with the Faculty of Pharmacy of Strasbourg (L. Valois) to identify the fractions carrying the bioherbicide activity on jimsonweed and to identify the molecule responsible of the activity. All the results acquired make it possible to meet the objectives of this ICE1 thesis by proposing two products, one of fungal origin, the other of plant origin, which can be used in a complementary manner and constitute a strong component of the biosolutions sought for the jimsonweed control.