Développement d’Ambrosia trifida L. en France : connaissances historiques et écologiques en vue d’une éradication de l’espèce

Giant ragweed (Ambrosia trifida L.) is an annual Asteraceae originating from North America introduced in France in the early twentieth century. Originally described in ruderal habitats, Ambrosia trifida has recently been reported in cultivated plots in South of France (Midi‐Pyrénées area). As this species is a major invasive weed in North America, its native area, the question arises about the future development of the species in France. Can we assume a low capacity of the plant to adapt to landcapes in France with a low risk of naturali‐ zation or should we consider a program to eradicate this species before it colonizes natural environments where its management would be more complex? Acquired data indicated that giant ragweed eradication remains a realistic medium‐term objective. KEY‐WORDS: invasive alien species, pollen allergy, Asteraceae, emergent plants, herbarium collection, polemo‐ chorous species