Mottet1, L. Lelevier1 and G. Fried2
1FREDON France, Ragweed observatory, 11 rue Lacaze, 75014, Paris, France
2Anses, Plant Health Laboratory, Montpellier, France
Common ragweed (Ambrosia artemisiifolia L.) is a well-known invasive species in Europe that causes allergic reactions in many people. But what about other ragweed species existing in Europe? The French Agency for Food, Environmental and Occupational Health & Safety (Anses) has conducted risk analyses for two ragweed species (Ambrosia trifida L. (1) and Ambrosia psilostachya DC. (2)) in order to contribute to the prevention and management of their introduction and spread in France and in Europe. Considering the conclusions of these two risk assessments, a strategy has been set up in France.
Ambrosia psilostachya DC. (perennial ragweed) – The risks of reintroduction in the current state of international trade is relatively low for this species. Its pollen is potentially allergenic but no evidences of social damage are available. A. psilostachya should be monitored and preventive action would appear necessary in some places due to local dense stands that may impact sensitive habitats or grazing.
Ambrosia trifida L. (giant ragweed) – Preventing introduction from the area of origin is difficult due to the large volume of (crop) seeds for sowing imported from North America. Numerous suitable eco-climatic zones for the species are found throughout Europe in areas where cropping systems have developed which could facilitate the spread of the species . Due to the great difficulty of fighting A. trifida in non-agricultural environments and the allergenicity of its pollen, it is a proven threat to human health and to the environment. A. trifida should be monitored and preventive (import controls) and curative actions are necessary. Following these recommendations, a strategy has been set up in France to prevent the spread of this pest.
The risks associated with these two invasive species are very different. The risks associated to A. trifida are much higher. Accordingly, we recommend that A. trifida should be added to the list of invasive species in the dedicated European regulation. In France, three Ambrosia species are now regulated by law: A. artemisiifolia, A. trifida and A. psilostachya.