Biology, introduction, dispersal, and distribution of common ragweed (Ambrosia artemisiifolia L.) with special regard to Germany

Ambrosia artemisiifolia L. (common ragweed) is an annual species in the Asteraceae from the prairie regions of North America, which occurs in many European countries. It can cause hay fever through its pollen and dermatitis by contact to the inflorescence. Due to its late flowering the period of suffering for allergic persons is lengthened. Because of its potential as a competitive weed, it is under weed control in several countries. Our study summarizes the knowledge about the population biology and ecology of A. artemisiifolia. Reactions to stress factors and to herbicides are pointed out. Bird seed is the most important pathway for the introduction into Germany. Currently, A. artemisiifolia shows three centres of distribution in Germany: the area Mannheim/Ludwigshafen, southern Brandenburg and south eastern Bavaria. There is no evidence for a threat to native species. At the present climatic conditions a continued occurrence of A. artemisiifolia in Central Europe is highly possible, even more so under global change conditions of elevated temperature and/or carbon dioxide. Although A. artemisiifolia plays no important role as weed at the moment, it should be controlled because of its potential allergenic properties.