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The main cause of allergy and pollen asthma in North America and Central Europe is pollen from ragweed (Ambrosia) a widespread genus in the Asteraceae. In Europe short or common ragweed (A. artemisiifolia) is prevalent.
Ragweed is monoecious: male flowers are numerous on top of the plant while the female flowers sit below, near the stem. The species produce large quantities of pollen from August to September. This pollen, highly allergenic, is transported by wind over far distances. Ragweed has an enormous invasive potential through the production of large quantities of seeds with very potent germination capacity. Actually, ragweed has a higher spread potential than most indigenous annual dicotyledonous and grass weed species in Central Europe.
This situation requires a tight monitoring of he plant and the implement of strong control strategy involving not only farmers but also the staff managing natural areas, road sides, building- and gravel industries.
The destruction of many single plant foci may help reducing the number of seeds produced and may slow therefore the spreading of ragweed.