[Dispersion of ragweed in the Drome-Ardèche region]

Over the last ten years Ambrosia has spread considerably in the middle Rhône area; this is especially true of the Drôme, along the river Rhône, but also in remote, very sheltered localities to the East and South-East of the province. Rural areas are not spared (grain crops, peach orchards). The Ardèche is also being invaded from North to South, and further to the West, Ambrosia is starting to besiege the mountains, up to an altitude of around 2,900 feet, despite its reputation of only growing in the plains. The 1990 season was an especially difficult one, of very great intensity, and did not respond to the usual therapy (desensitization, antihistamine drugs at the maximum dose, even cortisone derivatives). A record pollen density was registered on P. Cour's pollen counter at Lyon-Bron in early September: 340 grains per square meter of air. The curative and preventative treatment of this pollinosis remains problematic and deserves a consensus.