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RESEARCH PRODUCT

Impact of campaigns to control common ragweed on the pollen production in France

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National audience; The dispersion of common ragweed (Ambrosia artemisiifolia L.) is anthropogenic, and because it is an invasive plant, a number of control procedures have been implemented whose effectiveness was measured. Measures on pollen emissions were compared between areas with different level of management. In addition to pollen traps of the French aerobiology network (RNSA), passive traps (SLT: SIGMA2 Like Trap) were positioned near controlled or non-controlled areas. Two areas were selected: - infested areas, in Rhône-Valley, 12 SLT were set up: 8 in Estrablin, with 2 in non-controlled areas and 6 in well-controlled areas; 4 near Valence, with one in non-controlled area and 3 in well controlled areas - a few infested area around Dijon with 4 traps located in lightly infested areas of which one in an area without ragweed plants and three in areas with presence of small amounts of ragweed plants. Ragweed pollen amounts collected from controlled and non-controlled areas are different, with a difference of ten to hundred times of the number of grains for controlled against non-treated areas. On the area not really infested, the quantities of pollen are limited to low tens of ragweed pollens grains. Periods of heavy pollination of ragweed pollens are similar for SLT and Hirst pollen traps. Even if the amounts of pollen collected from the wellcontrolled infested areas are still high, they are significantly less important than the amounts present on non-controlled areas. The set-up of management practices enables to locally reduce the pollen pressure but only a generalized and integrated control will actually enable to relieve allergy threats to people.