[To be effective and not harmful, ragweed-trimming methods should be rigorous].

We decided to undertake the experiments dedicated to the height of Ragweed cutting. The experiment was focused on transplanted plants of Ragweed two months earlier to study the growth of male spikes. It took place near Lyon, on the second part of July 2000. We proved with the experiment that the number of male spikes produced is, to a significant extent, much more important when the height of cutting back is 10 cm instead of 5 cm. Moreover, to inhale or to be in contact with airborne matters because of Ragweed was at the origin of allergic symptoms for the author that was not atopic. It explains that Ragweed is a pollutant agent when inhaled in large quantities. Therefore, during the eradication campaign--last two weeks of July--it results better to cut back Ragweed close as possible to the ground. From spring to mid-July it is imperative not to abrade ground whereas after this period it is not really an essential point. Moreover, Ragweed has not enough grown to be cut with a mower or an edge so cutting back deals with other types of vegetal cover.