[The campaign against the spread of ragweed: the Quebec model]

In Canada, the "lesser flea grass" is a native species. Deposits of its pollen have been found to be over 60,000 years old, but it only started to spread on a large scale two centuries ago. The fight to eradicate ragweed began in 1937 when E. Campagna enlisted the help of school-children in Gaspesia to pull up the weed. Fifty years later, the effectiveness of this method is still visible. However, independent attempts made in Montreal in 1950 turned out to be insufficient. Later campaigns were first undertaken by the local councils, then by the Montreal Urban Community, and were later upheld by the Quebec Ministry for the Environment. Rulings by the latter have power of authority. They may take matters as far as prosecution. The decision-makers have financed pollen collectors, which are indispensable control measures. They have proved that the incidence of the disease was related to the quantity of pollen present and that the pollen index improved as more and more campaigns were implemented. G. Vincent has shown that weeding was the best method, but that mowing the weed at a height of 2 cm also good results, as long as this was done exclusively at the same time as in France, the second fortnight in July.