Ambrosia on the side of a road in Simard, Saône-et-Loire, August 16, 2023 (AFP / JEFF PACHOUD)
Between 59 million and 186 million euros per year: faced with the medical cost of ragweed allergies, the authorities are trying to stem this invasive and highly allergenic exotic plant, imported into France in the 19th century.
In Auvergne-Rhône-Alpes, a region particularly affected by this scourge, the massive arrival of pollen took place on August 11 this year. It extends over “a period of one month, that is to say until the first half of September”, explains Hervé Bertrand, environmental health technician at the Auvergne-Rhône-Alpes Regional Health Agency and regional referent on ambrosia.
“The problem is that it is a plant that is in the process of flowering and if we don’t cut before, there will be pollen, seeds, so the ideal is to cut to avoid that the pollen becomes allergenic (makes you allergic)”, explains Gabriel Freire, team leader in the road service of the Rhône department, who is mowing.
The leaves of ragweed, a very invasive plant native to North America, are cut, green on both sides, the stem is rather reddish, covered with white hairs.
Mowing ambrosia growing on the side of a road in Simard, Saône-et-Loire, August 16, 2023 (AFP / JEFF PACHOUD)
Rhinitis, conjunctivitis, itching: “What is typical of ambrosia allergy is that it generates a much higher risk of asthma. We are not on a little hay fever”, describes Hervé Bertrand .
According to Daniela Muti, allergist at the Clermont-Ferrand University Hospital, its pollen, “even at low concentrations, gives significant symptoms”. The quality of life is very degraded, to the point of putting the lives of asthmatic patients in danger if nothing is done.
On average, 10% of the population is allergic in the infested areas but this percentage can reach more than 25%, according to Mr. Bertrand.
The number of allergic people could grow further with the increase in CO2 in the atmosphere, up to 10 million in 2041-2060, according to scientists.
In 2020, ANSES estimated that medical care represented between 59 and 186 million euros per year, not counting production losses, such as work stoppages, between 10 and 30 million euros.
– Loss of crops –
Mowing ambrosia growing on the side of a road in Simard, Saône-et-Loire, August 16, 2023 (AFP / JEFF PACHOUD)
In Auvergne-Rhône-Alpes, the ARS implemented action plans in the 2000s.
The region – in particular the Rhône valley – is the most affected with 80% of reports, explains Frédéric Caray, in charge of the Auvergne-Loire ambrosia control plan for Fredon, national network for monitoring species harmful to human health. .
The departments most affected are Rhône, Ain, Drôme, Isère: “It is a plant which has spread via road works and which has a great capacity to settle in field crops. The east of Lyon met all the conditions that facilitated its installation”, says Mr. Bertrand.
But ambrosia is able to grow higher and higher, especially under the effect of global warming.
Other departments called “front areas”, less infested, are closely monitored such as Haute-Loire, Cantal, Charentes or Côte d’Or.
“The objective is twofold: to limit the quantities of pollen for the infestation zones, rather by crushing or mowing, and to prevent its spread in the front zones by uprooting”, according to Mr. Bertrand.
“It’s a struggle that interests everyone: communities, businesses and individuals,” he says.
Ambrosia growing on the side of a road in Simard, Saône-et-Loire, on August 16, 2023 (AFP/JEFF PACHOUD)
Uprooting campaigns are organized in the spring until the end of July, before flowering. A reporting platform has been set up and prefectural decrees make its destruction mandatory.
In Vendat in the Allier, the association Les Jardiniers du Bourbonnais organizes an uprooting operation every summer: “We have been practicing definitive uprooting for eight years and it works, we have almost none left”, welcomes its president Claude Grollet, while regretting that the surrounding municipalities do not do the same.
In addition to health nuisances, there are lower yields for corn, soybean or sunflower growers: “it proliferates so much (…) we can completely lose the crop” and “economically, it weighs, so we have to act upstream” , emphasizes André Coppard, vice-president of the Isère Chamber of Agriculture.
Finally, this species contributes to the impoverishment of the environments it colonizes, explains Frédéric Caray.
Only interest: it is edible for sheep and goats. Eco-grazing experiments have been carried out. “It can be one of the ways of management, but it will not be enough to eradicate it”, he assures.
© 2023 AFP
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