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Controlling ragweed: a multidisciplinary and international approach

22 Sep 2022

On 8 and 9 September 2022, the International Ragweed Society, the international committee for the fight against ragweed, met in Budapest (Hungary). This human-sized symposium gave the floor to some fifteen countries, including France.

The forty or so people invited to Budapest (Hungary), as part of the International Ragweed Society, the international committee for the fight against ragweed, came from some fifteen countries*. France was represented by Terres Inovia and Fanny Vuillemin, expert in weeds and alternative weed control techniques. Many topics were discussed.

  • The distribution and extension of the different ambrosia species, including the impacts of climate change.
  • Biology of the weed (germination parameters, competition of two ambrosia species with other weeds).
  • The different management techniques, including biological control techniques such as predation by the beetle Ophraella communa or carabid beetles.
  • Relations with authorities and institutions for ragweed management, aerobiology (monitoring of pollen presence and spread, forecasting).
  • Impacts of allergenic pollen on human health and populations.

Terres Inovia presented the different levers of integrated protection for the management of mugwort in rotations involving sunflower or soybean in France.


Combining levers to control ragweed

Based on the results of the technical institute's trials, the presentation covered a broad spectrum of levers: agronomic, mechanical and chemical, which must be combined if we want to successfully control ragweed.

While integrated weed management was widely developed (introduction of winter crops in the rotation, summer stubble ploughing to reduce grain stock, false seeding and shifting the sowing date of the spring crop, hoeing, harvesting of infested plots last and cleaning of the combine), herbicide programmes were also discussed for sunflower and soybean, including future solutions (currently being registered).

The main message was to diversify the different levers by relying as much as possible on prophylactic and agronomic techniques to both reduce the risk of ragweed resistance to herbicides and manage it effectively.

Finally, the "Geoadventice" service offered by Téléspazio, which allows for the precise detection of ambrosia in fields at the early stage of the crop and pre-harvest, was mentioned as a future prospect.

The economy seriously affected by ragweed

The symposium revealed that ragweed, which is widely present in Lombardy (Italy), the Rhône Valley (France) and the Pannonian Basin (including Hungary, Serbia, Croatia and Slovakia), causes serious damage to the economy for two reasons:

    The costs of caring for patients suffering from allergic respiratory diseases caused by ragweed pollen (rhinitis, bronchitis, asthma) are high.
    The agricultural impact related to crop yield losses, the level of which increases with the extension of the ragweed's territory.

Due to the ongoing global climate change, pollen concentrations are increasing, the pollen season is prolonged, the habitats of allergenic taxa as well as those of ragweed are expanding northwards, more and more people are affected by ragweed and its pollen, and thus the overall risk to public health is increasing

The aim of the conference was to draw attention to this context, as well as to provide an overview and solutions to the environmental and social challenges posed by ragweed and its pollen.

*France, Hungary, Italy, Switzerland, Belgium, Germany, Poland, Austria, Slovakia, Serbia, Croatia, Romania, Ukraine, Latvia, Spain and the USA.

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