Author
Zoé Rousset
zoe.rousset@inrae.fr
INRAE
Sophia Antipolis (FRANCE)
Coauthors
Sophie Agostini, INRAE, Sophia Antipolis, France
Romain Scherpereel, FREDON, Montpellier, France
Isabelle Le Moine, INRAE, Sophia Antipolis, France
Vincent Lesieur, INRAE, Sophia Antipolis, France
Nicolas Desneux, INRAE, Sophia Antipolis, France
Abstract
Common ragweed (Ambrosia artemisiifolia) is an invasive weed native to North America that was accidentally introduced into Europe in the mid-1800s. It causes major yield losses in agriculture and is a public health concern, due to its pollen triggering severe allergic reactions. In Europe, the public health costs of ragweed allergies are estimated at ~ €7.4 billion per year.
In 2021, INRAE initiated a biocontrol program using the leaf beetle Ophraella communa. It has been effective in Italy, where it was accidentally introduced to the Milan region in 2013, leading to an 80% reduction in airborne common ragweed pollen. Subsequently, O. communa spread to Eastern Europe and was first detected in France in 2023. Nonetheless, the first intentional release in France occurred in May 2025, targeting areas where the beetle had not established.
We investigated the population expansion dynamics and growth rate of O. communa, and quantify its impact on the target weed. We monitored herbivory damage and measured the relative growth rate and flower production of common ragweed, and continuously monitored O. communa population dynamics. Sampling was conducted in both naturally colonized areas and at release sites.
We expected an increase in established population size between 2024 and 2025 in naturally colonized areas and are studying factors that could explain success or failure of population establishment at release sites.
keywords
Ambrosia artemisiifolia
biocontrol
herbivory pressure
plant-insect interaction
population dynamics
Highlights
Ophraella communa has colonized the French Rhône valley spontaneously in late 2023
The control of common ragweed can be optimized by combining Ophraella communa with plant cover
The BC program enabled the establishment of 26 additional O. communa populations in France in 2025