The story of Asian ladybugs in France is a striking example of the unforeseen consequences that the introduction of exotic species into a new ecosystem can have. Imported in the 1980s to combat the proliferation of aphids, this species has today become a real ecological headache.
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Asian ladybugs or the story of a well-intentioned introduction that turns into tragedy
Originally, the introduction of the Asian ladybug (Harmonia axyridis) in France and Europe aimed to solve a major agricultural problem: the proliferation of aphids. These small pest insects caused considerable damage to crops, and researchers at the National Institute of Agronomic Research (INRA) saw this species, native to Asia, as a promising solution. The Asian ladybug indeed seemed to possess all the qualities required for effective biological control. Larger and more voracious than its European cousins, it could ingest up to 100 aphids per day. Additionally, its resistance to pesticides and its ability to adapt to different environments made it an ideal candidate for protecting crops.
Rapid and uncontrolled expansion
However, what seemed like an ingenious solution quickly turned into a major ecological problem. From the beginning of the 2000s, the first feral populations of Asian ladybugs were observed in Europe, particularly in Belgium. From there, the expansion of the species was meteoric. In France, the acclimatization of the species and its extension were recognized in 2006. Since then, the Asian ladybug has colonized a large part of the territory, from the plains from the Grand Est to the Paris Basin, via the Pays de la Loire. This rapid expansion can be explained by several factors:
- Particularly efficient reproduction (a female lays around 2,500 eggs per year)
- A great capacity to adapt to different environments
- The absence of natural predators in its new habitat
A voracious appetite and ecological consequences
One of the main problems posed by the Asian ladybug is its voracious appetite. If it does indeed feed on aphids as expected, it doesn't stop there. Its diet also includes other soft-bodied insects, their larvae and eggs. Among its victims, we unfortunately find other species of native ladybugs. This aggressive predation has dramatic consequences on local biodiversity. Populations of European ladybugs, less competitive, are weakened and in decline in many regions. This ecological imbalance could have cascading repercussions on the entire ecosystem.
A problem for agriculture and housing
Ironically, the Asian ladybug, introduced to protect crops, has itself become a nuisance to agriculture. Indeed, in autumn, these insects tend to gather in large numbers on bunches of grapes. When they are crushed during harvest, they release a substance which alters the taste of the wine (a disaster for New Aquitaine!). In addition, Asian ladybugs pose problems for individuals. As winter approaches, they tend to aggregate by the hundreds, even thousands, on the walls of homes or inside houses to spend the cold season there. Although they are not dangerous to humans, their presence in large numbers can be annoying.
Research efforts to understand and control
Faced with this situation, the scientific community has mobilized to better understand the mechanisms of the invasion and try to control it. Research projects, notably carried out by INRA, aim to retrace the invasion routes of the Asian ladybug and to analyze the factors which determine its invasive success. These studies notably revealed that the invasive populations in France are in reality hybrids, resulting from a mixture between the strains imported by INRA and Asian ladybugs from North America. This genetic complexity could partly explain the great capacity for adaptation of the species.
Towards sustainable management?
Today, managing the Asian ladybug poses a real challenge. Complete eradication of the species seems impossible, and control methods must be carefully studied to avoid worsening ecological imbalances. The Asian ladybug experience now serves as a warning about the risks of introducing exotic species, even with the best intentions. It highlights the importance of a cautious approach and a thorough risk assessment before any voluntary introduction of species into a new ecosystem.
Ultimately, the story of the Asian ladybug in France reminds us of the complexity and fragility of natural balances. It invites us to rethink our methods of combating pests and to favor approaches that are more respectful of local biodiversity.
Sources :
- https://www.ouest-france.fr/pays-de-la-loire/l-invasion-des-coccinelles-asiatiques-augmente-les-pays-de-la-loire-colonises-830e99ec-5ab2-11ed-8bfd-8dba71fb0669
- https://www.cbd.int/invasive/doc/meetings/isaem-2015-01/biocontrol/iasem-france-bio-02-fr.pdf
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