In thirty years, the multicoloured Asian lady beetle has invaded our regions, causing significant damage on an ecological, economic and societal scale. A recent study shows that rather than eradicating it, this lady beetle could be used in integrated pest management programs. Researchers from the Unit of Functional and Evolutionary Entomology at Gembloux Agro-Bio Tech (University of Liège), in partnership with the Laboratory of Analytical Chemistry, have recently discovered the existence of a sex pheromone emitted by female multicoloured Asian lady beetles in the presence of aphids. A volatile chemical signal that attracts males without fail. The team from Gembloux is the first to reveal the involvement of a sex pheromone in lady beetle reproduction. The blend of molecules was reconstituted in the laboratory and will soon be tested in field crops. If the field experiments meet the researchers’ expectations, these findings will allow them to control and manipulate the movements of these lady beetles, leading to a more efficient biological control of aphids. A study published in PLOS ONE.

At the end of the 1980s, multicoloured Asian lady beetles were imported into Europe. The aim of this importation was to biologically control the proliferation of aphids, these small harmful insects that are a source of fear for farmers and a delicacy for lady beetles. Acting as a natural insecticide, the multicoloured Asian lady beetle was restricted to greenhouses and confined areas. This exotic species wasn’t supposed to end up on the outside, and in any case, wouldn’t survive the wintry conditions of our country. However, it didn’t take long for this lady beetle to be found into the wild. This failure to foresee the acclimatisation of these lady beetles had already occurred ten years earlier in the United States. But humans don’t always learn from their mistakes. Shortly after its introduction, this species is found everywhere and is thriving (read the article The invasion of the multicoloured Asian ladybird…). "To survive during winter and avoid unfavorable conditions", explains Bérénice Fassotte, a researcher from the Unit of Functional and Evolutionary Entomology at Gembloux Agro-Bio Tech (ULg), "they find their way into homes to overwinter and aggregate in the corners of windows, frames and behind the curtains, and in the spring, they wake up and reproduce outside". In principle, it’s not a problem if an exotic species becomes acclimatised. However, this species proliferates rapidly and is becoming invasive and destructive.

Several negative impacts

“Today, the multicoloured Asian lady beetle is quite common in our ecosystems”, explains François Verheggen, research scientist at the Unit of Functional and Evolutionary Entomology. "This species is responsible for different kinds of damage. First of all, there’s a predation problem on some indigenous species. These lady beetles reproduce faster and their larvae are more voracious than native ones. They will even feed on larvae from other lady beetle species. A Ph.D. thesis recently defended by Axel Vandereycken demonstrated the decrease of native species over the last few years. During the last two years of his research, the two-spot lady beetle no longer appeared in the field inventories, as it had simply disappeared from the crops he was studying."

But predation isn’t the only damage caused by the multicoloured Asian lady beetle. "Before overwintering", Bérénice Fassotte continues, "they accumulate energy reserves. In the South of France, this behaviour has caused major damage to vineyards. In our regions, it’s mainly apple and pear orchards that have been affected. Finally, health issues are also reported during the overwintering period. When they invade houses, they can form groups of several hundred aggregated individuals." House-owners attempts to get rid of them are in vain. The lady beetles chemically mark their overwintering site and the odour helps them to find their way inside. If you try to get rid of them, they just come back again. But the main problem is when they feel they’re in danger, and they produce molecules that can be toxic. Some people develop allergic reactions to these substances, ranging from eczema to respiratory problems.

All these phenomena linked to the presence of the multicoloured Asian lady beetle, have of course sparked the interest of the laboratory’s members, who have been specialising in aphids and their predators for the past two decades. Since 2006, several research topics have been developed in order to find out more about this species. Its importation, its acclimatisation in our country and its impact on native species, its gregarious behaviour, its chemical communication systems, and recently, the chemical mechanisms involved in its sexual behaviour. In our research, there is no question of getting rid of the species. "Bérénice’s research is included in the AgricultureIsLife platform", François Verheggen explains. "The organisation regroup several Ph.D. students working on various themes relating to crop production in a reasoned, sustainable and ecological manner. The main idea is to promote the findings made in the laboratory in order to develop control methods against aphids. This can be achieved by manipulating this lady beetle species, which is a particularly voracious predator. Some people want to eradicate it. Personally, I don’t think that’s possible. So we might as well make the most of it."

(1) Bérénice Fassotte, Christophe Fischer, Delphine Durieux, Georges Lognay, Eric Haubruge, Frédéric Francis, François J. Verheggen, First evidence of a volatile Sex Pheromone in Lady Beetles., Plos One, décember 2014