The Asian ladybird beetle is mobilized in the fight against aphids
In Belgium alone there are several different species of aphids which attack a wide range of plants including rose bushes, ornamental trees, cereal crop fields, orchards and garden produce. The ladybird is one of their main predators. Why not, therefore, use the destructive power of the Asian ladybird beetle (Harmonia axyridis), which has proliferated in Europe, to defeat these tiny pests? In this area, integrated pest management has taken a giant leap forward. Published recently in the scientific literature, the identification of the insect’s sex pheromone by the Functional and Evolutionary Entomology Laboratory of Gembloux Agro-Bio Tech has constituted a major breakthrough in understanding this ladybird species that is so different from others. However, there is a great deal more work involved in getting from the laboratory phase to the field safely and efficiently. This is the reason why, despite the traditional hazards associated with applied research, work has continued apace at the Gembloux Agro-Bio-tech site.
Over the last twenty years or so, the Asian ladybird beetle (Harmonia axyridis) has established itself in the natural and artificial environments of our countries. At first it was only used in greenhouses to control aphids (and was expected to die when the appropriate season arrived), it accomplished its original mission “too well”. Reputed for its voracity (particularly its larvae), the small beetle showed itself to be capable of surviving low temperatures. More importantly, it has become a very serious competitor of indigenous species of ladybirds, particularly those with two spots (Adalia bipunctata) and those with ten spots (Adalia decempunctata), whose eggs and larvae it devours. In vineyards and orchards, Harmonia axyridis has the annoying tendency to head straight for the mature fruit and to cling to it in the form of clusters of several tens or hundreds of individuals. This alters the taste of the final products during harvesting and processing. Even private individuals in their homes soon begin to tire of this “ladybird from hell” that has come all the way from Asia: while its intrusion into people’s houses may be welcomed at first, this soon changes when it reveals all its habits. It can, for example, hibernate in even the smallest cracks in walls and nooks and crannies of chassis and, in some circumstances, to release a messy substance to which some people are allergic (leading to rhinites, skin rashes, etc.)
At the Functional and Evolutionary Entomology Laboratory of Gembloux Agro-Bio Tech (University of Liege), we followed the progression of the Asian ladybird in Europe and Belgium on a step by step basis: in Flanders first, then in Brussels and all of Wallonia. We tried to understand the mechanisms behind this very rapid expansion. A few years ago, for example, the researchers at Gembloux demonstrated the role of hydrocarbons secreted by these animals to “mark” the meeting places and encourage their fellow-creatures to assemble there. The research, which in its present incarnation is the AgricultureIsLife platform has concentrated on integrated pest control from the outset. The intention always has been and still is to ban the use of synthetic pesticides or reduce their use to a bare minimum. Integrated pest control prioritizes the use of a combination of various natural preventive and curative techniques over the use of pesticides. These techniques are more natural and by reinforcing each other, succeed in limiting insect infestations and the resultant damage to crops. Such techniques could involve using Harmonia axyridis or any other destructive species for that matter...
Simulation in order to attract
One of the most important recent discoveries with regard to the Asian ladybird beetle, was the identification two years ago of the sexual pheromone involved in its reproduction (See The hunt for aphids, a sexual matter). “We must see reason”, explains François Verheggen, head of work at the entomology laboratory: it would be completely delusional to try to eliminate this animal which has established itself so strongly throughout Europe. And who in their right mind would dare to call for the use of synthetic products which are toxic for the environment and the user? These products would also damage other species. We need to adopt a smarter approach, for example, by trying to use the Asian ladybird beetle to our advantage, notably in the fight against aphids. But this can only happen on one important condition! This time we need to fully understand and control its characteristics. We can no longer play the sorcerer’s apprentice as was the case in the garden products sector in the nineties”!