The Asian wasp has been gaining prominence in recent years and it is common to find, from time to time, with headlines that tell us about people who died as a result of their sting. This fact, together with the predatory nature of the species, which literally decapitates bees to keep their most nutritious parts (abdomen and thorax), has contributed to the Asian wasp occupying the role of murderous invader in the collective imagination. In this article we are going to talk about this species, how it has settled in our territory and what are the real threats that its arrival poses to health, the economy and ecosystems.
What is the Asian wasp like?
The Asian or vetulina wasp ( Vespa velutina ssp. Nigrithorax ) is a hymenopteran native to Southeast Asia of a similar size to the European hornet ( Vespa crabro ) but which can be easily recognized as it has a darker appearance than the other hornets present in Europe : its body is mostly black and dark brown, with few yellow and orange patterns.
It builds large nests on the treetops, although they have also been detected in abandoned buildings, in brambles and even, very occasionally, buried in the ground. These are large nests, up to one meter high , but which can also be confused with those of the native wasps of our country.
The Asian wasp was detected for the first time in France in 2006, a country to which it probably arrived due to an accidental import from China through trade. In Spain, the first date comes from 2010 in the Navarran region of Baztán, and since then it has spread throughout the northern third of the peninsula.
What impacts does it produce?
Vespa velutina is included in the Spanish Catalog of Invasive Alien Species and the consequences of its establishment in Spain are ecological, economic and on human health. However, it is necessary to emphasize that the Asian wasp is not more dangerous than its European counterparts: most of the people who have unfortunately died from one of its stings were allergic and, as the expert in biological invasions and researcher at the Center for Ecological Research and Forestry Applications (CREAF, Barcelona) Joan Pino: “as they are a little larger, their poison load is also a little higher, but they are just as aggressive as the rest of the wasps. There are and will continue to be deaths from an Asian hornet sting, just as there are also several deaths each year from attacks by other wasps ”.
With regard to the economic impacts, the main problem is that during the summer season, when it has to feed the young, vetulin becomes a specialized predator of honey bees. However, it is very difficult, at the moment, to quantify the extent of these impacts on the beekeeping sector. “It is still difficult to find reliable data on this issue,” explains Pino. “The world of beekeeping is subject to strong economic ups and downs due to various factors, some global, such as the importation of low-quality honey from other parts of the world, and other local, such as pests. In this sense, there is another invasion that was that of the mites of the genus Varroa (which cause varroasis) that has caused great losses in beekeepers, in the 90s this disease practically caused the extinction of feral bees. And to all this we must add pesticides, the effects of climate change, etc. ”.
Another problem the researcher refers to lies in the ambiguity of the term ‘mortality’ when we talk about animals such as bees: “talking about ‘mortality’ in bees is difficult because the individual is the colony. We can understand it better with the simile of a tree: a honeycomb would be like a tree that the more branches – bees – it has, the bigger it is. If branches – bees – die, the tree – honeycomb – will get smaller, will produce less … and in extreme cases it will even lead to the death of the colona ”.
On the other hand, and as is often the case with invasive species, the ecological impact of the Asian wasp must also be considered: this species not only preys on the domestic bee ( Apis melífera ) but also includes other pollinators and species in its diet. of wild insects (dragonflies, spiders, butterflies, flies, caterpillars, etc.). Again, quantifying these impacts is complex and it is necessary to take into account the evolution and adaptation of the ecosystem itself upon the arrival of the invader. “When there is an introduction of an exotic species in an ecosystem what we call the ‘liberation of enemies’ occurs, that is, this species arrives without its usual competitors and predators, which can lead to a great expansion and even displacement of other species ”, explains Pino. “This is what has happened with the Asian wasp, but there are also other positive impacts, because certain species are getting used to predating on the Asian wasp, for example the honey buzzard. In some areas such as Galicia they have even dared to give estimated figures of more than 20,000 nests liquidated in 2019 by this raptor. Birds like the bee-eater, which has a very bad reputation among beekeepers since it preys on bees, are also getting used to including vetulin in their diet. In short, the predator community is beginning to take this species as an interesting new resource. In the long run, this privileged situation of not having enemies will be appeased, with which I would bet, broadly and in the future, on a certain decrease or stabilization of the Asian hornet population ”.
How to stop or prevent the spread of the Asian hornet?
Since its arrival in 2010 to the present time, the advance of vetulin through the territory has been unstoppable, and it has established itself especially in the northern third of the peninsula, since its humid climate with mild temperatures meets the ecological requirements of the species. “The areas with a more continental climate, for example Aragon, are relatively more protected from the wasp”, Pino explains, “and as far as the south and the Mediterranean we will see what happens, there could be a process of local adaptation to these conditions, and that would be very harmful, because they are areas with more bee production. Although at the moment the expansion is slower ”.
The fight against the Asian wasp is complicated: we are talking about an insect with a great capacity for reproduction and dispersal of new colony founders that can also fly several kilometers in a day. “Once it has reached a territory, it is very difficult to control an invasive insect, because in addition the traps are very unspecific and can also trap other native species”, the expert explains. The Strategy for the management, control and possible eradication of the Asian hornet , published in 2015 by the then Ministry of Agriculture, Food and Environment, focuses on preventing its arrival and expansion in places where it is not currently settled and, in areas in which it is already established, minimize its damage to populations and beekeeping farms . “Although it is difficult to control the spread of the Asian hornet, we can and must act locally,” explains Pino. “We must remove the nests from inhabited areas to protect the human population and, on the other hand, establish local support measures for the agricultural sector.”
