The ‘killer wasp’ spreads across Spain at high speed

04/08/2021 at 9:03 AM CEST

Galicia, Asturias, Euskadi, Navarra, Aragon and Catalonia have already fallen under the dominion of the Asian or killer wasp, as this fearsome invasive species is known. However, all autonomies are in danger, because their expansion is advancing at a rate of 60 kilometers a year.

When in 2005 the presence of a rare wasp with a completely black thorax was confirmed in the south-west of France, nobody gave it much importance. Sixteen years later, that species has invaded half of Europe and has become a veritable plague: it threatens native bees and other pollinating insects, causes a strong ecological imbalance on the continent, and causes serious economic losses, especially in the sector of beekeeping. It is a massive predator of bees: it can destroy entire hives.

This species, which first arrived in Europe in 2004 on a cargo ship from eastern China that docked in the French port of Bordeaux, is the Vespa velutina nigritorax, popularly known as the Asian hornet, and is on the List of Exotic Species of Concern of the European Union.

Although it is not usually aggressive with people, unless it is believed in danger, in Spain it has caused a dozen deaths in the last three years and has brought the administrations upside down, which are promoting an all-out war to control their population, which is growing exponentially.

Experts argue that the Asian hornet has come to Europe to stay. And that after a first phase of expansion, its population will tend to stabilize. At the moment, what is also known as the ‘killer wasp’ has already spread throughout France, the northern half of Spain, Portugal, Italy, Belgium, the Netherlands, Germany and the United Kingdom. And it is estimated that each year it advances about 60 kilometers in all directions.

According to ecological niche models, the Asian wasp could colonize most European countries and, according to some scientific studies, the pest could be favored by climate change.

Velutina appears in the list and the Spanish catalog of invasive alien species. It was observed for the first time in Spain in August 2010, in Amaiur (Navarra). The Cantabrian communities lead the fight against this invasive species on the peninsula.

Its expansion in this area is extremely rapid due to its excellent adaptation to the weather, the absence of predators and the large amount of food available (mainly bees).

Galicia is the region with the highest presence of Asian wasps. In 2019, more than 15,000 nests were removed. The species already stars in more than 6 percent of calls to the Galician 112. In Cantabria there are no global data on the fight against this species since 2018, when more than 30,000 queens were captured.

The public-private operation to fight and control the Asian hornet of Asturias, with more than 7,000 volunteers With special permits to circumvent closures due to covid-19, it managed to capture 124,921 Vespa velutina last year, more than the rest of the Spanish autonomous communities combined, thanks to the 7,899 traps installed throughout the territory.

In 2018, the AvisAp web platform was launched in Asturias to coordinate the control actions of the species and, at the same time, be a channel for citizen participation. It already has more than 5,600 active users, who report data on the location of nests, captures, sightings and the placement of traps and it has become a fundamental tool in the fight against velutina.

Species characteristics

The Asian wasp measures between 17 and 32 millimeters in length, it is characterized by having a completely black thorax and the abdominal segments also black with a yellow border. Only the fourth segment of the abdomen is totally yellow or orange. The head is black with a yellow or orange face, and the legs are brown with yellow ends.

They can build huge, spherical nests, with the entrance hole on the side, and in which the cells cannot be seen from the bottom. They are usually located in the upper areas of the trees (mainly on alder, chestnut, walnut, apple, cherry or eucalyptus), and sometimes even in protected areas of buildings, stairs, barns, etc.

Currently, there are several investigations aimed at the fight against this species, some of them especially hopeful, based on biological control. But as long as there are no effective systems, trapping and nest neutralization are the only forms of control.

The means of struggle

Trapping, aimed at capturing queens founders, should last from February to June. There are several commercial traps on the market for this purpose, but it is easy to make them at home from a modified plastic bottle. In this case, special care must be taken to prevent the entry of insects larger than Vespa velutina and to offer exits to insects smaller than it.

A generic attractant based on sugary substances must be deposited in the traps, which can also be commercial or homemade (beer, wine, syrups, etc.) and must be renewed with a certain frequency (less than 15 days).

The traps should be hung one and a half meters above the ground, in sunny places, preferably facing South or Southeast and sheltered from the wind. Close to attractive plants, such as camellias, callistemos, citrus, flowering ivy and flowering fruit trees such as cherry or plum trees. Also in trees with aphids such as willow.

Refering to neutralization of primary nests, it is enough to apply insecticide in the form of an aerosol when the queen is inside. An interesting option is to apply the insecticide and maintain the nest, since it is frequently recolonized by another queen and in this way more founders can be eliminated.

When the primary nest has a considerable number of wasps, they form a secondary nest, usually on trees or buildings, but at high altitudes, with the consequent difficulty in their elimination.

The most widespread neutralization technique in this case is the application of biocides inside the nest, with the help of poles, drones and even compressed air weapons that fire insecticide pellets, such as those that have been used since last year in Asturias. .

Another technique more innocuous than the previous one for the environment is the use of explosives through which the nest and all the specimens inside (adults and larvae) are destroyed. This ensures the elimination of the queen and, consequently, the end of the colony. For both techniques it is necessary to have the corresponding administrative authorizations.

How to act in case of bites

The stings are very painful, but no more dangerous than those of native wasps. Most of the attacked people present local symptoms, such as pain, redness and swelling in the area of ​​penetration of the poison, which disappear in several days.

The affected area should be cleaned with soap and water, and ice or cold water applied. In the first moments you can try to denature the components of the venom using heat on the sting.

In allergic people, symptoms such as generalized itching, a rise in body temperature, a drop in blood pressure, respiratory problems, cardiovascular problems, nervous symptoms, glottis edema, etc. may appear.

In cases of multiple bites, the inoculation of venom can be very high and also cause general symptoms, such as lipothymia, severe headache, fever, and so on. In these cases, the damage caused can be significant, even if there is no previous allergy.

If after an attack general symptoms are observed, without losing calm but urgently, call 112 or go to a medical center to receive the appropriate treatment, as these symptoms are very serious and can lead to anaphylactic shock. .

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