Have Asian hornets arrived in your community? We’ve doubled our expansion area in 6 years. climate and environment

Asian hornet or Beltina (Vespa velutina nigrithorax) is an invasive alien species native to Southeast Asia that continues to advance inexorably. According to the latest data from the Ministry of Ecology and Transition, the insect’s distribution area in Spain has doubled since 2018, from 41,700 square kilometers to 88,900 square kilometers (17% of the peninsula’s surface) as of December 31, 2024. The Province of Barcelona was established over four departments, but it is the one that has experienced the greatest growth during this period (from 266 square kilometers to 7,333 square kilometers in 2012). Parallel to its expansion on the Mediterranean coast, Beltina also expanded in the north, particularly in La Rioja, Navarra, Asturias, and even parts of Badajoz and Cáceres. In Galicia, Beltina wasp was already established in 2012 and continues to be one of its main strongholds.

Once the wasps become established, the problems begin. The main damage is predation on other insects, especially bees, in addition to damage to fruit production. Although they pose similar dangers as other hornets, they also pose a risk to public health, as they can cause severe reactions in people with allergies and in repeated stings. This year, three people have died from Beltina bites in Galicia, which is rare.

The ministry updates its information every six years based on data sent by autonomous communities, as required by Europe regarding invasive species. In the map they created, wasp detections are represented by 10×10 kilometer areas (grids). However, these records do not reflect the density of Beltina present in each grid, i.e. whether one nest was found or more than 1,000, as in Vigo, the most affected town in Galicia, for example.

“The criterion we follow is nest detection. If we see that the nest is empty because the queen has already fledged, then the grid is considered settled,” a minister source indicated. Thus, the presence of wasps is not necessarily confirmed in every municipality included in this grid, but rather in their immediate vicinity. Important information to use extreme caution and report any sightings of specimens or nests, as early detection is essential to controlling nest expansion.

This insect is not easy to find, so its presence is usually underestimated. The queen’s first colony is about the size of an orange and is built in any corner so no one notices. Once they disperse, a secondary worker ants emerge, where there are over 1,000 workers in addition to the queen and males.

Due to the high population density, their numbers are much higher, but that does not make them easier to eradicate. They are usually located in leafy trees or high ground (10-12 meters) or in another human structure that is difficult to access. Authorities have warned that their removal will require specialized personnel and safety equipment.

Purpose: Early detection

“The aim is to achieve early detection and from there take measures to prevent the establishment of the hornet,” says Mar Reza, professor at the Department of Biology at the University of the Balearic Islands and coordinator of the Beltina Task Force working group on hornet invasions and impacts. He believes that “there is a lack of overall coordination at the level of biosafety measures in Europe. If there was more collaboration, it could prevent everyone from making the same mistakes, for example, when their presence is discovered.”

Initial control is working in the Balearic Islands, but invaders reoccur from time to time in Mallorca. Success lies in the creation of interdisciplinary working groups. “On the islands, we are like a laboratory. The entrance is very clearly defined, so you arrive by sea or by air, and you cannot come alone. In other places, like Galicia, you enter from the Cantabrian coast through Portugal…” he explains. What is not clear, he added, is that “if we do nothing, things will continue to progress.”

They have developed prototypes to automatically detect species and have installed traps in port and airport areas, “confirming that these biosecurity measures are working.” But there are other places in the country where “we can only protect honeybees or control invasive populations.” In these areas, it is suggested that traps be placed at the entrance to the nest to prevent wasps from hunting honey bees, their main food source.

In Galicia, a pilot program started in 2024 saw more than 14,400 nests removed between January and September of this year. As a result, the number of queen bees caught has doubled compared to 2024, from 230,000 in the first nine months to 113,000 last year. And furthermore, the number of notifications warning of its presence has decreased by almost 30% over the past two years compared to the previous year when the trap was not present, Kunta said in a statement. Informative lectures were also given to residents. Experts warn that the traps are not selective and that native insects will fall into them, seriously impacting biodiversity.

Zessus Fies, a veterinarian specializing in this pest, says the spread of Beltina in Galicia is an example of what can happen if intervention is not done in time. What’s important is that “the problem is getting worse, so rather than just implementing a spring trapping program, we need to develop a full-fledged plan that involves the government, emergency services, beekeepers, and the public.” He also warns that we need to rethink our strategies and integrate data collected in the field to see what role weather plays in this invasive cycle. “There’s a lack of research,” he sums up. Public notification is another fundamental pillar of this fight.

The species was first discovered in France in 2004, likely due to the hibernating queen being accidentally imported from China in some gardening product. In Spain, the first outbreak was confirmed in 2010 in Amayuru (Navara). In the same year, an outbreak occurred in Gipuzkoa in the Basque Country. Currently, it is widely distributed in Spain, France, Belgium, Portugal, Italy, and Germany. Prefers temperate regions without extreme heat or cold, especially humid regions.

Their annual cycle begins in spring, when the fertilized queen wakes up after spending the winter in hibernation and builds her first nest. There they lay eggs and the first worker bees are born. Starting in the summer, the colony grows and moves to a much larger secondary nest in a tall leafy tree (10-12 meters) or in a human structure. In the fall, the colony produces males and a new queen, mates and seeks shelter for the winter, while the rest of the colony dies from the cold. In this way, only the surviving queens resume the reproductive cycle the following spring, and the number of queens increases rapidly.