The role of the Asian hornet in the decline of bees is confirmed

Abellar experimental / colmenar experimental

After two years of compiling data on peri-urban conditions, the UABee Project confirms that the Asian predatory wasp represents a large menace to the survival of bees, but also demonstrates the possibility of preventing this decline by adequately managing beehives.


A team of researchers from the UAB monitored the UABee experimental apiary for two years, from March 2019 to February 2021. Initially, the apiary was formed by six beehives housing Iberian bees (the Spanish bee, Apis mellifera iberiensis). This is the first fully monitored apiary in Spain which is being monitored with both manual methods and sensors. The sanitary conditions of the apiary are premium (compulsory treatments against Varroa mites in absence of offspring), with support measures during critical periods. Researchers registered their weight, any incidences with the beehives, captured images of the bees’ activities and related this information to meteorological conditions. The study was completed with an analysis of the pollen and the origin of the nectar used to produce the honey.

The data shows that the weight of the beehives and the activity of the bees in peri-urban Mediterranean conditions (the apiary is located in a wooded area of the UAB’s Bellaterra campus) increase with the temperatures of winter and spring, but fall significantly in the summer and after the honey harvests, reaching minimums in autumn. For this reason, researchers recommend beekeepers to harvest the honey first in spring in order to allow the bees to increase their honey and pollen reserves for summer and winter.

The study also shows how the foraging activity, in which worker bees collect pollen and nectar, depends on the temperature, with maximum activity occurring at 19.4ºC and diminishing greatly once temperatures fall lower than 7ºC or rise above 31ºC. Thus, even if flowers are in bloom, the Spanish bee’s activities is limited to the winter and summer periods.

The mortality rate of beehives protected against the Varroa mite was 17% annually (1 out of every 6 beehives), below the Spanish average, and the attacks from Asian hornets (Vespa velutina) constituted the greatest menace during the months of June and November. The Asian hornet limited the movements of the bees throughout the day and was responsible for up to one third of all deaths within the colonies. To protect the bees, electric harps were installed which killed more than 4 predatory wasps per day, although bees and other species were also killed. Researchers estimate that the installation of these harps prevented the death of over 40,000 bees in 2020. Thanks to these measures, the average production of honey was 13 kg per beehive and per year, placing it between the Spanish (10 kg) and the European (15 kg) averages of yearly honey production.

“Thanks to the monitoring through weight, temperature and sound sensors, we were able to identify the beehives that were struggling or those in which bees were leaving, thereby recovering swarms of bees to make them stronger and maintain their activity”, explains director of the project Gerardo Caja. “Everything points to the fact that Spain and Europe are halting the decline of domestic bees, and our work demonstrates that a good handling and control of a new plage of Asian hornets can maintain the population and the production of beehives”, adds Gerardo Caja, who is also lecturer at the UAB Department of Animal and Food Science.

New Phase of the UABee Project

The UABee project began in May 2019 with the objective of constructing an experimental apiary which could be used for demonstrations (visits to discover beekeeping and the biology of bees), for teaching (university courses and specialised training for professionals of the sector) and research into apiculture and the biology of bees. This is the only experimental apiary to exist in all of Catalonia, and with this second phase of electronic monitoring now beginning, it will be the only fully monitored apiary to exist in all of Spain, and therefore will yield more detailed studies in the future. Initially built to include six hives housing standard bee colonies, scientists
included the possibility of modifying it according to the activity and size of the colonies. The construction was recently expanded to include a total of ten beehives.

UABee also will house research projects conducted in collaboration with other institutes, aimed at studying the bee’s metabolomics, chemical processes taking place within their organism’s cells. Participating as founder is the honey brand Granja San Francisco, and it is open to working jointly with other companies from the food, veterinary and social sector.