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Trapping Asian hornet queens now reduces summer nests: French study

The number of nests in part of one Brittany department where the four-year study has taken place has plummeted

5 April 2021
By Connexion journalist

Trapping Asian hornet queens as they come out of hibernation vastly reduces the number of nests, a study in northwest France has confirmed.

The study was intended to measure the effectiveness of methods of trapping the invasive insect in the Brittany department of Morbihan and was carried out by the Association Brechoise de Sauvegarde des Abeilles et autres Pollinisateurs (ABSAP), the Bee Institute and the National Museum of Natural History.

It found that catching the queens as they emerge from hibernation and search for food is highly effective in reducing the number of hornets' nests later in the summer. 

An invasive species, Asian hornets have a potentially devastating impact on the bee population and can wipe out entire colonies of the pollinators. They will also aggressively defend their nests if people get too close. Each animal is capable of stinging multiple times.

The queens begin to wake when temperatures reach about 15C. They build a small primary nest, no bigger than a grapefruit, with a few hornets. 

This four-to-five week period is the ideal time to trap them, according to the Brittany research, before the queen has had time to establish a colony by hatching workers.

"In Brittany, [they start appearing] at the beginning of April until around May 8," Gilles Lanio, beekeeper and president of API 56 abeilles et biodiversité, based in Kervignac, told broadcaster France 3.

The primary nest is abandoned before summer as the size of the colony increases. Secondary nests are much larger and are usually higher up in trees. These nests can house thousands of hornets. 

For the past four years, officials in Brec'h, near Vannes in Morbihan, and the Brechoise association for the Protection of Bees and other Pollinators (ABSAP) have distributed traps free of charge to residents in March. 

"This method has shown that in four years, the number of secondary nests has been divided by four," ABSAP president Michel Le Boudec said. 

Tips for trapping Asian hornets

Tips given for trapping by the ABSAP are:

  • Place your traps near flowers (camellias, flowering trees, etc.), old nests and household composters with exposure to the sun;
  • Bait should be slightly alcoholic to repel bees. It can be made up of dark beer, cider, white wine, to which sweet syrup is added: strawberry, grenadine, raspberry, banana… to attract hornets;
  • Traps that have already captured queens should not be washed to retain the pheromones which are the best attractant for trapping.
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