VESPA VELUTINA NIGITHRAX
Asian Hornets can be a danger to both animals and people; an invasive species, with no natural predators in Europe, which continues to gain territory. They prey on pollinators, so subsequently pose a problem for bees, bee-keepers, and agricultural crops.
The Asian Hornet first arrived in south-west France in 2004, in the Gironde region, in a cargo of Chinese potteries. From here in a matter of a few years they have colonised all regions of France, and extended their territory into Germany, Belgium, Spain, Italy, and Portugal.
How to differentiate the Asian Hornet from the European Hornet?
The Asian Hornet thorax is black, their abdomen is also dark, with only the 4th segment of the abdomen coloured yellow. Their legs are also pale yellow, and they have a more orangey yellow face. It can be easily distinguished from the European hornet, Vespo Crabro, which has a yellow abdomen with black stripes. The Asian Hornet is also smaller averaging 30 mm long, rather than the European Hornet which tends to be about 35 mm.
Lifecycle & associated actions
Phase 1, Feb-Mai : New Queens emerge from their winter refuges over this period, depending on the local climate, and will start looking for food, and building nests. Set traps for Asian Hornet queens.
Phase 2, April-June : The Asian Hornet queen alone builds a small primary nest, about the size of an orange, in which she lays eggs that will develop into her first worker Asian Hornets. Find and destroy primary nests.
Phase 3, July-November : From the start of July the Asian Hornet colonies develop and their nests increase in volume. More and more workers are active building the nests, and looking for food for the increasing number of larvae and the queen. From mid July Asian Hornets can be seen hovering around bee-hives. From August it is recommended to use entrance reducers, and muzzle cages to protect the entrance to bee-hives - not earlier as otherwise the free circulation of maiden queen bees or males could be hampered. Identify secondary nests.
Phase 4 : New Asian Hornet queens leave their nests from mid September, to mate and then find a lone refuge for winter. Although it is difficult to differentiate new queens from well fed Asian Hornet workers at this time of year, intense trapping will reduce the number of potentail queens, and therefore potential colonies for the following spring. Set traps for new Asian Hornet queens.
The Asian Hornet nest
The size of a mature nest can vary between 40cm – 100cm tall, and can reach up to 80 cm in diameter. The biggest nests can contain up to 20,000 cells which will be re-used for larva 2 or 3 times during the year. The Asian Hornet nest isn’t made only from a type of papier mâché like the European Hornet’s nest, but also can contain other material, like resin, wood and water which makes their nests more solid and more resistant to storms.
Asian Hornets & Bees
Typically, Asian Hornets hover 30-50 cms in front of a hive, waiting for bees to return from collecting pollen and nectar. As the bees slow down to enter the hive, Asian Hornets pounce, often capturing an unlucky bee, then, although weighed down by their prey they fly to a nearby support – often a branch within 4-5 metres of the hive. Here they quickly finish the bee off, rejecting the head and abdomen sections, carrying off only the thorax, the muscle rich chest section, which will supply their young with a concentrated supply of protein.
Sometimes Asian Hornets can be seen either on the ground by a hive, or on the threshold of the entrance waiting to catch any bees going in or out. If there are one or two Asian Hornets by a hive, then the hive should not be at serious risk, however if ten to fifteen Asian Hornets are seen surrounding a single hive, then the outcome is likely to quickly escalate to disastrous for the hive in question.
On cool autumn mornings, Asian Hornets may enter a weakened bee hive to raid the honey, breaking the honeycomb, and leaving little – maybe only the original wax starter sheet.
When several Asian Hornets are hovering in front of a hive, even if there is some form of protection in place, the bees appear stressed, waiting on the threshold of the entrance not keen to take off to collect pollen or nectar. Without bees regularly foraging, the lack of fresh pollen and nectar will disrupt the Queen, reducing the rate of egg laying, which further contributes to weakening the colony. The film by Zoé Delépine, “Frélon Asiatique, le loup dans la bergerie” (The Asian Hornet, the wolf amongst the sheep) demonstrates this perfectly
How and when to use traps
It is a good idea to use traps near bee-hives, and/or next to where Hornet’s nests were seen the previous year. In France, the best time is from mid-February onwards, when new Hornet queens start venturing out in search of food prior to building their first small preliminary nests of the season. However, traps need not be limited to these locations, elsewhere they can still be very successful in reducing Asian Hornet numbers.
Purpose built traps are available from bee-keeping suppliers, but serviceable home-made versions can easily be created from a plastic bottle, so long as the contents can be protected from dilution by rain. Whatever the type of trap, the recommended bait consists of the following cocktail: 2/3 brown beer, 1/3 white wine (repels bees), a tablespoon (or good dash) of blackcurrant or raspberry syrup/cordial concentrate
These traps should be placed between one to two metres from the ground, preferably in a sunny spot, and checked/topped up weekly.
A different type of trap using an adapted 30 litre sealable bucket is described by Alain Rouby, the President of the Limousin Syndicat of Beekeepers. As bait, he suggests using rotten fruit, or broken honeycomb trimmings, or grape juice. Two holes need to be cut in the lid:
- One 3-4 cm in diameter, into which the top of a bottle can be pushed, to enable the Hornets to enter.
- The other a rectangular window which should be completely covered by a section of a “Queen grill” (normally used to block the queen having access to top box sections of a bee-hive) This will enable other insects to escape, and enable the perfume of the bait to circulate freely.
What other defences can be used against the Asian Hornet?
Modifications to hives:
- It is essential to reduce the size of the hive entrance from the beginning of August, when the quantity of Asian Hornets dramatically increases. Earlier to this it would be inadvisable, due to the risk of trapping a young unfertilised bee queen, or male bees, inside the bee-hive.
- Attach a protective “muzzle” cage to surround the bee-hive entrance. These can either be constructed from supple wire mesh with 13mm holes, which can be bent around the hive entrance and fastened to the front, sides, and bottom of the hive, or created with wooden sides attached to plastic 1cm mesh which gives a more rigid protection.
- Protection by nets – for a small group of hives, a wooden frame can be built to enable the group of hives to be completely covered with a net with 1 cm mesh. A net system should last between 6-8 years. The front and top of the enclosure needs to be made from netting, on the other sides less expensive tarpaulin can be used. A system needs to be installed to enable the net to be opened to a height of 1 metre on the side in front of the hives at the beginning of winter, and then fastened down at the beginning of August.
- The Electric Harp – a system that has yet to prove its worth, as the cost of installation is relatively high.
- Sticky panels – the use of boards placed on the floor near to a group of hives with some bait (broken honeycomb bits?) and a substance called “mouse glue” in French. Asian Hornets are attracted to the bait, then are unable to fly away. Their noise prevents bees approaching. During a test of this method in 2015 each of ten traps became saturated with 60 to 80 Asian Hornets, against only 4 bee casualties. Once a trap becomes saturated, it can be covered with newspaper, turned over and the reverse side used.
Encourage as many people as possible to set traps.
Several times over the last 12 years in France, the authorities have reviewed the threat posed by Asian Hornets, acknowledging the risk whilst at the same time not supporting real action to slow down their spread across the country.
Since 2012 the species is classed as a 2category danger in France, which means that no national plan needs to be adopted to prevent their spread, but rather that any control, preventative actions, or campaigns to destroy nests, are left to be organised by each local authority. For example, in the Gironde region, nests that are reported to the authorities are destroyed thanks to a team of 30 experienced volunteers. On average between 1200-1500 nests are destroyed each year by this team alone, however not every department has the same set up.
The National Union of French Beekeepers continues to lobby the French Ministry of Agriculture to reclass the Asian Hornet as a 1st category risk, which would then entail the creation of a national plan of action to reduce their numbers. For example, they ask for the use of SO² to be authorised as the most effective and, in qualified hands, the safest way of destroying Asian Hornet nests, and for an intensive trapping programme to be adopted across the territory.
Translated from French by Jill Goodenough.
Original Document written by Raymond Saunier, September 2016.
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