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Asian Hornet - An update from the National Bee Unit

An update from the National Bee Unit and request for increased vigilance

The Asian hornet in the UK: Update and Request for Heightened Vigilance.

As you are aware, Vespa velutina nigrothorax, the yellow-legged hornet (a.k.a the Asian hornet) was found in the UK last season. The first European incursion of this hornet was reported in France in 2004. The Asian hornet has since spread around 80-100 km per year, invading Spain, Portugal, Italy, Germany and Belgium. Adult hornets are voracious predators of honey bees and other beneficial insects, resulting in colony losses in France. In September 2016, foraging Asian hornets were reported near Tetbury in Gloucestershire, and a trapped individual was reported from Somerset.

The nest near Tetbury was found and destroyed by National Bee Unit Inspectors and members of the Wildlife team in the Animal and Plant Health Agency. Despite extensive field inspections, no further foraging Asian hornets were sighted in Somerset. Whilst this is good news, the ability of the Asian hornet to spread rapidly means that we must remain vigilant and aware of any possible activity across a wide area and with spring fast approaching, there is an opportunity for us all to monitor and trap any potential foundress queens.

In spring, surviving V. velutina queens begin a small primary nest, often in a sheltered location such as in the eaves of a roof or in a garden shed. Here they raise the first clutch of workers who take over the queen’s foraging duties. At this stage the nest grows quickly, and the hornets often move to establish a secondary nest where there is more space to expand. These nests can become very large, and are often located high up in the tree canopy, close to a food source such as apiaries, (see images on BeeBase for further details).

From late September to October, the mature nest produces males and then virgin queens, which mate and disperse. However, the beginning of this stage of nest reproduction can vary, depending on climatic conditions. In France, a single mature nest produces on average 11 foundress queens after taking into account overwintering mortality of the potentially hundreds of queens that first disperse in autumn.

A consortium of scientists from the NBU and the Universities of Warwick and Newcastle have used data on the spread of the Asian hornet in France to develop a mathematical model that can estimate the hornet spread in the UK. The highly mobile nature of the hornet means that the range of possible additional nest locations in 2016, estimated using the model, covers a wide area, see the map for details.

The Map in the formal copy of this notice below shows the potential spread of Asian hornet in 2016 using a mathematical model based on Franklin et al. 2016 (In Press). The dark orange squares represent the locations of Asian hornet discoveries in Tetbury and Somerset. The yellow area defines a boundary, outside of which we would not expect, according to the model, to find a nest.

We are asking beekeepers within or bordering the area highlighted in yellow on the map in the formal copy of this notice below  to remain particularly vigilant to signs of the Asian hornet. During the remaining winter months, you can check for nests in trees. In France, Asian hornets can form nests in many types of tree. However, in trees which lose their leaves in the autumn any nests can become visible and clearly seen in the winter as the branches are bare.

In the spring, Asian hornets can be trapped by using either commercial traps, which are available off the shelf or a home-made model e.g. by using the NBU modified hornet monitoring trap. If we know they are present in an area we can take action quickly to prevent populations expanding.

There is a helpful Asian hornet identification sheet and poster on Beebase along with a fact sheet which outlines how to make our own NBU design, and, what baits would be suitable during the different seasons of the year. See: http://www.nationalbeeunit.com/index.cfm?pageid=208

Should you find a suspect Asian hornet or nest, please contact the Non Native Species Secretariat immediately using their alert email address: alertnonnative@ceh.ac.uk giving as much information as possible. Please include details such as your name, the location where the hornet was found and if possible an image of the specimen. Please do not put yourself in any danger of getting stung when trying to take a photo. Even if you are unsure of whether it is an Asian hornet, send it in anyway – it’s better to be safe than sorry.

We thank you in advance for your co-operation and vigilance.
Kind regards,
National Bee Unit