Invasive Predators, a New Threat to our Honey Bees
The Asian Hornet (Vespa velutina) is an invasive predatory pest that originates from Asia. There are several known sub-species of the V. velutina. It is almost entirely black with only the 4th abdominal segment being yellow. The head is black with an orange face and the lower ends of the legs are yellow. They are also slightly smaller than the native British hornets, with queens growing up to three centimeters long (NBU, 2011).
While typically all hornets are predators of insect species. The V. velutina has been seen as a significant problem for beekeepers due to its aggressive and effective predation of the European honey bees and wild bee populations, causing significant colony damage through direct predation and indirect stress and the spread of disease (Monceau, et al., 2014). The Vespa velutina is far more vicious than those native to the UK, and can spread from just one nest; usually predators of social wasps, honeybees, but can also consume a wide variety of other insects and spider prey. Observers in France have reported that the hornet hovers over the entrance to a beehive at a distance of 30–40 cm, then will attempt to catch foragers, primarily those returning with nectar or pollen. The hornets charge at them from below and force them to the ground before paralysing and carrying them away. Each hornet only consumes a portion of the prey itself, the remainder being pulped for use as larval food.
The hornets make numerous attempts to access beehives, especially late in the season (September to December) when the production of new queens makes high demands on hornet workers (Hubble & Roy, 2015). Wilkes (2015) suggests that the V. Velutina decimate entire colonies, and can kill up to fifty honeybees each day to feed their larvae and as a result there is of great concern for UKs native honeybees. In Asia and Japan, the native honeybees are able to defend themselves by creating a cluster around the hornet and raising their body temperature to effectively both burn and suffocate the hornet. However UK native bees have not evolved to deal with them and are therefore completely defenceless against attacks, causing a potential decline in native bees (HBH, 2016).
How can you help?
Monitoring - To improve the likelihood of early detection, raising awareness to beekeepers and the public is key. This can be achieved through a species alert ID/Identification sheet issued in 2011 by the NNSS, this enables the public to report sightings to them via alert_nonnative@ceh.ac.uk
A photograph and details of location must be provided and the public are also invited to send a suspect sample to the National Bee Unit (NBU) laboratory for examination. If the evidence supplied by the public or a beekeeper suggests that the pest is likely to be an Asian hornet, a National Bee Unit Inspector will investigate the sighting and commission the destruction of the nest (Brown, 2012).
The National Bee Unit has confirmed a sighting of the Asian hornet in the Tetbury area of Gloucestershire in September 2016, this is the first time the hornet has been discovered in the UK. The places it is most likely to be found are in southern parts of England or goods among which it could be accidentally imported (such as soil with imported pot plants, cut flowers, fruit and timber). Active months between April and November (peak August/September). Inactive over the winter (NNSS, 2017).
The National Bee Unit, also advise beekeepers to introduce traps into their apiaries, including spring trapping targeted at mated queen hornets as they emerge from hibernation, to limit numbers of new nests established and restrict access points to hives (Brown, 2012). Although reports from France suggest that in areas where spring trapping has been used, subsequent numbers of Asian hornet nests are reduced by as much as 97% (2 or 3 nests in trapping areas versus over 70 nests where no traps have been hung). They cannot be expected to reliably eliminate V. velutina from an affected apiary.
Figure 1- shows how a V. velutina trap can be made (NBU, 2012).
Figure 2- Nantes botanical garden found dead Asian hornets in a Sarracenia stem (BBC, 2015).