Last month I wrote about the discovery and predicted spread of the Asian hornet (Vespavelutina) once (if) it gets established in the UK.
New Asian hornet isolation in North Devon
The National Bee Unit (NBU) and DEFRA have today (26th September 2017) reported the identification of an Asian hornet in the Woolacombe area of North Devon. This is about 100 miles from the Tetbury site (near Stroud) where the Asian hornet was isolated in September last year. There was an additional isolation in North Somerset in autumn 2016, though the precise location was not publicised.
Asian hornet …
Genetic analysis by the NBU will determine whether the new isolate is related to previous isolates. This would imply, though not prove, that the hornet may be established and breeding on mainland UK.
I’m speaking at the Devon Beekeepers Convention in Totnes next month and expect to hear more about efforts to track down and destroy the (or nests) at the meeting.
Extrapolation in mathematical terms means “the extension of a graph, curve, or range of values by inferring unknown values from trends in the known data”. There’s a rather poor scientific joke which involves ‘extrapolating the line’ from a single data point.
Here’s the same joke from the incomparable xkcd.com …
Extrapolating (with thanks to xkcd.com)
… which brings us neatly to the Asian hornet† (Vespa velutina). This invasive species predates honey bees and other pollinators and is a threat to beekeeping for two reasons:
by killing honey bees (which comprise > 50% of the diet) it can destroy colonies
by hunting at hive entrances it prevents bees from foraging, so reducing honey yields
Vespa velutina …
As many will be aware, at those who members of a beekeeping association or internet-savvy, an Asian hornet nest was discovered in Tetbury, near Bristol, in September 2016. Although the nest was destroyed (and other nests were not found) there remains the concern that the Asian hornet may be established here. If that’s the case, or if when it arrives again, how far and how fast will it spread in the UK?
A recent publication by Matt Keeling and colleagues has attempted to to address this. You’ll appreciate the relevance of the cartoon above … August 2016, no hornet nests, September 2016, one hornet nest. How many can we expect in the future?
A long way from home
Asian hornet distribution …
Unsurprisingly (the clue is in the name) the Asian hornet comes from Asia. The native distribution includes tropical South East Asia where it exists in a number of different colour morphs or sub-species. However, it spreads – naturally on its own and with the inadvertent help of man – and is now established in Korea, Japan and North West Europe.
The Asian Hornet appeared in South West France in 2004. It was thought that overwintering queens were imported with a shipment of pottery from China (it is the V. velutina nigrithorax subspecies – see map for native distribution). Since 2004 the Asian hornet has spread widely across France, Spain, Belgium, Portugal and Italy. You can view a dynamic Google map showing location and time of detection here.
It’s a short hop across the Channel from Northern France for an insect that flies strongly and disperses widely, so there was every expectation that the Asian hornet would appear in the UK in due course. Remember that bluetongue virus of sheep was introduced to the UK in 2006 by tiny Culicoides midges wafted across the Channel on the prevailing South Easterly winds.
Brexit or not, the Asian hornet can easily get to Southern England.
Closer to home
Asian hornets were first found in Tetbury, Gloucestershire, in September 2016 and subsequently in North Somerset. A nest was found in Tetbury and destroyed. Haplotype analysis demonstrated that, unsurprisingly, the hornets were related to those in Northern France. Worryingly, this analysis also demonstrated that the hornets were related, but no closer than at the grandparent level.
This suggests one of two scenarios. Either there were two separate incursions from France by hornets that were closely related or the Asian hornet was established in the UK before 2016 and the Somerset and Gloucestershire finds represent progeny (two generations later) of this initial invasion.
There have been no further reported Asian hornet finds on the mainland (as of early August 2017 and remembering that absence of evidence doesn’t mean evidence of absence) though additional nests have been found on Jersey and it’s possible that the hornet is established in the Channel Islands.
How far, how fast?
Whether or not the Tetbury hornet incursion has been contained there remains the question about how far and fast will the Asian hornet spread in the UK.
This is the sort of thing that can be modelled by epidemiologists. Taking account of a variety of factors such as the numbers of queens produced per nest, the environmental suitability for the hornet, the dispersal distances and – importantly for a species originating in tropical regions – the latitude (and hence temperature).
Much of the real numbers for these various factors come from studies of the spread of the Asian hornet in France. For example, the mean dispersal distance of new queens is about 18 miles i.e. Tetbury to central London in about 5 generations.
Predicted spread of the Asian hornet in UK …
In the figure above A-D are the early years (<5), E and F are the predictions for 10 and 20 years hence. Remember, this is an inexact science as the predictions are being made from a very small founder population. G shows the confidence limits which, at 90% (the palest shading) are very broad.
Is Scotland safe?
As a beekeeper in Scotland the potential to spread North is a concern … those of you living further South can simply jump ahead to the conclusions.
A key feature of the prediction Keeling and colleagues made was that increasing latitudes (and possibly altitude going by the pale shading of North Wales and the Pennines, though this could also be lack of suitable nesting environments – the Asian hornet prefers oak trees apparently) will restrict breeding success and hence spread due to reduced temperatures.
They modelled this by assuming reproductive success/spread (actually queens/nest) was 100% in Andernos-les-Bains, France (where much of the data used for the modelling was derived) and 0% in the North of England. This mirrors the situation for the European hornet which is much less common in Northern England. Assuming a linear decrease in queens per nest over this distance they reproductive success in Tetbury is only 38% that in Andernos-les-Bains.
With these assumptions, Scotland is safe. I should add that I’m talking about natural distribution and spread. A single Asian hornet was discovered at a “retail warehouse in the central belt of Scotland” in March 2017. Although there’s no further official news about this discovery it seems likely it was imported ‘on the back of a lorry’ (and the SASA/NBU people will be able to tell where from after genetic analysis) to one of the giant distribution warehouses in Motherwell or Livingston. If the assumptions made about reproductive success at increasing latitudes are correct, this type of introduction is unlikely to result in the Asian hornet getting established in Scotland.
All of the modelling discussed so far assumes no intervention by FERA or by protective and vigilant beekeepers. The impact of nest destruction will be discussed in the future … but don’t get your hopes up 😉
Conclusion
Asian hornet nest …
With only one (or two?) incursions and no further reports in 2017 it’s possible that the Asian hornet is yet to become established in mainland UK. Once here – and I think it’s pretty certain it will get here and become established – the speed with which it spreads may look like the model proposed here. If the underlying assumptions on reproductive success, dispersal distance etc. are representative of the situation in the UK then – without effective intervention – we can expect it to be widespread within a couple of decades.
However, a feature of all epidemiological modelling is that they are subject to revision and reinterpretation … inevitably leading to further publications.
Full analysis of 2016 isolates published in PLoS One. Budge GE, Hodgetts J, Jones EP, Ostojá-Starzewski JC, Hall J, Tomkies V, et al. (2017) The invasion, provenance and diversity of Vespa velutina Lepeletier (Hymenoptera: Vespidae) in Great Britain. PLoS ONE 12: e0185172. https://doi.org/10.1371/journal.pone.0185172
† Don’t mistake the Asian or Yellow-legged hornet (Vespa velutina) with the Asian giant hornet (Vespa bloodyenormousandterrifying). The latter has a wingspan of 7.5cm and its proper scientific name is Vespa mandarinia. A number of newspaper articles in autumn 2016 made this mistake. Many also chose to use images of the European hornet (Vespa crabro) or other large stingy-looking insects … none of which are likely to help the public correctly identify the invasive Asian hornet.
The National Bee Unit has confirmed the discovery and identification of an Asian hornet in Tetbury, Gloucestershire. The press release has further details.
Asian hornet …
These hornets are smaller and darker than the European hornet. Note in particular how dark the abdomen is, with only the fourth segment predominantly yellow (in contrast with our European hornet where at least half of the abdomen is yellow). The National Bee Unit has a very useful guide to identifying the Asian hornet (Vespa velutina) and distinguishing it from the European hornet (Vespa crabro).
Inevitably there’s going to be a lot of statements about “the end of beekeeping as we know it” and speculation of the impact it will really have on our colonies. Time will tell whether it’s been identified early enough to eradicate, how it arrived in deepest Gloucestershire and where it came from.
The Asian hornet has been established and spread widely in France since inadvertent importation in 2004 from China. It was discovered in the Channel Islands earlier this summer. It’s arrival on the mainland was expected, but is nevertheless disappointing.
Disappointingly, but not altogether surprisingly, small hive beetle (SHB) has reappeared in Southern Italy again.
Just when you thought it was safe to import bees again
History
The beetle was first detected in mid-September 2014 in the Calabria region. The following couple of months saw a further 60 reported infested apiaries in Calabria and neighbouring regions, with a single apiary in Sicily – containing migratory hives – in which the beetle was also detected. The Italian authorities surveyed over 1200 apiaries during the last four months of 2014 with over 3200 hives in infested apiaries being destroyed. Beekeepers were compensated, but this must have been devastating for those involved.
Then everything went quiet … Spring testing (March to May), which involved both a national surveillance programme and specific activity – including sentinel nucs – in Calabria and Sicily, didn’t detect any infested apiaries.
September 2015
SHB 2015 Calabria
In mid-September this year (English link in the top right corner of page) an apiary was discovered with hives containing both larvae and adult beetles. At the time of writing (23/8/15) a further 16 infested apiaries have subsequently been discovered, all within the western part of Calabria (PDF map of the current situation) in the ‘toe’ of Italy. This is a disappointing development as it suggests strongly that the beetle remains well established in Italy and that eradication was not achieved.
An alternative suggestion – promoted by the Federazione Apicoltori Italiani (FAI) – is that this new detection represents a re-introduction of the beetle to Italy. This seems a bit far fetched … the infested apiaries are some distance from the coastal ports or large cargo airports but are instead slap-bang in the middle of the area with the largest number of infested apiaries in 2014. If it walks like a duck etc.
Unlike Varroa the beetle isn’t restricted to honeybee colonies. It can fly long distances (kilometres) and, although the larvae feed on pollen, brood and honey in the hive, they pupate outside the hive buried 10-20cm deep in soil and have been known to crawl 200m in search of suitable soil in which to pupate. Presumably the reappearance of the beetle in Italy is either due to low level infestations being missed or to beetles emerging after pupation and re-infesting colonies. Or both.
“Once here it is unlikely that we will be able to eradicate SHB. The USA failed, Hawaii failed, Australia failed, Canada failed and it looks almost certain that Italy has failed.”
Indeed, the only time I’m aware that ‘eradication’ was achieved was when the beetle was introduced in an illegal shipment from queens to a single apiary in the UK. In addition to destroying the colonies, the ground was ploughed up, soil removed and the area drenched in insecticide1. I’m not aware in this case whether the beetles had even become established after introduction. In contrast, by the end of 2014 the beetle was widely distributed and well established and it is therefore not surprising, despite the concerted efforts of the Italian authorities, that they have failed to eradicate the beetle.
The National Bee Unit also consider that eradication is almost certainly impossible. In their excellent guide to the beetle (PDF), under the heading “Could we eradicate the Small Hive beetle from the UK?” they state:
“Probably not. Unless the Small hive beetle is detected very soon after its arrival, it will rapidly spread into the surrounding honey bee population, making eradication very difficult. A major limiting factor to eradication would be the unknown distribution of managed bee hives and the potential for populations of the beetle to survive in wild hosts (eg. feral bees and bumble bees).”
So what can be done?
In time-honoured EU tradition an export ban on the affected region had been imposed, but it’s seemingly difficult – if not impossible – to impose an import ban to protect our bees and beekeeping. My concern is that nucs or packages imported to the UK from a region not currently under an EU-imposed movement ban might introduce the beetle into this country. The original movement ban on Calabria and Sicily (actually, not on the entire areas, but instead lying within a 20km radius from the known infested apiaries) was due to end in November 2015. Had the beetle not been detected it would have been at least theoretically possible to import bees from these regions, either directly or indirectly, for the start of the 2016 season. Presumably the movement ban will be extended in light of the failure to eradicate.
It’s also worth noting that only about 10% of imports are checked as they come into the UK and that the volume of illegal imports is not known.
There’s already discussion on the various beekeeping web forums about “when, not if, the beetle arrives” and that UK beekeepers will “cope with it”, just as they’ve coped with Varroa*. There’s a sort of resigned acceptance that, sooner or later, SHB will arrive. If it does, I expect we’ll attempt eradication by destroying colonies in infested apiaries. Again, devastating for the beekeepers involved …
* This is a pretty weak statement in my view … although we do cope with Varroa I’m sure the vast majority of beekeepers would much prefer to not have to deal with the mite.
In the meantime, there are steps that can be taken to reduce the chances of the beetle arriving in the UK, or make us better prepared should it arrive. These include:
Registering your apiaries on Beebase. The National Bee Unit will then both keep you informed of developments and know where colonies are should there be an outbreak and the regional inspector needs to check them.
Plan to become self-sufficient as a beekeeper … perhaps forego a little honey by preparing an additional nuc to overwinter for security, learn how to raise queens or – if you do already – raise a couple of additional queens.
Buy local bees or queens if you need to buy any. Sell your own surplus locally.
Encourage your association to become self-sufficient for bees and queens – establish a queen rearing group, or guarantee all those attending a beekeeping winter training course will be provided with a locally raised nuc for the following season.
Don’t buy imported queens or bees and discourage others from doing the same, for example by not allowing imported stocks in association apiaries.
Locally raised queen
Obviously points 2-4 are all aimed at avoiding the need to import bees or queens. This is because the most likely route by which SHB will get to the UK is in imported nucs, packages, queens or other beekeeping materials (e.g. wax). Don’t believe some of the nonsense about ‘pupae in contaminated soil’ as the most likely route … the NBU have conducted a thorough risk assessment (PDF) and by far and away the most probable route the beetle will gain access to the UK is with bees or beekeeping (hive) products. Where known, this is how it got into all other countries that currently have the beetle.
Is there any good news?
Not about small hive beetle I’m afraid. Other than it’s not here … yet.
However, taking some of the steps listed above will both improve your beekeeping skills and provide lots of enjoyment. Queen rearing can be incredibly simple … you can modify a straightforward vertical split to generate a number of queen cells and divide these with some frames of bees and stores into nucs. No grafting, no handling anything smaller than a brood frame and no need to find the queen more than once. Simple, satisfying and self-sufficient …
STOP PRESS
Michael Palmer started a discussion on the Beesource forum with the prophetic words “The UK will soon have Small Hive Beetles in their area” helpfully requesting comparisons in climate between US locations that find the beetle a nuisance and those that do not. It’s worth watching. Clearly climate is only part of the equation … soil type – and temperature (as pointed out by knowledgeable contributors to the BKF thread on this) also has a significant influence, with the beetle preferring light and/or sandy soils to pupate in.
But all this would be irrelevant if we manage to keep the beetle out of the UK …
Bibliography
1.Murilhas, A (2005) Aethina tumida arrives in Portugal. Will it be eradicated? EurBee Newsletter: 7‑9.
The West Sussex Beekeepers Association have proposed the following motion to the BBKA Annual Delegates Meeting (ADM) in January “Following the discovery of Small Hive Beetle, Aethina tumida, (SHB) in Italy in September 2014 this ADM instructs BBKA to urgently seek a ban on the importation of bees and unprocessed bee products into the U.K”. Further details can be found in their newsletter (under the heading Jim’s Jottings, from the illogically named Jim Norfolk, Chairman of the West Sussex BKA). The full proposition from West Sussex BKA, the supporting notes and the response from the BBKA Executive Committee can be found here on the Beekeeping Forum. The Executive Committee of the BBKA does not support the proposition – as summarised in the sentence “At this point in time the Executive does not consider it appropriate to seek or it be possible to achieve a ban on the importation of honey bees and unprocessed honey bee products and does not support the proposition“.
There is little justification explaining why the BBKA Executive Committee do not consider it appropriate to seek a ban on imports. As explained in a recent post, the National Bee Unit have conducted a risk assessment (in 2009) which concluded that “The pathway likely to present the greatest risk of introduction [of SHB] was the movement and importation of honey bees”.
Time is short … discuss this with your association
Please discuss the potential introduction of SHB and how it might be prevented with your own local association. If you feel strongly about it persuade your delegate at the January BBKA ADM to support the motion proposed by the West Sussex BKA. Remember that the UK imports thousands of queens and bees from Europe every year, many are from Italy, but others are from countries like France that also import thousands of queens and bees from Italy. Do you know where the nuc you or enthusiastic beginners purchased in April/May originated from?
The precautionary principle
The precautionary principle is that there “is a social responsibility to protect the [public or environment] from exposure to harm, when scientific investigation has found a plausible risk. These protections can be relaxed only if further scientific findings emerge that provide sound evidence that no harm will result“. There is a plausible risk of SHB entering the UK during the importation of bees. Until evidence is provided to the contrary – presumably by the BBKA and others who do not support a ban on bee imports – the precautionary principle should be applied.
The Native Irish Honey Bee Society has “calling for an immediate ban on imports of honey bees on animal health protection grounds“. Malta has already banned imports from Southern Italy. The Local Association Secretaries of the SBA have discussed the threat of SHB where there was considerable support for the following proposition “The SBA urges that all possible measures are taken to prevent the introduction of small hive beetle into the UK. These should include a cessation of trade in live bees from the rest of Europe for 2015 until the true spread of the pest is better known“. The Welsh BKA are discussing the issue shortly.
Eradication after arrival …
With the exception of the introduction of SHB to Portugal in 2004, no country has managed to eradicate the beetle after it has been introduced. In Portugal the beetle was introduced as larvae with a single shipment of queens (illegally) imported from Texas to a single apiary. All colonies in the apiary were destroyed and the ground was ploughed up and soaked in insecticide. Rather than rely on the contingency plans and sentinel apiaries in the UK to detect the beetle after arrival we should use the age-old doctrine of prevention being better than cure … we should do our best to stop the beetle getting here in the first place.
Other benefits of a ban on imports
Decreased reliance on imported bees and queens is likely to significantly benefit UK beekeeping in the long run. We may have to alter the way we train beginners, we might have to do a lot more autumn requeening, we might have to improve our integrated pest management, we will have to increase local queen rearing activities … however, none of these are insurmountable problems and all are likely to improve the quality of UK beekeeping. Bees and queens might become more expensive, but only until local association queen and nuc rearing activities have geared up to cope with the additional demand. I would think that any increase would be insignificant if compared to the cost of lost colonies should SHB arrive and become established in the UK. I accept that there might be issues for commercial beekeepers, but am unconvinced that a business model that relies upon cheap imports is sustainable in the long-term.
Further details on the biology of Small Hive Beetle can be found in this recent Current Zoology paper (PDF download) written by NBU scientists.
