Before the wind-down to the end of the year and the inevitable review of the season I thought I’d write a final post apparently supporting the benefits of local bees. This is based on a recently published paper from the USA 1 that tests whether local bees perform better than non-local stocks.
However, in my view the study is incomplete and – whilst broadly supportive – needs further work before it can really be seen as an example of better performing local bees. I suspect there’s actually a different explanation for their results … that also demonstrates the benefits of local bees.
This is a follow-up to a post three weeks ago that provided evidence that:
- Colonies derived from different geographic regions show physiological adaptations (presumably reflecting underlying genetic differences) that seem pretty logical e.g. bees from Saskatchewan express more proteins involved in heat production, whereas Hawaiian bees show higher levels of protein turnover (which would make sense if they had evolved locally to have high metabolic rates).
- In a study by Büchler, European colonies survived better overwinter in their local environment; a fact subsequently attributed to the colonies being stronger going into the winter. In turn, this agrees with a recent study that clearly demonstrates the correlation between overwintering success and colony strength.
I suggest re-reading 2 that post as I’m going to try and avoid too much repetition here.
Strong colonies overwinter better and – if you’re interested in that sort of thing – are much more likely to generate a profit for your honey sales.
So how can you ensure strong colonies at the end of the season?
What influences colony strength?
One thing is colony health. A healthy colony is much more likely to be a strong colony.
In the ambitious 600-colony Büchler study in Europe they didn’t do any disease management. The colonies were monitored over ~2.5 years during which time 84% of colonies perished, at least half due to the ravages of Varroa.
Clearly this is not sustainable beekeeping and doesn’t properly reflect standard beekeeping practices.
The recent Burnham study makes a nice comparison to the Büchler study.
It was conducted in New York State using 40 balanced 3 colonies requeened in late May.
Queens were sourced from California (~4000 km west) or Vermont (~200km east in the neighbouring state, and therefore considered ‘local’) and colonies were assigned queens randomly.
Unlike some previous studies the authors did not evidence the genetic differences between queens.
However, the queens looked dissimilar and the stocks were sourced from colonies established in California or Vermont for at least 10-15 generations. I think we can be reasonably confident that the queens were sufficiently distinct to be relevant for the tests being conducted.
Colonies were maintained using standard beekeeping practices, Varroa levels were managed using formic acid (MAQS for European readers) and the colony weight and productivity (frames of bees) was quantified, as was the pathogen load.
In contrast to the Büchler study, Burnham and colleagues only followed colonies over one beekeeping summer season. This was not a test of overwintering survival, but mid-season development.
The take-home message is that colonies headed by the ‘local’ Vermont queens did better. The colonies got heavier faster and brood levels built up better.
It’s notable that colony weight built up before any brood would have emerged from the new queen (upper panel) and that brood level in colonies headed by the local queen recovered much better after formic acid treatment (arrow in lower panel).
However, Nosema levels were significantly different (above) as were the levels of Israeli Acute Paralysis Virus (IAPV; below).
There were no significant differences in the Varroa loads before or after treatment (not shown), or in the levels of DWV or Black Queen Cell Virus (BQCV).
Taken together – bigger, heavier, stronger colonies and lower pathogen loads (at least of some pathogens) – seems good evidence to support the contention that local bees are beneficial.
The benefits are precisely what you want for good overwintering – strong, healthy colonies.
That’s a slam-dunk then?
IAPV is a virus rarely detected in the UK. It causes persistent and systemic infections in honey bees and can be found in every caste (drones, workers, queens) and at every stage of the life cycle.
As IAPV is detectable in eggs and larvae – neither of which are Varroa-exposed – it is assumed to be vertically transmitted from the queen. IAPV is also found in the ovaries of the queen, which is additional evidence for vertical transmission.
At the first timepoint (12 days post requeening) the levels of IAPV are different between the two colony types, but not significantly so. However, by 40 days (T2) the levels are very different. At this later timepoint all the bees in the colony will be have come from the introduced queen.
The authors explain the differences in IAPV levels in terms of local bees being more resistant to ‘local’ pathogens … in much the same way that Pizarro’s 168 conquistadors, being more resistant to smallpox, defeated the might of the Inca Empire with the help of the virus diseases they inadvertently introduced to Peru.
I suspect there’s another explanation.
Perhaps the Californian queens were IAPV infected from the outset?
If this was the case they could introduce a new and virulent strain of IAPV to the research colonies and – over time – the levels would increase as more and more workers in the colony were derived from the new queen. IAPV is present in ~20% of US colonies so it seems perfectly reasonable to suggest it might have been largely absent from the Vermont queens and the test colonies, but present in the queens introduced from California.
How should they have tested that?
The obvious thing to do would be to characterise the IAPV present in the colony. IAPV shows geographic variation across the USA. If the predominant virus was of Californian origin it would suggest it was brought in with the queen. This is a relatively easy test to conduct … a sort of 23andme to determine bee virus provenance.
Alternatively, though less conclusively, you could do the experiment the other way round … ship Vermont queens to California and compare their performance with colonies headed by Californian queens on their own territory. If the Californian queens again performed less well it undermines the ‘local bees do better’ argument and suggests another explanation should be sought.
Nosema is sexually transmitted but it is not vertically transmitted, so the same arguments cannot be made there. Why the Nosema levels drop so convincingly in colonies headed by the local queens is unclear. Nosema was present at the start of the study and was lost over time in the stronger colonies headed by the local queens.
One possibility of course is that the stronger colonies were better fed – more workers, more foragers, more pollen, more nectar. Improved diet leads to a more active and effective immune system and an increased ability to combat pathogens. Simplistic certainly, but it is known that diet influences pathogen resistance and colony performance.
So what does this paper show?
I suspect it doesn’t directly show what the authors claim (in the title) … that local queens head colonies with lower pathogen levels.
This largely reflects the lack of proper or complete controls. However, it does not mean that local bees are not better.
More than anything I think this paper demonstrates the impact queen quality has on colony performance.
Perhaps the Vermont-sourced queens were just better queens. Local certainly (on a USA scale definition of the word local), but not better because they were local, just better because they were better.
However, if my interpretation of the source of the IAPV is correct i.e. introduced from the Californian queens, I think the paper indirectly demonstrates one of the most compelling reasons why local bees are preferable.
If they’re local – your apiary, your neighbours, someone in your association – there is little chance they will be bringing with them some unwanted baggage in the form of an undetected exotic pathogen.
Or a more virulent strain of one already circulating relatively benignly.
Extensive bee movements, whether of queens, packages or full colonies, risks spreading parasites and pathogens.
There is compelling evidence that hosts and pathogens co-evolve to reduce the pathogenicity of the interaction. Naive hosts are always more susceptible to introduced pathogens, or novel strains of pre-existing pathogens. After all, look what happened to the Peruvian Inca when they met the measles- and smallpox-ridden conquistadors.
So, when thinking about the claims being made by bee importers (or, for that matter, strong advocates of local bee breeding), it’s worth considering all of the factors at play – queen quality per se, genetic adaptation of the queen to the local environment and the potential for the introduction of novel pathogens with introduced non-local stock.
And that’s before you also consider the benefits to your beekeeping of being self-sufficient and not reliant on others to produce your stocks.
I never said it was simple 😉
- Burnham et al., (2019) Local honey bees (Apis mellifera) have lower pathogen loads and higher productivity compared to non-local transplanted bees in North America. Journal of Apicultural Research 58:694-701.
- Or reading for the first time – in which case, welcome ;-)
- i.e. the numbers of brood frames and bees were equalised across all colonies.
Here in BC urban bee keeping is growing rapidly with no less than hundreds of packages sold each spring. Most packages come from New Zealand, California and some Hawaii. Local NUCs and queens are available – usually later in the season – but the sheer abundance of non-local bees would suggest the gene pool of urban bees is dominated by outside sources. Queen performance is incredibly difficult to judge – so many variables and almost impossible for we who have few colonies to pass credible judgement over local versus non-local queens. That said, queen rearing is a necessity given the frequency at which both local and non-local queens are lost. If it were not for splitting and grafting I would have no colonies headed into winter – this year – all colonies going into winter (4) were derived from a lovely NZ queen that died in mid-summer. Going to be interesting to see how her daughters perform over their first winter. 3-are just summer NUC’s, but one is a strong colony that was re-queened using a split from her brood after she was lost.
I suspect your situation isn’t unusual. Wherever I’ve kept bees and there have been a lot of other local beekeepers the mix has been very great. The demand for early season colonies is high and too few beekeepers overwinter nucs – either for replacing their own stocks or for sale – so there’s a big market for imports. These are of variable quality. Some are excellent. Some are complete rubbish. New beekeepers are unlikely to be able to tell the difference until it’s too late.
Inevitably locally reared queens are ‘Heinz’ i.e. 57 varieties. This doesn’t necessarily make them worse. The majority of my own queens are like this. I’ve bought a few queens over the years, but none have consistently outperformed my local stock. I’ve not been beekeeping long enough to have personal experience of the reduced longevity of queens – certainly anything over two full seasons is unusual here.
I think it is relatively straightforward to improve your stocks – simply ruthlessly cull the worst (and get rid of drone brood from that colony to reduce their impact on the gene pool) and generate splits from your best. Sure, there will be some duds along the way, but it’s a reasonably dependable way to improve things.
Good luck for the winter and the season ahead.
As you point out, the trial could just mean that the Vermont queens are simply better that the Californian ones and it’s nothing to do with the location of the colonies at all, so the trial doesn’t mean much. It would have been much better to have done a California trial at the same time. IF the vermont queens in California were proven to be ‘worse’ than the local girls, there would be a good argument that ‘local is better’
Absolutely. As a scientist I’m aware that there are logistical problems to conducting this sort of experiment. The apiaries would be managed by different beekeepers … an alternative explanation would be that the Californian management regime ‘better suited’ the queens sourced from California. You’d then need another control with Californian beekeepers managing colonies in NY state. And vice versa. Before too long you’ll realise that this relatively simple experiment is going to cost $0.25M and take three years.
We work with a lot of beekeepers and there are enormous differences in management strategies – those that leave alone, doing the bare minimum when necessary, or the ‘fiddlers’, constantly tweaking things and intervening. Neither is inherently worse (or better), but this can have a major impact on the colony. For example, lots of splitting likely reduces mite numbers due to enforced brood breaks … but colonies may never reach their full potential for honey-gathering.
However, in the Burnham study cited I’d be concerned about IAPV being introduced by the queen. The bar chart showing virus levels is particularly damning. DWV and BQCV have very high prevalence so you might not expect to see a change, but IAPV shoots up once all the brood are derived from the newly introduced queen. Suspicious!
And easy to test … and, if that’s the source, a very good example of the potential dangers of importing (not even necessarily from abroad) new stocks into your apiaries.
How many viruses are routinely screened for?
I wonder to what extent “local queens” is really shorhand for “well bred queens”. As Vince pointed out, here in the Pacific NW of British Columbia, the one country we can import packages from is New Zealand. So every year, the DCA’s are filled with the drones from this year’s spring packages from NZ…New World Carniolans, which research at the Beaverlodge, AB research station found are pretty terrible at dealing with Varroa mites. So if you are wild mating queens in my area, you are getting largely Carniolan genes from New Zealand.
However, the Ministry of Apiculture and general club reports tell us that around 60% of package queens are superceded/go AWOL in their first season. This is really hard on new beekeepers.
So…we advise our club members to breed up a replacement queen for their package(s) ASAP. And offer advice and support in how to do that successfully.
The advantages of breeding your own queens is: you can make better than you can buy. Have you ever bought queens are found them kinda small?? That suggests less than optimal rearing conditions. You can correct for that easily. If you have more than one hive, identify your best colony and breed from that. You can be sure the queen larvae are well fed by supplementing the queen rearing colony with pollen and syrup (queen larval nutrition is a huge factor in making good queens). If well fed as larvae queens tend to be quite large, which makes them easier to spot on the comb. You can in most urban areas be sure she finds lots of dates on her mating flight. And you can ensure she returns to a colony large enough to raise up all the brood she lays. She is not exposed to shipping stresses and is never hungry or taken off-lay.
I wonder if it is that difference in attention to queen-rearing detail (better rearing conditions, low stress) that accounts for much of the belief that local queens are better than non-local.
Final point: in breeding my own queens I have the feeling that their quality reflects the bell curve. Some are duds, most are decent, but a few are fabulous. So even within a batch of local queens there is variation in quality.
In the Burnham study they used commercially-available queens for both the local and the non-local colonies. However, for most reasonably experienced beekeepers I suspect that ‘local’ probably does mean ‘better reared’. I’m convinced it’s a better and more reliable approach to beekeeping, but the reality is that probably less than 20% (and possibly even 10%) of beekeepers I meet activity rear their own queens.
I usually make a point of asking for a show of hands when I give a talk at a beekeeping association … I define actively as specifically selecting stock to rear from and culling unwanted stock and drones, or words to that effect. I don’t care how they rear the queens – grafting and mini-nucs, de-queening a good hive and distributing queen cells etc. Not only do you get better queens (on average … I agree about the ‘bell shaped curve’, there are always a few duds in the season but the peak of the curve is shifted to the right i.e. better quality) but it’s just about the best possible way to learn to be a better beekeeper. Firstly you have to do more beekeeping, but you also have to be able to judge the colony better.
And if those benefits aren’t sufficient to persuade you it’s also very satisfying 🙂