Tag Archives: drifting

Apistan and residues

This is the first of two or three posts on Apistan, a widely used yet often ineffective miticide sold for Varroa control. I was originally going to title this post “Don’t do this at home” and restrict discussion to Apistan misuse and resistance in the UK. However, having drafted the article it was clear there was more than could be covered in a single post (or at least comfortably read).

I’ve therefore split it up; the first focuses on what Apistan is, how it’s used and the consequences of use for the hive. Next time – though possibly not next week – I’ll cover the molecular mechanism of activity and mite resistance.

What is Apistan

Apistan

Apistan … tau-fluvalinate

Apistan® is a miticide used to kill Varroa. It is a registered tradename used in the UK and other parts of the world. The active ingredient is a synthetic pyrethroid tau-fluvalinate (or sometimes τ-fluvalinate). Synthetic in this instance means it is not a natural compound, but is produced using a chemical process. Other miticides containing the same active ingredient include Klartan® and Minadox® – precise compositions may vary, but the important component is the tau-fluvalinate. In the UK, Apistan is supplied by Vita (Europe) Ltd. and sold by all the leading beekeeping equipment suppliers. I’ll use the name fluvalinate and Apistan interchangeably in the remaining text.

Instructions for use

Apistan can be used at any time of year but its use is recommended in late summer after the honey harvest. The active ingredient, fluvalinate, is supplied as impregnated polymer strips, two of which are hung vertically in the brood box, between frames 3 & 4 and 7 & 8. It is a contact miticide and needs to be located near the centre of the colony to get trampled through the broodnest. Nucs and weak colonies only should be treated with one strip. The treatment period is 6 to 8 weeks i.e. a minimum of two full brood cycles. The instructions specifically state that it should not be used for less than 6 weeks, or more than 8 weeks. This is to avoid the selection of a resistant mite population. Apistan should not be used when there is a nectar flow.

How effective is Apistan?

On susceptible mite populations Apistan is fantastically effective. Cabras and colleagues in Italy reported greater than 99% efficacy in studies published in 1997.

Fluvalinates and foundation

Importantly, because of its chemical formula, Apistan is fat soluble, meaning it is readily absorbed into or dissolves in fats … like beeswax. It is also a very stable compound. In a relatively recent study by Jeff Pettis and colleagues all 21 samples of commercial foundation tested were contaminated with fluvalinates. This was a US study and I’m not aware of an equivalent analysis of UK foundation suppliers. However, there is an international trade in beeswax and fluvalinates are used globally. I’d be very surprised if any commercially-purchased foundation – perhaps other than the certified organic stuff – was  not contaminated with fluvalinates.

Are fluvalinates in wax foundation a problem?

These studies are difficult to conduct using field-realistic levels of miticides. Nevertheless, despite the fact that the absolute toxicity of fluvalinates for honey bees is very low (i.e. a lot is needed to kill the bees – the compound has a high LD50 0%) there is compelling evidence that sub-lethal levels are probably detrimental. Drones reared in fluvalinate-treated hives exhibit increased mortality, reduced bodyweight and decreased sperm production. Similarly, queens reared in treated colonies exhibited lower body weight. More recent studies by Keith Delaplane and colleagues tested emergence weight, memory, learning and longevity of workers exposed to fluvalinates and did not show any significant differences between treated and untreated colonies. In contrast, coumaphos – an organophosphate used for Varroa control – was clearly detrimental in these studies. Perhaps the most significant result in this study was that mite levels in treated and untreated colonies were unaffected … there was no evidence that the Apistan worked. I’ll discuss resistant in a future post.

Avoiding fluvalinate residues in comb

There are a variety of ways to avoid fluvalinates in comb. The first would be to use certified organic wax foundation. Thorne’s sell this for about twice the price of their standard worker brood foundation. This foundation is manufactured from beeswax sourced from New Zealand. Although certified organic, it’s not clear whether the wax has been tested for the presence of fluvalinates (an expensive process … so I’d be surprised if it had been). For reasons that will become clear shortly, just because the colonies used to source the wax had not been treated does not mean that there are no fluvalinates present in the comb from which the wax was rendered. Apistan was licensed for use in New Zealand seventeen years ago, shortly after Varroa was imported to the country.

An obvious way to reduce fluvalinates in comb is to use foundationless frames. Even if commercial foundation contains traces of the chemicals, by using only thin starter strips you can significantly reduce contamination. Perhaps even better, by making your own starter strips from wax recovered from your own brace comb, cappings or foundationless frames, you can exclude the need for commercial foundation – and all the ‘extra goodies’ it contains – completely. I’m also investigating the use of unwaxed wooden starter strips this season, removing any chance of initial contaminants (note that this is not my primary reason for trying these).

And now the bad news …

Unfortunately, avoiding commercial foundation of any sort and letting the bees draw comb directly from unwaxed starter strips still might not prevent the appearance and accumulation of fluvalinates in your hives. In the Delaplane study they used brand new hives and foundationless frames with plastic starter strips. After one year they compared treated and untreated colonies for the presence of fluvalinates in drawn comb. Unsurprisingly, treated colonies contained high levels of residual Apistan. However, untreated colonies also contained statistically significant levels of Apistan, four times higher than their detection limit. Coumaphos was also detectable at significant levels in untreated colonies. The authors suggest that the presence of both Apistan and Coumaphos was due to drifting of bees from treated colonies carrying the miticide into the untreated colonies. Therefore, even if you don’t use Apistan, if your neighbour does you are likely to get low levels of fluvalinates accumulating in comb – even when using foundationless frames.

The Delaplane study appeared in 2013. An earlier article appeared in Bee Culture in 2009 which described the fluvalinate contamination of both commercial foundation and comb supplied by ‘chemical free’ beekeepers. It’s much easier reading than the data-rich Delaplane article.

Conclusion

If used appropriately, at the right time of the season on a susceptible mite population, Apistan is very effective at killing Varroa. If used like this, Apistan levels will accumulate in the beeswax in the colony. This may be detrimental for drones or queens reared in the colony, but current studies indicate is probably has negligible effects on the worker bees.

However, widespread use of Apistan has resulted in the rapid and widespread selection of resistance in the mite population … meaning that Apistan often has negligible effects on Varroa. I’ll discuss this in more detail in another post.


What do you think happens to all the reclaimed beeswax traded with Thorne’s and other companies? It’s recycled into new sheets of foundation. You might not use fluvalinates, but many beekeepers do and this will be generously divided up across all the new sheets of pressed foundation.

Keep your distance

A recent paper by Nolan and Delaplane (Apidologie 10.1007/s13592-016-0443-9) provides further evidence that drifting/robbing between colonies is an important contributor to Varroa transmission. In the study they established multiple pairs of essentially Varroa-free colonies 0, 10 or 100 metres apart and then spiked one of the pair with a known number of Varroa. They then monitored mite build-up in the paired colonies over several months. By comparison of the relative mite increases in colonies separated by different distances they showed that the more closely spaced, the more likely they were to acquire more Varroa, presumably through robbing or drifting.

This isn’t rocket science. However, it’s a nicely-conducted study and emphasises the importance of colony spacing on the transmission of phoretic mites between infested and uninfested colonies – through the normal colony activities such as robbing and drifting – as a primary cause of deformed wing virus (DWV) disease spread in the honey bee population. The paper only studies mite levels, but the association with DWV transmission is well established and unequivocal.

Related studies on the influence of colony/apiary separation

The introduction to the paper provides a good overview of the prior literature on the impact of drifting on disease and Varroa transmission, some of which has already been discussed here. However, some of these studies have not previously been mentioned and deserve an airing, for example:

  • Sakofski et al., (1990) showed that there was no difference in mite migration between colonies in closely-spaced rows from those located up to 10m apart.
  • Frey and Rosenkranz (2014) showed that high-density colonies (>300 within flight range [2.5 km] of the sentinel colonies) experienced approaching 4-fold greater inbound mite migration than when located in areas containing a low-density of treated colonies. Over a 3.5 month period the difference was 462 +/- 74 vs. 126 +/- 16 mites. This would have a very significant impact if allowed to subsequently replicate in the recipient colonies.
  • Frey et al., (2011) previously investigated mite transfer between colonies located 1m to 1500m apart. Strikingly, in this study (which was conducted during a dearth of nectar) mite transmission was effectively distance-independent, with the recipient colonies acquiring 85 – 444 mites over a 2 month period.
Frey and Rosenkranz (2014) Mite invasion ...

Frey and Rosenkranz (2014) Mite invasion …

What can we conclude from these studies?

  1. Closely-spaced colonies – for example, the sort of distances used to separate colonies in an apiary – should really be viewed as a single location as far as mite infestation is concerned. A single heavily-infested colony in an apiary will quickly act as a source of mites to all other colonies.
  2. High densities of beekeepers – assuming the usual range in both the timing and vigour with which Varroa control is practised – is probably detrimental to maintaining low mite levels in your own bees.
  3. Significant mite transmission occurs over distances of at least 1.5 km … not just between hives in a single apiary. How many colonies are there within 1.5 km of your own apiary? Even if you are careful about controlling mite levels, what about all the beekeepers around you?
  4. Colonies wth uncontrolled levels of mite infestation, abandoned colonies (or swarms that occupy abandoned hives) and feral colonies located at least 1.5 km away are potential sources from which your carefully-maintained hives get re-infested …

Recent experience with high and low density beekeeping

One mile radius ...

One mile radius …

I’ve moved in the last year from the Midlands to Fife. Beebase and my involvement with local beekeepers suggest that these represent areas of high and low colony-density respectively. For comparison, Beebase indicates that there were over 230 apiaries within 10 km of my home apiary in the Midlands and that there are currently 20 within a similar range in Fife. In the Midlands I was aware of at least 25 colonies (in several different apiaries) within a mile of one of my apiaries. Furthermore, apiaries might contain lots of hives … one of those previously within 10 km of my home apiary was our association apiary which held up to 30 colonies from ~15 beekeepers. In contrast, the closest beekeeper to my current home apiary is almost 3km away … though I acknowledge there may well be hives “under the radar” belonging to beekeepers that are not members of the local association or have not bothered to registered on Beebase (why not?). It’s far too early to be definitive but mite levels in my colonies have been reassuringly low this season. This includes uncapping hundreds of drone pupae – the preferred site for Varroa to replicate – without detecting a single mite. I’d like to think this was due to timely and effective Varroa control, but it is undoubtedly helped because my neighbours are further away … and perhaps better at controlling the mite levels in their own colonies.

This study provides further compelling evidence of the importance of either keeping colonies isolated (which may not be possible) and ensuring that all colonies in the same and adjacent apiaries are coordinately treated during efforts to control mite numbers.

Gaffer tape apiary

Gaffer tape apiary …

The Drifters cont.

The Drifters ...

The Drifters …

Not the legendary American doo-wap/R&B vocal group but instead a quick follow-up to a recent post on drifting in honey bees. I discovered an interesting article in a 2011 issue of American Bee Journal in which Wyatt Mangum (Mangum, W. [2011] Varroa immigration and resistant mites ABJ 151:475) quantified mites introduced with bees from other colonies. The experiment was straightforward and quite clever … a number of colonies were prepared with very low mite numbers, overwintered and then miticides (unspecified, but from the remainder of the article I’m assuming Apistan) were applied continuously for the rest of the season. This would kill all the mites present. With a Varroa tray in place it was therefore possible to count newly introduced mites throughout the season. These must arrive with drifting workers, drones (not sure if drones ‘drift’ as such … perhaps there’s a better term for their itinerant wandering?), bees that have abandoned other colonies or potentially robbers. The newly infesting mites would of course be killed by the miticide after introduction and before reproduction. They could therefore easily be counted on the Varroa tray under the open mesh floor.

The results were striking … in one year between mid-May and early October an average of 1415 and 1001 mites were introduced to each of the seven ‘recipient’ colonies in two separate apiaries. Mite arrivals weren’t evenly spread, but peaked during a late summer dearth of nectar … perhaps, as suggested by the author, as other colonies started to run out of stores. The source colonies were not identified, but were not within the test apiaries. Whatever the cause, this represents a very significant influx of up to 7-10 mites per day. In Mangum’s experiment these mites could not replicate (due to the miticide that was always present). Had they been able to do so the impact on the recipient colony, in terms of numbers of mites transmitting viruses within the hive, would have been much greater.

The impact of drifting and mite reinfestation

The impact of drifting and mite reinfestation

Using BEEHAVE this impact can be modelled. In untreated colonies (solid lines), primed with 20 mites at the beginning of the year (and default conditions as previously described), the average mite level at the year end is ~430 (n=3) having reached a maximum of ~600. Using the same infestation period as reported by Mangum¹, with a mite infestation rate of 7/day (the lowest he observed), the average mite levels at the year end were ~2700 (n=3), with maximum levels reaching ~3800 in late summer (dotted lines). In this simulation the introduced mites can reproduce. Therefore, within just a few months, phoretic mites carried on workers and drones from other colonies, have the potential to raise mite levels in the recipient colony to dangerously high levels – significantly higher than the maximum recommended level of 1000/colony. This is potentially of fundamental importance in strategies to effectively control Varroa.  It should be noted that in a repeat of his study this large scale infestation was not observed. This suggests that this type of infestation – from outwith the apiary – may only be a problem in certain years or under specific conditions. One possibility that comes immediately to mind would be a collapsing feral colony or abandoned (or potentially not abandoned, but just completely ignored and untreated … or ‘abandoned‘ as some might say 😉 ) hive within foraging distance.

Ample opportunity ...

Ample opportunity …

Interestingly, a recent study has looked at the influence of a number of honey bee pathogens on drifting (or inter-colonial transmission as they rather long-windedly call it) behaviour. Of the viruses, Varroa and Nosema tested, only the presence of high mite levels influenced drifting … but not in the direction that might be expected. Distance between colonies in an apiary was the major factor that influenced drifting and ~17% of tested workers had drifted (with a third to half of these being apparently unrelated to other colonies in the test apiary). Surprisingly, colonies with high Varroa levels were more likely to acquire drifting workers, though the mechanism for this was unclear. The increased mixing through drifting would ensure that these colonies would likely end up with a greater diversity of viral and other pathogens though whether these colonies could, later in the season, act as a source rather than a sink for mites was not tested.

Drone

Drone …

Finally, returning to the subject of drifting bees and the ABJ … in the February 2016 issue there’s an interview with Tom Seeley (of Honeybee democracy fame … Sharashkin, L [2016], ABJ 156:157) in which he states that, when quantified, 34% of drones in his apiary colonies were from other hives. This article – on Surviving without Treatments: Lessons from Wild Bees – also discusses the importance of colony separation to coping with Varroa. The feral colonies Seeley studies are located at least half a mile apart in woodland. When recovered and relocated together in apiaries (‘beeyards’ as they’re called in the US) they rapidly succumb to mite-transmitted viral diseases, whereas those maintained some distance apart (30+ metres) survive. Seeley makes the point that pathogens evolving in closely-spaced colonies are likely to be more virulent, whereas those that are in distantly spaced colonies should be less virulent (or they’ll kill the host colony before being transmitted). Seeley is referring to the virulence of Varroa but I think his comments apply better to the viral payload carried by the mite. This is a relatively minor distinction but these observations further emphasise that drifting in honey bees is clearly a major factor in mite, and consequently disease, transmission … and therefore needs to be considered in control.

STOP PRESS – A recent Bee-L post highlighted a further study on the influence of re-infestation. Greatti et al., (1992) showed that ~2-14 mites/day/colony were acquired in their test apiary during June-August, and that this number rose to up to 75 mites/day/colony in September and October². This type of re-infestation can occur by drifting as already discussed, or by workers in the sentinel colonies robbing out mite-infested collapsing nearby hives or feral colonies.


¹In the Mangum study the mites did not infest the sentinel colonies at an even rate of 7+/day. Instead there was a marked peak in mid-season. I’ve not attempted to model this. Clearly if mites don’t arrive earlier in the season the overall levels would be lower (as they wouldn’t have the chance to reproduce). However, an influx of mites in mid/late-season might just arrive at the wrong time to damage the all-important winter bees … the topic of a future post.

²Greatti, M., Milani, N. and Nazzi, F., (1992). Reinfestation of an acaricide-treated apiary by Varroa jacobsoni Oud. Exp. Appl. Acarol., 16: 279-286

Drifting in honeybees

During previous research on deformed wing virus (DWV) biology and its transmission by Varroa I’ve moved known Varroa-free colonies (sourced from a region of the UK which the mite has yet to reach and maintained totally mite-free) into apiaries in the countryside. Within 2-3 weeks Varroa was detectable in sealed brood, showing that mite infestation occurs very readily. I know other researchers who have made very similar observations. Where do these mites come from?

They’re not all ‘your’ bees

The obvious source would be the phoretic mites transported on workers ‘drifting’ from nearby infested colonies, or on drones which are known to travel quite long distances and may be accepted by almost any colony. If you want to see how frequent this is try marking a few dozen drones with a dab of paint. To avoid confusion use the colour used to mark queens next year. There are unlikely to be 4+ year old queens in the apiary and the drones will all perish before the end of the current season. Over the next few days and weeks the drones will appear in adjacent colonies, and some will likely leave the apiary and be accepted in your neighbours colonies.

How to encourage drifting ...

How to encourage drifting …

Beekeepers are usually aware that colonies at the ends of rows often ‘accumulate’ bees that have drifted when returning to the hive. In shared association apiaries some crafty beekeepers will site their colonies at the ends of rows to take advantage of the ‘generosity’ of other colonies. However, many beekeepers probably do not appreciate the extent to which drifting occurs. Pfeiffer and Crailsheim (1998) report that 13-42% of the population of a colony are ‘alien’ i.e. have drifted from adjacent hives, depending upon the time of season. Remember that drifting occurs in both directions simultaneously, so the overall numbers of bees in a colony may not be adversely affected (or boosted). In other studies Sekulja and colleagues (2014) showed that ~1% of marked bees drifted between colonies over a three day observation window. Interestingly, American foulbrood (AFB) infected bees drifted slightly more than uninfected bees. Spread of foulbroods during drifting is one reason the bee inspectors check nearby apiaries when there is an outbreak. These studies were all on workers where drifting primarily occurs during orientation flights before the bees become foragers. Drones drift two to three times more than workers (Free, 1958).

The likelihood of drifting must be closely related to the separation of hives and apiaries. Although workers will forage up to 2-3 miles from the hive I suspect the proportion of bees that drift this distance is extremely small. However, unless you’re very isolated I expect there are other apiaries within a mile or so of your own. Drones are known to fly up to about five miles to reach drone congregation areas for queen mating and are accepted by all colonies. I’ve regularly found drones appearing in (relatively) isolated mini-nucs. I’m not aware of studies that have formally tested drifting between apiaries (though it is reported in passing in the Sekulja et al., 2014 paper cited above).

Consequences of drifting

So, your hives probably contain workers and drones from other nearby colonies, and you can only really be sure that they’re all “your” bees if you live – as the sole beekeeper – on an isolated island. Not only does your neighbour generously exchange bees with you, he or she also kindly shares the phoretic mites those bees are carrying, the viral payload the bees and mites are infected with and – if you’re really unlucky – the Paenibacillus larvae spores responsible for causing AFB infection (and vice versa of course).

There are lessons here that should inform the way we conduct our integrated pest management to maintain healthy colonies. 

This post provides background information for an article (“Viruses and Varroa: Using our current controls more effectively” by David Evans, Fiona Highet and Alan Bowman) in the December 2015 issue of Scottish Beekeeper, the monthly magazine for members of the Scottish Beekeepers Association.

More later …