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 … 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 (online copy has disappeared – apologies) 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.