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When a beekeeper asks what the best treatment for varroa is, they are probably asking a question that is too simple for a problem that is not simple at all. We would all like to have a product that is effective enough, inexpensive, easy to apply, and independent of temperature, brood amount, time of year, and any resistance the mites may have developed. We would apply it when the time came, and the problem would be solved. Unfortunately, varroa does not make life that easy for us.

A study published this year by Mazur and colleagues helps explain why [1]. The researchers analyzed 8,655 beekeepers from Austria, Czechia, Poland, and Slovakia, representing 171,756 colonies, and related varroa control strategies to colony mortality. The result I find most interesting is not the victory of any particular product. That victory simply does not appear. Practices varied considerably among countries and among operations of different sizes. And the strategies associated with the lowest losses combined, at different times, biotechnical methods, organic acids, and synthetic acaricides [1].

Mazur and colleagues’ study

It may therefore be more useful to stop thinking only in terms of treatments and start thinking in terms of control strategies. An excellent treatment may produce an insufficient result in our own apiary. It may have been applied too late; there may be too much capped brood for a product that acts on exposed mites; the temperature may be unsuitable; or the mites may be resistant to the active ingredient being used. The medication has not changed. What changed was everything around it.

And there is one variable that seems particularly important to me: timing. This is not a new idea on this blog. In January 2017, I published “The Timing of Varroa Treatment: Putting the Pieces Together.” Based on data from my own apiaries, varroa population dynamics, and the literature available at the time, I concluded that treating too late could mean arriving after the point at which we should already have been protecting the bees that would carry the colony through winter. I wrote then that “later may be too late” [2].

Eight years later I returned to the subject in “One of the Main Causes of Varroa Treatment Failure.” A study based on 4,339 beekeepers and 18,700 colonies in England and Wales found lower winter losses associated with correct treatment timing, rather than simply with the fact that a treatment had been applied [3]. Evidence has continued to accumulate, but the essential idea has changed very little. A 2% infestation does not mean exactly the same thing in March, in July, or when we are producing the winter bees. While brood is present, the varroa population can grow rapidly. Stephen Martin’s classic model showed very clearly how a population that is initially modest can become a very different population a few months later [4].

There is an important difference here between killing mites and controlling varroa. Killing mites is relatively easy. Controlling them throughout the year requires thinking about the timing of interventions, the sequence of treatments, the presence of brood, reinfestation, and what exactly we are trying to protect at each point in time.

This is where windows of opportunity come in. A natural or induced brood break, for example, exposes a much larger proportion of the varroa population to oxalic acid. The product is exactly the same; what has changed is the opportunity we have given it to act. When brood is present and conditions are suitable, formic acid offers other possibilities. And there will be circumstances in which an authorized synthetic acaricide, used correctly and against mites that remain sensitive to the active ingredient, will be the most appropriate tool. The strategy begins when we stop asking which of these tools is best and start asking when each of them may be most useful.

And timing is not everything. As early as 2017, in a post about colony mortality and management, I referred to data presented by Dennis vanEngelsdorp showing important associations between beekeepers’ management choices and colony survival [5]. A large pan-European epidemiological study published that same year, involving 5,798 apiaries in 17 countries, likewise found a strong association between survival, beekeeper experience and training, and disease control [6]. The new study by Mazur and colleagues now adds another particularly interesting piece. The best strategies varied among countries and among operations of different sizes [1]. The authors suggest that differences in experience, training, sources of knowledge, and management organization may help explain why different strategies can still achieve satisfactory results.

This matters to me because it reinforces an idea I have repeated many times on this blog: we cannot completely separate the treatment from the beekeeper who uses it and from the management system in which it is used. Interestingly, in Mazur’s study, larger operations consistently showed lower mortality. This does not mean that simply having more colonies causes fewer bees to die. It may reflect, among other things, greater experience, organization, and discipline in carrying out control strategies [1].

And that brings us to monitoring. A treatment is not effective simply because we applied it. We only know whether it was effective enough when we check what remained afterward.

Monitoring infestation rate in a sample of approximately 300 adult bees during a recent technical visit to an apiary

Among other factors, the speed or slowness with which an acaricide acts helps explain why something that “has always worked” may stop working under conditions of high infestation.

For that reason, the search for the “best treatment” seems less and less useful to me. To understand why a treatment succeeded or failed, we need to know when it was applied, what the infestation level was, how much brood was present, how sensitive the mites were, what level of efficacy was achieved, and what was done afterward. The name printed on the package tells only part of the story.

Nor would I take from this the comforting conclusion that “every apiary is different” and therefore everyone can simply do whatever they want. Some principles remain valid. A high varroa population is dangerous; treating too late has consequences; and an active ingredient to which mites have developed resistance does not regain its effectiveness because we change our management philosophy. What changes is the way we apply those principles to the specific circumstances in front of us.

Perhaps that is the main value of the study by Mazur and colleagues. It does not offer the recipe many people would like to find. It shows that the best results are associated with strategies, with timing, and with the combination of tools, rather than simply with choosing a product [1]. The question therefore becomes less simply “what is the best treatment for varroa?” and more:

how much varroa do I have now, where is this population likely to go, which bees do I need to protect, what window of opportunity lies ahead, and which tool makes the most sense at this particular moment?

It may sound like only a change in the question. In practice, it is a very different way of controlling varroa.

References

[1] Mazur, E., Biemann, O., Brodschneider, R., Chlebo, R., Gajda, A., Iller, M., Vencálek, O., Brus, J. & Danihlík, J. (2026). Varroa control strategies of different beekeeper groups and corresponding honey bee colony mortality in Central Europe. Journal of Advanced Research. DOI: 10.1016/j.jare.2026.06.003.

[2] Gomes, E. (2017). The Timing of Varroa Treatment: Putting the Pieces Together. Abelhas à Beira, January 30, 2017.

[3] Gomes, E. (2025). One of the Main Causes of Varroa Treatment Failure. Abelhas à Beira, September 7, 2025. Based on A large-scale study of Varroa destructor treatment adherence in apiculture.

[4] Martin, S. J. (1998). A population model for the ectoparasitic mite Varroa jacobsoni in honey bee (Apis mellifera) colonies. Ecological Modelling, 109, 267–281. DOI: 10.1016/S0304-3800(98)00059-3.

[5] Gomes, E. (2017). Honey Bee Colony Mortality in the USA: What Is the Relationship with Management? Abelhas à Beira, December 27, 2017.

[6] Jacques, A., Laurent, M., Ribière-Chabert, M., Saussac, M., Bougeard, S., Budge, G. E. et al. (2017). A pan-European epidemiological study reveals honey bee colony survival depends on beekeeper education and disease control. PLOS ONE, 12, e0172591. DOI: 10.1371/journal.pone.0172591.

[7] Bertola, M. & Mutinelli, F. (2025). Sensitivity and resistance of parasitic mites (Varroa destructor, Tropilaelaps spp. and Acarapis woodi) against amitraz and amitraz-based product treatment: a systematic review. Insects, 16, 234. DOI: 10.3390/insects16030234.

References

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