varroa mites

Small cells do not control Varroa mites

Whenever I write about small-cell combs and Varroa mite control I incur the wrath of the believers. It’s the one subject that delivers something very close to hate mail. So with that in mind, I will say it again: small-cell combs will not control your Varroa mites.

In a 2011 paper by Thomas D. Seeley and Sean R. Griffin[1]—both of the Cornell University Department of Neurobiology and Behavior—small-cell combs were once again found to produce no fewer mites than regular-sized combs. This work, along with similar experiments reported by Ellis et al. 2009, Berry et al. 2010, and Coffey et al. 2010, demonstrates that small-cell combs given to European honey bees do not significantly reduce either mite loads or mite drops compared to hives with similar genetics and similar mite infestations.

In their experiment, Seeley and Griffin studied seven pairs of colonies. Each pair was started from a strong colony with a high mite drop. In order to assure that each pair had similar genetics and similar mite loads, the bees were shook from the parent colony and then divided into two packages. Each package was then given a new Minnesota Hygienic queen and fed sugar syrup. After three days, one package from each colony was put in a hive with standard-size combs (5.38 mm) and the other package was put in a hive with small-cell combs (4.82 mm).

Once a month for five months, the seven pairs of colonies were measured for colony strength, mite infestation, and worker size. The paper contains many interesting tidbits but, to make a long story short, by the end of the experiment Seeley and Griffin found no significant difference in either infestation rates (mites per 100 worker bees) or mite drops. They also found very little difference in worker size. Even though the small cells were 10.4% narrower than the average standard cells, the worker bees showed only a 2.1% decrease in head width and a 3.5% decrease in thorax width.

Taking this a step further, they divided the average thorax width of workers in standard cells (3.95 mm) by the cell width (5.38 mm) to get a “fill factor”– or the percentage of cell filled with bee (73%). Similarly, dividing the average thorax width of a small-cell bee (3.81 mm) by the small-cell width (4.82 mm) yielded a fill factor of 79%. This throws doubt on the commonly held belief that there is not enough room inside a small cell for mites to reproduce effectively. Neither 73% nor 79% are very tight fits, so there is plenty of room to grow many mites in either case.

I hear plenty of conflicting stories—anecdotal evidence of how changing to small cells cured the mite problem. But when researcher after researcher cannot reproduce those results, I have to wonder if the anecdotal cases aren’t due to exogenous variables or just plain luck. Sometimes we want something so badly we can’t think beyond the wishing. Believe me, if I thought there was a breath of truth to small-cell mite control, I would switch tomorrow.


[1] Seeley, Thomas D. and Griffin, Sean R. 2011. Small-cell comb does not control Varroa mites in colonies of honeybees of European origin. Apidologie 42:526-532, DOI: 10.1007/s13592-011-0054-4.

Other references:

  • Berry, J.A., Owens, W.B., Delaplane, K.S. (2010) Small-cell comb foundation does not impede Varroa mite population growth in honey bee colonies. Apidologie 41, 40–44.
  • Coffey, M.F., Breen, J., Brown, M.J.F., McMullan, J.B. (2010) Brood-cell size has no influence on the population dynamics of Varroa destructor mites in the native western honey bee, Apis mellifera mellifera. Apidologie 41, 522–530.
  • Ellis, A.M., Hayes, G.W., Ellis, J.D. (2009) The efficacy of small cell foundation as a Varroa mite (Varroa destructor) control. Exp. Appl. Acarol. 47, 311–316.
  • Zhou, T., J. Yao, S.X. Huang, Z.Y. Huang. 2001. Larger cell size reduces varroa mite reproduction. Proceedings of the American Bee Research Conference, American Bee Journal 141: 895-896.
  • Taylor, M.A., Goodwin, R.M., McBrydie, H.M., Cox, H.M. (2008) The effect of honeybee worker brood cell size on Varroa destructor infestation and reproduction. J. Apic. Res. 47, 239–242.


  • Hi Rusty.

    I hear you sister! I have also tried to explain these studies, but many beekeepers, I have found, don’t want to be bothered with the facts. There is just no logical reason why mite reproduction would be hindered by a smaller cell unless it somehow shortened the pupal stage period (which it doesn’t) giving the mite less time to produce more offspring. Furthermore, these small cell advocates talk about the bees regressing to a smaller size which would then increase the space around the pupae within the smaller cell making it compatible with the space in the commonly used 5.38 mm cells.

    I think you are right on target about the anecdotal evidence, i.e. exogenous variables or just plain luck. Under the exogenous factor category, when beekeepers are going through the procedure of regressing their bees through several generations, we may logically conclude they are using survivor stock which may be survivors because they have inherited some hygienic traits and, therefore, are more mite resistant. Just a thought.


  • Yeah but . . .

    No hate mail. Just ponderings. Would love to see that experiment performed over a year or two. For sure, the population trend changes with mites from year one. Logic might have it that the stats would be on a continuum, but it does – in my mind – raise the question, due to so many positive touts of small cell, of whether mite control might be something that progressively gets better with the age of the colony. Is 5 months enough generations? The other thing this account doesn’t mention is whether the splits were from respectively sized cells. (Is this implied by “similar genetics”?) I can’t help but wonder if there was some regression involved. If yes, a year or two might prove differently? I don’t know enough about any of this yet to have a strong opinion just yet, but I have been keeping a watchful eye on small cell research and I do like small cell just for the fact that it is the natural size bees used to be.

    • I don’t discount the possible value of small-cell bees. As I’ve mentioned before, some research has shown that natural-sized bees may be more efficient pollinators and more healthy in general. My only point here is that I don’t believe small cell size will cure the Varroa problem.

  • Thanks for this Rusty, it’s good to know this has been confirmed by independent research carried out by respected scientists. I have Thomas Seeley’s brilliant book on honey bee swarm behaviour.

    • Emily,

      I agree. When I saw Thomas Seeley did the research I knew it was something we had to take seriously. I can think of no one who is more respected as a bee researcher. And, yes, I have a copy of Honeybee Democracy as well.

  • I agree that small-cell won’t “cure” varroa. These studies are only very short term studies and need to be carried out for 2-3 years as regression is a major factor in using small-cell. I have met with and spoken directly to several life-long beekeepers such as Michael Bush, Kirk Webster, Mike Palmer, Dee Lusby, and Erik Osterlund, and all switched away from conventionally- sized foundation and switched to small-cell regression and had extremely beneficial results. These are folks who don’t have laboratory apiaries, but lifetime real life trial-and-error experience with varroa from the beginning in the 90s. I really don’t think anyone has claimed that small-cell will “cure” the infestation of varroa, but it has made a huge difference in the way bees deal with them over several years. I have also seen a big difference in how my bees cull infected brood when comparing large-cell and small-cell colonies. It is my belief that giving our kept bees any advantage that we can, short of chemicals, is what we should be looking for.

  • I do think it is sad that everyone believes research monitored over such a small time frame. Beekeepers like Dee Lusby, Michael Bush etc with well over 30 years of small cell experience should be taken very seriously…perhaps the researchers should start studying their methods…..It is hard to argue with success.

    • Bev,

      I think it is sad when people do not understand the scientific method. You say it is hard to argue with success, but it is not success when so few people can make it work. One of the major precepts of scientific inquiry is repeatability. That is, for a theory to be considered valid, many scientists in many places must be able to repeat the experiment and obtain the same results.

      Let’s say fifty scientists repeat an experiment and only five get the same result as the initial experimenter. In that case, something is clearly wrong. Either they weren’t doing the same experiment, or the parameters being tested have no bearing on the outcome.

      In the case of small-cell combs and the suppression of Varroa mites, many scientists have tried to replicate the success of people like Bush and Lusby and they have been unable to do so. Does that mean that Bush and/or Lusby are wrong? Does that mean they are lying? Of course not. I have no doubt that they accurately report their findings.

      But scientific experimentation is fraught with things known as exogenous variables. These are variables that the experimenter is probably not even aware of. For example, most people have at one time or another followed a “fool-proof recipe” that bombed. Mine was a cream pie that curdled like cottage cheese. I went back through the recipe and checked every detail but couldn’t find my error.

      Does that mean the author was wrong? Or that he lied? Of course not, but maybe my cream was older than his, maybe my eggs were bigger or smaller, maybe my kitchen was too cold, or my beaters too hot. Maybe the altitude of my kitchen was different, or my timer was inaccurate, or his timer was inaccurate. Maybe I interpreted his instructions in a way he didn’t mean. Any of these—and many others—could affect the outcome. Unless every condition is identical, the results may be different. Until we know which variable is the important one, the recipe can’t reliably be repeated.

      Maybe Bush and Lusby (and I use these names simply because you did) have hives that are in a better location or in a particularly good microclimate. Maybe the paint they used on their hives, the feeding supplement they used, or the forage they have available made a difference. Maybe the particular way they handle their bees, or the exact strain they raised, or the length of the daylight, or the temperature of the hive made a difference. Maybe they sang to them.

      The point is, until we can isolate the specific element that made the difference, other people cannot repeat the experiment and get the same results. We don’t want to trust our bees to a technique that might work, especially when we don’t know why it works in some cases and not in others.

      If an aeronautical engineer with 30 years of experience designed and built a crash-proof airplane and flew it many times without crashing, should we all trust that plane or should some other engineers try to replicate the design? And if 20 engineers replicate the design and they all crash, should we still trust the first guy and all climb aboard? I don’t think so.

      In our modern lives, we have peer-reviewed science, independent testing councils, and all manner of protocols to guard against assuming something is scientifically sound when, in fact, it is not. In the case of Varroa mites, we all want something as simple as small cell size to be the magic bullet, but when researcher after researcher can’t make it happen—or can only make it happen sometimes—we have to revisit the theory. Believe it or not, most researchers just want to discover the truth; they rarely have hidden agendas.

      The beekeeper who can raise bees year after year with no Varroa mite problem is probably onto something. But what exactly? That is the real question. Until we find an answer—a formula—that works reliably for most beekeepers most of the time, we have to keep looking.

  • What about the fact that the reason they want to do these small cell size is because they think it is more natural. If this were the case, wouldn’t top bar hives not have mite problems? and wouldn’t the size of the top bar hive cell size be the smaller size? When i was discussing with my beekeeping buddies who have both top bar and langstroth, they said they noticed no difference in mites, but also not a significant difference in cell size.

    • Chini,

      You are right, of course. There are many aspects of small cell vs natural cell vs foundation-sized cell that don’t add up. Plus, as the bees adapt to the new cell size, so do the mites. If small cell resisted mites significantly, we would all be doing it by now. No question.

  • I’m all for well researched studies and read both the Barry and Seeley papers referenced above and find what appears to me to be the same pretty significant problem in both. Please correct me if I’m wrong as I’m no scientist and may be completely missing something here.

    In the Barry paper, they start with hives containing already drawn small cell and standard cell comb. Then, “bees were collected from a variety of existing colonies (irrespective of rearing history) and combined in large cages to achieve a homogeneous mixture of bees and Varroa mites.” Packages then were created from this mix of bees and installed in either small cell or standard cell hives. They don’t indicate the cell size of the ‘existing colonies’, but since they were mixed together, there will inevitably be the wrong sized bees on the wrong sized comb. Additionally, since “Queens from a single commercial source were introduced into colonies.”, again, you have almost definitely a standard sized queen trying to lay in small cell comb.

    The same error appears in the Seeley paper. Again, they start with pairs of hives containing either small or standard cells. Then, “The two colonies in each pair were started as artificial swarms made form the same source colony”. If the bees are coming from the same source colony and being put onto both small and standard cell comb, one of those colonies has the wrong sized comb for the bees that were installed.

    Have I completely overlooked something or does this introduce a major flaw in having standard sized bees / queens trying to work small cell comb?

  • I don’t usually post on the blogs or try to convince others on my operating procedures concerning bees. Fine people like Rusty are doing just fine! No, I don’t totally agree with her, (no two beekeepers are the same) but her goals for beekeepers are sincere!
    That being said, I need to make a change of position statement/opinion that I have carried for several years. “Beekeepers must try and allow the bees to regress to their natural element”. The bees know what they are doing, but we sometimes get in the way…we sometimes tell ourselves that we know better! For example: why do the bees produce more drones on foundation-less frames than foundation? “Maybe” the answer is to help get rid of the mites. Maybe we helped force the mite problem with contaminated pressed foundation and to increase honey production. Feral hives have more drone comb for a reason and I just don’t think it’s totally for reproduction purposes. Allow the bees to regress and adapt naturally. There are IPM practices that will keep the mites down, and If those practices fail for the beekeeper, then other mite control choices are then available. I personally believe that there is more to the equation. I have a nearby feral hive that we will take down in April. I have personally investigated the feral hive. The bees are now almost 2/3 the size of their related Carni. Why did they regress? What is their reasoning? My belief is that they know better! In my years as a beekeeper I have tried to force the bees into doing what I think is right….It doesn’t always work and you can talk any of the possible answers to death! Science and scientists are great, but you need people to understand that some people are part of the bees problems, i.e., home pesticides, herbicides, and that people must convince governments to take steps to protect the bees from massive spraying practices.
    Bees have been around a long, long, long time and have evolved over time on their own and have done so naturally!
    I have a dear friend who is a certified beekeeper and taught me much of what I know and what we now both believe…the bees know better and to go natural is the logical thing to do!