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.
Rusty
[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.
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.
Jim
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.