March 2026
Jamie Trimby asks (in the February ABJ) whether a mite count of ―3 or less mites per 300 bees‖ (a 1% infestation) would be acceptable in a nuc for sale, and if not, whether oxalic acid would be an acceptable treatment.
As Jamie suggests, consensus is hard to find, but here in the United States I see recommended treatment thresholds ranging from 1-2% mite levels (3-6 per 300 bees). That said, if you‘re selling a nuc, especially to a beginner, it‘s best to bring that level as close to zero as possible. And that would not be accomplished via oxalic acid when there is capped brood, as OA is a flash treatment and does not penetrate the cappings. I would recommend treating the parent colony (prior to splitting off the nuc) with an extended treatment such as thymol, thus taking out a whole generation of varroa as they emerge from brood cells.
Sincerely,
Eugene Makovec
Editor, American Bee Journal (that other ABJ)
Hamilton, Illinois, USA
www.americanbeejournal.com
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Having just read the article ‘Sugar Shake’ (January ABJ) I appreciate being fully informed in the context of the parameters of the research done.
Has the same research been applied to the CO2 vm testing method?
I do appreciate the need for accurate information regarding Mite numbers etc. And, I do not want to kill bees unnecessarily, so if this information is available I would be most grateful to read about it.
My question is . .
Is it only the shaking which kills the bees, or does the sugar coating exacerbate the mortality rate?
Thank you all very much for your ongoing and dedicated efforts, and I look forward to ongoing reports and information.
Sincerely,
Jananta Dwipa
Reply courtesy of Andrew Wootton
The advantage of using CO2 to anaesthetise the bee sample for mite counting is that it will be non-lethal. However, a study comparing CO2 with sugar shaking showed it to be less reliable, with release of only about half the mites found with the sugar shake.1 Earlier, Randy Oliver investigated the CO2 method and wrote an extensive and approachable article2 (his website is recommended as essential reading for all matters varroa). Randy‘s comparison was with the gold standard of alcohol washing, finding only about half the mites were detected and concluding the method greatly underestimated the mite count.
We now know that the sugar shake results in significant mortality3, 4 and is less reliable than alcohol (or soapy water) washing. I suspect it is a combination of shaking and the sugar blocking the bees respiratory spiracles that causes death, remembering that shaking is required to dislodge the mites from the bees to allow detection.
Another non-lethal method of mite monitoring is to measure mite drop using a sticky mat and this is reportedly popular in the UK. Interpretation of the results is much trickier, varying substantially with size of the colony and time of year. Because of this, the National Varroa Mite Management Program has not recommended its use. Instead, we must reluctantly use the alcohol wash, consoling ourselves with the thought that this insignificant sacrifice will save the colony.
1 Bava, R., Castagna, F., Carresi, C., Cardamone, A., Federico, G., Roncada, P., Palma, E., Musella, V. and Britti, D., 2022. Comparison of Two Diagnostic Techniques for the Apis mellifera Varroatosis: Strengths, Weaknesses and Impact on the Honeybee Health. Veterinary sciences, 9(7), p.354.
2 https://scientificbeekeeping.com/a-test-of-using-co2-for-bee-friendly-mite-monitoring/
3 Allerton, M., 2026. Sugar Shake Let‘s Stop Sugar Coating It: The Powdered Sugar Shake Is Not Harmless. Australian Bee Journal, 107 (1), 8-9.
4 Bruckner, S., Williams, G.R., Tsuruda, J. and Underwood, R.M., 2025. Let‘s not sugar coat it: the powdered sugar shake is not harmless for honey bee workers. Journal of Apicultural Research, pp.1-6.