Essential Oils to Suppress Varroa Mites

Thursday 9 December 2021

During the upcoming holiday season, we will be partaking in those indulgences saved only for this celebratory time of year.  The odor of cinnamon, cloves and nutmeg will fill the air.  As we gather together not only will we be surrounded by these favorite smells and flavors, we will be exchanging gifts.  We all recognize the offerings by the Magi of gold, frankincense and myrrh as the original gifts of Christmas.  What might you ask has this to do with beekeeping?  You will be surprised, so read on to learn more.

Another launch of a “Beekeeping Minute” video.  These short videos are bite size pieces of beekeeping presented to help new entrants understand basics of both the art and science of keeping honey bees.  This week's video is on cleaning hive tools and can be found here: Atlantic Bees:

Essential Oils to Suppress Varroa Mites

Beekeepers are continually battling varroa mite with all the weapons available to us!  Experienced beekeepers know that high varroa mite levels will result in lost colonies.  The arsenal to fight these parasites is down to only one reliable chemical treatment and there is concern that this may be coming to the end of its life cycle.  Resistance seems to be inevitable and we have had a good run with Apivar.  Beekeepers who are keeping their fingers crossed and hoping it remains effective are likely also expecting Santa Clause to come this Christmas!  So alternatives need to be considered.  We have options that due to their mechanism of action and being naturally derived will not create resistant mites as far as we know.  One of these options is essential oils.

What are essential oils is a fair question to ask.  The definition from the Commission of the European Pharmacopoeia, essential oils are odorous products, usually with a complex composition, obtained from a botanically defined plant raw material by steam distillation, dry distillation, or a suitable mechanical process without heating1..  Closer to home, the government of Canada definition states, “Essential oils are complex mixtures of volatile compounds produced as secondary metabolites in aromatic plants. They can be extracted from these plants by distillation, solvent extraction, cold pressing, and other means.”2.  Therefore, these are plant-based products extracted so as to be little altered from the original botanical compounds found naturally.  Along with the definitions above, these oils must maintain the “essence” of the original plant which for our understanding would mean odor.  The odor being the volatile products, or vapors, of these substances and important for their mode of action as a pesticide.  The original purpose of these substances in the plant are complex but often act as insect repellants.

How do they work?  The mechanism of action is poorly understood.  They operate at a molecular level to perturb cellular, ionic and enzymatic activities.  It would seem that evolutionarily, there are target insects for these plant compounds as either repellants or attractants.  It could also be suggested that entomophilous plants, requiring insect pollination, would not target bees negatively with these natural defenses.  This suggests why certain essential oils are not as toxic to bees as they are to mites!

So a few examples of essential oils include frankincense and myrrh, to bring us back to our Christmas theme.  An additional list of other examples reads like part of a Christmas pudding recipe: cinnamon, cloves, nutmeg, ginger and mace.  For a more extensive list of essential oils tested experimentally as controls for varroa mites, read Evaluating the Efficacy of 30 Different Essential Oils against Varroa destructor and Honey Bee Workers (link provided below)..  With all these examples, we must remember that we can only treat our bees with products which have been registered for use in Canada.  There are two essential oil products available for beekeepers in Canada to control varroa mites.

Thymovar is derived from the herb thyme with the active ingredient thymol and has been licensed in Canada in 20162.. ApiLife Var is a combination of essential oils including Eucalyptus oil, levomenthol, camphor, and thymol; licensed in Canada 20204..  Recent research in Canada has demonstrated that thymol based acaricides can be up to 96.6% effective in controlling varroa mites5..

Hundreds of essential oils have been tested as acaricides 6..  We have two essential oil products available for use here in Canada.  These are proven effective and also have the advantage of being a natural plant derived product.  If used correctly they also have no effects on human health and a reduced chance of harmful residue compared to synthetic acaricides.  There seems to be no concerns of resistance developing in mites with these products.  Current research indicates low toxicity for honey bees and even less than formic acid or oxalic acid.

As concern over the long-term efficacy of chemical treatments grows, we are looking optimistically at alternatives.  As part of an integrated pest management approach to controlling Varroa destructor we must use varied strategies to ensure the health of our bees.  As we are now planning our IPM strategies to control varroa mites this coming season, consider all treatment options including essential oils.  As wise men knew in the past, essential oils are to be valued whether as Christmas gifts or in maintaining healthy honey bee colonies! 

 1. Hýbl, M.; Bohatá, A.; Rádsetoulalová, I.; Kopecký, M.; Hoštiˇcková, I.; Vaníˇcková, A.; Mráz, P. (2021) Evaluating the Efficacy of 30 Different Essential Oils against Varroa destructor and Honey Bee Workers (Apis mellifera). Insects, 12, 1045.

 2. Pest Management Regulatory Agency (2017) Regulatory Directive DIR2017-02, Essential Oil-based Personal Insect Repellents (EOPIR)

3. Pest Management Regulatory Agency (2016) Registration Decision RD2016-16, Thymol,

4. Pest Management Regulatory Agency (2020) Racemic camphor,eucalyptus oil, lmenthol and thymol and Api Life VAR,

5. Qodratollah Sabahi, Nuria Morfin, Berna Emsen, Hanan A Gashout, Paul G Kelly, Stephanie Otto, A Rod Merrill, Ernesto Guzman-Novoa, Evaluation of Dry and Wet Formulations of Oxalic Acid, Thymol, and Oregano Oil for Varroa Mite (Acari: Varroidae) Control in Honey Bee (Hymenoptera: Apidae) Colonies, Journal of Economic Entomology, Volume 113, Issue 6, December 2020, Pages 2588–2594,

6. Abdessamad Aglagane, El-Mustapha Laghzaoui, Sana Ben Elfakir, Omar Er-Rguibi, Abdelaziz Abbad, El Hassan El Mouden & Mohamed Aourir (2021) Essential oils as sustainable control agents against Varroa destructor (Acari, Varroidae), an ectoparasitic mite of the western honeybees Apis mellifera (Hymenoptera: Apidae): Review of recent literature (2010-onwards), International Journal of Acarology, 47:5, 436-445


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