Miticide Resistance in Varroa Mites

Thursday 14 July 2022

With high overwintering losses reported this year, the importance of Varroa mite management has been reinforced.  Last season, with an early spring, was longer than usual, providing ideal conditions for unchecked Varroa mite levels to dangerously increase.  In consideration of ongoing reports of high overwintering losses and the suggestion that Varroa mite management contributed to these losses, a look at Honey Bee pest control is topical.  This week’s blog looks at this alarming subject and summarizes a recently published review on acaricide resistance!* 

Also, a reminder Bleuets NB Blueberries is having a Field Day 2022 in Aulac on July 21st, 2022, from 10am to 2:30pm. Full details can be obtained through the Association:

Miticide Resistance in Varroa mites

There are three classes of chemical miticides that are used by most beekeepers: pyrethroids (fluvalinate and flumethrin), organophosphate (coumaphos), and formamidine (amitraz). Repeated usage of these miticides may cause accumulation and persistence of chemicals in the hive products (wax and honey). This suggests a health risk for honey bees and humans.  Long term use of these hive products, and accumulation of chemicals has the potential to reduce the efficacy for treatment against Varroa mites. This threat of resistance is something beekeepers should understand and therefore be able to work towards extending the efficacy of current treatments.

There are many ways that mites can adapt to survive prescribed doses of miticides, which can help to create widespread resistance (Mitton et al. 2022).  Physiological mechanisms for resistance in Varroa mites can be split into five different categories (Mitton et al. 2022). Mechanisms can be inherited which reduce or prevent the penetration of miticides into the body of the mites. Mites have enzymes and proteins in their body which can bind to molecules in miticides and transfer them away from the targeted site to the fat body or hemolymph for storage. Behaviors can be developed by mites to avoid toxic compounds. Mites can increase the level of enzymes in their body, which increases the rate of metabolism, and breaks down miticides to less toxic forms. Also, the target site for the miticides can be altered, which results in the miticide being less toxic (Mitton et al. 2022). It is important to mention that resistance can also be caused or compounded due to poor management practices of beekeepers.

A healthy frame of bees: queen, worker bees, drones and brood!

When trying to control Varroa mites, the type of miticide, the amount, the concentration, the mode of action of the miticide to mites, the persistence of previous treatments, the number of applications, and the hive and apiary conditions can all cause the spread of resistance in Varroa mites, if not managed properly (Mitton et al. 2022). These variables should be considered before treating for Varroa mites, because this will prevent the emergence of resistant populations of mites. Some ways to avoid these issues is to use a rotation of miticides and to exactly follow the instructions on the label for application.  Also, ensure the correct amount is used and treat at the correct time.  Only treat when mite levels are above the economic threshold and follow correct Integrated Pest Management (IPM) practices. Please check out the ATTTA factsheet for economic thresholds

When there is resistance suspected in an apiary, it is important to test the miticides being used, by doing a Pettis test. If resistance is found it is crucial to use different control methods. An integrated pest management plan should be used by every beekeeper to prevent the spread of resistance in Varroa mites to miticides. There are a number of alternative methods that can be used for the control of Varroa mites to prevent resistance, including “soft miticides”. These miticides include organic acids and essential oils, which have been shown to have high efficacy, a low probability for resistance in mites, and low risk to accumulation in hive products. See the ATTTA factsheet for more treatment options. ApiLifeVar® is another option for a soft miticide, which has just been recently registered for use in Canada.


*G. Mitton, F. Arcerito, H. Cooley, G. Fernandez de Landa, M. Eguaras, S. Ruffinengo, and M. Maggi. 2022. More than sixty years living with Varroa destructor: a review of acaracide resistance. International Journal of Pest Management.

Written by John MacDonald, ATTTA Seasonal Apiculturist

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