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: https://nbwildblue.ca/
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.
.JPG) |
| 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. https://doi-org.ezproxy.library.dal.ca/10.1080/09670874.2022.2094489
Written by John MacDonald, ATTTA Seasonal Apiculturist johnmacdonald@perennia.ca
Connecting with ATTTA Specialists
If you’d like to connect with ATTTA specialists or learn more about our program, you can:
visit our website at https://www.perennia.ca/portfolio-items/honey-bees/
Email abyers@perennia.ca