As the 2026 beekeeping season approaches, Canadian beekeepers are continuing to learn what Varroa mite treatment products and applications are approved for use in Canada. So far, this past fall and winter, the Pest Management Regulatory Agency (PMRA) has approved of Apivar 2.0®, Amiflex®, and VarroxSanTM which will provide beekeepers with a few new options to select from in the near future. Adding to the list, the PMRA has recently approved of a new application method for oxalic acid, which is the use of glycerin strips. To learn more about the glycerin strip method, and how this may benefit beekeepers to manage Varroa mites, read this week’s blog.
New Application of Oxalic Acid: The Glycerin Strip Method
Previously, in Canada, the only approved application methods
for oxalic acid were the solution method, also known as the dribble method, and
the use of vaporizers. Beekeepers can continue using either of the mentioned
methods, but now there is a third option available known as the glycerin strip
method. It is important that beekeepers understand that all three methods
deliver the same product and have the same active ingredient, however,
beekeepers can select the application method that works best within their
operation.
The glycerin strip method requires some effort and work to
prepare the product for application. Beekeepers must be willing to devote the
time to properly preparing the product if choosing this method. According to
the label instructions, the product should be prepared with 99.7% food-grade
vegetable glycerin and oxalic acid dihydrate at a 1:1 ratio. The solution
should slowly be heated until the oxalic acid dissolves within the glycerin and
the solution becomes transparent. When heating the solution the temperature
should remain between 45°C and 70°C. Then beekeepers can saturate absorbent
strips (e.g. cellulose or other natural fibres) and place them in an open
container. Strips should be used within one month of preparation.
Each hive should be treated with 40g of oxalic acid. In order
to determine how many strips are required to achieve 40g, beekeepers must
weight a strip before it is saturated with solution, and again once it is
saturated, and determine how much solution has been absorbed. For example, if
one strip absorbs 20g of solution, then half of that would be oxalic acid (10g)
and, therefore, 4 strips would be needed to achieve the 40g dosage. Beekeepers
can trim strips to achieve the required dosage. Strips can be placed on the top
bars of frames or allowed to hang down between frames. Strips must remain in
the hive for 42 days.
A main advantage to using this application method is that
treatment can occur with honey super on hives, which differs from application
using a vaporizer or the dribble method. Another advantage to this treatment
method is that oxalic acid is relatively inexpensive, and both the dribble
method and glycerin strips do not require an expensive applicator (i.e.
vaporizer).
There are a couple of disadvantages to preparing these
chemical strips at home compared to purchasing a commercially prepared product.
In addition to the time and effort required to prepare the strips, there are
also associated risks if the product is not prepared safely and correctly. To
start, beekeepers must be diligent when measuring the vegetable glycerin and
oxalic acid to get a precise 1:1 ratio, and they must weigh each strip to
ensure the correct dosage will be administered to each hive. Providing too much
or too little of the active ingredient can be harmful to the bees, will impact
the efficacy of treatment and potentially contribute to future reduced
efficacy. Furthermore, when heating the solution, it must remain between 45°C
and 70°C. Underheating the solution will prevent oxalic acid crystals from
dissolving, and overheating the solution will degrade the oxalic acid, both of
which will reduce the efficacy of the treatment.
Another thing to be mindful of when preparing these strips at
home is your own safety. Oxalic acid dihydrate is a hazardous chemical that can
cause acute dermal toxicity and has the potential to cause serious eye damage
and/or irritation. Oxalic acid dihydrate has multiple health hazards if the
chemical is inhaled or ingested. Therefore, proper personal protective
equipment (e.g. gloves, protective eyewear, and a properly fitting organic acid
respirator) should be worn while preparing the solution. Ideally, the solution
should either be prepared in a fume hood or a well-ventilated area, and extra
caution should be taken to prevent contamination of any area, or equipment,
food is prepared or consumed in.
It is important to recognize that this treatment does not
target mites under capped brood cells. Therefore, the best time for beekeepers
to use this treatment is when there is a low amount of brood present (e.g.
after a queenless split, early season, or late season).
As with all Varroa mite products and application methods, it is essential that beekeepers follow the precise instructions provided by the PMRA regarding dosage, treatment period, frequency of application and application methodology. Not following the instructions can be harmful to bees, impact the efficacy of treatment and could contribute to future reduced efficacy of products. If you have questions regarding oxalic acid glycerin strips, or other Varroa mite products and applications, reach out to the ATTTA team.
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 attta@perennia.ca