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Home > International > Beekeeping techniques > Thymol and Oxalic Acid

Thymol and Oxalic Acid

Until 2008, we were struggling against varroa with thymol treatments, in summer, and oxalic acid, in winter, by following the standard recommendations.
-* In September (maximum temperature < 25°c): 2 thymol treatments (10g per hive and by treatment) at a 10 day interval,
-* end of December (without brood): 1 oxalic acid treatment.

We were not satisfied with the effectiveness of the treatments on Varroa and above all, we noticed that our colonies were not at their best during spring.

Between 2008 and 2011, following Dominique Micheletto advices, we modified our summer treatment:
- 3 treatments of ¼ dose with a smaller interval, instead of 2 treatments of ½ dose each 10 days.


-* Conditions of use: Do the treatment during hot temperature (>25°c). Noteworthy, there is no maximum temperature (until 40°c). The treatment must be ended by the end of August, before the winter laying.
-* Dilution of the Thymol: 1 kg of thymol + 1 L of 90° alcohol. Calculate 1 kg of thymol for 65 hives or 130 small hives.
-* Dilution of the oxalic acid: 40 to 50 g of oxalic acid (dihydrate) in 1L of diluted syrup at 50%.


-* For the hives, 1 piece of cardboard on the top of the frames, more precisely 50g of thymol ( 50 cc on each cardboard),
-* For the small hives, we only put half a cardboard for each treatment,
-* For the Maxi+, it is ¼ of cardboard.

    • Number of treatments in summer: 3 treatments with a 5 day interval,Number of treatments in winter: 1 treatment without brood (when the queen stops laying eggs).


-* We realized the importance of controlling the Varroa during the month of August, just before the bees’ winter birth.
-* In a case where the summer treatment is not effective, but the winter one is very effective, the colonies’ potential will strongly be limited for the next season.
-* By improving our summer treatment, we strengthened the immune defence of the colonies. Even if the thymol treatments don’t reduce sufficiently the Varroa pressure, we succeeded to improve significantly the colonies’ dynamics.