Winter treatment for varroa

[cheomar23]

 Winter treatment against varroa is essential. The natural cessation of the queen's egg-laying results in the absence of capped brood and therefore all varroa mites will be affected by the treatment product.

When to treat
Varroa mites reproduce in capped brood. As no product penetrates through the operculum, treating with brood does not reach 100% of varroa mites. Residual varroa mites are those which restart the infestation of the colony after treatment.

The ideal period is therefore to treat in the absence of capped brood.

There is another opportunity that should not be missed. In winter, three weeks after the first frost, these optimal conditions are met. The frost stops the queen's egg laying and three weeks later all of the capped brood has hatched.

Which product to use?
During this period, the best is to use oxalic acid, which is very effective and easy to apply.

Be careful, oxalic acid is toxic. Do not breathe vapors and watch out for splashing in the eyes. If you spill it on the skin, rinse it off thoroughly. For these reasons, I recommend using it as a drip. It is also possible to use it in sublimation but this requires suitable equipment. By sublimation, the vapors given off are toxic. Better to wear a mask.
How to prepare the product?
First prepare a 50/50 syrup of water and sugar. Carefully measure the prepared amount. Approximately 30 ml per hive is needed. Read the product leaflet.

Then heat the syrup to 35 ? C in a water bath.

When the syrup is at the right temperature, add the oxalic acid. Use pure oxalic acid and not a product found in supermarkets that contains residue. Add 35 grams of oxalic acid per liter of syrup.

If you have a small number of beehives or if you don't want to be a little chemist, I recommend the Oxuvar which is an oxalic acid solution that is easy to prepare before use.
Apply the treatment

Draw 35 ml of syrup into a syringe. Open the hive, count the number of occupied lanes and pour with the syringe 5 ml per lane between the frames.

In the fall, I leave the beehive drawers ajar to ensure good ventilation and prevent condensation. During the treatment, I close the previously cleaned drawers.

This has two advantages:

On the one hand, to promote the temperature of the hive to help the queen's egg-laying recovery
Then, to allow control of the fall of varroa mites. A count two or three days after the treatment, allows to measure the degree of infestation.
If you count after three days and find fifteen varroa mites, that makes 5 varroa mites per day.
It is considered that one varroa fallen per day is equivalent to 100 varroa present in the hive. Remember that the number of varroa mites doubles every month in the hive. One hundred varroa mites in December is 200 in January, 400 in February and 3,200 in May and 6,400 in June. From 4000 varroa mites, it is considered that the survival of the colony is strongly compromised. It is therefore in December that we must solve the problem to stop the proliferation of varroa mites.

Source: Beekeeping World

[TheHoneyPump]

If one waits until the hive is supposedly broodless before treating, the hive will still perish after all exposed mites have been eliminated. The reason is because the mite damage is done to the winter bees being raised in the 6 to 9 weeks before the hive goes broodless for winter.  To be successful at controlling mites and maintaining healthy hives year after year .. one must be treating for mites much much earlier in the Fall/Winter schedule to protect those winter bees brood from damage. Yes, that means the main treatment regimen must be done at late summer during the Fall brooding period, while the hive is raising those critically essential winter bees. Then followup with a mid-winter broodless treatment which is very effective as a `MOP-UP` of the remnant mites. The advice is do not hold off and depend on a broodless winter treatment. View the winter treatment as the `polishing` treatment, not the main treatment.  An effective winter polishing treatment usually means that no treatment is necessary in the Spring.  However come late summer, the treatment cycle is to be repeated.
In northern hemisphere ..
- If the late summer treatment is missed or skipped, the beehive is dead by Christmas.
- If the Fall treatment is missed or delayed hoping for broodless, the beehive is weak in January and dead by mid February.
- If late summer treatments are completed and mid winter broodless treatment done the beehive in March thru April is robust, strong, and overflowing with vitality.

Hope that helps!

(edit, to fix typos)