Mid-winter Oxalic Acid Treatment at the Branch Apiary

The  first meeting of 2013 was held at the university apiary on Saturday 5th January and was very well attended. The weather was dry but quite cold.


Julie gave a demonstration on how to administer oxalic acid (for varroa control) to your winter hives. A midwinter treatment of oxalic acid is usually used in conjunction with an autumn thymol treatment. Julie explained that it is best to apply oxalic acid when there is no brood in the box so that the mites will still be on the adult bees. Oxalic acid damages open brood but can’t kill mites in sealed cells. So the depth of winter (between Xmas and mid-January, say) is the best time to apply it when the bees are in a cluster and before the lengthening warmer days send signals to the queen to start laying.

In view of the cold weather it’s important to make this a quick visit so it’s a good idea to have everything ready, have had a practice with your chosen method and be able to limit yourself to 5mls per seam.   If you have only a few hives Thorne’s have produced a new contraption – a plastic bottle holding enough to treat two hives, with an ingenious easy fill compartment holding exactly 5mls for each seam. Treatment will be better received if the acid is at room temperature.


After you  remove the crown board the cluster should be clearly evident, and you can trickle your 5 mls along each seam and  close the hive up quickly

Care should be taken not to inhale the acid or get it anywhere near skin or eyes.