Oxalic Acid Treatment

Oxalic Acid Treatment


Oxalic Acid is labelled as a poison and may be fatal if swallowed.  It causes severe irritation to skin, eyes and the respiratory tract.


With the dangers in mind, I think its best to purchase a ready made solution of Oxalic Acid ready rather than mixing the Oxalic Acid crystals with sugar and water.  Also – when you buy ready made Oxalic Acid there is less risk of killing the bees due to too incorrect concentrations.

UK Supply: Most beekeeping suppliers sell Oxalic Acid.  It is also available online from Simon The Beekeeper.  You will also need a 50ml Syringe.


The literature says this treatment can remove 90% of varroa mites in a colony.  There will be a big mite fall on the first day and they will continue to fall for about two weeks after treatment.

When I applied Oxalic Acid in December 2013 I got a 40% reduction in Varroa (Post: Acid-Resistant Bugs).


The acid will kill varroa providing they are not in a capped cell.  When there is brood in the hive normally only about 15% of the mites are found on the bees.  The rest are in the brood. So treat when colony is broodless.  Another reason to ensure colony is broodless is that oxalic acid will kill open brood.

It is difficult to judge when the hive is broodless.  Most colonies stop raising brood when the temperature remains below 5C. After 3 weeks at temperatures below 5C the hive will be broodless.  Hence, the beekeeper has to judge when they believe the longest sub-5C spell has come to an end and then treat.

In the UK research has shown that between 10-25 December is the optimal time for applying Oxalic Acid with December 21/22 (Winter solstice) often often quoted as the best date. Typically, the Queen will start laying again in early January.

Oxalic acid can be used on both natural and artificial swarms during their broodless period.

Trickling Method

  1. Wear your bee suit, washing-up gloves and goggles.
  2. Trickle 5ml per seam of bees (a seam is the gap between 2 brood frames) using a syringe.
  3. Do it as quickly as possible and its probably best with a bee buddy.

Here I am applying Oxalic Acid:

Another good clip for the trickling method is from the Newton Abbott Beekeepers Association.  Please view below:

Evaporation Method

This method is less safe and more time consuming.  There is the risk of inhaling Oxalic Acid fumes.  I am not going to describe or recommend this technique.

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These how-to guides are provided for general interest and information only.  No liability is accepted for any injury or loss arising out of the contents of these pages.


Oxalic Acid Treatment — 3 Comments

  1. Hi Roger,
    It worried me that you still have your queen excluder on your double brood colony. If the cluster moves up into the upper brood box later in the winter they could leave the queen stranded in the lower box and DEAD. Remove the QX as quickly as possible; there is no problem if the queen starts the brood nest in the upper box in the spring….. just swap the boxes over. Hope you manage to keep them through the winter!

    • Thanks Mike and well spotted! I’ve done some googling and you are right I should remove the Queen Excluder. I’ll do it very soon (when this rain and wind stops).

      Also at present I have the crown board (with one hold open) between the two brood boxes. Would you put this crown board on top? Or add a second crown board to the top?

      • Hi Roger,
        From your oxalic acid video, it looks as though the colony is too small to occupy two brood boxes and you look to be treating 5 or 6 seams of bees in the lower box with nothing in the upper box.If it were me, although it is very late to do this now, I would wait for a quiet, mild day, check the store frames in the lower box, replace any empty frames with full frames from the top box. Shake any bees in the top box down into the lower one replace the crown board and place a slab of 50mm insulation above this and replace the roof(assuming you have an open mesh floor). If, however, you don’t have any full stores frames to stock the lower box you will have to resort to fondant (Ambrosia or similar) placed directly on the top of the frames. Use a shallow eke to give room for the thickness of the fondant and cover as above. The bees will be able to maintain the temperature more easily in one box as opposed to two. This will carry them through the winter without a problem; just check the fondant occasionally to see if they need more. We managed to bring 3 very light colonies through last winter like this. I hope this helps. I’m willing to answer any more questions (if I can!) you may have.
        Have a very happy Christmas an a bee problem free New Year.

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