Sunday, 9 February 2014

Oxalic Acid Varroa Treatment.

Got a little bit of an update from Stewart Maher on 18/01/14....He said....

'Carried out my first ever Oxalic Acid Varroa treatment today. I wasn't sure whether to bother or not as I haven't seen any Varroa in three weeks of monitoring but decided to give it a go anyway. Armed with my pre mixed bottles courtesy of Thornes I opened them up today. All 3 colonies seem to be doing well even our small Nuc that we rescued from the Gamekeepers feeder in August. I was particularly taken back by the sheer strength in numbers of one colony in particular which seemed huge for the time of year and had to drip the mix on 8 frames !'

oxalic acid treatment for varroa
Stewart giving his oxalic acid treatment.

On 19/01/14 Stewart checked his hive again....

Post treatment note

Mire drop 24 hrs after treatment (numbers of dead varroa counted )
 1 hive x 16
1 hive x 4
1 hive x nil (very healthy nuc)


(Not being familiar with oxalic acid myself I did a little research and found this article to share with anyone who was/is as clueless as me!!)


Oxalic acid is a treatment that only kills mites that are living on the bees (those in the phoretic stage). It does not kill mites in the brood. When there is brood in the hive normally only about 15% of the mites are found on the bees (the rest, 85% are in the brood). It follows that oxalic acid works best on colonies that are broodless at the time of treatment. In addition oxalic acid will kill open brood. Oxalic acid can be used on both natural and artificial swarms that offer a broodless period.
Treatment should be delayed until colonies are in a broodless state; most likely this is found late December to early January. Removing the catch tray to ensure good ventilation will encourage the bees to have a broodless period.

The treatment material is 3.2% Oxalic acid in 1:1 sugar solution. The recipe for making this is:
1. Make a sugar syrup consisting of 1Kg sugar in 1 litre of water.
2. Add 75grams of Oxalic acid dihydrate and mix well.

This will make 1.76 litres of oxalic acid solution. Accurate weighing of the oxalic acid is essential as under strength will give a poor mite kill and over strength will kill the bees.

This solution is poisonous and should be stored safely.
Oxalic acid crystals are deadly poisonous and every care must be taken when handling including use of a protective mask, eye protection and gloves.


Treating with oxalic acid

Fill the 50ml syringe with oxalic acid solution.
Open the hive to expose the clustered bees.
Trickle 5ml of solution along each seam of bees.
Close Hive.
This procedure is best carried out when the weather is cold and dry and the bees will be well clustered.
The efficacy of oxalic acid is about 90% and will mop up mites that escaped the Apiguard treatment and will also kill mites that have been bred since that time and those that have come into the hive from external sources.
After the oxalic acid treatment has been completed any top ventilation should be closed and the catch tray repositioned. Mites will continue to fall for about 2 weeks after which the catch tray can be removed.

(this article from Gwent Beekeepers Association)

Thanks for sharing your experience Stewart.


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keep it clean...keep it relevant...I look forward to reading your comments!!