Topical Tips – “Many of us are going to have a varroa problem this year” – by Malcolm Wilkie

I treated all my colonies in August. Most colonies were treated with Apiguard (2 trays of thymol in each colony over a period of a month. A further note of warning to everyone – if you use a product you must follow the instructions carefully as if a full treatment is not done you will not kill the number of mites needed and numbers will just build up again). My nucs and one colony were treated with varroa med. So of course I was feeling virtuous. A case of hubris, I am afraid. I have just checked three of my colonies. The one treated with varroa med had a natural mite drop of over 154.

 (Beginners sometimes become confused and assume that this is the number of mites in the colony itself. This, of course, is not the case. An open mesh floor enables you to calculate the natural mite drop. That is to say the number of dead mites that  have come to the end of their lives and are falling off the bees onto your inspection board).

 That means the colony contains over 1500 mites and is in imminent danger of collapse. The other two colonies in the same apiary both had drops of 54 and 45.  So according to the varroa calculator on Beebase they contain 540 and 450 mites each. And that is not good either! So that is why I am concerned with the weather. A cold snap is beginning and that will encourage the bees to cluster and the Queen to stop laying. A brood cycle lasts three weeks. Today is November 30th so I am going to apply an Oxalic acid treatment on December 21st or 22nd, thereby hoping to treat my colonies during a broodless period. Why do I do this? It is because when a colony is broodless all varroa mites will be phoretic and if I can treat when this is the case I will kill the maximum number of mites.

 For a beginner it is probably best to apply oxalic acid mixed into sugar syrup. A syringe and gloves need to be used. You take the roof off the hive, remove the crown board and trickle your warm syrup mixed with the correct dose of OA onto each seam of bees. The acid damages the mouthparts of the varroa . Some bees are damaged but it will be for the greater good of the colony in the long run.

For those who are more proficient bees can be sublimated with oxalic acid but one needs to wear a mask as the fumes can damage your lungs if inhaled. I refer you to my past article about sublimation.

Be warned if you do trickle acid onto your bees, keep a record as a queen should never receive a second dose in a subsequent year. In fact legally any medication that is used needs to be recorded and the document kept (Look on our website for a copy of that document). However for some reason colonies and queens can be sublimated several times without any harm being done. Gasing the bees with OA seems less damaging than tricking OA onto the bees. I do both.

 In conclusion, put your inspection boards in again and ascertain how many mites you have in each colony. The window for treatment is about to open but it won’t last long! If you need to treat, order Apibioxal now so the treatment can be done just before Christmas. Order a syringe and gloves if you are using the trickle method.

 Finally the weather has turned cold. I am relieved for my bees as it is high time that they started to cluster and stop munching! In my last missive I told you I was worried about stores and whether the bees would have enough to get through the winter. It seems the National  Bee Unit agrees with me! Those of you who are signed up to Beebase will have got an email alerting them to a risk of starvation.

 The other reason I am looking at the weather is I am trying to calculate when would be the best time to put a varroa treatment on any colonies that need it. My prediction is that this year you are all going to have a major problem with varroa. Why is this? It is because the bees have continued to raise brood well beyond the time I would expect them to do so in a normal November. A warm November means more brood cycles and more brood cycles mean more varroa mites.

These photos were taken last week. I found these bees just chucked out of the hives so I just knew I had a problem.

Refer to my previous tip about sublimating the bees with oxalic acid.

 Malcolm Wilkie – 30th November 2020

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