This is a follow up post to this one on the Bee Health Day I went to held at Roots & Shoots (a wildlife garden and base for the London Beekeepers’ Association), which is an annual event run by our government bee inspectors. Below are my notes from the Varroa control workshop given by Caroline Washington later in the afternoon.
It’s well known that varroa mites prefer to breed in drone brood. Drones take 24 days to develop whereas workers take 21, so drones give the mites time to fit in more breeding cycles. The mites identify the drone brood by its different smell, which is a result of the more protein rich diet fed to drones.
In South East England drone trapping can be used as a method of varroa control during April, May and possibly June. To do this put a drawn super frame into the brood box, to encourage them to build drone comb in the gap underneath. Put the super frame at the side of the brood nest, not the middle.
Once the drone comb is sealed, cut it off the super frame and feed to your chickens or burn it. You can do this 2-3 times during the summer. Do not leave the drones to hatch out! Before you destroy the drone brood you can uncap some to see how many mites are inside. Put your uncapping fork in deep, right into the neck of the drones. Fork out a hundred drones and count how many larvae have mites to get an idea of mite numbers in the hive.
By July the bees will not be producing drones anymore but your supers will still be on, so it’s too early for Apiguard treatment. What you can do instead is an icing sugar shake.
Icing sugar treatment is easiest done in pairs. Get someone to hold each frame out horizontally for you and then sprinkle over icing sugar using a shaker. This encourages the workers to groom each other, removing mites in the process. Check your varroa monitoring board afterwards to see how many have fallen down. Just sprinkling over the tops of frames without pulling each one out is not effective enough, that way the sugar just falls down the gaps between the frames.
Apiguard is a natural thymol based treatment done in August once your supers have been removed (otherwise your honey will stink of thyme). Starting in August allows the hive to produce several generations of healthy bees before going into the winter.
Tape up your varroa monitoring board whilst treating so the fumes stay in the hive. Do not be tempted to treat using your own home made thyme concoctions. These do not regulate the release of thymol in the way Apiguard gel does, and Caroline has known bees to abscond as a result of home made treatments being too overpowering.
You only need half a dose of Apiguard for a smaller colony, or a quarter for a nucleus. If you give too big a dose the bees will be hanging outside the hive.
This can be done during winter whilst you have no brood – around Christmas/early January in SE England. You need the bees to be in a cluster. You literally whip the hive lid off, trickle the acid over the top of the cluster and put the lid right back on before they get too cold. I have a post on our 2011 acid trickling here: https://adventuresinbeeland.wordpress.com/2012/01/01/drizzling-oxalic-acid-on-bees.
Why varroa is such a problem
Historically bees have always had viruses. But in the past they were not such a problem. However, certain conditions can trigger viruses to become a problem. Viruses are now getting into bee larvae via varroa. If you have nosema in your colony, viruses are transmitted by nosema too.
The deformed wing virus associated with varroa mites causes bees’ wings and bodies to become deformed and stunted. Affected bees are often unable to fly and have a severely reduced life span. The virus can affect queens too. Drones have not been as good as they were for some time.
Caroline advised us not to keep weak colonies out of sentimentality but to bump them off, because weak colonies are more likely to be carrying viruses. You can destroy a small number of bees by having a big bowl of hot water with washing up liquid in and shaking the bees into it. The washing up liquid gets through the bees’ waxy exoskeleton.
On the saucer are bees Caroline found suffering from deformed wing virus earlier in the day.
For in-depth, official advice on varroa see the National Bee Unit Beebase website: https://secure.fera.defra.gov.uk/beebase. This has a detailed 35 page pdf leaflet called ‘Managing Varroa’ available to download from https://secure.fera.defra.gov.uk/beebase/index.cfm?pageid=93, which the bee inspectors recommend all UK beekeepers read.