The following is a technique called split and treat, described by the German scientist and beekeeper Dr. Gerhard Liebig.
It is a good way to do summer varroa mite treatments after the honey has been harvested while making extra late splits. The drawback is that you will need a super of drawn comb, (ideally your harvested honey supers), and you need to be able to find the queen. Also, you need to do certain things at certain days.
It is also assumed that the beekeeper intending to use this technique has no signs of AFB in his apiaries.
Usually after the honey harvest beekeepers will be hard pressed to do a varroa mite treatment as quickly as possible because good practice forbids the use of miticides (especially synthetic ones) while honey supers are on the hive. Especially if your winter/spring treatment has not been overly efficient or mite drift has been a problem in your area.
The problem with treating against mites in (late) summer is that most of them will be sealed within the capped brood, and thus protected from most miticides. The only miticide that is capable of penetrating the caps of brood cells is formic acid by the way.
Most treatments compensate for this issue by doing a long-time treatment over the length of at least 1 brood cycle (21 days, 24 for drones). This means that during the duration of the treatment each mite that was protected inside the capped brood eventually had to come out (as the bee hatched from the infested cell), getting exposed to the treatment and dying.
As more and more beekeepers would like to use organic miticides instead of synthetic strips they only have 2 options basically: formic acid and oxalic acid.
Formic acid is perfectly suitable for late summer treatment (as it can reach the mites inside the capped brood), but it is highly dependent on the weather. Too hot and the treatment will be harsh on the bees, potentially even leading to queen loss. Too cold and the treatment will not be potent enough.
Oxalic only kills the mites outside the capped brood (“phoretic” mites), thus normally requiring a long-time treatment (at least 21 days as explained above), which can become quite tedious if OA spraying or vaporization are used. A common technique in this case is do a treatment every 3rd day for 4 weeks. While this is a lot of work, I have to stress out that I have tried this approach myself successfully and found it a very good way of knocking down your mite levels to essentially zero. OA-glycerine strips are another very good way of achieving a timed release of oxalic, and we will discuss them in a future article. Their drawback is that they work very slowly.
In a situation where mite levels are already very severe, and you see many signs of parasitic mite syndrome you will want to reduce the mite number fast. At the same time it is safe to assume that a lot of the bees inside the capped brood will be damaged by the mites and the viruses that they help spreading.
This brings us to the core of this mite control technique. The removal of all capped brood. By doing so you have suddenly removed 90+ % of all mites in the hive, practically all viruses and all the damaged pupae. At the same time all mites that are left in the hive are phoretic, meaning they are sitting on adult bees and not hiding in capped brood (since you removed all). Any varroa treatment will be quick and efficient at eliminating those.
Simply shake the bees (and the queen of course!) off all the frames that contain capped brood and put them into a separate box.
Depending on the original infestation level the removed capped brood can be used to make splits or culled via wax melter (killing all viruses, mites and damaged bees).
If the capped frames are to be used to make splits only shake off the bees of half of the capped frames and make sure you shook off the queen. The splits will raise their own emergency queens, do not insert a caged queen! As it takes around 4 weeks for a new queen to start laying it is ensured that all capped brood will be hatched by that time, thus giving you a good window to treat against mites.
Those splits will be heavily laden with mites and require effective treatment, but if the initial infestation was not too severe will give very strong hives.
Needless to say, that all frames that have been removed need to be replaced with drawn comb, to enable the queen to start laying immediately. Some frames with just foundation can be used if there still is a flow going on. Make sure that the hive is left with at least 2 frames of honey/feed as feeding sugar water is not advised at this stage for the risk of robbing. Somehow the absence of capped brood will make the remaining bees less “enthusiastic” about defending their hive against robbers. Once a new brood nest has been established (2-4 weeks) everything goes back to normal. I also would advise to reduce the with of the entrance, especially if the honeyflow is over.
The fear of weakening the hive treated this way is unfounded due to 2 mechanisms: The aging of adult honeybees has been linked to the juvenile hormone of hatching bees. Essentially: if no young bees are hatching adult bees can get older. This is the reason swarms with virgin queens do not die off and beehives can survive brood breaks over the winter. Secondly the queen will start laying much more strongly to make up for the loss of brood. All this new brood will be healthy as the mite infestation has been taken care off.
This technique in itself by the way is used successfully by many commercial beekeepers and hobbyists in Germany.
But what if I told you there is even an easier variant, where the bees will do most of the splitting?
Enter “Split and Treat”
This ideally is done right around the time when the honey flow ends and there still are a lot of forager bees in the hives. The weather still needs to be good for this technique to work.
You need (at least) 1 super with drawn comb and some honey in it, 1 spare bottom board and 1 lid (inner and outer). The super can also be a half filled honey super of the hive you want to treat.
You start with moving your original hive a few meters, but within the same apiary (meaning you only move it a few meters to a new spot).
On the original spot you put up the new bottom board and super with drawn comb plus the lids, this will be the new hive.
Now for the only tricky part, you need to find the queen in the old brood chamber and put her into the “new” box. Simply find the frame she sits on and shake the whole frame into the new box, no need to catch her or cage her or anything.
Any forager bees will now return to the old spot where the hive used to be. What they find is a hive with a queen but no brood. The queen will immediately start laying but there will not be any capped brood inside there for 8 days, meaning you now have a window to treat this hive with a fast-acting miticide like oxalic acid (spray or vape). I prefer to do 2 vaporizations, 3 and 7 days after the splitting.
The old brood chamber(s) have all the capped brood, plus open brood and eggs, they have no queen but all the means to create one. It is important that you do not try to requeen this part with a caged queen! They must raise their own one as this takes around 4 weeks till the queen is laying, during that time (after 21/24 days) all capped brood will have hatched, giving you a nice window where this hive will not have any capped brood. Treat it the same way you treated the original hive with oxalic spray or vape.
Assuming that the honeyflow has stopped by this time in your area it is important that you start feeding both hives if they do not have enough stores. Only feed hives that have a laying queen and capped brood (meaning they are established and will defend their stores) and keep entrances reduced.
In the end if everything works out perfectly you end up with 2 healthy hives with laying queens.
It is now up to the circumstances and you what to do with them.
If you started the whole process sufficiently early, both hives will grow strong enough to overwinter on their own (but will likely require feeding of sugar syrup).
If you were too late or the mite infestation already was too high one of the two might be too weak for you to consider overwintering it on its own. In this case you can simply recombine both hives by putting one hive box on top of the other. Many beekeepers advise putting a sheet of newspaper in between the two boxes. The bees will slowly chew through the paper which allows some time till the bees are used to each other. I honestly never bothered and it worked just as fine.
If you combine both hives the bees will sort out themselves which queen they want to keep. If you want to make sure that one of the queens survives you have to find the other and remove it. You could use this one to requeen another hive for example.
This technique can also work to deal with a hive that wants to swarm by the way, as hives that lose all their forager bees tend to lose their desire to swarm.