Varroa mites have been a big problem for honey bees in most of Europe and North America for thirty or more years. Many colony deaths stem from varroa and associated viruses, and many beekeepers probably don’t even know that mites were the culprit. After all, who does mite washes on all of their colonies? Answer: Randy Oliver & his sons.
I recently discovered that one of my hives, which seemed fine at the end of September, is now empty. No bees at all, alive or dead. How odd, thought I. Richard Noel told me that this happens when the mite load gets too high, which appears to be supported by this Rusty Burlew article. I had treated with Apivar on 08 September, which was late for me but I was waiting for them to cap the supers. Result: I got honey, but my bees died. I only checked a couple of frames but will do a full post mortem later.
Reports of mite resistance to amitraz are beginning to circulate, but I have no data on this. Sometimes people may get a defective batch (just guessing – no manufacturing process is error-free), or not follow the instructions correctly, so not all treatment failures are due to resistance. This research suggests that the next miticide off the conveyor belt may be fenazaquin. Autumn is a typical time for colonies to succumb, and once that happens bees from neighbouring hives will rob them and bring a load of mites back home. Even if you do everything right, your hives can pick up hundreds of mites after treatment has ended through robbing of collapsed colonies, and drifting of bees.
Some bees do better than others at dealing with varroa mites. Africanised honey bees, specific isolated populations of wild honey bees and the original host Apis cerana all have behaviours that enable them to survive. The truth is that the majority of honey bees kept by most beekeepers are going to die without some form of intervention. I have not seen this better described anywhere than by Dr David Evans, aka The Apiarist.
I see it as part of my responsibility to my bees, and surrounding beekeepers, to try to keep mite levels down. Sometimes I get it wrong, as described above, but hopefully, I’ll figure this beekeeping malarky out one day. Monitoring mites using alcohol wash is a pain in the backside to do, especially for all colonies, but it might be the way to go. Other than that, we are working blind. The so-called ‘mite bomb‘ colonies that Randy Oliver refers to can crop up randomly, and if we don’t know about them, they’ll spread their payload.
I know people will tell me that they don’t treat their bees, and everything is fine. I also know commercial beekeepers who sell nucs every year to people who don’t treat their bees! They didn’t die of anything related to varroa, you understand – oh no, it was something else. If there were prolific, gentle honey bees that produced a good honey crop, over-wintered well and coped perfectly with mites, surely we’d have heard about them? I wish it were true, and I wish that all of the hard-working queen breeders looking into this one day crack the problem. It has to be something that sticks, passing from one generation of bees to the next, for it to take hold.
How do they survive?
There seems to be a common theme with bees that survive varroa without treatment; they are relatively small colonies that swarm frequently. No use to beekeepers who want honey, but I don’t suppose the bees are too concerned about that. Swarming leads to a brood break; a period when there are no babies in the nest. Given that varroa mites reproduce in the brood, it makes sense that an absence of brood would set them back. Furthermore, once brood is absent, the mites are sitting ducks for an oxalic acid treatment, which is highly effective, organic, found in honey naturally and seemingly not too harsh on bees.
A lecture given by Ralph Büchler at the 2019 National Honey Show entitled ‘Sustainable Varroa Management Based on Biological and Technical Methods (Part 3 of 4)’ was a real eye-opener. He explained why brood breaks helped with varroa control and described a method used in Italy, involving caging the queen for 25 days. That looks very interesting. The idea is to have the brood break about two weeks before the main nectar flow, which is generally later than when the bees would naturally swarm. Swarming can seriously hurt the honey crop but managing a brood break at the right time can give it a boost.
Managed Brood Break
In my case, swarming is generally a May/June thing, and the main summer flow (blackberries, lime) is in July. If they do swarm in late May, then it hits the honey crop from the July flow. If I prevented swarming then trapped the queen in early July, I’d get a beneficial brood break without losing honey. Win, win!? I hope to try it out next season, with a control group being hives that get my usual treatment. It may well be possible to manage mite levels effectively using just ‘mechanical’ methods such as queen trapping, brood breaks, bait comb etc. I can’t see commercial beekeepers doing that given the extra work involved, but who knows? To me, any time when there is no brood means it’s time to get the sublimox out (or VarroMed) and zap the mites while they are out in the open.
All this talk of brood breaks got me to thinking about bees in winter. The way successful beekeepers take their colonies through winter varies considerably, as do the conditions and climate according to location. In some areas, with mild winters, the queen never really stops laying. I’m not sure that the timing of queen laying (or not) is entirely to do with temperature. I know a bee farmer who regularly finds little or no brood in his hives at the end of August when it’s still warm. Many years ago Mobus wrote about brood rearing in the winter; November was the time when, on average, brood was lowest, even though December and January were colder.
There is always much discussion about insulation and ventilation about now in the Northern Hemisphere. It can get quite heated! (see what I did there?). My experience of polystyrene hives is that bees do not cluster so tightly as bees in timber hives. I have no idea whether this is a good or a bad thing. My bees do well in both types, although the ‘solid floor plus poly hive’ combo results in a dirty wet floor.
For all I know, maybe the cooler timber hives and the resulting tighter bee clusters mean less winter brood and are possibly beneficial in an age of mites. Even if somebody figures it all out there’s unlikely to be a universally applicable answer; so much varies from area to area. Talking to experienced beekeepers to see what they do, especially if they are local, seems like a good plan…but, of course, they rarely agree on anything!