Varroosis/Parasitic Mite Syndrome

Introduction

Introduction

I woke this morning to the sound of whooper swans flying south. A couple of weeks ago, about a hundred of them stopped overnight in a field beside a busy road so I only got a brief glimpse of the amazing sight as I drove past. A couple of years ago, I was able to visit a field where they spent a nearly a week resting. That was pretty spectacular. This lot were on their way south by the following morning. The morning is still and frosty and the sky suffused with pink and purple, and it will not get much above freezing today. Varroa mite drops are low single figures in all five colonies.
This week I discovered how to check the six-month BroodMinder statistics, thanks to Isobel. I see that all five colonies stopped thermoregulating their brood nests in September. The first to stop on 8^th was the native Amm colony, removed from church roof in April, followed by the rest on 14^th, 15^th, 22^nd, and 29^th.

Dubious Online Advice

Last week I wrote about my discovery that not every beekeeper has heard of tropilaelaps despite it being on the hit list here in the UK as a notifiable pest. Bartek Maleta in Poland reminds me that not everyone even understands the problems that Varroa destructor cause. It’s understandable that a beginner might not, but it’s a shame, and hard on the bees, that so many of them seek online advice where they are so often given inaccurate and uninformed information from self-appointed ‘experts’ who know even less than they think they do. Very often these ‘experts’ are inexperienced themselves but unaware of their limitations. See Kruger-Dunning effect https://www.beelistener.co.uk/beekeeping-education/why-we-need-beekeeping-education/

You will remember the recent launch of Bartek’s book Beekeeping in Harmony with Nature and review here https://www.beelistener.co.uk/book-review/beekeeping-in-harmony-with-nature-book-review/ . Well, Bartek has kindly offered to share some of his work with us this week, and he discusses parasitic mite syndrome and what to do about it. You can also follow the Facebook page, of the same name, where this piece first appeared. I have only lightly edited the original piece for this blog adaption. Thank you very much, Bartek, for sharing your experience and work with us.

Bartek’s Guest Post

It is so very strange for me that in our modern beekeeping times so many people still don’t understand how the Varroa destructor mite and varroosis/parasitic mite syndrome are linked, and how to identify the latter.  Since I started this profile, I’ve visited some of the online beekeeping groups to look at what people post there. It’s autumn, the season ends, and so there are many colonies collapsing just right now —unfortunately some of mine as well!
There are so many “newbies” that post pictures of what clearly is varroosis effect or varroosis + nosema effect. Those hives look more or less normal, however… empty of bees, or just with a handful of bees, with or without queen. And there are so many theories there! The most common are:
1) bees swarmed! —well, they did not swarm. That’s not how swarming works. Swarming is reproducing, it’s in peak season—and bees don’t leave the hive like that (especially leaving queen behind). Swarming happens when the colony is at its peak health and it’s thriving —they decide that some of the bees can leave and start a new colony. What is left behind is not an empty hive! What is left behind is a busy organism full of life, lots of queen cells (if seen early enough still unhatched), lots of brood and lots of bees buzzing with life! It’s not happening like that!
2) bees absconded from the hive. Apis mellifera bees (western honey bees) do not, or very, very rarely abscond the hive! Absconding means that all (or almost all) of workers (with the queen) leave the hive that is seen by bees as doomed. They “feel” that they cannot do anything more there to repair the damage (of any sort either in the roof of the hive with rain flooding on their “heads” or with disease or parasitic factor) and so to save the superorganism they would leave. That would be more consistent with what you can see in the empty hive than swarming, however as I’ve written Apis mellifera rarely or almost never do it. They just don’t have this evolutionary solution fixed in their genome. Apis cerana (eastern or Asian honey bee) however has this adaptation and they often abscond the hives if something happens or they are often disturbed (that is one of the reasons why it’s so difficult to keep them and select them for honey production).

3) bees vanished! disappeared! — No, bees do not “vanish” or “disappear” (and I know that people don’t mean magic disappearance here), there has to be a reason for that —and I know, you know it.

4) no queen / queen failure / bad mated queen or other queen issues—I’d say that this might happen, and maybe even in 1% or so of such cases this is the reason. In the long term this would lead to depopulation of the hive, too. But it does not look like that—it is a longer process, mostly with laying workers—and bees that are not raising brood are very long-lived, so they actually could even go into the winter and survive it. So, in 99% of such described cases your queens are perfectly alright —except that they do not carry enough varroosis tolerance (varroa resistance) in their genes to cope with the virus epidemics in the hive.

So, what happens there?

As I’ve written, there is a varroosis effect. Varroosis is the name of disease caused by the parasitic mite Varroa destructor with combination of the pathogens (mainly viruses) it transmits. When mite population grows it’s also the reason for virus infestation growing rapidly in the hives. The more mites there are, the more worker bees are weakened by varroa feeding on them (mostly in the larval or rather pupa stage of development) and more and more of them are infected with viruses. In most cases it goes together with the season ending. It happens like that because of two reasons
1) mite infestation grows constantly until there is brood in the hive—so at the end of the season it’s at its peak;
2) colony numbers naturally decrease in the second part of the summer and autumn.
So, when bee numbers drop, mite numbers (and viruses) grow. In some time (it really depends on many factors, so you cannot really tell when will it happen in specific colony, just that it mostly happens between late summer and winter) the mite and virus infestation exceeds the capacity of the colony to replace numbers with new workers and with coping of the immune system of the bees with that high virus infestation. Bees infected by viruses are short lived —one day they just fly off the hive to die somewhere and it happens by the hundreds, if not thousands, in such cases. Sometimes this effect is in conjunction with nosemosis disease. It is caused by another parasite (now reclassified as Vairimorpha spp but still referred to in many texts as Nosema spp) —a fungi that lives in the guts of the bees and causes malnutrition in workers —they just die off similarly as with the virus infestations.

Then the depopulation of the superorganism starts (dying off / collapse / dwindling —you can call it many names)—and that is exactly what you observe in your hives that I described. Bee numbers plummet even to a few workers, with or without the queen. This is varroosis. This happens in just a few weeks —so one time you inspect a great looking colony, but in 2-4 weeks it can be just a frame of bees or fewer.

Sometimes what happens here too is bees from other hives, or yellowjackets/wasps, are finishing off the dying colony. They rob, they take honey, they kill off the rest of weakening worker bees. It is also connected with transmitting the mites with viruses from the robbed to the robbing colony —which can cause similar collapse in them. As Prof. Thomas Seeley said, if I him remember correctly, “crime doesn’t pay”!

So, what can you do with that?
At this time and level of mite/virus infestation and depopulation of a superorganism… actually You can do just nothing. You can just watch a colony dying of varroosis. That’s how nature works.

If you see the first symptoms of depopulation (e.g. a quarter of the bee population “disappearing”) it is already 99% too late to save that specific colony. Even if it survives the winter —which is highly improbablethey will just by a handful of bees. By treating then, maybe you can prevent at least some of the exploding “mite bombs” going into other hives, but I would say that the worst and most harm (or large amount of it anyway) has already happened. Some, including Prof. Seeley, also suggest euthanizing the colony —for the same reason.

What to do?

What can you do for the future so it doesn’t happen in the upcoming years? You can do many things! Unfortunately, none of them guarantees 100% colony survival, but you can be a part of the solution to the varroa problem! There is a long answer to that, but this post is already long enough for most people to quit reading to that point… It’s a very complicated process —I invite those that are interested in details to get my book on the subject: Beekeeping in Harmony with Nature, the evolutionary solution to the varroa problem.
In short: be a part of a community that breeds for resistance and keep up the locally adapted stock which is by far better equipped to cope with the varroa mite, pathogens that it transmits, and other diseases. This is what you can do:

1) breed only from your local stock or the best, involve the local beekeeping community so your influence on local genetics and diversity of the bees is broader; breed from best surviving colonies (no matter if you are treating bees or not);

2) if you have possibilities, get some local resistant stock to start with. Note that it will not solve your problem at once, but you can save a few years of looking for bees that have genetic traits to slow varroa infestation growth in your bees.

NOTE:

Varroosis (meant as a disease) resistance/tolerance does not transmit easily (or not at all?) by genes/queens. So, getting “resistant stock” does not guarantee you have bees resistant to varroosis. It’s probably because mites are not killing factors, but the pathogens it transmits are. So, introducing foreign queens might not mean that they will cope with your local pathogenic flora or other local conditions which cause some genetic mechanisms to work in your specific condition. But by introducing local queens you can bring to your apiary bees with genes responsible for some traits that slow varroa reproduction. By breeding from such stock, you can increase the probability of finding your local resistant stock.

3) if You are treating —treat only those that need it—i.e. mite population grows rapidly, or you see many symptoms of some disease (e.g. “shotgun”/ “pepperpot” brood, bees with deformed wings etc. Do not treat bees just because it’s the end of season — for some colonies to survive they need treatment earlier, some do not need it at all, or at least at this time. Breed from those that don’t need it and keep the parasite population in low numbers (the dynamics of infestation is low).

There are very well-prepared instructions on the internet e.g. Erik Österlund’s page and blog www.elgon.es  or www.varroaresistant.uk

4) You can also instantaneously quit treating with chemicals and start using biotechnical methods. They are well described by Ralph Büchler and you can find his lectures on the National Honey Show YouTube channel here: https://www.youtube.com/watch?v=KwuR3uMkMF0 ).

There are also many instructions on how to keep bees and provide them with all the best chances to survive. If you want, you’ll find it because it’s just everywhere if only your wish is to reach for that knowledge —and this post has already grown much longer than I wanted it to be.