Keeping track of the infestation level

In the search for breeders for this season I tested a number of hives for the infestation level of Varroa mites in the beginning of May. Those choosen had not been treated for mites either not at all last season, or very little with thymol in the spring last year after showing an odd wingless bee. This was before the time of the Beeshaker with me. Better hade been to use the Beeshaker before using thymol to really know the infestation level.

I used the Beeshaker (more info about it and how to use it: There were colonies with 0 mites from somewhat more than 300 bees. The best of those I use as breeders this year.

I also gave a number of colonies a thin tray with a coarse mesh that bees couldn’t pass hrough. High enough from the bottom of the tray so the bees couldn’t clean the tray. It covered almost the entire bottom. The purpose was to collect natural downfall of mites over a period of time.

I send some queens abroad and the Board of agriculture wants to be sure I have no tropilaelaps mites and no small hive beetles. (Both of those two pests have not been found in Sweden, tropilaelaps not even in Europe, the small hive beetle only in Italy.) Three weeks before the veterinary and the bee inspector came to visit for checking my bees I inserted these thin trays. Of course the inspector and vet also checked for American foul brood.

Varroagaller Varroa trays for checking natural downfall of mites. The one to the left without mesh cover.

Two of those hives I had checked with the Beeshaker got a tray. Three weeks later one of them had 7 mites on the tray. The other had 8. The bee shaker had given 1 mite each for these two hives.

1 mite per 300 bees is 0.3% infestation level on the bees (not counting the mites in the brood, those are usually at least the double amount).

Let’s say I missed 2-3 mites of the natural downfall. That would then be 10 mites in let’s say 20 days for easy math. That gives 0.5 mite per day. It’s been said that natural downfall per day during the brood season multiplied by 120 gives about the total number of mites in the colony. That would make 60 mites in total in those two colonies. The number of bees in those colonies were more than 30,000 each. But let’s say it was 30,000. If we divide 60 by 30,000 we get an infestation level of 0.2%. This level is though including the mites that had been in the brood during these 20 days, so the figure is not directly comparable with the 0.3% to confirm that the two methods give about the same result. The estimation of multiplying with 120 and other uncertainties makes comparison and/or the methods not exact anyway.

Does this comparison give an indication that these methods are good enough for checking the varroa infestation? Both methods have been used by others to decide when to treat or as a selection help for varroa resistance.

When the infestation level is so low as given above, it’s not possible to check the VSH trait either, as you will find too few pupae with mites. You can ask yourself if it’s at all necessary to test for mites anymore. I agree. But all my hives are not as good as these and reinfestation occurs. So I think I have to keep track in some way. Not in first place I think to find the best ones, but to find the ones with most varroa so I can protect the others from reinfestation.

The perfect resistant colony is of course such a one that is not very much affected by reinfestation, not letting in bees with mites on them for example. I will test colonies in August as well and I will check the hard boards in front of the hives for crippled wing bees or grey young bees crawling around as indications for viruses following to high varroa infestation.

A passionate treatment free beekeeper 

Cory Stevens lives in southeast Missouri. There are some hives of hobbyists some miles from him. A larger beekeeper is 7-8 miles from him, but he uses Cory Stevens’ queen cells.

Cory family The whole Stevens family works together

Started with resistance traits

Cory Stevens ceased treatments for Varroa mites in most of his then 20 colonies 8 years ago.  6 years ago the number had grown to around 45 colonies. Then a few got some formic acid. Then no more treatment. When he stopped treating he had acquired queens of different origins with resistance traits, VSH from Tom Glenn and Pol line Hygienic Italians crossed with local ferals.

Cory Hive&comb Healthy colonies are the base for a thriving bee operation.

Low winter losses initially

Initially he had very low annual losses. He has brought in new stock every year besides breeding from his best lines. This hasn’t been good for the development of his stock so he has stopped that and will focus on selecting from his own best colonies. He will evaluate the need for bringing in new stock again later.

Cory odlingslist He will now focus on breeding from his own selected lines.


Increased winterlosses

Winter losses has always been lower than average nation wide. But the last years it has reached 30%.The winter of 2014-15 he lost 60% of 95 wintered. 45 of those (47%) were too small 5-frame nucs. The winter was severe and all of those nucs died. He says it was his fault, not the bees’. The winter losses 2015-16 will be much lower, it looks like cose to 20 %.

Initially some viruses

In the beginning when he saw more than a few bees with crippled wings (DWV) and K-wings (KWV) two different viruses, followers of Varroa and Tracheal mites respectively, he requeened those hives. Today he never sees any crippled wings. A few K-wings can be seen.

Removal of infested drone brood developed

Initially he didn’t see removal of varroa infested drone brood by the bees, only Varroa infested worker brood (in which the mites have offspring – VSH). But after breeding from the best survivors without any treatment he has seen this trait developing. He thinks that’s good as Varroa prefer drone brood and should continue doing it leaving as much worker brood as possible alone.

Cory drönarpuppor He has developed his stock to remove Varroa infested drone brood. It has simply turned up when breeding from the best survivors.

Some characteristics

He doesn’t use small cell combs, but standard rite cell foundation. He does use screened bottom board on several hives, but he doesn’t think they contribute that very much to Varroa control.

Planned focus

This season he will check natural downfall to look for the percentage of mutilated mites. He will also be utilizing liquid nitrogen to test for hygienic behavior for breeding candidates. Some of his virgins will be inseminated with semen from ankle biters (mite ankels) from Purdue University to test if this will contribute to his stock. He will also put out more swarm traps to hopefully catch feral swarms.

The goal

Cory wintered 120 colonies last autumn. The goal now is adding 25-30 per year until he reaches 5-600. Then he will “retire”.

The bee shaker and varroa resistance

Skak botten 2lc One mite from 300 bees.

I understand that sometimes it’s a good idea to get an idea of the infestation level of varroa mites in bee colonies. You can take samples from a couple of colonies in an apiary to get an idea when to treat. But my first concern is breeding varroa resistant bees.

I have never monitored the varroa infestation level in my colonies. I haven’t had time and I haven’t found any reason for it because I thought I had found a good compromise – treating with Thymol when I saw wingless bees on the hardboard in front of the hive entrance, checking every 10 days or so.


Good results up till now

I give a colony one or two pieces of dish wash cloth containing 5 grams of Thymol each when I see wingless bees crawling on the hard board in front of the hive. But this means I don’t treat every colony at the same time (hopefully some not at all in a season). This results in some colonies with higher mite loads not showing wingless bees yet. So these colony (-ies) will through reinvasion increase mite levels again quite quickly in those colonies recently treated.

But this way I’ve been able to develop more and more resistant bees and still produce a good crop. There have been a number of bees not producing any honey. Winter losses have been reduced from 30 % to 10-15 % (except the first year with varroa trouble when I lost 50 %).

The bees have been better chasing mites and remove infested brood. I’ve got good reports from for example Poland and Germany of low populations of varroa in colonies headed by Elgon queens, compared to other bees. And the VSH trait is becoming better and better. Daughters of my colony with the highest VSH % (80) gave colonies that in Poland dropped 2-5 mites after effective treatment while other colonies dropped more than 1000.


Thymol is useful but hinders total adaptation

I now have been aware that by having this regime I have a constant quite high varroa population in the apiaries as a whole, and thus probably a climbing virus pressure. In a way this is good as selection is done also on virus resistance.

How do I know that? Now when I’ve used the bee shaker somewhat this year I’ve seen that colonies may show wingless bees (DWV-virus) at low mite infestation. Such low infestation you didn’t expect them to do so, sometimes even as low as 2 % infestation (a daughter from a colony with high VSH trait [80%]! This experience and others similar, raise the question if very high VSH comes with higher susceptibility to viruses.). Wingless bees at 2 % infestation is totally different from a report I’ve got from a test further down in Europe. (There they normally treat effectively every year.) In that test where they didn’t treat at all, my bees didn’t show any wingless bees at 35% infestation while other bees had a lot.


How to explain the high infestation level in the test

Now I have to try to explain why my good bees could arrive at 35 % mite infestation. This is interesting and brings up another topic as well. The importance of memories of the worker bees (their knowledge how to chase mites), not only their genetics (and epigenetic history). My queens in this test down in Europe were introduced to bees that had not been selected the same way as mine, and those bees had been treated effectively every year. The bees could probably not chase mites as well as mine.

But of course the genetics from my queens would more and more influence the workers to build up a better behavior when it comes to chasing mites. When the bees have arrived at a good mite chasing mood they learn new bees born in the colony what they have achieved, more than what just come directly with the genetics. In Norway with Terje Reinertsen and Hans-Otto Johnsen experiences are achieved pointing strongly to this.

In an apiary where many colonies are non-resistant as in this European test, you get a mixture of all bees in the apiary through drifting and robbing. This is taking place more and more when the mite populations in the colonies rise. As it did in this test as the colonies were not treated at all.

In a situation when colonies are receiving a lot of mites from neighboring colonies, even the very best kind of mite chasing behavior is maybe not enough to keep mite levels low.

In the test apiary previous to this test, effective treating every year had kept the mite and virus levels low, so the mite population could grow much in the test without showing wingless bees – like in the beginning when the mite first arrives to an area. Then the virus levels are usually very low and there could be 10 000 mites and more in a colony without any signs of viruses (documented case in Sweden in 1987 when the mites were first detected on the island Gotland in the Baltic).

The bees in this test were on 5.5 mm cell size, while my bees are kept on 4.9 mm.


Also Thymol hinders total adaptation

I have talked to some beekeepers whose bees are totally treatment free since many years (Hans-Otto Johnsen in Norway, Richard Reid in Virginia and Myron Kropf in Arkansas). Their bees have now small populations of mites and are showing no wingless bees.

I have come to realize that also Thymol is a chemical that hinders the bees to fully adapt to handling the mites successfully on their own. It is in first place the epigenetic adaptation I have come to think of that is disturbed when alien chemicals (like miticides of all kinds) are present. Epigenetic changes take place when a chemical change occur due to environmental changes, like for example the presence of the mite. (But it should be said also that if you use Thymol regularly spring and late summer in a system not selecting better bees like I do, winter losses can be kept low. I know because beekeeper friends do like this.) Also Thymol like other miticides is lowering the immune system of the bees.

How do I then integrate these insights to go further in becoming totally treatment free?


A new strategy to try

I’m planning a new strategy, at least to start with in one quite isolated apiary. I have to stop using Thymol. First though I think I have to knock down the mites effectively to reduce the virus level. And then get a better control of the number of mites and take action without any chemicals if varroa populations are rising too much in colonies.


The role of the bee shaker

Here the bee shaker will play a role. And I have looked more into how Randy Oliver uses it. It’s much easier to shake a frame of bees into a bowl or pan and then with a measuring cup scope somewhat more than a deciliter (3.5 oz) of bees and pour them into one half of the bee shaker, half filled with alcohol (for example methylated spirit or rubbing[isopropyl] alcohol). Then screw it together and shake for a minute before reading the result. Compared to holding the bee shaker close to a frame side with bees and pour bees into it moving it slowly upwards, the alternative of Randy Oliver is quicker (at least for me). The next step is to test the VSH trait in the best colonies.

Skak yngelrum Start checking from one side in the uppermost box with brood. The queen hopefully will run to the brood if she is outside the brood area (probably not). The comb closest to brood you check so the queen is not there. 

Skak deciliter Shake the bees into a pan or bowl. Scope up somewhat more than a deciliter of bees (3.5 oz)

Skakburk sprit Pour the bees into one of the halfs of the bee shaker, which is half filled with alcohol. Screw the other half tight on top. Shake it for a minute.

Skak botten1lc Turn the shaker upside down and continue shaking until all the alcohol has poured down. Lift it up against the sky and count the mites. This colony had 14 mites on 300 mites and it got two pieces with 5 gram Thymol each. It showed no wingless bees.

What I hated to do

So what I’ve done so far is something I hated to do. In one quite isolated apiary I used an effective chemical miticide (only this time I promised myself) in August 2015. I wanted to use something else than Thymol to give the bees a break from that chemical. And I wanted to knock down the mite population effectively to lower the virus pressure in the apiary. I collected the knocked down mites. (In the rest of the apiaries I plan at the moment to continue as before.) The colonies that had needed most Thymol earlier in the season had the highest downfall of mites. They got probably continuously reinfested from other colonies that happened to not show wingless bees while they anyway had quite high mite loads. The defense system of these quickly reinfested colonies was probably lowered by Thymol, which made this relatively quick reinfestation possible.

One colony that hadn’t needed any Thymol at all (and very little the year before) and still had given me 80 kg (175 lb) of honey with 20 kg (45 lb) left for winter dropped less than 200 mites. And this happened in this very bad season of 2015. This colony is of course a breeder for the coming season.


The new strategy

Next year I will in this new strategy apiary make splits from the best colonies and place them in the same apiary (or if the number is enough there, place in other apiaries). In the least good colonies in this apiary (those with highest infestation level) I will kill the queen and give them a ripe queen cell bred from a good colony in this apiary. I check the number of varroa (infestation level) with the bee shaker twice a season in all colonies in this apiary. Each time it will take about 5 minutes per colony. And I look for eventual wingless bees on the hard board in front of the entrances. Before the number of mites rise too high (whatever that is), or when I see wingless bees, I plan to remove all capped brood (worker and drone brood) once or twice with a week in between. I haven’t decided what to do with those brood frames yet. Any suggestion?



Changing plans

I make notes. I’m sure you do to. How much is a good question. I made more notes as a beginner and quite some years after that. When I got well above hundred hives I began to question each kind of note and how much I could benefit from it. I wanted to save time, if I found it possible to skip doing some kind of notes.

For each year I use a fork binder. First I have a graph paper. On a horizontal line high up all the apiaries are numbered. On a vertical line to the left I make a note of the date, then an X for the apiary I have gone through that day. That’s the most important note, to be sure I don’t forget any apiary and to make sure it doesn’t take too long between my visits.

Fork Binder A spread in my fork binder.

I have made a map in the computer in the Excel application showing each apiary. On the spread is the map to the left. On the opposite side a blank graph paper for making notes. In the very early season (still winter/spring) I make note of the colony strength, how many “comb gaps” the bees occupy. Then of the progress of the colony (putting on boxes). At the end of the season, very late autumn/winter, again how many comb gaps the bees occupy.

I only make a thorough check of a colony if it doesn’t develop as expected. I check for eventual disease, if it has brood (thus a laying queen), and eventual other things to observe. I make notes only of things that depart from the average or the normal. No notes for a colony indicates an average or a normally functioning colony. Also notes are made concerning hot temper, no brood, wingless bees. I make notes of how much thymol in grams a colony get and what date, estimated amount of honey taken in kilograms (it doesn’t matter if I do a wrong estimation with 10-20%, the estimation is for comparison between the colonies).

When the season is over I compile the notes and do stats. Then I make a first probable selection concerning next year’s breeders and which queens I will shift next year. The final selections are made during May and June the coming season. Here the notes are invaluable as I tend to forget some colonies that I discover again when I’ve done the stats.

Before May comes there’s often a hard winter ahead, and a tough spring. And the spring this year was really tough, which changed the preliminary plans a lot. But the winter had been mild.

The spring was very rainy and very chilly. May was the coldest since 1962 in Sweden. The bees had small opportunities to get enough of fresh pollen for their usually quick buildup. And proteins they need desperately for everything for their rapidly expanding colony to function properly.

My bees have a higher varroa pressure than most others maybe, to let the least good colonies reveal themselves. Due to the season the immune system (rather defense system as their defense against diseases are different compared to mammals) among other things didn’t work fully due to lack of proteins. Viruses showed up even if the varroa population wasn’t big.

Maybe I should have stayed cool and not used varroa treatment, I don’t know. Varroa treatment affect the bees negatively as well, but of course not as much as mites. When should I stop treating altogether? And how should I do it? Just stop at any moment or do it in a certain way? I don’t know.

I have used more thymol this season than last. The colonies with high VSH value (VSH 80% the best one, included) and their daughters, most of them, showed wingless bees and many dwindled. I was surprised and disappointed. How was this possible? Can high VSH-value mean less good other traits than VSH? Sometimes such phenomena can appear with strong selection for strengthening a trait, as such selection often is made with the help of inbreeding.

Anyway, when I should decide which queens to breed from I went through the notes and found some interesting colonies I hadn’t payed enough attention to. Those colonies hadn’t needed any treatment for two years. So I made a VSH test. The S241 colony had three mites of 103 pupae checked. Two of the mites had no offspring. The third had one white daughter mite and no male. The H101 had one mite of 110 pupae checked, with no offspring. The neighbor colonies of these two colonies had wingless bees and many were dwindling. Of course I bred from these two good colonies.

Quite soon afterwards the H101 showed a wingless bee. I had split that colony and put the big split with the queen in the same apiary as the “mother” colony. The split with the queen lost most of its field bees that way. Was that a cause?

The S241-split was moved to the home apiary and kept its field bees. The split grew fine and is now a big colony. All the daughters are doing fine and building fine colonies. Both S241 and H101 are colonies that have shifted their queens themselves, whatever impact that may have.

To sum it up. I had to change my breeding plans quite a bit for this year, after this unusually cold and rainy spring. But I think it’s important to make good notes and from them plan for next season. Then when next season comes you know what to change and how.

The VSH 80%-colony was a disappointment and I don’t understand that, yet. There are though a couple of daughters from it that are very interesting. Those havn’t needed any treatment and didn’t show any wingless bees. One has shifted it’s queen. The second are showing a lot of bald brood and spotty brood (cleaned out brood with mites?). The queen is laying well. It seems it’s fighting reinvasion of mites and doing it well. So good that the colony hasn’t grown and hasn’t given any honey.

Bald brood One of the daughter colonies to the VSH 80-colony is fighting hard against the mites and havn’t shown any wingless bees, not yet anyway. Maybe a breeder next year.

This season is a disaster. The month of July has been the rainiest I have experienced ever. The honey crop is in average maybe 5-10 kg per hive (including winter losses and failing colonies) to compare with 25-35 kg for several years. And many colonies may need a good sugar feed to survive the coming winter.

But, the season isn’t completely over yet…



Checking list for a VSH test

I have done some VSH-tests by now and maybe my experiences can inspire some of you. I have made a checklist that maybe can be of some help.

VSH-test avstånd

What I use

I use a reading lens with a ringlamp with about 2.5 times magnification. I also use a couple of reading glasses with the same magnification to get about 6 times. But you can try what combination works the best for you.

Place the comb under the reading glass about 10-20 cm (4-8”) from it. You work out the best distance, also where to place your eyes above it.

As you drag out the pupae you may have to move the comb somewhat for best sight into the cells. Also you can tilt the comb back and forth a little for the same reason.

Use a pair of tweezers of your like. I use one with a slanted tip. You get a grip on the pupa a little better, but on the other hand it can be easier to torn it into pieces.


Three piles of pupae

  1. Pupae without mites go to one pile. It will be the biggest. When you have 10 in it you push it up a bit and away somewhat. I do the same with the next 10 and keep it separate from the first 10. This way it’s easier for me to count them. When I have got 5 piles like that I push them together. Then I go on with the next 10-pile. When I’ve got 100 pupae without mites my patience is over. Sometimes, to be sure about the result you may have to pull more pupae, especially if you have treated the colony effectively the previous season.
  2. Pupae with mites that have no offspring go to pile 2. Some pupae will have just one male or one female. Those will not be reproductive and I put those in pile 2 as well.
  3. A pupa that has a mite with at least one male and one female offspring goes to pile 3. The male is white and somewhat smaller. The form is not as even roundish like a crab as the females look like.


What I look for

  • The eyes of the pupa of the bee should have at least a dark purple color, not a light pink. The rest of the pupa may be white, but it will darken with time. This is to give the mother mite enough time to reproduce, if it will. The pupa may also have transformed fully into a bee with a dark moving head, and wings. If this is the case when you pull it, expect the bottom to look a little different.
  • The first to look at is the bottom of the cell when the pupa is pulled. If it’s not a fully transformed be that is pulled but a pupa, and there is no mite in the cell you will just see a whitish thread-like tangles on one side of the bottom, often the upper side. If you just see that and nothing else, you don’t have to look more. There is no mite in that cell. (Well, when you get a little more experienced, I’m not yet, you may have once in a while see a trapped mite upside down at the bottom under the cocoon.)
  • If it is a fully transformed bee you pull, then you will find the threadlike tangles. But also a more compact whitish lump, most often in contact with the tangles. The tangles is the rest of the larva-skin, the lump the rest of the pupa-skin, both from the different transformations to the fully transformed bee.
  • If the there is a mite in the cell you will also see a still whiter compact lump of feces of the mite, often somewhat prolonged. Especially you can see the prolonged form when there’s just somewhat feces. Most often also the feces is a little higher up on the cell wall. It’s resembling the pupa-skin more than the larva-skin. The easiest way to avoid confusion and wrongly take the feces for pupa-skin or the other way round is to avoid pulling fully transformed bees.

VSH-test rester The light made the tangles, the larva skin look more compact. In some cells you also find the more compact pupa skin. In only one cell there was this small piece of prolonged very white varroa feces. And yes, in this cell there was a mite, and a mite with no offspring. The only one I found in this colony. Of course it’s interesting for breeding even if there is no statistical significance for the very highVSH value, due to the low number of mites.

The feces of the Varroa

Sometimes it’s only a small somewhat prolonged stain of feces. Most often then the mite has no offspring, or possibly a non-reproductive offspring. Maybe the mite hasn’t been able to eat enough nourishing food, or it’s too old, who knows.

If it’s a lot of white on the cell bottom and the cell wall, you find a lot of feces and quite some offspring. Also nymph skins from the young mites. Then you will most probably find a whole Varroa family, one male and several females, white and light brown, as well as the dark brown mother mite. In such a big family, the mites are vital and run around on the bottom and cell wall. Sometimes there’s more than one mother mite in one cell.

In a cell with a lone mother mite without offspring or with a single offspring they most often just move slowly. Maybe the mother mite is old and stiff and have bad food.:)

A good film showing the development stages of the bee and of the mites can be seen here:

VSH-test hög In the big pile there is 100 pupae and fully transformed bees.


Add the number of pupae in piles 2 and 3. Let’s say there are 3 pupae in pile 2 and 7 in pile 3. Then you get 3+7=10 pupae in total with mites. 3/10=30%, which is the VSH-value. Just about enough to be able to use in breeding better VSH.

If you have 100 pupae in pile 1 you have pulled in total 100+3+7=110 pupae the degree of infection in the brood is 10/110=0.09=9%. It’s difficult to compare this with the degree of infection on the bees, the amount of phoretic mites, which you get with for example an alcohol wash. Maybe it’s half this value, maybe it’s more, maybe less.

If you have done an effective treatment the previous season you may have to pull at least 200 pupae. Maybe you have to wait to late summer to make the VSH test.

Varroa feces, larval and pupal skins

I found a good description of what happens in the brood cell here:…44&page=14

There are good pictures of different stages in the development of the bee and of mite reproduction.

There I also find the answer to my question and it’s yes. There are more remains of the bee development than just one piece of whitish/yellowish.

The first remain is from the larva when it becomes a pupa and the second is from the pupa when it becomes a fully grown bee.

Why this is important is because I have to take in consideration the age of the pupa/bee when I remove it. Do I find “extra” remains even if the pupa has not changed into a fully grown bee (but not hatched), the extra is varroa feces and there is a mite even if I don’t see it. That can happen when the mite doesn’t have progeny. i then don’t have to find the mite to know there is one.

Varroa defecation and pupa remains

I’m checking my, as I think, most promising colonies for the VSH trait. ( After dragging out more than 1000 pupae I have learned a lot about analyzing what I see. But I understand it’s more to learn. And I’m becoming faster doing the VSH-test. I have tried a reading lens with a ring lamp + extra 2.5 reading glasses. Together 5 times enlarging. Works great.

HDRtist Pro Rendering -

All pupae leave some white remains at the bottom of the cell. Mites defecate and leaves more white stuff often little higher up on the cellwall. When there’s a whole varroa family you find quite a lot of white stuff, sometimes covering the bottom.

VSH Pupa remains

A mite without offspring leave most often just a little extra white, sometimes almost nothing (can be hard detecting such a mite, but if missed doesn’t result in too good figures). New white wax comb makes it easier to detect mites without offspring.

VSH defecation? VSH defecation2

Now some questions.

  1. Does an older pupa than a younger one (with just darkened eyes) give more whitish remains at the bottom of the cell? (Just from the pupa and not from a mite?)
  2. If you find pupa remains AND just above it a small whitish stuff, more compact like varroa defecation, (I know it could be varroa defecation) is that always varroa defecation or could it, in case with an old pupa just about to emerge by itself, be more pupa remains due to the older pupa?

This could be important questions as if it is varroa defecation there is a mite even if I can’t see it. Once I saw a mite popping out from a pupa after it had been laying for a while on the table, a pupa from such a cell. This was seen on a dark comb, where it’s more difficult to detect a single mite without offspring. Often such single mites also are not as movable as one in a cell with a whole varroa family.

Anyone out there that has detected pupae remains in the cells after dragging them out? Have you seen the varroa defecation? Differences between them, and compared to pupae remains? It would be interesting to know.

Small cells and VSH

There have been numerous tests of varroa reproduction with bees on different cellsizes throughout the years, with the assumption that you then test varroa resistance. As far as I understand that can be true, but you don’t know to what degree it is true. One thing is clear – testing varroa reproduction is focusing on mite behavior, not on bee behvaiour. Bee behavior is for example VSH (

VSHtest-14 VSH test in 2014. I use a reading glass with lens lamp plus a pair of reading glasses 2.5+ and tweezers.

Leaving out bee behavior when trying to understand varroa resistance is not a good choice. But mite reproduction is also interesting if you want to get full understanding of Varroa resistance. For the practical beekeeper though the easiest is to focus on VSH, maybe measuring mite population once or twice a year ( ( and listening to nature to get the fittest kind of bees, using small cells at least in the brood nest ( (

What about mite reproduction in small cells? At first when mites arrive in an area, mites reproduce well enough to grow very big mite populations, also in colonies with small cells, in South America and in South Africa – and with me. But after 5-6 years the bees have developed what is recognized as mite resistance. Maybe with me too soon, this is the fifth year and I have seen very promising results.

The best reproduction test

The best test on mite population growth in different cell sizes I find “Brood cell size of Apis mellifera modifies the reproductive behavior of Varroa destructor”, by Matı´as Maggi, Natalia Damiani, Sergio Ruffinengo, David De Jong, Judith Principal and Martı´n Eguaras in Exp Appl Acarol (2010) 50:269–279 (

It’s a test under natural conditions, not a designed test. The scientists have collected data during a natural condition, well, a natural beekeepers condition of today. But they didn’t treat for varroa the 18 months before the data collection to have an enough big varroa population to get reliable data. I think the paper is interesting enough for anyone interested to buy the full text. It contains a good discussion, which reveals a lot of knowledge on the subject.

The test confirms other tests showing that Varroa mites prefer bigger cells. This test also shows that the distribution of mites in the brood with different sizes of cells is in line with that preference, the smaller the cell size the less probability that the cell is infested with a mite.

SC Maggi

But what then if there are only small cells in a brood nest – would the Varroa population grow at the same rate as if there were only large cells. That’s the really interesting question to get an answer to. That’s not what this test tried to get an answer to. But there is an interesting discussion in it.

They took a capped brood frame from a number of colonies, uncapped all brood and registered and measured all cells with mites. When a colony in this test had a comb with different cell sizes the reason was that it was such an old comb that the bees had reworked the comb with patches of smaller cell sizes. Also old combs had smaller cell sizes due to a lot of cocoon residues. Some of the brood combs tested came from combs relatively newly drawn from foundation with 5.4 mm cell size imprint (personal information).

The colonies had a mite infestation between 16 and 63 % in the worker brood. So the group of colonies did not form a resistant stock. The more resistant colonies (with lower infestation) would have big problems with reinfestation from more susceptible ones if all were left untreated in the same apiary.

Why do mites avoid smaller cells?

Why did mites avoid cells with smaller size? Probably because they and their daughters will become infertile quicker in those. Last sentence in the abstract:

“Infertile mother mites were more frequent in narrower brood cells.”

There is a discussion why this is so. A probable answer is the food for the mites. They feed on larvae and pupae and bees. Larvae in smaller cells get different food, the phenotype becomes different. This is a logical explanation why mites are more attracted to larvae in bigger cells. The food is tasting better there and is more nourishing for the mites giving them a longer and more fertile life.

Yves Le Conte

In a lecture in Versaille in France 2006 on the SICAMM conference, the association for breeding the dark honeybee Mellifera mellifera, Yves Le Conte showed the graph on the picture here, taken by a Swiss beekeeper attending. The graph shows results from tests LeConte had done (most probably involving the varroa resistant feral stock he is working with), showing a decrease in fertility for mites in cells with smaller volume.

SC Le Conte Varroa cellsize

This is almost the same as saying cells with smaller cell size. It’s just adding the depth of the cell to the bottom area (“cell size”, mm between the parallel sides of the cell, is a way of presenting the bottom area of the cell). Maybe this also indicates that the distance between the combs might influence if it’s narrow enough to give shorter cells.  If the distance between the combs are bigger than necessary the depth of the cell will though not be bigger. The space to the other comb will though be bigger if on that side there is brood as well. The results of Le Conte and Maggi et. al. are confirming each other.

“Infertile mother mites were more frequent in narrower brood cells.”

Mites don’t lay eggs forever. After a number of rounds in capped brood cells laying eggs (about three normally) their fertility is over. Next time they enter a brood cell they are infertile, lay no eggs.

Fewer rounds in smaller cells you might well don’t see in a short test, all those tests from two and a half month to a year that have been done. Especially if large cell control colonies are close by sharing their mites, more the higher the mite population grow.

In an area with only small colonies then, why did the mites develop at all so heavily, in the beginning few years (with no or relatively little treatment)? Good question. Evidently some kind of adaption to the presence of mites had to take place. It seems the bees had to learn how to chase the mites. They developed better hygienic type of behavior against the mite, both a general reaction against mite infested brood and a more specialized like VSH (where only mites with offspring are cleaned out of brood). On top of that genetic selection that favor these behaviours.

When queens from resistant feral bees from France were tested in Canada against “native” stock the result showed no difference. The queens were introduced in bee colonies that hadn’t learned how to deal with the mite because the mite pressure was in general to low, the bees were on large cells, the control colonies were to close to the test colonies sharing mites and the test period was too short.

Could some of the VSH-result obtained in small cell bees be caused of or explained by the small cells? Are the small cells helping the bees and the beekeeper finding the VSH trait in the selection process? Will good VSH queens on small cells not give so good VSH bees on large cells? Or to put this another way.

Do small cells contribute in expressing the VSH trait through making the mites infertile quicker? The results of Yves Le Conte and Maggie indicate that.

Are the more phenotypic changes from small cells that have impact on resistance against varroa and viruses?

My selection parameters

I have prepared for and selected for varroaresistance for quite some years. Last year I learned how to test a colony for VSH, a simplified method described by John Harbo, easy for everyone to use.

 DWV-bees on the hardboard

Before that I just allowed a mite pressure in the colonies until they showed virus problems. That meant in practice appearance of wingless bees, DWV-bees, either on the comb, but still easier, on a hardboard in front of the entrance. (Bees with very little resistance are though not quick in throwing out of the hive DWV-bees, or other virus-troubled bees.) You have to visit the apiary every 10 days or so, but a quick look will tell you, plus a look in the hive after opening the inner cover to check how the colony develops. No need to check down in broodnest unless you register something seems to be wrong.

Breeder candidates

Those colonies that keep going and develop normally without any symptoms, during which time no treatment has been done, they are of course then candidates for being breeders, especially coming spring.

 First breeder

In autumn 2011 I had three colonies that had been big colonies (not newly started splits during that year) without treatment for the whole season with no signs of varroa or virus. The winter and coming spring would tell which one, if any, or all, would be able to be used as breeder in 2012. That happened to be only one, H157.

Good to remember is that varroa first began to be a problem in 2008 with first bad winter in 2008-09 and 50% losses. Next winters no such losses.

Next years 5 breeders with VSH as most important

In autumn 2012 I had 11 breeder candidates. In spring 2013 I had at least 5 I judged I could breed from, but that year focused most on VSH. I had just learned to know I could.

I learned about VSH testing that spring in 2013 and did VSH-testing on three colonies.


One was a swarm that looked promising and nice. The mother colony was a feral colony in the wall of the dogtraining center, well within the area of my type of bees. The swarm showed 50 % VSH, half of the pupae with mites had mites without offspring. So even if this colony hadn’t been going for a whole season plus another winter without treatment I used it as a breeder in 2013.  I named it S120.


The second I VSH-tested colony had been a very small the year before and not really a production colony then. But it was in an environment with big colonies which needed thymol so I decided to test it and it showed 40 % VSH (4 pupae with mites had no mite offspring of the 10 pupae with mites found).  K25 it was named. But it was quite aggressive. I decided though that varroa resistance in this stage was more valuable.


The third VSH-tested colony was a walk away-split from a colony that hadn’t been treated for two years. It wintered with such a tiny cluster and still developed so promising and had such a good pedigree background I choose to VSH test it. Well, it wasn’t possible to get any VSH value as it hadn’t any mites in the brood. I was so amazed I decided to breed from it. And I named it R137, as I decided it was resistant, instead of H137.  It must have had a good resistance behavior, but resistance is complicated…


The mother of R137, H109, of course also was used as a breeder due to its history, but she was old and layed 50 % drones in worker cells. Couldn’t really make any VSH test I decided. I grafted one time and killed her.


The fifth I used showed itself to be very old as well and fell off the comb and died just after taking her home in a small split. No VSH-test. That colony I had thought had a new queen that had past the test. But this colony with this the old queen, though good, had been treated every second year with 10 grams of thymol (very little actually relatively) during four years. M176.

Some observations

Why do I tell you all these details? To come to the point for my situation, soon, be patient.

Late in season 2013, S120 showed a couple of wingless bees and got 10 grams of thymol. K25 which really hadn’t had a real production season before it was choosen swarmed thee times in July in 2013! I have never experienced that before, ever. R137 has some peculiar traits. It supercedes its queen every year it seems. And some daughters do too. This year a few wingless bees were seen and it got 10 grams of thymol.

I never do regular swarm controls in my colonies. Usually about 5 % of my colonies swarm. This year many daughters from two breeders from last year 2013 swarmed, from S120 and K25. And almost all daughters from these breeders needed thymol. Some of the daughters of K25 were very aggressive. Remember all queens are mated naturally in the apiaries. The apiaries together form an area with only my type of bees.

Breeder candidates for 2015

BUT maybe it was worth it using the breeders that disappointed me. I must have genetic diversity in my stock. I can’t make queens from just one line (H157).

I have one daughter of S120 and one of K25 that are really outstanding in resistance, honeycrop (more than 150 kg (300 pounds)), very good temper and no swarming tendency. H109 has more than one good daughter. M176 as well. And then there are walk away splits with heritage from the first breeder chosen for resistance H157, which are breeder candidates for 2015. Maybe I will use as well the three breeder used this year, or two of them.

Breeders used 2014

The autumn of 2013 I had 36 breeder candidates. I could have bred from more, but I choose to breed from three this year 2014, of which two are sisters, daughters of H157. These are H112 and H105. H157 had quite some daughters worthy of breeding from.  The third breeder this year was L242. After using these three, in the middle of July I made the VSH test on them. In all three the infestation rate in the brood was about 5 %. H112 had a VSH value of 80 %. H105 – 67 % and L242 had 33 %. No treatment was needed for this year either for H112 and H105. L242 got 10 gram thymol late in season. L242 came from a quite isolated apiary with small reinvasion and was moved to my home apiary and probably got more reinvasion here. But all three are wintered very strong.

Maybe I will use H112 and H105 in 2015 as well, we’ll see.

Selection parameters

Now to my point. It seems under my conditions it’s better to focus in first hand on one whole season as big colonies during which no treatment should have been needed (including winter and coming spring), to select breeders. BUT then use VSH testing to tell you which one probably are the best among them, and get confirmation of their status. Of course the breeders must be good in other respects, good honeycrop, good temper and low swarming tendency.

VSH is a good tool for selecting for Varroa resistance, especially when there are difficulties  using anything else, but also as a complement when other methods are used.  I’m glad I can make VSH tests, in addition to the DWV-test I use.

Reading the hardboard

Board colony

One of the most important parts in my management system has become a simple thin hardboard in front of the entrance. The first thing I do when I come to an apiary is going reading them. They give a lot of info, important for eventual actions.

If the hardboard is empty of  dead bees, litter etc – it’s the best. Very often you find a few dead worker bees there. It seems this is of no concern.

If you find a dead queen there, the old one or a virgin, you know the hive is shifting its queen, with or without swarming. Even if the colony has had no problems with mites or viruses for a short time with the last of capped brood, you can find a few wingless bees. It seems in such a circumstance it’s of no big concern. But be careful and watch the colony carefully for eventual thymol treatment.

Board Queen etc A dead queen! Drones, some workers and one old worker pupa (to the right).

If you find a lot of dead bees. Even without wingless bees among them, I consider it to be showing the bees are fighting something. Maybe another virus than DWV.

If the colony has a lot of drones maybe due to a lot drone comb, they might start throwing them out in the middle of the season, or at least some of them. I’m not sure  sometimes how to interpret this. Sometimes it seems the colony has shifted its queen and now it’s laying and the bees have no need for many drones.

When you see white parts or whole drone pupae, the bees most probably are fighting varroa, throwing out pupae with mites. And this is a very good sign actually. Varroa mites should be a drone parasite and not a workerbee parasite. And the bees should identify them in drone brood and clean those cells with mites (that have reproducedand and have offspring) – VSH in drone brood, or just cleaning out drone brood with mites.

Board 2 Drone pupae, quite some. This colony hasn’t needed any thymol, yet anyway. And given a good crop.

The next step that I usually see among my bees after seeing drone pupae on the hardboard is seeing wingless drones there. No big concern at this stage. If the reinvasion is big, if there are some colonies not fighting the mite very well they will spread many mites to other colonies. For some colonies that may mean they will need help in fighting the mites.

Next step among my bees may be seeing young grey bees walking on the hardboard, but with ok wings. Maybe another virus than DWV. And the next step wingless bees, one or two to begin with.

Now the colony gets one or two pieces of dishcloth with thymol (5 grams each), but not immediately before harvesting honey. I take away honey first. If there will be more than 14 days to harvesting they get thymol. It’s more important to have healthy bees that pollinate well, than some more thymol in the honey you can’t taste and is of no problem for health for anyone – and a dying colony. I know out of experience.

The breeder queens have not tasted any thymol for at least one year. My stock is making progress.