Only real treatment tell real mite population

Marco Moretti made a valid comment to the sugar shaker post. It doesn’t surprise me that Antonio Nanetti found checking mite populations besides a real treatment is unreliable. It is many factors making the results uncertain. Why beekeepers want to do this anyway is to get an idea when it’s time to treat against the mite.

If you do an oxalic dribble, or trickling, you make a real treatment. And that’s okey with me, if you choose to do that. Before making a real treatment the most reliable mite test is said to be alcohol washing like with the bee shaker described in this blog. The sugar shaker might do well for others. According to findings in USA described by Dennis van Engelsdorp those beekeepers that checked mite populations with alcohol wash, thus keeping track of the mite population had the lowest winter losses, of those beekeepers treating regularely.

John Harbo and his collegues at Baton Rouge lab found in the early 1990:s when they took help of a statistican to find out that checking mite population increase during a period of time was not a good way of testing mite resistance. That’s why they finally ended up checking  infertility of the mites, which finally became the VSH method. (Information from Harbo)

That’s also one of the resons I don’t count mites. I check for virus problems in the hive before treating. The easiest virus and the one most common when mites are becoming many is Deformed Wing Virus (DWV). Maybe that’s too late normally to save the colony. I don’t know. But fortunately I don’t have ”normal” bees. Also a reason for me not counting mites, but looking for DWV, is that I want my bee stock to develop strong varroa (and virus) resistance.


Bee shaker

I wrote about counting mites recently. Even if I don’t, others do, and sometimes it gives information that may help you make a decision.

John Harbo mentioned when he lectured in Sweden in May 2013 that before choosing the method for selecting for varroa resistance at the lab in Baton Rouge in the 1990th, their statistician helped them evaluate different methods. Their conclusion was that selecting for infertility of mites, then called SMR, later VSH, was the best method. Using one-drone insemination on 43 queens from a source of collected survivors they started the work in 1995 and in 1998 the goal was achieved. Impressing to say the least. Why havn’t this result have had more impact during the years. The queens produced at that early stage in the process were so inbred they were superceded quickly and the honeyproduction was low. They got bad reputation and beekeepers didn’t understand how to use the resistant queens fully. The situation today is very different.

One selection method among those not choosen, was checking the mite population. Though this method is still promoted buy others and used as well. Maybe because some have found it valuable in this matter. And most of us are living in free countries and can do our own choice.

Another reason for doing mite counts is for making a desicion if or when mite tretament is needed. In US it’s been said the threshold for treating is 3 mites per 100 bees in an alcohol wash. Some say this number seems to have to be lowered as viruses are worse nowadays. That probably is valid for all those moving their bees to almond pollination, where the bees share the latest in pathogens, pests and pesticides. Maybe all this treatment used during the years has forced the mites to answer with reproducing quicker in that they stay in the phoretic stage (on the bees and not in the brood) for a shorter period before they enter brood cells again.

Anyway, my small scale beekeeper friend cooperating with me, Leif Stromberg, quite on his own with his bees but not totally; he has 15 colonies, use the threshold 5 mites per 100 bees for treating, in october only when there’s no brood. It’s a help for deciding if he shall trickle oxalic acid. He trickled 4 colonies in autumn 2013. His winter losses are small. He lives 100 km north of me and cooperates there with Bjorn Lagerman, 90 colonies, with basically the same stock of bees as me too. His story could be told in another post.

HDRtist Pro Rendering - Pouring bees in the bee shaker (pictures used with the kind permission of Randy Oliver).

Leif has compared natural dropping of dead mites through the season and this late alcohol wash. And there is actually very little correlation, if any. His conclusion is that natural downfall of mites is of no practical value to get a good idea of a mite population having an impact on the bee colony, at least when it comes to his bees (he gets a couple of virgin queens from me every second year or so) that apparently has some resistance to varroa. Randy Oliver has also lost faith in the natural mite drop method for determining the actual mite population.

Shaker2 After shaking for 1-2 minutes, turn the shaker around…

Randy Oliver uses a very practical way of alcohol wash, the bee shaker. For some time John Williamson produced it for sale, but doesn’t anymore. As far as I know, no one does at the moment. But it takes 5 minutes to make one yourself from two suitable cans with plastic lids and a piece of beetight netting that let through mites. Follow the instruction here:

Shaker3 … and count the mites

Breeding varroa resistence: Germany versus USA

The other day I received Imkerfreund 12-2013 in my postbox. In this issue of the German bee magazine I found an interview with the scientist leading a varroa breeding project involving beekeepers. It’s a project that has made some progress.

A German strategy

Germany has had varroa for about 40 years. And they mostly try to breed pure Carniolan bees (carnica) and pure Buckfast with the help of isolated mating stations (and insemination). The main varroa treatment concept is the following in the south of Germany.

  • April-June    Cut dronebrood and make splits
  • July              After harvest in July treatment with Formic acid
  • August          Four weeks later the second treatment with Formic
  • September   The third treatment with Formic if mite downfall after treatment no 2 is too high
  • December    Treatment with Oxalic acid, trickling of sugarsolution with oxalic


Their breeding program has two resistance parameters: pinkilling a square decimeter of brood (similar to freeze killed brood) and measuring the development of the varroa population during the season. Besides traits like low swarming, good temper and a honey crop. Their progress: being able to skip one of the summer treatments with Formic acid (as far as I understood the German article).

An American strategy

USA has had varroa for about 25 years. Few try to breed pure race bees like the Germans. Ineminated and naturally mated queens are used. The main varroa treatment concept for smaller operations are aimed at organic treatment (involving formic acid, thymol, drone cutting, hops) and treatment free (involving small cell size, topbar hives). Bigger operations most often trust different syntetic miticides, formic, thymol and hops.) Americans are more focused on treshold counts of mites for the time to treat.

The Russian bees from the very east of Russia, the Primorski area, is one quite succesful undertaking started and developed by the USDA. A number of beekeepers have formed an association to take care of the 18 lines of these bees. They are treated much less than ordinary bees against varroa. With these bees you have to watch out for swarming.

The VSH-bees are influencing most of the other efforts of breeding resistant bees to varroa mites. These bees are a mixture of all kind of bees. Here you find most of the traditional beekeepers that don’t use any treatment against varroa mites, for example John Harbo, , and Adam Finkelstein,

HarboBeeCo Carol and John Harbo

Beekeepers in different states are forming breeding organisations funded by the governement, like this one:

There are those in Europe forming good projects and those already not treating against varroa either, but with this article I want to get attention to how little progress is made with the strategy mentioned above in Germany and how great achievement is made with the VSH-breeding, focused at the start on one trait: VSH. Then on the other. Something has to be learnt here.

Actually resistant bees were achieved already after very few years, by Harbo and Harris in 1995-98 in USA. They started with survivor colonies of any type of bee they were given. The only one parameter they focused on first was VSH: Varroa Sensitive Hygiene. See other articles here in the VSH category. This development of resistant bees have to be done in all kind of regions differing in climatic and other local characteristics, mites and pathogens for example.

It’s time for Europe to learn the lesson and form breeding projects together with beekeepers where ’central’ areas are formed fairly isolated from other bees. All bee colonies in these ’small starter’ areas are part of the program. An effective way of using funding money from European Union would be to support such projects.

Every breeder bee colony should be VSH tested


  1.  VSH (Varroa Sensitive Hygiene) is a trait in worker bees.
  2.  Worker pupae with Varroa mites that have offspring are cleaned out.
  3.  The fertile female mite survives, but all offspring dies, as well as the worker pupa.
  4.  Worker pupae with Varroa mites that don’t have offspring are not cleaned out.
  5.  VSH-trait is governed by two genes. As the genes comes in double (in two sets of chromosomes) there are two pair of genes, which makes four alleles (variants of genes).
  6.  The alleles that contribute to VSH are additive, not recessive or dominant. Two is better than one, etc.
  7.  Two alleles in a bee makes it show the VSH trait in such a strong way the colony acts as resistant

The above list is some of the things I learned from John Harbo when he was lecturing in Sweden recently. That VSH trait is governed by two pairs of genes is a working hypothesis that is contributed by breeding tests. No observation contradict this.

Harbo lecturing

This makes the VSH-trait to something different compared to the hygienic trait keeping bee colonies free from American foul brood and chalk brood. This later hygienic trait is most often tested checking how fast bees clean out freeze killed brood (or pin killed). The working hypothesis is here that the trait is goverend by three gene pairs and this hygienic trait is contributed by recessive alleles (gene variants), which makes it necessary that individual worker bees have all six alleles to show the trait. I have understood that the more individual bees in a bee colony that have all six alleles the more effective is the colony in this hygienic trait.

But with VSH you can for example have a queen with two alleles that are mated to drones with two alleles. Thus the virgins from such a colony always will have two alleles. Those virgins can mate to any kind of drone, with or without VSH-alleles, and still show the VSH-trait – AND be Varroa resistant.

On the other hand it is not necessary that all individual bees in a bee colony have two VSH-alleles for the whole colony to be Varroa resistant. It is unclear how many are needed. But in a test where a resistant colony and a non-resistant were combined – the combined colony was resistant. This means that you don’t have to use an inbred breeder colony with all four alleles to produce varroa resistant bee colonies. If your breeder colonies have a high VSH-value and you open mate the daughters in an area dominated by drones from colonies with high VSH-index it’s good chance the queens produced will give Varroa resistant colonies, if not reinvaded heavily by mites…

You can test your bee colonies for the VSH-trait and breed from the best and with a good strategy develop the Varroa resistance in your bee stock, even if you don’t use instrumental insemination. But if you do, you can develop a strain quicker with higher number of alleles.

All bee stocks have the VSH trait, at least at a low degree. The alleles are there, but spread out in the population. Not concentrated enough in the bees in a non-selected stock. Also mites get old and stop reproducing. So “background noise” of non reproductive (infertile) mites in a colony is about 10%. Maybe even up to 25%. If an individual bee have one VSH allele the VSH trait doesn’t show up in that bee. I think that’s the info I got.

Harbo & Carol

After retirement John Harbo bought queens from Glenn Apiaries in California to start his own bee business. He continued breeding VSH bees and he doesn’t treat his bees against the Varroa mite. He doesn’t need to. He is now running his bee business together with his wife Carol.


Harbo explained a simple test every beekeeper can and every bee breeder should do. He uses a microscope with 0.5 magnification of the eyepiece. Thus getting maybe about a total of 5x magnification. The working distance under the microscope need to be about 10 centimeters  (4 inches).


I use a reading magnification lense for elderly people with a ring lamp (much cheaper), plus reading glasses (2.5x).


(Click on the picture to enlarge it and on back arrow up to the left to come back to the text.) When the pupae are at least 4 days old and the eyes are getting dark is the best time to check them. With tweezers around the head (or somewhat further down) you pull out the pupa, look at the pupa for mites and mite feces (mites that don’t reproduce often put there feces on the pupa instead of 10 or 2 o’clock closer to the bottom of the cell but on the cell wall. You then look in the cell for mites and mite feces. Often you see white remnants of the pupa on the bottom of the cell. The mite feces are somewhat whiter than pupa remnants and more up on the cell wall, but still close to the bottom.

What I saw when I did my first test was that mites with good reproduction and whole varroa families, those mites were very active and ran around on the bottom. Mites with  just one type or very few offspring moved slowly in comparison. Which also did the mother mites with no offspring, that didn’t reproduce. The mite feces amount in such cells with no reproduction seemed to be smaller.

  1. If a bee colony shows 100% VSH trait – 100% of the pupae with mites (of the total number of pupae with mites, that is all of the pupa with mites), the mites in those do not reproduce, they have no offspring – the bee colony have all four alleles for VSH.
  2. If a bee colony shows 60% VSH-trait (60% of the pupae with mites have no offspring), it has three alleles.
  3. If it shows 30% VSH-trait, it has two alleles – and is varroa resistant.
  4. If a colony shows 25% and below it has no breeding value according to Harbo. The figure is too close to ”background noise” of infertile mites of other reasons than influence of VSH-trait.

If 25% would be the best I could come up with I would personally use it anyway as a breeder if it is a good colony in other respects. I would also consider the possibilitty to increase other efforts of enchancing the Varroa resistance in my stock.

Why did I test the colony I did test as the first one of mine? Because it showed very little signs of varroa present. It is very good in other traits. It didn’t need Varroa treatment when neighboring colonies did. It showed  8 pupae with mites out of 110. 2 had whole Varroa families, 1 had just a male offspring. 1 had only two female daughters. The rest no offspring. This makes 50% VSH. Time will tell how resistant the colony is. It’s on small cells as well.

The VSH test is so easy and so valuable, that every bee breeder should tell the customers what VSH value their breeders have. And every queen customer should ask for it.