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Hygiene behaviour against losses caused by Varroa
(Detlev Biel) At a time when many beekeepers are experiencing significant colony losses and there is widespread uncertainty as to how to treat the bees, some beekeepers are looking at their colonies and praying that they will survive the winter and won`t be killed off by the effects of the Varroa mite. We can certainly understand these concerns, although most bees are not killed directly by the mite itself but rather because of the secondary consequences of the Varroa mite.
In principle, it should be noted that our bee colonies are exposed to a constant danger from viruses and bacteria. These are ubiquitous (present) in many places, sometimes by chance or reinforced by neighbouring colonies. They can also have a seasonal effect. One only has to think of the American or European foulbrood, lime, stone or non-pit brood, Nosema, dysentery, amoebic disease, although the viruses with 18 different types clearly stand out. Having said that, all viruses and bacteria have one thing in common, they must manage to get into the body of bees. This can happen via food, amoebae, Nosema apis or Varroa. These viruses and bacteria multiply in the bee and the diseased bee then becomes the “vector” of the further infection chain. As a result, these events can lead to the demise of the entire colony.
Dr. Christoph Otten from the Centre for Bees and Beekeeping in Mayen, for example, has clearly established this with the help of bee monitoring. The more mites there are in the colony, the higher the probability that the col-ony will be lost, since the Varroa, when it sucks at the haemolymphe (the bee blood), intro-duces the viruses that are present into the bee and provides for the further distribution among the colony. These viruses then damage the colonies to such an extent that they often die before winter from the wing deformation virus or the acute bee paralysis virus.
If one considers this statement further, one inevitably concludes that a clear reduction of the number of afflicted bees within the colony significantly increases the chances of survival of the colony as a whole! In addition, this is exact-ly where we come in and where we would like to help you in the future! Our drone line in 2019 is characterised by a special characteristic. Our drone line has a particular, pronounced hygiene behaviour of at least 85%. What does this mean? The bees of the drone line recognise in at least 85% of the cases, if in a cell the brood is sick and/or dead. This behaviour is crucial when considering the health of a bee colony. The earlier a dead larva is detected and removed, the less likely it is that the viruses or bacteria present in the dead larva will develop further. Thus, the viruses no longer reach the stage of spore formation, since they were al-ready removed from the colony before the transformation process.
This hygiene behaviour should be a central breeding goal of all further beekeeping efforts, in particular when one considers the situation of the American foulbrood with the pathogen Eric II, which spreads in many areas in Germany. If bees with a particularly developed hygiene behaviour remove large parts of the dead brood before the viruses spread further, then it is conceivable that colony losses and the imposition of exclusion zones can be avoided.
In addition, the drone line 2019 also shows that bees recognise Varroa-infected cells and often remove them. We see this repeatedly when we look at brood nests and come across open combs when bees that have not yet reached hatching maturity confront us. The bees have recognised the mites in the comb and opened the cell. This behaviour is sufficient to prevent the mites from developing further in the cell and thus not becoming sexually mature. Some of the bees have then been known to remove the brood from the comb, but this is not decisive. The critical factor is the opening of the comb, since the metamorphosis of the mite can only be completed in the sealed comb.
We are always happy to see such behaviour, which is referred to as VSH behaviour. Having said that, this behaviour should be viewed as a possible additional characteristic/performance of our bees, because in order to evaluate it and quantify this activity, all drone colonies would have to be infected with a standardised number of mites at a certain point in time and later brood combs would have to be opened and evaluated on a large scale. It is simply not practical to realise this kind of work given the large number of drone colonies that are to be found in the mating station and in the protectorate band. It is, however, possible to observe the hygiene behaviour of all drone colonies and only select colonies with at least 85% hygiene behaviour.
This approach is particularly interesting and appealing when mating is possible with queens that also have a comparable hygiene behaviour. Queens that have been mated in this way can be ordered from Detlef Biehl, Friederike Brondke or Dr. Peter Stöfen. And if you can take note of the hygiene behaviour of your queens and only allow for mating of the descendants of such queens, then you will be making an important contribution to all beekeepers in their efforts to support their colonies against viruses and bacteria.