In our works, we have repeatedly said that one of the best zootechnical methods for combating Varroa mites without the use of chemicals is the method of removal of sealed brood of worker bees. This method, applied at the right time, allows you to remove from the colony up to 85% of mites and suppress the development of Varroa mites population at the most important moments. Two years of experiments confirmed this fact.
During beekeeping season, there are two critical moments when removing of mite-infested worker brood can significantly improve the health of the colony and slow down the growth rate of the Varroa mites population:
1. The first and main moment is early spring. The efficiency of brood
removal at this time has been tested by us for two seasons and is fully
confirmed. By removing of 1-2 full frames of sealed brood in April-early May
(for rather northern countries), we sharply reduce the possibilities of the
Varroa mites population for a sharp increase in future. But two clarifications
need to be made here.
• First - it is necessary to remove exactly the complete frame of sealed
brood. Our attempts to remove or destroy the earliest sealed brood in the form
of small spots on the frames in mid-late April did not give any effect.
Apparently too few mites enter this brood to reproduce, and most of the mites
were still on bees on other frames away from this small brood spots.
• Second - brood destruction is a poor alternative to brood removal. We have tested this experimentally twice. Having destroyed the cells of the combs with brood, we observed how the mites, which were under the covers of sealed cells, after their destruction, began to spread in all directions in order to climb the bees again later. And although this method will surely kill the second generation of mites in the combs, but the first will be preserved almost completely. We received the second confirmation when in the colony in which in April we destroyed all the early brood that was present on the frames in the form of small spots, by July we got a mites infestation, not much less than in colonies in which no manipulations with brood were made. Thus, it can be argued that removal of brood at the moment it reaches the size of 1-2 frames and is completely sealed, gives the best result for the fight against Varroa mites.
2. The second moment is the summer time after or in the second half of the main honey flow. At this time, the population of mites already had time to increase quite strongly and approximately 85% of it is in the sealed brood of worker bees and drones. At this point, sealed brood removal can cause a significant impact on the mites population. At this time, the number of brood in the colony partially decreases on its own due to the filling of part of the nest with nectar, but, nevertheless, its number is still quite large. When we checked the brood infestation using the method of alcohol wash, we often saw that the infestation of brood was much higher than that of the worker bees. We believe that this concentration of mites is not only due to their number as such, but also due to the reduction of the place suitable for their reproduction. If there is a lot of brood and it is impossible to completely remove it, then it is possible to limit the queen in an isolator with Hannemann bars on 1-2 frames and keep it there until all the brood will come out of the other frames and there will be no other brood in the hive except the brood in isolator. And then, this sealed brood, containing all the mites that were ready for reproduction by age, can be removed. After that, the queen can be released from the isolator to continue laying eggs and prepare the family for wintering. This will clean up the colony before rearing of young generation of bees, which will overwinter and become the basis of the colony in spring. Their infestation will be much less, and wintering will pass without complications.
It should be noted that during the whole summer season it is desirable to have a building frame for the drone brood. Regular removal of drone brood can significantly reduce the number of mites without compromising the working capacity of bee colony. But, this is a classic recipe.
Further, as we wrote earlier, it is important to switch to cold wintering, stopping the late brood rearing. This will not give the mites opportunity to breed an additional young generation which will overwinter on bees, which will endure winter better than old individuals, and which will give much more young mites in spring. Cold wintering will not allow the bees to start brood rearing at the end of winter, which will further increase the interval for mites during which they cannot reproduce, but only die off. If it is possible to keep the bees from brood rearing till the flowering of the first pollen-giving plants, then the bees will start brood rearing in concert and in big quantities. This will allow beekeeper to move on to the phase of first spring removal of sealed brood in the next beekeeping season with much less mites population.
Another factor that is important when applying this method is the egg-laying qualities of the queen. This parameter depends on many conditions, both pedigree and climatic, as well as on the nutrition of the queen and the possibilities of the colony to heat the brood. It should be borne in mind that when applying this method, the best breed is Karnika, whose colonies are characterized by explosive growth in spring, and the queens are able to lay up to 1900 - 2000 eggs per day, that is, almost two full frames. Caucasian queens have the worst egg production, their average productivity is 1600-1700 eggs per day, although this is not unambiguous and depends on various conditions. Egg-laying of queens is maximum with good nutrition and the presence of fresh pollen and nectar, which is consistent with the fact that cold wintering should last until the first pollen-bearing plants bloom. Families of bees in such conditions make up the loss of brood in just a couple of days. Family size also has an effect. It is large families that are able to heat the brood and feed the queen, allowing them to dramatically increase the output of brood and compensate the loss of first sealed brood.
Thus, we are confident, and experiments confirm this, that the timely removal of sealed brood, especially in early spring, can significantly reduce the number of mites and interrupt the chain of their reproduction. That will allow, with the use of our new hive, to reduce the reproductive activity of Varroa mites and stabilize their population at a low level. This will allow, if not completely abandon the chemical treatments of bees, then significantly increase the interval of their life even without minimal chemical treatments, and it is possible that the duration of such intervals can be up to several years.
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