In early spring of 2021, when we began experiments on suppression of the development of Varroa mites in honeybee colonies, we noticed characteristic trends associated with the reproductive cycles of mites and bees. We called them small peaks of the mites reproduction. These peaks have a negative shape and an interval of about 16-20 days between the negative peak and the positive peaks of the mites drop, and they are associated with the maturation of the bees brood and the gradual release of young bees from the cells. We consider these negative peaks to be the moments of mass entry of Varroa mites into the brood for reproduction.
This statement may raise some doubts. After all, it is theoretically possible that these cycles are associated with the cyclicity of the mites entering the brood for reproduction and, accordingly, leads to the cyclicity of peaks of the mites mortality... But this is too correct for wildlife ... Even being born almost on the same day, it is unlikely that all the mites will die also in one day. It is not for nothing that scientists talk about the lifespan of the mites equal to 2.5-3 months or about three reproduction cycles in their life ... And again, "approximately"! And there are always exceptions, both in one and the other direction. But most of all, we are convinced of the correctness of our statement by the fact that, according to the graph, at the same exact moments, there are the same minimums in free fall of a young immature mites ... And they are definitely not connected with any previous cycles of reproduction... They die and are thrown away by the bees when young fully matured individuals leave the cells and old females that have lost their strength die. And these peaks ( death and fall of old females and fall of immature females) are clearly linked to each other. The the dips are also related and are strictly the same for both categories of the mites!
That is why we believe that the dips or negative peaks are associated with the mass entry of founding females into the brood cells, and the following positive peaks of the mites drop are the result of natural death of immature females, as well as old founding females who have lost their last strength in the process of reproduction.
The same
peaks are clearly visible on the mites drop plot for 2019-20. They are
characterized by a temporary complete, or almost complete, cessation of the
fall of old females. This is apparently because they are all in the brood cells
for reproduction, and only some of the mites which are feeding on adult
bees unexpectedly die and fall down on
sticky board.
But besides this, it was noticed, that these peaks, so characteristic in spring, begin to blur and disappear in summer and winter, turning into an almost flat line ... At first this puzzled us, but after thinking and analyzing the data of 2019-21, which we received in our apiary and in the apiary of our partners, we understood the reason for this phenomenon.
The source of this phenomenon, most likely, lies in a
fairly simple phenomenon - the lifespan of the mites, which, according to
scientists, is 2.5-3.0 months. We have already written, that free fall of the
mites which we see at the moment, reflects the process of their birth that took
place those same 2.5-3 months ago. Usually, the mites fall, dead from natural causes. While the mites are
young and full of strength, they live, multiply and feed on bees and do not
fall down dead or exhausted ... But each reproduction process takes away their
vitality ... And after 2-3 months, having worn out enough, they can already die
and fall down. Weaker and because of this earlier dying mites make up the small
and even drop, which we can see in summer and in winter. And the main, mass
death of the mites occurs 2.5-3 months after their birth, and exactly this we
observe in the form of two peaks of the mites drop - the spring pre-swarming,
and the summer post-honey harvest peaks of the mites drop! Let's see how it
happens ...
If in the autumn the bees were treated against mites and the wintering was cold, then from January to early April there is a slow and unobtrusive process of mites reproduction in a relatively small amount of brood. The result of this process is the death of a limited number of old mites, plus a small number of mites dying from other natural causes. This creates a small, more or less even mites drop onto the sticky board. April, May, June, due to the rapid increase in the number of brood in bees, become the months of rapid growth of the mites population ... But it is difficult to notice this from the fall on sticky board ... If in the first half of spring we see the growth of the fall of old females, which have lost their last strength in the process of reproduction , then in the second half of spring season, the fall stops abruptly and drops to almost zero values. This does not mean that there are no mites in the bee colony! This means that the last females of the previous year of birth died out and only young females of Varroa mites, born this year during the winter and early spring, remained in the family of bees! They are full of energy and will not die and fall on sticky board for another 2.5-3 months! This means, that their death and fall will occur only in July, August, September ... Moreover, in the interval between mid-May and July, the fall of the mites will be insignificant, since these mites die before their due date ...
If the wintering was warm and the bees begin to actively grow brood in January, February and March, then the peak of their death and fall will occur in April, May, June, and the peak of the rapid reproduction of the mites and their population growth will occur during the same period. In this case, a dip in free fall of the mites may not occur and, on the contrary, immature individuals will appear in it, which are the sign of a peak in the process of the mites reproduction! In fact, the winter peak of the mites reproduction and the early spring peak will merge into one powerful peak in the mites reproduction, which in practice will most likely lead to the death of the bee colony in late spring or early summer.
Thus, if during the control of free fall of the mites in May, June and July you will see the average values of the number of mites falling per day close to zero, this, unfortunately, does not mean that your bees are free of Varroa mites. This means that the peak of active reproduction of the new generation of the mites has passed and a period of smooth and imperceptible increase in their number has begun. And this will continue until the summer post-honey harvest peak of their reproduction.
Unfortunately, in temperate latitudes this is the time
of the main honey harvest and the fight against the mites at this moment is
practically impossible. Therefore, the main moments suitable for suppressing
the development of Varroa mites are, firstly, the moment of the appearance of
the first mass brood in the amount of one, but not more than two brood frames
of sealed brood (the end of April), and the end of the honey collection when
there is a minimum amount of brood in the nest (August). In the first case, the
brood can be removed, and in the second, it can be removed or destroyed. In
both cases, the bees have enough time to recuperate the colony both before the
main honey flow and before hibernation. The main thing is that new generations
of bees will be healthy, and no chemicals will be used.
