It is
possible that we will repeat ourselves a little and once again talk about the
features of the study of free fall of the mites on sticky board, but this is
extremely important. It is important because if you know and understand all
this, then one glance at the debris on the sticky board will be enough for you
to determine the degree of infection and the danger level of the state of your
bees. So, on the basis of data obtained by us over several years of
experiments, we can assert that the mites drop in the hive is heterogeneous. It
consists of two main groups of individuals.
The first
group consists of young underdeveloped or unfertilized females that did not
take part in the increase in the parasite population. The second group consists
of dark-burgundy old females that have participated in several breeding cycles
and have already outlived their term. Among them there are also two subgroups
of individuals, the presence of which can give us information about the events
taking place in the hive.
Usually we
are accustomed to notice and to count the mites of the second group in the
mites drop. Its first subgroup is the old maroon females, which can be seen lying more or less evenly over
the entire surface of the sticky board. They die while feeding on the bees, and
fall down, most likely due to death from age. Sometimes there are live mites
among them, which for some reason fall down and die already on the board from
hunger. What all these mites have in common is that they fall from worker bees,
on which they have been parasitized between reproduction cycles.
Parasites
can fall both in the presence of the process of reproduction of new generations
of mites in the brood of bees, and in the complete absence of brood. Basically, this type of the mites drop simply show the
presence of parasites as such and, to a greater or lesser extent, indicate
their number. But this information is unreliable, since there may be periods
when only young and strong Varroa females remain in the bee family and they are
not going to die. The absence of the mites on sticky board at such moments
cannot indicate the absence of parasites in the bee colony. This usually
happens in May – June, when the overwintered females gradually die off, and in
the bee family remain only mature juvenile females of Varroa mites. That is why
we do not want and do not recommend using a specific number of the mites falling
down on sticky board to predict specific values of Varroa mites population in
a bee colony.
The second
subgroup is old mature females that die during the reproduction process. We
believe that reproduction is the most costly process in terms of forces, which
stimulates the death of old females at the end of the egg-laying process. Their
death occurs in sealed cells, in which dead immature or infertile young females
also remain. All these individuals are thrown down by the bees when cleaning
the cells, after the release of young bees. Such kind of the mites drop appears
synchronously with the emergence of young bees from the brood and that is why
all these dead mites lie between the frames with the brood. This is a specific
sign of the mites drop of the second subgroup.
What can
all this say to the beekeeper?
The uniform
fall of old maroon females on sticky board in all parts of the hive, or the
fall of the mites of the first subgroup of the second group, speaks primarily
of the presence of Varroa mites in the bee family as such. And their number
speak about the infestation of the bee
family very conditionally.
The
appearance in the mites drop of the mites of the first group, that is - deutonymphs,
young immature females, young infertile females, from almost transparent to
bright red, marks a new stage in the development of Varroa mites population. We
believe that they end up at the bottom of the hive due to unsuccessful
conditions for their development: most likely, due to inappropriate thermal
conditions in the brood, which is very far from the center of the nest. And
this means that the mites have already occupied the entire centre of the brood
part of the nest and came out to its periphery.
As a rule,
the fall of this type of the mites indicates a sharp increase in the parasites
population, which takes up a lot of space in the nest and goes to its borders,
where it is colder and conditions for the development of young female mites are
worse. An increase in this particular type of mites in the total mites drop with a small number of old dark
mites indicates an upcoming powerful surge in the growth of the mites
population in the bee colony, or the very beginning of this growth. It is from
this moment beekeeper have to take emergency measures must be taken for their
neutralization.
As a rule,
an increase in the mites drop of such type of mites precedes an increase in the
fall of old maroon mites by 15–20 days. This is a very good indicator for
predicting an increase in the number of mites and the imminent appearance of an
emergency situation in the bee colony! This is especially important for those,
who do not use chemical preparations for mass and repeated treatment of their
bees.
On the picture you can see the graph of a
separate count of two types of mites for five bee colonies over a year and a
half. But the most indicative are two graphs - the graph for the E-1 family and
for the 8-1 family. Let's consider the E-1 schedule. It is clearly seen that in
the interval 13-14 (April) the growth of free fall of mature mites is not
observed, while the increment of free fall of an immature mites warns about the
beginning of the mites population growth, which occurs in the interval 14-15
(May) and especially in the interval 15-16 ... (June) This bee family did not
survive after point 16. The infestation level
became fatal for it. Schedule for
family 8-1 is flatter. The initial infestation level of this family was lower.
But on the interval 13-16 (April-June), it shows the same tendency as the E-1
family - the growth of free fall of an immature mites outstrips the growth of
free fall of a mature mites and predicts a significant increase of Varroa mites
population. The trend was interrupted by the removal of drone brood, but as can
be seen from the graphs, this only delayed the explosive growth of the mites
population in this family until the end of
honey harvest. This pattern is typical for the spring development of the
mites in a bee colony.
The
appearance in the mites drop in a sufficiently large number of old maroon mites
of the second subgroup of the second group under the frames with brood mixed
with young immature mites of the first group, indicates the development and
deterioration of the situation with the quantity of Varroa mites in the family
of bees.
If the
appearance of young immature mites indicates the beginning of the growth of the
mites population, then the appearance of this mixture of mites of different
ages under the brood frames indicates a peak in the reproductive activity of
Varroa mites. Measures must be taken immediately. The population of mites could
already reach enormous sizes. So the most radical and urgent measures need to
be taken.
So, for a
practicing beekeeper, this means that if in the spring, pale-colored and/or
translucent mites appeared in free fall on sticky board, then urgent measures
must be taken to combat Varroa mites. This is a sign, that after 2-3 weeks, the
growth of Varroa mites population will become fatal for the family in the
absence of measures to combat it. It doesn't matter how many mites you will see
on sticky board. The less the better ... As long as there are no pale mites in
free fall, you can still calmly do your job. But when they appear, the fight
against the mites must be started urgently! Otherwise, the bee family will die.
The same
situation is possible after honey collection. But at this time, it is warm
enough and the death of young and immature mites decreases. Therefore, the
growth of free fall of the mites can proceed in parallel in groups of mature
and immature mites in any quantity. But despite this seasonal difference, the
appearance and growth of free fall of immature mites suggests that the
beekeeper needs to take action urgently.
We assume, that
the adoption of measures - is primarily
the selection of all brood, sealed and
open, from the families which should work on honey collection into one family
(or several families, depending on the size of the apiary), followed by
treatment of only this family with formic or oxalic acid. This will drastically
reduce the quantity of Varroa mites in working families and will leave them
free from chemicals and acaricides, with which are usually treated all families
of the apiary, and which strongly worsening the condition of bees, (and
sometimes killing them) and which are making honey unsuitable for export.
Thus, the
control of the appearance and growth of free fall of pale immature or infertile
mites - is an excellent indicator of the moment when anti-varroa measures
become vital to maintain the strength and vitality of bee colonies. And while
it is not too late, beekeeper can use environmentally friendly methods of
dealing with Varroa mites, and that is not unimportant !
Copyright Sergey Glebskij 2021
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