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The
colonies of bees in Hives 11, 13, & 15 have survived without treatment
since May 2000.
The detailed weekly monitoring of varroa drop from Feb - Dec 2001
confirms that although the varroa population increases during the
summer period it does not follow an exponential curve.
This is due to natural limiting factors within the hive.
Effective grooming and hygienic behaviour, made apparent by the presence
of live varroa and dead embryo bees observed during the weekly examinations,
are the main reasons for the bees continued survival.
There is no overall increase of the varroa population, year end to
year end, when the weekly varroa drop figure for the winter periods
are of the same magnitude.
There are other supplementary factors that assist in the bees survival
against varroa. However these asides have been omitted to avoid distraction
from the core issue of this experiment.
The judgement reached by reasoning, using the results of the experiment,
confirm that the varroa population in a colony of honey bees is limited
by natural grooming and hygienic behaviour and enables co-habitation
without treatment.
It might be expected that the varroa mite was reasonably safe whilst
latched onto a honey bee or breeding singly within a cell, and that
the most vulnerable time would arise during transfer between these
two situations, or the occurance of multiple mite occupation of the
cell.
Let us assume that a hive consists of a brood box with queen excluder
plus two supers and that the hive is full of bees.
Under these conditions the varroa nest sites would be say- halfway
up the brood box.
If the bees carrying phoretic mites are evenly distributed throughout
the hive, the centre of this mass of bees may be taken to be above
the centre of the brood box.
The distance between these two centres may be increased by using a
narrower hive.
A narrow hive increases the varroa travelling distances and also presents
to the varroa a smaller initial area of suitable nest site availability,
which would enhance multiple mite infestation and curtail the successful
varroa breeding capacity.
The removal of the two supers and containing all of the bees within
the brood chamber, would nullify these advantages.
The above experiment used narrow type hives, and did not require hive
management of this nature.
Ian Rumsey
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