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Informed Discussion of Beekeeping Issues and Bee Biology

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Subject:
From:
Robin Dartington <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Thu, 26 Aug 2004 09:57:46 +0100
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 "Peter Edwards" if there is virus present
> then higher levels of varroa will cause more virus to be injected and
> therefore more bees will die; ...  fairly obvious ......"

We have to go beyond the obvious to devise a control strategy.  Mark Winston
shows charts of the % of colonies that die with various varroa loads...some
numbers.
The UK strategy so far has been to allow varroa to rise to a peak in late
summer (say 2,500), and reduce with Apistan (95% efficient) to say 125 -
then apply Apistan again in spring if varroa level is too high to wait until
late summer once more.  This has ignored the virus effect - that a high
level of virus in late summer will take until say mid autumn to die back
when the effected bees die out(and their direct contacts) die.  And , as has
been said, noone has got to the point of sophistication where we can
estimate the loss of honey production due to the rising level of virus
during the early summer.  So we need more numbers on the effect of virus and
the associated varroa level.  Perhaps the varroa problem is 'solved' when we
know the  level varroa should be kept down to throughout the year (say 300
and 1,000) - calling for a succession of mild treatments, each of which does
not need to be highly efficient.  A 50% reduction would curb 1,000 back to
500 - and substances (such as thymol) that reduce varroa reproduction might
slow if not stop population growth.  So we could consider again various
substances (?tea tree oil?) that have been discarded because they were not
efficient enough for the one big annual hit strategy - but could help in a
persistent attrition strategy.
These thoughts are not new but where is the leading edge today on this
approach?  Can anyone say?  We do need an alternative to the breeding of a
few super-lines of resistant bees that would make all beekeepers dependent
on a few queen producers.
This thread started on the question of how to relate mite fall to overall
varroa population.  That is an essential part of any control system - and we
do not seem to be too sure whether the factor in summer is 30x daily mite
fall or 100.  Still a very confusing picture to explain to the new
beekeeper.

Robin Dartington

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