"Robin Dartington" wrote:

> We have to go beyond the obvious to devise a control strategy.

The 'obvious' is sometimes overlooked by those who bury themselves in a
surfeit of data.

> Mark Winston shows charts of the % of colonies that die with various
varroa loads...

But only under the conditions applying at that time - he could not possibly
have looked at every possible variable.

> 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.

'The UK strategy' is a bit too broad brush for me!  It may be the official
line from the NBU, but their hands were tied in the strategies that they
were able to recommend.  Many of us have used alternative strategies very
successfully for a long time.

> 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.

Surely that is not entirely correct?  Which virus are we talking about here?
My understanding is that APV present in late summer will, if there are
sufficient varroa present to act as vectors, lead to winter bees that will
only survive for an average 88 days - so the colony probably dies out,
slowly, and probably collapses in January.  DWV can reduce the number of
foragers dramatically, leading to early collapse of the colony.

> 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

Not necessarily.  It depends on your definition of control system - and
there are other ways of monitoring.

>we do not seem to be too sure whether the factor in summer is 30x daily
mite
> fall or 100.

And never will - there are just too many variables.  A single multiplier
could only work under standard conditions - colony strength, type of bee,
type of hive, the season, forage, numbers and type of other pathogens
present - need I go on?

Peter Edwards
[log in to unmask]
www.stratford-upon-avon.freeserve.co.uk/

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