From: "Bob Harrison" "Mark Winston is simply repeating what was learned
early on at the
start of the varroa problem."
Yes, but this theme has shown beekeepers are forgetting. To solve a problem,
you must remember what the problem is. So, again, it is virus that kill
colonies - as virus cannot be treated directly so we control varroa as the
'carrier' (in a loose sense). However, kill all varroa and the colony still
has the same high level of virus - until it dies down naturally, perhaps
over say 6 to 10 weeks.
What we have been discussing is not the importance of controlling varroa
but to what level - at what threshold to treat. The agricultural concept of
'economic injury level' and treatment threshold were introduced and I feel
made clear that varroa control is far less calculable than crop IPM where
beetles eat berries on bushes. Farmers treat if the value of saved berries
will be greater than the cost of treatment, not when the bush itself will
die if they delay - whereas beekeepers have not yet reached the stage of
thinking of saving honey, but only of stopping colonies from dying.
In UK, we have taught to treat if varroa will exceed 2,500 by autumn - not
to treat if only at a low level. Now lower figues are mentioned - because
virus increases with much lower levels, and takes time to clear. I begin
to wonder if we will not end up feeling 'a good varroa is a dead varroa' -
that ANY level is harmful to honey production. If so, then the best
strategy will be constant attrition, not an annual treatment that goes for
one big kill.
Again , Bob, nothing new, but worth discussing. Your concern is for the
honey industry and you are clearly going hard for bees that will keep varroa
at low levels by themselves. But as u say, beekeepers will become
dependent on buying all new queens from a few pure lines. As said before,
that may suit the honey industry but not hobbyists who far outnumber the
professionals. We will stay interested in ways to introduce attrition into
the management of our locally-adapted bees. It will help us when the
association of virus with varroa is better understood and we knew better
what maximum level of varroa an attrition strategy should really aim for.
Till then, we are shooting blind when culling drone brood, forming
artificial swarms, adding formic acid pads, spraying SOE or whatever.
You say: " Come up with a solution other than a reduction in varroa load in
the hive and beekeepers might pay attention" Still the search for the Holy
Grail. I suspect enough solutions for a workable attrition strategy already
exist, after the vast efforts of the last 15 years. The problem now seems
to be to find more practical ways of applying them - not new ideas, but
better practice. Perhaps releasing thymol vapour at low levels all year
round by pressing capsules into the centre of the brood nest, rather than
from cages partly dependent on outside temperature. Perhaps quickly dumping
bees outside and spraying SOE as they run back, rather than frame by frame.
Perhaps simpler, cheaper ways to vapourise oxalic acid, on the analogy of
self-heating soup. I appreciate any such approach will always be too
labour-intensive for professional beekeeping. As professionals have more
influence than hobbyists on research grants, and you are going for bee
breeding, amateurs and professionals may have to go different ways on this -
I have been told several times in UK that beekeepers will have to take
responsibilty for finding their own ways to manage varroa post-Apistan - and
have a fear I know what underlies this - that we are indeed on our own.
We can start by remembering what Mark Winston explains on virus/varroa -
then try various combinations of successive treatments that lower varroa at
each stage - record results - and hope a world-wide database on experience
so gained will be set up one day.
Robin Dartington
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