In message <000901c4c096$efc4b550$1db85ad1@Nemo>, allen dick
<[log in to unmask]> writes
>One thing we have now noticed is that the hives with high mite loads are all
>in polystyrene hives.  On is in wood.  The low infestation hives are all
>wood.
>
>Just guessing -- unless this is a fluke -- it looks as if the longer brood
>rearing that takes place in styro hives may favour varroa!

 From what I can see Allen, there is something in this observation.

Here we get the colonies carrying their strength much later into the
season in these boxes than in the wooden ones, with a lot of brood still
present in late August, where the wood ones had, to a large extent,
closed down.

However, the colonies we see are larger as well, and they produce more
honey late season, so the bees in general do seem to favour these hives
over the wood. The winter losses in them here are far lower than in the
wooden ones, even allowing for the mites issue. I think I would still
prefer a generation of young bees for winter over an early shut down,
even if there is a cost in terms of increased varroa load.

The spring development of a brood nest also seems to get underway a
little slower in the polys for some reason, but catches up and overtakes
very quickly. It does seem as if the bees have less temperature
regulation to do in these boxes in the winter months so the 'ticking
over' brood nest is not universal in them as it is in wood here after
the shortest day.

I suspect that the presence of significant amounts of brood late in the
season, when the growth of the mite population is also at its steepest,
gives rise to this effect. However, it does seem to be manageable, and
at this time, even after a big varroa hit last year, the problem with
polys is not keeping the colony numbers up, it is keeping the numbers
down.

I suspect from observation that the increased mite load given rise to by
the extra breeding is not sufficiently large to accelerate collapse by
any more than a few weeks in a 'don't treat and lets see what happens'
situation over 3/4 year cycle from clean.


--
Murray McGregor

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