>> One thing we have now noticed is that the hives with high mite loads
>> are all in polystyrene hives.  One 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...
> 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

> 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.

Our observations are somewhat accidental, a byproduct of an oxalic
experiment. (FWIW, the drizzling of oxalic did not seem to work, possibly
because it was done too early).

From the table at http://www.honeybeeworld.com/diary/, it is clear that the
styro hives are in serious danger of loss after about 18 months from the
last Apistan(r) treatment, while the wooden hives (except one) show very low
levels.

The difference between the two hive types is very apparent.  We did not
treat the wooden hives (except one), but we did treat all the styro hives
(except two), and then treated them again when the oxalic failed to control
the mites.  Even at that, I am quite sure we will lose some of the hives,
particularly the one with 84% mite load. (That means that there are 84 mites
for each 100 bees!)

All this is not to say that styro hives are not superior.  Our Winter
survival is the same in wood (wrapped) and styro.  Production seems about
the same (not actually measured).  We got as many or more Spring splits in
styro, and there is less work, since there is no need for wrapping or
unwrapping.

My strong suspicion, based on a chance discovery that needs further proving,
is that, given the same bees and location (one only so far), varroa may
build to problem levels much more quickly in styro boxes and need controls
sooner.

allen
A Beekeeper's Diary: http://www.honeybeeworld.com/diary/

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