> Each frame must be removed and all bees sprayed in order to get
> contact with those mites on the bees. It is suggested that you do
> this once a week for three weeks in order to get the mites
> protected in the sealed cells.

This method has a lot of people excited, and it may work in some areas where
it is warm all year, but I suspect that in the North, where I live, it will
be of limited usefulness for reasons detailed below.

One of my main concerns is that, if done in the fall, after brood has
hatched, such extreme and repeated manipulation of the hives, even without
the spraying, would result in at least 50% subsequent losses over winter.

> This varroacide kills approximately 68% of total mites contacted in
> the first spray. So, after three sprays, assuming complete coverage,
> 99% of mites should be dead.

I don't get the same result when I do the numbers.  Maybe I'm missing
something, so please correct me if I am.  Here are my calculations:

If the treatment begins when the brood rearing is 100% over for the year,
and assuming that each treatment kills 68% of the mites, there will be
(100%-68%)=32% left alive each time.  For three treatments, we calculate
thus:  100%*0.32*0.32*0.32 = 3.3% left.  Depending on original levels, that
may not be too bad, but that is not 99%, and, besides, then half or more of
the hives die over winter from the aftereffects of manipulation late in the
season...

We must also consider that, at our latitude, in the fall, after the brood
rearing ceases, the weather is probably not warm enough over three weeks to
remove all the combs and wet the bees safely.   Moreover, when we do have a
warm spell, the warm part of the day can be very short, and there is not
much time to accomplish much if more than a few hives must be treated.

If the treatment is done in late spring or summer, when there is normal
brood rearing and the bees can stand the man-handling, we can assume that,
say, 50% of the mites would be hidden in the brood and thus protected each
time, so the efficacy would be 68%/2 each time, or 34%.

If a 34% treatment is repeated three times, then, since 66% remain each
time, it seems that 100%*0.66*0.66*0.66 = 29% of the total remain after
treatment.

In some cases, that may be a sufficient reduction, but, from the
description, it seems to me to be an awful lot of work and expense to
achieve that small a result.

Maybe I'm missing something, but for my region, I think that it would be a
lot of work for small results.  This process may have application for
beekeepers with a few hives and lots of time to play with the bees, and it
is safe for the beekeeper.  That is good.  However, for the Northern
commercial beekeeper, it seems to me that something a bit more effective, a
lot quicker, and much less invasive is needed.

allen
http://www.honeybeeworld.com/diary/

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