> I would stay, and use the trickle method...
> The oxalic will overlap a important part of the closed brood, so it
> will still kill most of the emerging varoa's.
> The affect will not be as high as with broodless, but will prevent the
> colony from collapse.

I guess the question is what to do next, after that, since the season is
still ahead in the case we are discussing (in the South), and the varroa are
only cut back a little.  As an example, let's take a look at what happened
in my own operation after oxalic was trickled into my hives at the end of
September:

Take  a look at the red cells in the table at
http://www.honeybeeworld.com/diary/2004/diary110104.htm, and compare them to
the cells immediately to the left.

We see that, on October 22nd, in a matter of about a month after the
treatment, with various amounts of brood in the hives, the *phoretic* varroa
numbers have either stayed the same or increased by up to ten times!

The *total load* of the hives remains unknown, however, since we assume
there was still lots of brood in some of the hives when the oxalic was
applied and we can also assume there was much less brood a month later.

Therefore, maybe the load has not increased -- or actually diminished, but,
if the mite load has diminished, it has not gone down by as much as we might
hope -- or, perhaps, by as much as a southern beekeeper would need, IMO.

This is one specific case we happen to have measurements for.  The case we
are discussing might be different, in a number of ways.  For one thing, I
can safely assume, from previous observations, that we had no drone brood in
Fall.

The problem with trickling, is that -- I am told -- we can only use oxalic
*once* on a generation of bees, and must wait until the bees have replaced
themselves -- about six weeks in summer -- to treat again with trickling.

Is this true?  I had heard that in respect to elevated wintering loss in
cases where the trickling was done more than once in Fall.  Maybe it is not
a concern in Spring and Summer?

Anyhow, I have read that repeated treatments with oxalic vapour do not
increase losses, and so have tended to favour evaporation over trickling.
Some of these things may not be proven, but just speculation.

Anyone know the facts?

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

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