> Can anyone tell me what percentage of the total mite population can
> be detected in a 24-hour natural mite drop?  Is there a formula to
> suggest how many total mites each fallen mite represents?

Natural drop has been my chosen method of monitoring for some years now, and
my experiences can be found in the selected topics section of my diary
(http://www.honeybeeworld.com/diary/menus/topics.htm).  A Google search from
the bottom of that page using the words 'natural' and 'drop' yields a few
hits.  Somehow, I had thought that I had documented my experience and
thinking better, maybe I have -- somewhere (here?) --but there there is some
practical info (illustrated) there.  Also on that page there is a listing of
varroa resources that might turn up something you have not seen.

There are problems with any measurement method, and the natural drop is
dependant on assumptions.  One is the lifespan of the varroa in the hive at
the point in time that the measurement is taken.  Season, phoresy, varroa
levels in the hive, hive populations, brood area, history of the hive and
more will have an influence on this number. Moreover, bees have been
observed to stage episodes of mite detection and ejection (Thanks, Dee),
that might just happen to coincide with the days of your measurement and
give inflated results.

For those reasons, ND is just a rough guide, but a good and easy one.  If ND
turns up unexpected results, then the beekeeper needs to drill down further
by consulting previous data, doing brood inspections, acohol washes, asking
neighbours what they are seeing, etc. etc. -- or just treat ...whatever
seems to be appropriate to the size of operation, resources, and the
timeframe available before remedial measures are not possible.

We use 100 days as varroa lifespan, and hence a multiplier.  Others use 30.
No matter.  What you get is merely a number, and your decision will depend
on what you turn up in additional investigation, your location, your
appetite for risk, your opinion of chemicals, and the weather.

As GEORGE says, I hope I have helped.

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

 In theory, there is no difference between theory and practice; In practice,
there is.   -- Chuck Reid

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