>> If a hive drops 244 mites in 24 hours, then drops 78 in the next
>> 24 hours. Is this a typical response?

> Yes, it is.

Not necessarily.

Several competent authorities who have looked at this in detail
hold the view that there is no "typical" number that can be
expected from a 24-hour drop that can produce statistically valid
data for studies, or even "accurate" data for treatment decisions.

This is a bit of a longish story, but perhaps worth reading...

I was surprised myself when I heard this, as one hears everyone
speak of "24-hour drop tests", but the use of a 24-hour drop has
been shown to the satisfaction of MAAREC and the Great Lakes IPM
Group to not yield consistent data.  As a result, they use a
checkerboard pattern sticky-board card that looks like this:
http://www.greatlakesipm.com/pictures/varroa2.jpg

And can be ordered here:
http://www.greatlakesipm.com/wingtraps.html

Now, the white areas are where one counts mites cover 1/3rd of the
board, and one leaves the Vaseline or oil-coated card in for 3 days,
so I had viewed this as adding nothing but complexity versus simply
counting all the mites that fall in a 24-hour period.

Nancy Ostiguy and Maryann Frazier, both of Penn State, gave a talk on
mite monitoring at EAS 2004, and they showed these cards, and even
gave a few to each attendee.

I asked them via e-mail about the intent behind leaving the board in 3
times as long, only to (try to) count mites in 1/3rd the area, and with
more "trash" to confuse the eye as a result of the longer drop period.

Nancy said in an e-mail reply:

  "The reason for needing to leave the sticky board in the
  hive for 3 days is that there is a large variation in mite
  drop within a 24 hour period.  The variation in mite drop
  diminishes with 3-day sticky boards to a statistically
  insignificant level.

  I agree that the amount of debris is greater with a 3-day
  board than with a 24 hour board but making a decision with
  data from a 24 hour board is only slightly better than
  looking for mites on bees as you watch bees fly in and out
  of the hive.

  The boards we leave in for 3 days aren't too debris laden as
  long as we haven't put newspaper between the hive bodies or
  something like that.  Maybe I'm just used to looking through debris."

Quite an eye-opener.

So it appears that one can be massively misled by 24-hour drop tests,
and we should all consider 72-hour tests, with or without the plastic-coated
checkerboard cards.


         jim ("Anarchy" means "spider without legs")

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