Me and a collegue are trying to maintain some experimental Varroa
colonies.  We would like to have an absolute estimate of Varroa at any
given point in time to better allocate mites to experiments (and not run
out of mites or have the mites run off on us).  We have been sampling
phoretic mites by both 24 h natural drop onto sticky boards and
collecting bees in ethanol.  Anyone know a study that correlates these
counts with absolute mite numbers ?
 
This spring we brought Varroa infested colonies through the winter
and in :
 
Febuary - 20-90 % of adult bees carried phoretic mites and  24 h natural
drop ranged from 1 - 30 (9 colonies)
April - 3-18 % of adult bees carried phoretic mites and 24 h natural
drop ranged from 24-209 (6 colonies)
 
I think two things are contributing to lower % of phoretic mites on adult
bees and higher natural drop :
 
1 - brood rearing started and there are relatively more bees to mites in
April than in February (hence a lower percentage of mites per bees, but 24 h
drop continues to increase because the absolute number of mites increases)
2 - more mites are reproducing under the cappings of cells in April than
in February, and fewer mites are out on adult bees at a given time
 
So how many mites do we have ?  Without an estimate of mites in the
brood can we really ever know ? Do we really need to sample brood to get an
accurate estimate or can we rely on out of brood estimates (sticky board
counts and adult bee samples)?  How far do we have to go to know if a cell has
mites in it ?  Can we simply knick the cell and the mites will crawl out or do
we have to take the pre-pupa / pupa out of the cell an inspect the whole cell
completely ?
 
If anyone has any leads or ideas and time to reply I would appreciate
your help.
 
Cheers
Adony
 
***********************************
** Adony P. Melathopoulos *********
*** Center for Pest Management ****
**** Simon Fraser University ******
***** Burnaby, British Columbia ***
****** Canada, V5A-1S6 ************
***********************************
 
Tel : (604) 291-4163
Fax : (604) 291-3496
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"The pursuit of agriculture promotes the strength of the mind
 as well as the body"
         - Rev. John L. Blake, 1853