I'd like to direct this question about tracheal mites testing to
those who are knowledgable about the question of mite testing and
treatment - specifically bee scientists and commercial beekeepers:
 
First some background:
 
Last year we found that the 25th bee sampled from the honey house
windows had tracheal mite damage.  Tests this year, we had exactly
the same results.
 
I've gathered samples of about a hundred bees from a number of
yards, now and started pulling them apart.  I've done about 20 from
each of several yards and found nothing.
 
The Problem:
 
I'm wondering how many bees I should do from each yard.  We have
about 24 hives per yard and I guess the number to look at from each
sample depends on the level of infestation that is considered the
threshold for requiring treatment.
 
I unfortunately don't know how to do stats (I really should learn),
but I do know that if you are looking for - say 20% infestation in 1
of 24 hives that may have lower or no infestation - that there is a
function to determine the number to do that would give 95%
certainty.  can someone help me with this?
 
Some Considerations:
 
The management decision involved here is that there is a cost in
testing and there is a cost in treating.  The sum of these should
ideally be lower than the expected loss resulting from undetected or
untreated hives dying in winter. Therefore, testing costs are only
worth incurring if there is a a reason to assume some measure of
risk exists.
 
However the testing cost is already spent by the time one knows if
there is any risk of loss. So at that point, only the costs of
treatment (including any loss due to treatment) must be less than
the expected costs of not treating.
 
My first run at this assumes that a surviving hive is worth $75
in the spring and that a hive dying of TM is going to consume about
$10 worth of feed before succumbing and it will cost $5 to clean up
the mess.  So if it costs $90 to treat a yard to save only one hive,
It is only questionably worthwhile.
 
Here are the questions:
 
1. At what infestation level in an *individual hive* should
       one treat in the fall?
 
2. What sampling level of *each yard* should provide adequate
       indication of such a need?
 
3. Is it sufficient to only look for darkening in the trachea
       when checking (very fast and easy), or is it necessary
       to look for more subtle signs of mites in bees?
 
 
 
 
 
 
Regards
 
Allen
 
W. Allen Dick, Beekeeper                                    VE6CFK
Rural Route One, Swalwell, Alberta  Canada  T0M 1Y0
Honey. Bees, Art, & Futures <http://www.cuug.ab.ca:8001/~dicka>