An IPM question:
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The Scenario

We have about 2,400 hives in winter.  They are in about 66 yards.  That
gives us around 35 hives per yard average.

We went out and opened all the hives in 10 yards -- chosen at random -- and
took out 5 bees each and put them into sample bottles with 70% isopropyl
alcohol, using one such bottle per yard.  4.5% of the hives examined were
dead.  No samples were taken from them.

We then had a trained person shake each bottle and look for varroa in the
alcohol, which was poured through a screen, examined, and then returned to
the bottle.  No varroa were found.

A suitable amount of water was added to dilute the alcohol to 50% and 24
(+/-) hours later, 20 bees from each sample were pulled apart and the
trachea examined for mites and eggs.  None were found.

The abdomens of each group of 20 test bees were then macerated and the
slurry examined for nosema spores.  The tests were all negative.

(The following is mentioned only to show that the lab can be considered
capable of finding mites: At the same time, in the same lab, three samples
were processed for another beekeeper.  One revealed one varroa mite.  Two
revealed some tracheal and eggs, and none showed nosema).


The Questions:

Considering only the 2,400 hive operation described, and neglecting the
friend's problem(s)...

* Can you state the results numerically and also calculate the degree of
confidence?

* Were sufficient bees examined to give reasonable certainty?

* What are potential sources of bias or error?  Do you suspect and errors in
sampling?

* How much should we trust the results?

What, if anything, can we conclude from the tests performed here?

* Is any treatment indicated?  If so for what disease or pest?

* What further action, if any, is indicated?

* The balance of the original samples are being preserved.  At what point
may they be discarded?

* Compare the cost of an IPM approach like this to routine blanket treatment
without sampling.

Have fun.

allen
http://www.internode.net/HoneyBee/Diary/