Trevor said:
Several scientists, from north America, I have spoken to urge caution with
the pin kill method.  The reason is that the hemolymph leaks out of the pin
hole.  It is suggested that bees will respond to this and uncap and remove
the pupae even if they do not have "hygienic behaviour".

 I believe the problem will be eliminated if you come in from the back side
or mid rib.

I believe both the pin test and the liquid nitro test will give satisfactory
results if done correctly.

The Liquid nitro test has its drawbacks also. If you squish brood in an
effort to seal the canister from leaks. This massive assault to the comb in
that general area will also trigger the cleaning out of the area  thus
leading to inaccurate readings.

I believe Pettis did some work and found he got 100% with pin kill. Pin kill
is certainly harder to do than liquid nitro.

Bottom line liquid nitrogen is better  and less expensive if doing more than
twenty five colonies which  is the bare minimum for any viable breeding
program.

Bob

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