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Date: | Thu, 16 May 2013 11:55:05 -0400 |
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Bee-Quick gave a good explanation. Personally, "everyone uses" isn't a
good justification for freezing LARGE areas. Three inches is a tad on the
large size - don't go bigger.
Our initial data demonstrated that smaller areas, at least 2 or 3 over
more than 1 side of one frame provided a MORE ACCURATE test. Freeze too
large an area, and any hive will uncap and remove. Keep the frozen patches
small.
I prefer keeping the freeze area down to no more than 2 inches in
diameter, and you can reduce the amount of liquid nitrogen per tube proportionally.
I use thin-wall aluminum tubing from the hardware store. Medhat used a
butter dish.
As per dry ice, CO2 from fire extinguisher, any number of gases that freeze
when they hit the air (like the ones used to freeze off warts) - I agree,
the liquid nitrogen is hazardous. We developed this method for EPA as a
test to be used in assessments of brood survival in colonies placed on
hazardous waste sites. The data had to be able to hold up in court.
We did NOT anticipate the average beekeeper would be using this. Pat
Heitkham was one of the first, and he borrowed a dewer from his local cattle
AI guy. Marla said he couldn't use my test, and he decided and proved that
he could.
So, I'm all in favor of a SAFER alternative. Cold is cold. For accuracy
of the test, you need to minimize damage to the comb AND you need to
thoroughly freeze the brood. Frost-bite isn't sufficient. We found dry ice to
be slow and CO2 will put bees to sleep and even kill them. Not a problem
in open air, but don't drop into a hive - we use it to kill off colonies at
the end of experiments where we need to gather bees.
When we were developing a way to be sure the bees were frozen (DEAD), our
criteria was simple. Pick an area of the comb that has pupae on both
sides. Freeze the test area with your method of choice. When you go in to
complete the test, flip the comb over. If you completely froze the test
area, you should have frozen at least some of the pupae in the same place on
the reverse side of the comb.
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