> The method I was made aware of is to use a crystal form and to vaporize
> it into the hive from the entrance.  The treatment would last 3 minutes
> and then the entrance would be sealed off for 10 minutes.  This type of
> treatment would supposedly cost $0.05 a hive.  They are boasting a "up to
> 99% effectiveness" with 5.0G of Oxalic Acid.

My neighbours have a German bee magazine that had an in-depth article on
this last winter.  Apparently it does work very well.  There was also a
Canadian beekeeper who was spamming everyone on the topic back in the
spring, and apparently trying to sell the appliance.  I think that turned a
lot of us off.

The evaporation method is cheap and simple, and apparently very effective.
Even one application has effects lasting for weeks, apparently due to the
vapour condensing to small crystals that endure for a while.  The honey
contamination hazard is low, and -- for that matter -- I believe that when
ingested in very small amounts, oxalic acid is not particularly harmful.
It is however dangerous in larger amounts and higher concentrations, and
can be dangerous to handle in bulk.  I know it from using it in a
heavy-duty automotive radiator flush, and from use as a special-purpose
laundry bleach.  It is also used to bleach wood, I believe.

I have been sent some translations of some German documents that outline
some scientific tests of the method, and think I am at liberty distribute
them.  If anyone cares to follow this up, I can look into it further (but
I'm hoping that others will come forward here and save me the trouble).

I think we all can see the hand writing on the wall as far as fluvalinate
and coumaphos are concerned, and although having to find a replacement has
its risks and inconveniences, I don't think any of us will grieve much to
see them go.  They were emergency stop-gap measures which saved the day for
many of us while we got ready to learn more about less hazardous controls.
I think vaporized oxalic may be one.

allen
http://www.internode.net/honeybee/diary/