Great discussion!

Dick, I agree with Charlie's observation--formic vapors definitely drop
down over the combs, out the entrance, and then down onto the ground in
enough concentration to kill grass.  Amrine suggested that formic dissolved
50% in water behaves oddly in air, and I have searched the literature for
confirmation, finding only one chemistry resource that suggested as much,
so don't know.

There is thus the strong possibility that formic vapors indeed pool on the
bottom board.  Ruzicka (without presented data) says that putting a dam
across the entrance helps to trap those vapors on the bottom board,
increasing efficacy of his product.

Chapleau used a bottom flash board with good effect.  A bottom treatment,
if appropriately applied, would mean that any incoming air (provided that
there was only one entrance) would mix with the formic vapors, and thus
fumigate the entire hive.

I recently purchased an air sampling kit, and plan to get data on the
actual behavior of formic vapors in the hive.

>Canadians now have a different formular where they start at 40 mls and
take off a ml for every degree of temperature to stop bee damage on hot
days. eg 40 - 15 degC = 25 mls

I tested various amounts of 65% flash on singles and nucs this spring at
around 26C.  40-26 = 14 ml.  This figure seems far too low to me, and would
not give much efficacy.  I found that about 40 ml on a single was about
right, slightly less on a nuc.

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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