Bill wrote: >>>  Just a data point, but I treated both hives Friday and
mite counts Saturday
were 1 mite in the strong hive and zero in the weak hive. Recall from my
prior posts that both hives had mite counts after robbing/invasion in
Sept/Oct of about 4-600 for first treatment, 200 for second and about 100
for third and those were followed with a single Thanksgiving Friday
treatment. So more than five months have passed since the last treatment.<<<


Bill, I am following your notes on OAV with interest as you are relatively
close to my location and I am also evaluating OAV (fourth year using it
this year).

I am interested whether you were able to get a drop count for the last
treatment?  My final treatments were Nov 19 - Dec 1, the Dec 1 treatment
was done at a temp of +5/+6C  (about 41-43F).  This final one gave a drop
of 3 mites/sq inch in scattered clusters.  Most squares were nul, no
mites.  I have not been counting total drop, but will try to do so this
year to enable experimentation with Randy's model.   I would guess my last
treatment total drop was less than 50.

Do your colonies have open brood yet and are you concerned about using OAV
if so?  I found mine very late to start brood rearing this spring due to
the cold weather, several had no brood at all on May 2 (hives are
insulated).

There was a discussion back in March regarding OAV and open brood but only
anecdotal information surfaced regarding adverse effects.  I have searched
for published work regarding OAV/open brood effects, but pretty much all I
found was about OA dribble.  The closest I got to something useful was:

Vaporisation of oxalic acid in a field trial with 1,509 colonies. Thomas
Radetzki (2001)
http://www.honeybeeworld.com/diary/files/__www.mellifera.de_engl2.pdf

However this was still not enlightening regarding actual effects of OAV on
brood.  The author found a slightly lower efficacy of the OAV treatment if
brood were present, but did not report on any effects on the brood.

I am still evaluating spring mite levels and have not treated yet.

Rob Hughes

Upper Kingsclear, NB

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