> >>From what I understood, based on a study that OA
> > miticide effect is mostly due to low pH solution
> (and
> > not from oxalate salts as originally expected)...
>
> Could you cite the study?

Here is the link (copied and pasted from a post on the
Belgian list):

http://www.apis.admin.ch/host/varroa/udine.htm

The
> oxalic is diluted so
> organic acids like vinegar should also work but some
> do and some do not.

As a small amateur beekeeper, I have not the full
explanation.
But, with regard to pH, it seems to me that most of
organic acids are weak acids. Some acids constants :
Oxalic : pKa1(25C)= 4.19
         pKa2(25C)= 1.23
Acetic (vinegar) : pKa(25C)= 4.75
Formic (in solution) :  pKa(20C)= 3.75

Oxalic is a diacid the second acidity is quite strong
compared to most organic acids in solution. It could
be compared with strong inorganic acids as sulfurous
acid : pKa2(18C)= 1.81.

Moreover, even if low pH is the main factor for oxalic
acid according to the above link, it does not mean it
is the same for others (weaker).

> And why does a sugar solution of oxalic work better
> than just water? It
> appears something else is at work, not just contact.

I would agree with you, but it would just be an "a
priori". Last time I asked a reseacher for the OA
mechanism of action on varroa, he answered to me he
did not know while he was presenting a study comparing
field results with OA and other products. So I guess
the issue is still not clear.

> Not unusual to have a lot of theorizing as to how
> something works, but
> this one seems counter to other observations.

???
I just tried to answere the original question
(reporting hearings about similar observations) and
tried to share information. The more people will
share, the more I could progress, and respectively I
hope.

Respectfully,

Hervé








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