Jorn Johanesson wrote:
> Hello beekeepers!
>
> The reason for the brood less and thereby autumn  treatment by oxalic acid
> is that the oxalic acid is not killing varroa mites in capped cells, it will
> simply not go though the capping. That's why it is recommended to do a
> spring treatment with formic acid, because this treatment will also kill
> varroa in capped cells.

If you needed to use Oxalic Acid for a summer treatment because of mite
load, it would be as effective as many of the unauthorized (and
authorized) treatment methods. 70% is the general range of effective
mite kill when brood is present.

The reason it is used in the fall is because it is effective but only as
a single treatment (the vapor/evaporation method does not seem to have
that drawback). Hence, when used with a broodless colony, you get the
same or close to the same efficacy as approved strips.

Oxalic is an excellent miticide in any of its application methods. It
leaves little residue (over what is natural) in honey compared to Thymol
or Formic Acid. In vapor form, it can be applied easily and gives
excellent results.

But. We are not talking about a benign chemical. If you are going to use
it in an evaporator, unless you dress accordingly and have a respirator,
you are in about as much danger as the mites you are treating. It is too
easy to get casual when doing many repetite actions. Just ask a short
fingered carpenter.

Even thought the additional Oxalic does not show up in honey (like
Formic it is in honey naturally), the publicity surrounding a serious
incident to a beekeeper treating with Oxalic would be as damaging as if
it were in the honey. How do you explain to the public that the "poison
gas" the beekeeper was "spraying" into the hives and hurt him will not
cause them harm if they eat that honey?

Bill Truesdell
Bath, Maine

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