Tom Barrett wrote:

> If you go to the following website you can download an excellent booklet
> from New Zealand which gives (IMHO) excellent information on all varroa
> treatments including oxalic acid.
>
> http://www.maf.govt.nz/biosecurity/pests-diseases/animals/varroa/control-of-
> varroa-guide.pdf

In my research (on the web) of Oxalic Acid drip treatments one thing
that came across is the variability of concentrations of the acid used
in treatment, along with the dosage. The only site which had any trials
done that were fairly rigorous and where they trialed different dosages
gave the following:

Quote:
RECOMMENDATIONS for the drip treatment with oxalic acid
(Switzerland and Central Europe)
Composition of the solution: 35 g oxalic acid dihydrate in 1 litre sugar
syrup 1:1
Quantity: 30 ml for a small colony
40 ml for a medium colony
50 ml for a large colony
This quantity corresponds to 5 – 6 ml for each occupied bee-space of a
Dadant or Swiss
hive.
Unquote:

This is less than the concentration recommended on the NZ site. It also
looks like more frames are treated in the NZ recommendations. So the NZ
recommendations are well above the dosage recommended for Europe.

When greater concentrations were used in the trials in Europe more bees
died (and they only got up to about 50gms). I have seen recommendations
of 100 gms per liter (litre)!

Of interest. If you use too little it is ineffective but too much kills
bees. Since greater concentrations will weaken a hive going into a cold
winter, you might get away with the greater concentrations in NZ but not
Europe, since the bees will recover in a warm climate. Local climate
plays an important role in treatment.

So caveat emptor when it comes to using Oxalic Acid (drip treatment) and
treating bees.

Bill Truesdell
Bath, Me