Several European countries joined to study oxalic acid dribbling. If I remember right that was during years 1996 - 1999 or somewhere there. Same tests we done in different years in different countries.

First  result was that  the effect was much better in sugar/water solution than in water alone. After that the right dose was searched.

Some were too small with only 60 - 80 % effect, some were too much. Overdose makes the bees to be restless during winter and kills a lot of bees.  The optimum was found to be 75 g of acid / 1 litre of water / 1 kg of sugar. And the application 4 ml / langstroth frame fully covered with bees.  With this dose there is as many bees in spring as in untreated controls.

In Finland we have not seen any delay in spring brood development. At the moment about 60 % of hives in the whole country  are treated with oxalic. Mainly by dribbling, less than 10 %  by vapour method.

Based on my experience the problems in spring brooding could come from overdose rather than the treatment itself.

Ari Seppälä
Finland

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