Because of potential damage to brood and young bees from Oxalic, the
best time to use it would be in the autumn (fall) when there is not much
brood. This is also fortuitously the time of year when temperatures are
a bit variable and thus not too suitable for Formic evaporation. Formic
is more suitable for stable temperature periods (when there will also be
more brood).

The two acids therefore appear to be complementary as treatments.

In addition "integrated" treatments with different solutions throughout
the year is a healthy method of avoiding varroa resistance.

Alan R
Edinburgh
Scotland