Odla wrote:

OK. Oxalic acid kill the varroa. No doubt about it. But it is not the
> whole picture!


I would definitely say that idea that oxalic acid is very harmful to bees is 
also not the whole picture. I have been looking the situation in Finland. 
During 5 past years use of oxalic has risen from about 0 so that last fall 
almost 80 % of hives ( = 40 000 hives) were treated with it. For many hives 
it was the only varroa treatment. I have a friend who has treated his bees 
only with it for 3 years one tricling / year at late fall. His winter losses 
average for these years less than 5 % and last year he got a 120 kg average 
crop from his 100 hives. His varroa levels are down to average of 200 / hive 
before treatment in fall. ( In Finland we have a long broodless period so 
one treatment is enough for many of us) .

When I look the picture in whole country the past two years we have got 
excellent crops, with national averages that we normally see only once every 
10 - 20 years. OK good weather has lot to do, but if oxalic is really 
harmful, how could this be with 75 - 80 % of hives treated with it ?

One explanation to comments about harmful oxalic is misunderstandings about 
its abilities. If you have a hive with a lot of varroa/ virus at the fall, 
oxalic is no miracle. If the winter bees have already been damaged in pupal 
stage by mites they will not live long even when the mites are removed by 
oxalic. Oxalic in late fall is not a safe for the coming winter but for the 
winter after that. It is a tool that gives you a very low mite count next 
spring so that you can in many situations in north go through the summer 
without any problems and even at next fall have only few hundred mites in 
hive., which again are easily cleared by oxalic.

I know what I say because I have been conduction a study of varroa 
treatments for 6 years. I have had 13 beekeepers doing the tests with about 
150 hives/ year. So at least here in Finland I can say that if you have a 
lot of mites ( mote than 300) in end of July you must treat with something 
to protect the developing winter bees for the hive to survive. + use oxalic 
later. If you have less only oxalic is enough. During the 6 year study 85 % 
of the hives have come down to mite levels that only need one oxalic 
treatment. We have not seen any disease outbreaks in the hives in the study. 
Their overwintering has been much better than national average. And the 
other  beekeepers using oxalic have not reported it othervice.

All chemicals are bad to bees at some level. But when used the right way 
oxalic is not a danger for the well beeing of honeybees.

Ari Seppälä

Finland

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