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Date: | Wed, 2 Dec 2009 10:00:32 +0200 |
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> What we do not know is what type of drop will a lighter dose provide?
At some posts about oxalic there was pointed that a lot more experiences is
in Europe. That might be true. I wrote a story '10 years of oxalic use' in
our bee magazine last year.
In 1997 - 1999 the basic research about oxalic acid use was done. The work
was done as group research. People from different countries agreed on the
tests and the methods. This way it was possible to test many variations in
different situations. First tests concluded that oxalic+sugar+water worked
much better than just oxalic and water. This is most likely because water
solution dries much faster in the hive.
Then next year we had test for different concentrations. In the end the dose
75 g oxalic + 1 kg sugar + 1 litre water gave most consistent results for
90 - 95 %mite drop in hives without brood. 50 g worked too but results
averaged about 85 % drop, but variation is big. That why 75 grams was
recommended for use. There was also follow up for spring development. In
these results differences were not big, but 50 gram group tended to have
more bees. No statistical difference.
As a advicer I always recommend the beekeepers to mix like this: 75 g oxalic
+ 1 kg sugar + 1 litre water. Easy to remember. To use ready sugar liquid is
more work cleaning the measuring cup than making it with water and dry
sugar.
My friend is going for resistant bees and he gradually stopped oxalic
treatments. From his data we saw that oxalic gave surprising good drops of
mites with just 10 ml/ big hive. If you give the same small amount of oaxlic
in more diluted solution t will not work as well.
So in summary I would say that you can give less than recommended oxalic
treatment and still get reasonably good results, but variation in efficacy
will be bigger than in recommended amounts.
During last few years the trend here has been that many are going for fall
and spring treatment with tricling. This way they use only oxalic against
varroa. Spring use is just after first flight before the bees start to raise
brood in bigger amounts. Some years you can treat in spring without any
brood, but time window is small.
Treating twice in fall will result in big problems. It was hard for me to
believe that bees that can not tolerate 2 treatments in fall with 1 - 2
months apart, do tolerate treatment in November and again in March. It must
be in more time and chance to fly.
I have treated 80 % of my own bees this fall, and need to do the rest fast
before winter really starts.
Ari Seppälä
Finland
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