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Date: | Wed, 21 Sep 1994 16:11:00 -0700 |
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Hello Jean-Pierre
I've consulted with a few researchers from Europe with experience over
several years, with formic acid treatments. Dr. Ingemar Fries from
Sweden has been very helpful. As I've said, the queen rejection problem
hasn't been enough to measure in the trials (about 500 colonies over 4
years) or in the cooperating operation I work with (1700 hives treated
over 3 years).
A good answer to your question about how much queen rejection to expect
from formic acid treatment, would start with a discussion about the
details of the treatment regime. Different frequencies, and especially
dose size and concentration, can be used to get effective control of
several mite species.
Ingemar says 5 % queen loss from 4 treatments with a commercial source
of pre-moistened blotter material, which is labelled as having "14.2 g
waterfree formic acid", is a typical expectation. (Since waterfree
formic is very expensive, I imagine the plates actually contain some
standard dilution ( 85 % perhaps) with the equivalent of the labelled
amount. His 1989 paper, "Short Interval Treatments with formic acid for
control of varroa .. in cold climates", had 5 of 91 queens lost (all
after the first treatment, 3 were found dead), with that sort of
treatment. He says losses of queens are avoided with the extended or
prolonged-release plates (Kramer).
Two other cases from Canada I could mention: ( 30-40 ml 65% liquid
applied on absorbent paper on top bars)
10 of 30 queens were lost when hives were split in the middle of a 14
day treatment period. The queens lost were some of the ones being
introduced in cages. Not surprising.
In a small group of treated hives, 1 queen (marked) was found on the
bottom board the day after the first treatment. It was found that there
had been 2 queens in the colony.
Generally it sounds not serious, but it's worth finding out how to avoid
things like the case of 150 queens lost of 500.
regards
Kerry Clark, Apiculture Specialist
B.C. Ministry of Agriculture
1201 103 Ave
Dawson Creek B.C.
V1G 4J2 CANADA Tel (604) 784-2225 fax (604) 784-2299
INTERNET [log in to unmask]
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