(I was asked for some clarification of an article I wrote, on the loss
   of queens (or at least peception by the colony, of a loss of the queen)
   following application of formic acid for mite control. I'm responding
   via the list, in hope of hearing from anyone who has experience with the
   problem.)
 
   (Background: Formic acid liquid is used in some areas, for killing
   parasitic mites in honey bee colonies. Sometimes (rarely in my
   experience) colonies which have been treated behave as if their queens
   have dissappeared: building emergency queen cells. At that point, a
   beekeeper would likely introduce a mated queen to keep the colony going.
   Sometimes, when such queens were not available, the original queen
   reappears. In other cases, the queen has apparently been killed by the
   bees.)
 
    I have reports of the following cases:
   1) 10 queens reported lost out of 10, with the use of 85 % acid (as
   opposed to the usual 65 % concentration),
   2) 124 queens gone out of 220, using about 40 ml 65 % (field diluted
   from 90 %) at about 90 deg F.
   3) 60 queens gone out of 380, in single Langstroth hives, using 15 ml of
   65 %, at 16 deg C.
   4)  a single hive which built emergency cells after treatment (30 ml x
   65 % liquid on bottom board), but subsequently had the old queen still
   laying.
   5) several of about 10 hives (of about 20 treated) which did as in # 4
   6) 153 of 480 2 box Langtroth colonies, built emergency cells after they
   were treated May 20, 17 deg C. with 32 ml 65 %, on absorbent pads on the
   top bars.
 
   While cases 1 and 2 appear explainable by the concentration or
   temperature, the others are not as easily explained. No these are not
   controlled observations, with untreated control groups to indicate
   whether the cells resulted from the treatment, but the presence of so
   many synchronised emergency cells convinces most beekeepers who
   experience it, that the effect is real.
 
   The beekeeper reporting Case #3 suggested that the hives losing their
   queens were (maybe) the stronger ones. Other cases, with less specific
   losses (not counted) the beekeeper suggested the hives with older queens
   were the ones most frequently affected. Another suggested it was mostly
   queens from a specific queen breeder. Another speculated that the lost
   queens were infested by tracheal mites.
 
   The effect has been reported often enough to be a consideration in
   formic acid use, but not enough to make it a high prioity to try to
   reproduce and study, yet. I've been hoping that a pattern would emerge
   in the beekeeper reports, that could then be confirmed experimentaly.
 
 
 
   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
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