Below are some notes from a conversation with a beekeeper who felt he=
 has=20
experienced queen loss from the use of formic acid. I'd be interested=
 to hear of=20
other similar situations.
 
He had 120 colonies in 2 box hives in fall 1993.
 
Concerned with tracheal mites, he got some 85 % formic acid and dilut=
ed to 65 %.
Using a liquor dipenser, he lifted the box and poured 30 - 40 ml  ont=
o the=20
bottom boards of 60 of the hives, in September, evenings, 65 - 70=
 =B0F, 3 times at=20
1 week intervals. Immediately after application, bees bubbled out of =
some hives=20
but not others. The other 60 hives stayed untreated.
 
In late January, early Feb, he briefly looked at all hives and was pl=
eased to=20
find all alive, better than in other years.
 
Hives not treated in fall:
In late Feb, however, he noticed large numbers of bees dead or dying =
outside a=20
group of untreated hives. He took samples of bees, concentrating on t=
he dying=20
hives. The samples were checked and found to be heavily infested with=
 tracheal=20
mites. In about the first week of March, about 20 of the 60 untreated=
 colonies=20
were found either dead or very weak.
On March 11 (and 18?), he treated the remaining untreated hives with =
formic=20
acid, on napkins on the top bars (about 10 =B0C). On March 29, one of=
 these=20
treated colonies was found to have a virgin queen (from the loss of t=
he original=20
queen on March 11?). Another hive had no brood but acted queenright a=
nd was not=20
checked further.
 
Hives treated in fall:
In mid-late March, these colonies were inspected. 12 to 15 (of 60) ha=
d "queen=20
problems". In most cases this was "no worker brood" and the colonies =
were=20
amalgamated with others without further examination. In a few cases, =
the drone=20
brood eggs were examined and found to be singles, indicating a (drone=
 laying)=20
queen. In  2 or 3 others, queens were found, but no worker brood. Act=
ual absence=20
of a queen (laying workers ) was not confirmed in these colonies.=
=20
 
Interpretation (this might be a good Beemaster question)
(Is this an example of queen loss from formic acid use?)
I'd say the Mar 29 observation of a virgin was quite possibly a resul=
t of queen=20
loss on Mar 11, maybe triggered by formic acid disturbance.=20
The apparently large proportion of queen problems in the fall treated=
 group of=20
colonies is less clear. Without knowing if the queens were indeed gon=
e, it's=20
hard not to have a reasonable doubt that the treatments were the caus=
e. I don't=20
know of any recorded cases of formic acid exposure causing queens to =
become=20
drone layers, and the mode of such an action is hard for me to imagin=
e.
 
In future? It might be a good idea for beekeepers who use formic acid=
, to check=20
the treated hives for queenrightness, within a few days after the fin=
al=20
treatment (about 15 days after first exposure). The presence of emerg=
ency cells=20
and unemerged worker brood would be good evidence of formic induced q=
ueen loss.=20
When the possibility of "months ago" queen "loss" or "damage" appears=
,=20
beekeepers should distinguish between queen "absent" or "drone laying=
", then=20
perhaps we can narrow down the circumstances under which actual loss =
may occur.
(Although European reports indicate one might expect up to 10 % queen=
 loss, it=20
is not consistent. Some have treated hundreds of colonies without any=
 noticeable=20
loss)
 
Since unplanned-for fall queen loss has a more serious effect than si=
milar loss=20
in spring, an option would be to use formic acid around May, when col=
onies could=20
requeen themselves if necessary (this spring option might not be as e=
ffective=20
against varroa, since most would be in cells). An adjustment to the f=
all option=20
would be to plan for fall queen loss by producing summer queens, and =
check=20
treated colonies early enough in fall to replace any queens that were=
 lost (this=20
is more work).=20
 
Again, any similar observations or discussion would be appreciated.
 
Kerry Clark, Apiculture Specialist
B.C. Ministry of Agriculture
1201 103 Ave=20
Dawson Creek B.C.=20
=09V1G 4J2  CANADA=09=09 Tel (604) 784-2225=09fax (604) 784-2299=20
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