------- Forwarded Message Follows -------
 To:  Multiple recipients of BEEL
 Gary wrore:
 
> I've been having more than my share of acarine related winter losses
> the last 4 years . Way more. What I'm wondering is are there truly   acarine
> resistant queens out there? I bought queens from 4 sources last year
> all of whom claimed at least some resistance. Initial spot checks on my
> outdoor wintered colonies show up to 50% loss in some yards. With the boxes
> still heavy. Lots of dead bees out front.  Bees I sent to Calif. have fared much
> better but they too show losses that  lead one to believe acarine is the cause.
> 80 colonies placed in the hot room all look exellent at this time. Anyone else
> have any knowledge of how indoor wintered bees compare to outdoor
> wintered  as pertains to tracheal mites?
 
Dear Gary and Recipient of bee-L,
 
Colony thermoregulation is a critical feature of honey bee biology
and survivership. Bees actively thermoregulate their cluster in
winter and summer. Lindaur (1954) and Southwick (1987) showed
that bees can keep their cluster temperature at 35 C under ambient
temperatures ranging from -80 to +70.
Tracheal mites as all you know live & reproduce in the tracheae.
These mites puncture the trachea to feed on the hemolymph (blood) of
the bees. The number of developing mites and adult mites in
the tracheae can increase to the point they block the air passages.
An additional observation was that colony mortality execceds 60%
during winter month in northern climate. These two observations
trigged us (M. Nasr, P. Kevan & E. Southwick) to look at the impact of
mite infestation on bees' ability to thermregulate their cluster at 5
and -20 C. we kept cluster of 300 bees with different levels of mite
infestations(0 - 90% infested bees) in an incubator at 5 C. Then, we
decreased the temperature to -20 C for two hours. All groups of bees
were provided with sugar syrup to feed and produce heat when it was
necessary. We monitored the oxygen consumption and cluster
temperature during the incbation period using a complex electronic
system.
 
We found the following:
 
1. the Oxygen concumption was relatively constatnt at 5 C. When
temperature was lowered to -20C the oxygen consumption of the non-
infested bees (0 infestation) was increased by four times. Whereas
only slight increase in the oxygen consumption was detected in
infested bees.
2. Cluster temperature of all groups of bees was around 27C  when
the the bees were incubated at 5C.In the uninfested group
temperature was 30C. When the temperature decreased to -20C the
cluster temperature droped significantly to temperature ranged
from -19 (frozen) to 22 in the infested groups. whereas the
cluster temperature of the uninfested group stayed around 30C. 20-
100% of the bees in the infested groups entered a chill coma and died
within 12 hours after taking them out of the incubator, only 1.6%
of the bees died in the uninfested group of bees.
 
 
These were the first evidence to show the failure of tracheal mite
infested bees to maintain the cluster temperature when the bees were
incubated at low temperature (-20C) and may explain increased winter
mortality in norther climate.
 
In practical terms, any way to reduce the impact of cold temperature
on bee colonies will help to reduce the winter mortality of infested
bees.
 
Mehdhat Nasr, Ph.D.
Research Scientist
Ontario Beekeepers Association,
Guelph, Ontario, Canada
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