Dear B-liners:
 
We are back to debate if tracheal mites can kill bee colonies or not,
effectiveness of breeding bees to tolerate mite infestation,
resistance as a result of natural selection (survivors of heavy
infestation) vs. laboratory selection, breeding and then
implementing in our bee population, and relationship between winter
mortality and tracheal mite infestations.
 
     First of all, I agree with Carry Clark's observations. I have
been doing similar work in Ontario for the last 7 years and I found
similar results. Bees colonies infested with mites above 40-50%
(based on dissection of a sample of 50 bees/ hive) most likely will
not make it through the winter. This conclusion was reported by Dr.
Otis and Scott-Dupree at the University of Guelph and later supported
by my research. There are several factors can effect the survivorship
of bee colonies infested with mites.
 
These factors are:
 
1. Mite prevalence in bee colonies.
2. Bee cluster size in late fall and early spring
3. Length of winter and the average temperature during the winter
month.
4. Start of the spring season and the average temperature during
spring.
5. Nosema infestation levels and susceptibility of bees to nosema.
6. Bee managements (Feed, providing protection dusring wintering).
7. Location of operation; Canada, northern states, and southern
states.
 
Secondaly, I would like to discuss few issues regarding variation of
reported winter mortality. For those who reports that bees survived
witer without treatment. I like to ask a question. What were
the mite infestation leveles in those bee colonies before winter? In
most cases , There is no answer. There is no monitoring by sampling
bees and dissection to find out what was the mite level in bee
colonies before winter. Therfore, the cause of colony mortality may
or may not be due to tracheal mites. The  assumption of bees with
heavy mite infestations or untreated survived winter is wrong. It is
unfortunate that most of the winter mortality reports have never
mentioned the infestation levels in these hives before winter.
 
Regarding late winter mortality, the tracheal mite infestations can
be responsible for late winter mortality and can be complicated by
nosema infestations assuming that there is enough feed. Sofar,
research have shown in some places and certain operations during
certain years there is a positive correlation between nosema
infestations and tracheal mite infestations. However, in some
years bee colonies with only heavy nosema infestations die in early
spring. Other bee colonies with low nosema inestations and high levels
of tracheal mites die, too.
 
     Befoer we make any conclusions we need qualified data to support
these conclustions. Research in tracheal mites is laborious and needs
carful experimental designs with appropriate controls and good
experience with the biology of bees and tracheal mites (epidemiology).
Just to give you an example, I have a beekeeper who complained to me
about slow build up of his new requeened colonies in early summer. The
beekeeper suggested that the slow build up of his colonies may be due
to heavy tracheal mite infestations in these colonies. Though
some call the scientists (.......) I did not take this beekeeper's
word. I examined the colony and found that the new larvae starved to
death though there was a lots of pollen and honey in these colonies.
There was no royal jelly in the cells. I took bee samples and examined
them for mites. There was no or very low mite infestations. We did
examine for nosema and found heavy loads of spores. He could not
believe this conclusion because he fed thsese colonies medicated
syrup for nosema the previous fall. This example can give an idea
about the value of sampling and examination of bee colonies to
understand the problem. Rememebr in Canada, tracheal mites have not
yet widely spread across the provinces and even within each province.
 
     For mite resistance, in early report to this group, I metioned
the results of the field test for 17-18 month. We compared mite
resistant bees to non-selected bees. In the test, we showed that
90% of the mite resistant colonies had less than 10% tracheal mite
infestation (out of these colonies, 40% of the colonies had 0%). For
the 8 control colonies, 6 colonies died the first winter due to high
mite levels (>50%). This experiment was clear and clean
demonstaration to Ontario beekeepers about mite resistant bees. By the
way, this experiement was done in one of the Ontario Beekeepers'
yards. He did all the managements and no formic acid use.
 
In another note, Konna queens had send two time several frames of
hatching brood from Hawaii to Buffalo, NY and I did screen their bees
for mite resistance. The test was done in Buffalo, NY.
 
I hope this will shed some lights on the efforts that are done to
keep the mites under control in Ontario. Keep your eyes open, sample
your bee hives, and treat when it is needed.
 
Good Luck,
 
 
Mehat Nasr, Ph.D.
 
Ontario Beekeepers' Association
c/o Dept. Environmental Biology
Univesity of Guelph,
Guelph, Ontario
Canada