>However, we did have _one yard_ where we lost 15 out of 24 hives.  This
>particular yard produced very well last year and plugged up badly a couple
>of times, including once in September when they had only one super (above
>the double broods and excluder) during a very intense late flow.
 
This is the key to your troubles in my opinion.
 
 
What I'm wondering is if the queens could have been shut down
>enough to prevent raising winter bees and that the colonies might have
>died of old age.  I have never seen it before.
 
I have seen this.  The relevant factors are:
1.  a very late flow, far from the hives, but within range, so that the
workers are over-extenened.  This causes younger bees to forage, and "ages"
the bees.
2. Pluged brood chamber prevents the raising of bees to replace forager
"ageing".
3.  Pluged brood chamber forces the bees to eat honey, and the stress on
their gut from all the "misc" in the honey is an additional "aging" stress.
 
>A subsequent poor wintering was blamed on that fact (lack of winter bees),
>but I had personally sort of pooh-poohed the idea because September is a
>little late for much brood rearing in Alberta .
 
Yes, but the brood rearing must accompany, and make up for any flight
activity that wears out the population.  Normally there isn't much brood
rearing in sept.  but there isn't much activity either, so the right balance
is achieved.
 
>On the other hand, I *have* always claimed that even good hives can be too
>heavy for good wintering and that there is an ideal weight range.  I have
>had trouble recruiting believers to that latter position however -- with
>most commercials saying "Give 'em all they'll take".
 
I certainly go with the "all they can take" theory, since it is too much to
tailor the diet of each hive.  However, in a comercial operation where each
hive gets approximately the same volume of feed (uless they don't take it)
the heavy ones are likely to be ones full of sugar _and_ honey.  This may be
a stress that decreases their wintering success.
 
 
Well that's my two cents worth.
 
pHIL
**************************************
Phil Veldhuis
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Winnipeg Manitoba.