To Dick and all,
Dick wrote: <I don't really think so. But: 15 hives looked fine in spring. Some early
splits some old hives and 2 packages. Treated all by sublimating O/A.
Harvested honey in July. Mite drops low. 0 to 20 per day. Went hunting etc
and came back in late sept. No more crop and mite counts too high.>

Back in the summer of 2000 we had an extremely dry spell here in Kansas that really endured throughout the fall.   I had moved bees to soybeans and had hoped for enough of a flow to put the bees into shape and it just didn't happen.   By the time I started feeding the first of October, it was too late.  There had been little brood production during August and September, if any, and many queens were reluctant to restart laying in October as it turned cold very fast.
It had been over 100 degrees the second week of Sept. during our state fair and then we had a killing frost around the tenth of Oct., quite unusual and extreme.  By Thanksgiving I knew I was in serious trouble as clusters averaged the size of softballs.  For a hive to maintain critical mass for a production unit the coming year we need basketballs at christmas, a good box of bees.  Anyway almost everyone here in eastern Kansas and western Missouri lost from 80-90 percent of our hives because there were no winter bees produced during August and September and clusters were just too small to survive the resulting winter we had which was the last really cold one we have had. 
Since then I have made it a practice to feed my bees during the nectar drought of late July and August after pulling honey of course.  We only have a fall flow once every three or four years that is sufficient to collect in supers. This keeps the queens producing brood and believe me this is the most critical time of the year for preparing for next years crop.    Fall management begins when you pull your honey.   Without stores of honey or a nectar flow, why should and how can the bees produce brood?
I also have treated the those hives showing stress from mites when I pull my honey the last few years.  If you wait till October........too bad.
Hope this might help a little and provide a possibility of an answer.
Tim
 

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