> When we tipped up the top brood box and looked at the lower one, there
> was a cluster of bees that covered about 75% of the area.  I think this
> is larger than should be at this time of year?
 
No, that is good.  If you tip back the whole hive and there are bees on
three or four bottom bars or more, then they are about right for
reversing, and then splitting a week or two later.
 
> One colony of Robert's nucs was very very low on stores and bees and one
> was dead....probably from Tracheal Mites, since there were hardly any
> dead bees present.
 
That actually is more likely be queenlessness, especially if there was
no sign that they had been raising brood.
 
> the other was a Buckfast which produced 205 lbs of honey in 1997, and
> seems to have died from Foul Brood, although I treated with Terr. both in
> sugar syrup and powder on the top bars.
 
The problem with oxytet on the top bars is that the bees can't always get
it.  Sacks, or placement too far from the cluster can make it useless.
The sign of success is that it is immediately consumed.  Nonetheless, the
doses usually recommended are too small for full-sized hives, and I
recommend a dose of about double what the literature usually says.
 
We use as much 5:1 icing sugar mix as will heap up the last 1-1/2 inches
of the flat end of a standard hive tool per strong colony.  Anything less
than that will not work.  Frequent application during the brood rearing
season is essential, too.  Skip application during the honey flow.  That
does not seem to affect the efficacy, since the queen is not laying in new
cells during that time unless you do not use excluders or unless you muck
around with the brood.  Moreover they are not using old honey that might
contain spores to feed brood as they do at other times.  Medication must
be applied at least every two weeks during any dearth periods if AFB has
been seen in any hives recently.  Otherwise a less frequent application
can be successful.
 
FWIW, we are quitting dusting and cutting back on medicating syrup
with oxytet this year, since we used grease patties last year and reduced
our TM costs drastically and saw zero (and I do mean zero) AFB in our
colonies.  Moreover the overwintered hives that had the patties on over
winter looked better than some that were missed.
 
Losses here are running exactly 4%, a low figure which is unheard of in my
last 25 years.  Of course we will lose another 4% by mid-May as the weak
ones are shaken out.  Some of this success is due to a good queen season
last year in Hawaii and elsewhere.  Some of it is due to a long summer
season last year, a mild winter, and an early spring this year.  But, we
think some of it is also due to feeding pollen supplement all spring and
the use of extender patties.  Although we observe 10% (average) tracheal
mite levels in some yards each fall, we have never treated for mites.
FWIW, using grease patties last year did not change the levels of tracheal
mite activity observed noticably, although some yards tested zero and
should have shown positive.
 
Allen