Hi all
I live towards the East end of Toronto, here in Ontario.  I keep bees just
outside Toronto. I use formic acid and make my own pads following Medhat
Nasser's research.  By the time we reach the temperatures required for
success makes my bees are definitely into brood rearing in a big way.  I have
never noticed any problems at all.  I do not do research but certainly would
notice dead brood being pulled out if there was a serious problem.  Sometimes
the bees have started to build comb on the veggie bag containing the homasote
pad since they are at the top of the hive and spaces 1/2 inches above the top
of the frames.
.......george