It is saddening to lose a good colony and alarming to hear of a possible
case of Coumaphos resistance in the USA.

I wonder if much resistance is perhaps developed due to our lack of
appreciation of the fact that pesticides have slopes of toxicity that vary
with concentration.
The ones with steep slopes can be tricky.  Hit the slope too low and you
risk resistance, too high and the stuff might be deadly to the bees.  I
know little about the slopes of any of our approved miticides.  Maybe I
should know more.

Bill Morong