I haven't tried it my self, but I saw a video last winter at the local bee assoc. meeting about handling AHB in Texas.  They would put a teaspoon of high nitrogen fertilizer in the smoker with their regular smoker fuel.  When the fertilizer burns it apparently makes nitrous oxide (laughing gas) which completely knocks out the bees for about 10 minutes.  During that time they made preliminary measurements and if they thought the bees were AHB they soaked the unconcious bees with a dish soap solution to exterminate them.
Michael