Yeah Mick, you know you mentioned a trap outside the hive before they enter. it's probably something for more of a chemist that myself, but what if you could duplicate the alarm pheromone so well that you could put it in a "roach motel" type trap for the beetles (far away from the hives of course - or they'll be irritated all the time - say 30 or 40 meters). just a powerful scent to draw and trap the pests before they ever get in. - I may try it with some bananas and a sticky trap and see how it goes.
That's the sort of thing I have been thinking of. Maybe not the alarm pheromone but certainly using attractants like pollen patties perhaps in a cd case with an appropriate insecticide bait. I have never used pollen patties but intend to get some pollen and mix up a test sample over the next few days to see if they will work outside the hive in traps.
I imagine they would work inside the hive and have seen pics of something like that with heaps of dead shb in them but I am reluctant to put them inside the hive with chemicals in them