Everyone wants to catch a feral swarm for those good local genetics, and everyone has heard of using lemon grass oil to attract them to an empty hive or swarm trap.
But, apparently, if you replace queens occasionally, you can stuff the old queen into a small bottle, crush her up in some alcohol, and her natural pheramones will permeate the solution. A cue tip can be used to apply it, and the solution must be replaced periodically, especially after a rain.
Any thoughts on this technique?
Check out an ongoing experiment in permaculture and community: Dancing Rabbit Eco-village
if a beekeeper is replacing a queen anyhow, it's certainly a better way to dispose of her than in the compost heap. my understanding is that queen tincture does work as well or slightly better than Cymbopogon citratus, though I don't think there's a dramatic difference in performance.
from my own experience and paying some attention to the chatter on a couple of e-mail lists, I would guess that the most likely bait hive to succeed has a strong smell of having been occupied by bees previously. the easiest way for me to get that is to make bait hives from used Warré boxes, two of which are close to the 40 liters recommended by Seeley. if I don't have any of those to spare, I rub some old brood comb all over the inside of a new box and leave a chunk of comb in there.
covering a lot of territory will certainly improve the odds, too. one bait hive, no matter how many tricks are used, just isn't likely to successfully lure a swarm, unless it's placed relatively near one or more established colonies (either by luck or deliberately). using a bait hive near one's own apiary to prevent swarms ditching stands a reasonable chance of success, but that's a whole other issue.
it's good to keep in mind that in some regions the feral population still hasn't recovered substantially from varroa yet, so bait hives might involve a lot of wishful thinking. where I'm at, the numbers have jumped back to pretty healthy levels. I wasn't beekeeping before varroa arrived, so I can't compare current conditions to the pre-collapse situation, but collecting feral swarms is a relatively common occurrence around here in season.