The last I used was a Dragon product. I am surprised because it shows up as a popular botanical that has been used for centuries, but a google search could not find a current vendor. http://www.scorecard.org/chemical-profiles/pesticides.tcl?edf_substance_id=8051-02-3 Here is a link that might be useful: Sabadilla

Well Peggy, maybe they eat what ever is available regardless of whether it is to their liking or not. Not much at all bothers my domestic onions and the only thing that I have ever had the harlequin beetles bother in my garden has been the greens. First preference seems to be the broad leaf mustard greens, when they are gone they will eat radish and move to something else when they are gone. The only way that I have been able to control them is to stay right on top of them and never let them get a very big population going. They do multiply rapidly. I have left a couple of big broadleaf mustard greens as trap plants which did work and there were a bunch to dispose of every day, but I do not know if they would have been there if the greens had not been there, or not. Bill P.

I tried this and then confirmed it from another website: Spray them with a mixture of water and Dawn dishwashing liquid. You have to drench them directly so you might have to come back for another treatment, but it does killed them (by suffocation?). Labor intensive but not as bad as hand picking them off of the plant.

I think you have established that they are not beneficial so I would spray with something. Sometimes you can spray in the evening to try to avoid bees. I hate poisons and try to handpick etc. I have not had any luck with mild methods on any stink bug relatives. Last year I spent lots on a trap that didn't work. I wasted lots of time hand picking them and throwing them in soapy water. To me a harlequin bug is just a decorated stink bug. The problem is the spray may not kill them. The babies look like adults but don't have a tough shell yet. Maybe yours are babies.