Harlquin beetles are tough, Carbaryl (Sevin), endosulfan (Thiodan) or if you wish to stay organic the botanical Sabadilla. It is a beetle not a stinkbug. They are very destructive of brassicas.

Correction to above post. It is the bug (Murgantia histrionica)not the beetle (Acrocinus longimanus) that is destructive of brassicas. Insecticide suggestions still apply.

Here is a link that might be useful: Harlequin Bug

Famerdilla, where would one find Sabadilla?

Thanks

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