The most effective and legal cockroach killer as of 2105 is Harris Roach Killer Powder, according to Confirmedbest.com. The second-best rated product to eradicate roaches is Pic Orthoboric Acid Roach Killer.
Harris Roach Killer Powder gets rid of cockroaches quickly, and the bottle can last up to a year. The main ingredient is boric acid powder. Cockroaches carry the powder back to the nest and other gathering points, which helps kill the whole infestation of insects. The bottle comes with a straw that allows users to place the powder in hard to reach spaces. Pic Orthoboric Acid Roach Killer works the same as the Harris brand, but it doesn't contain any bait.