Diazinon (O,O-iethyl-O-(2-isopropyl-6-methyl-pyrimidine-4-yl)phosphorothioate), a colorless to dark brown liquid, is a thiophosphoric acid ester developed in 1952 by Ciba-Geigy, a Swiss chemical company (later Novartis and then Syngenta). It is a nonsystemic organophosphate insecticide formerly used to control cockroaches, silverfish, ants, and fleas in residential, non-food buildings. Bait was used to control scavenger wasps in the western U.S. Residential uses of diazinon were cancelled in 2004; it is still approved for agricultural uses.