Organophosphate Insecticides

Organophosphorous Insecticides (OP) are a rather diverse group of chemicals that were derivatives of compounds developed for chemical warfare in WW II.  OP insecticides were relied upon when insects developed resistance to the chlorinated hydrocarbons.  These compounds may be classified into several chemical groups (phosphonates, phosphates, etc.).  Examples include dicrotophos (Bidrin®), methyl parathion, chlorpyrifos (Lorsban®), acephate (Orthene®), and diazinon.  Many agricultural uses of OP insecticides have been restricted in recent years, but OPs are still commonly used in many field crops and on a worldwide basis because they provide a broad spectrum of insect control.  Organophosphorous insecticides are classical inhibitors of acetylcholinesterase, the enzyme which stimulates breakdown of acetylcholine at the post-synaptic nerve endings.  In general, these insecticides are toxic to insects and mammals and should be handled with care.  However, they are less persistent than organochlorine insecticides, and thus have less long-term environmental impacts.