Understanding the Mode of Action of the Chloroacetamide and Thiocarbamate Herbicides

Chloroacetamide and thiocarbamate herbicides have many properties in common: both herbicide classes are effective only as preemergence herbicides; they inhibit early seedling growth and cause similar injury symptoms in susceptible species; they are detoxified in plants by glutathione conjugation; they have a similar spectrum of selectivity; they can be applied safely in certain susceptible grass crops when applied with antidotes; and they can inhibit the synthesis of lipids, isoprenoids, and other metabolic processes requiring coenzyme A. It can be hypothesized that these similarities are due to the ability of the chloroacetamides and the sulfoxide of thiocarbamates to bind covalently to enzymes, coenzymes, or metabolic intermediates containing sulfhydryl (-SH) groups.