Imazethapyr is an imidazole compound used as a selective herbicide. It is applied preplant incorporated, preemergence, at cracking, and postemergence. The compound controls weeds by reducing the levels of three branched-chain aliphatic amino acids, isoleucine, leucine and valine, through the inhibition of aceto-hydroxyacid synthase, an enzyme common to the biosynthetic pathway for these amino acids. This inhibition causes a disruption in protein synthesis which, in turn, leads to an interference in dna synthesis and cell growth.