Triketone bleaching herbicide for use in maize. Inhibits 4-hydroxyphenylpyruvate dioxygenase, an enzyme involved in the biosynthesis of plastoquinones. Prepn: W. J. Michaely, G. W. Kraatz, EP 137963; eidem, US 4780127 (1983, 1988 both to Stauffer Chem.). Field trials in corn: J. S. Wilson, C. L. Foy, Weed Technol. 4, 731 (1990). Soil adsorption: eidem, ibid. 6, 583 (1992). Mode of action study: J. Secor, Plant Physiol. 106, 1429 (1994). Comprehensive description: J. M. Beraud et al., Brighton Crop Prot. Conf. - Weeds 1991, 51-56.