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Benzfendizone belongs to the 2-[(4-heterocyclic-phenoxymethyl)-phenoxy]alkanoate class of herbicides which are potent inhibitors of the plant enzyme protoporphyrinogen oxidase (Protox). Benzfendizone, when applied postemergence, provides control of a number of key grass and broadleaf weeds in orchards and no-till crop situations. Benzfendizone can also be used as a potato desiccant and cotton defoliant. Crops such as soyabean and corn showed no injury when planted 2–3 days following postemergence application of benzfendizone.

L-Aryl-4-substituted-1,4-dihydro-5H-tetrazol-5-ones (I) represent a new class of herbicides, which, when applied pre- or post-emergence in the presence of light, control several agriculturally important weed species. Forty-eight analogues have been synthesized and their herbicidal activities determined in order to study structure-activity relationships. In general, these compounds demonstrated: (l) optimum herbicidal activity when the 4- substituent on the tetrazole ring was – CH2CH2CH2F, and the aryl group 2- fluoro-4-chloro-5-substituted phenyl; (2) optimum herbicidal activity over a broad spectrum of grass and broad leaf weeds, with marginal crop selectivity when the C5 substituent on the phenyl group was – OCH2CCH; and (3) a high degree of selectivity on several major crops and primarily broadleaf weed control when this substituent was – NHSO2CH2CH3.