Development of a Selective Herbicide, Quizalofop-ethyl

Abstract

Quizalofop-ethyl, ethyl 2-[4-(6-chloro-2-quinoxalinyloxy)phenoxy] propionate is a selective grass herbicide developed by Nissan Chemical Industries, Ltd. Quizalofop-ethyl possesses a wide herbicidal spectrum for grass weeds with a quick action at low application rates by foliage applications. It shows good safety for non-gramineous crops. A research for a grass killer herbicide, focussed on heterocyclicoxy phenoxy proionic acid, began in 1978. During investigations on the various condensed heterocyclic moieties, the quinoxalinyloxy phenoxy propanoic acid derivatives were found to have a high potential for grass herbicides. Through the optimization of derivertives, the title compound was selected as a candidate for development. In field trials conducted in major producing areas of soybeans, cotton, sugar beet and other broad leaf crops, quizaolfop-ethyl demonstrated sufficient control at 0.5-1.5g a.i./a for annual grass species and at 1.25-2.5g a.i./a for perennial ones. Quizalofop-ethyl was translocated from treated leaves to meristem tissues of grass weeds within a day and attacks these parts, followed by causing necrosis. Quizalofop, which is the metabolite of quizalofop-ethyl, was proved to be a potent inhibitor of fatty acids synthesis through acetyl-CoA carboxylase inhibition. A main metabolic pathway of quizalofop-ethyl was the hydrolysis to quizalofop in plants, soil and mammals. Following hydrolysis, cleavages of ester bonds, hydroxylations and conjugation of quizalofop occurred. Toxicity of quizalofop-ethyl in mammals, fish and birds was very low. Its potential hazard to the environment was minimal.