<p>Title ures of formula (I) (where R is ethoxy or ethylthio) are used for selectively combatting weeds in cultures of crop plants. (I) are particularly useful against Alopecurus and Avena fatua in cultures of cereals (wheat, barley, rye) and maize. High rates of application give a total herbicidal effect. Results of greenhouse trials demonstrating the pre- and post- emergence selective herbicidal action of (I) are given in the specification.</p>
