Abstract: Novel herbicidal N-cyanopyridazinones of the general formula ##STR1## in which the radicals R.sub.1, R.sub.2 and R.sub.3 independently of one another denote hydrogen, halogen, amino, nitro, cyano, alkyl, aryl, aralkyl, alkoxy or aryloxy groups, a process for their preparation, a herbicidal composition comprising them, and a method of controlling weeds.

Abstract: A method for combatting weeds by applying to the weeds or their environment, a phenylpyridazine, wherein the phenyl group is substituted by hydroxy, halogen, cyano, nitro, amino, alkyl, alkoxy, cycloalkyl, cycloalkoxy, phenyl, phenoxy, alkylthio or an alkylsulfonyl group and wherein the pyridazinyl ring is substituted in the 4-position by hydroxy or by a --O--C(O)-- derivative.

Abstract: Process for the preparation of pure, unsymmetrically disubstituted ureas of the general formula ##STR1## in which R denotes a phenyl radical which is unsubstituted, or monosubstituted or polysubstituted by halogen atoms or alkyl, alkoxy, aryloxy or trifluoromethyl groups, an oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, benzoxazolyl or benzothiazolyl radical which is unsubstituted, or monosubstituted or polysubstituted by halogen atoms or alkyl, alkoxy or trifluoromethyl groups and R.sub.1 and R.sub.2 independently of one another denote a hydrogen atom or an alkyl group, where R.sub.1 and R.sub.2 are not simultaneously hydrogen or R.sub.1 and R.sub.2 together denote a butylene or pentylene group, by reaction of an N-alkyl- or N,N-dialkylurea with an unsubstituted or substituted arylamine or a heterocyclic amine in the presence of that amine which is already present in the starting material, the respective N-alkyl- or N,N-dialkylurea.