Pyridyloxy-phenoxy-alkanecarboxylic acid derivatives which are effective as herbicides and as agents regulating plant growth

A pyridyloxy-phenoxy-alkanecarboxylic acid derivatives of the formula I ##STR17## wherein A represents hydrogen, halogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxy, cyano, or nitro,

• B represents hydrogen, halogen, cyano, C.sub.1 -C.sub.4 -alkyl, a mono- or di-C.sub.1 -C.sub.4 -alkylamino group,
• C represents hydrogen, halogen, cyano, or nitro,
• wherein at least one of A, B or C is cyano,
• D represents hydrogen, halogen, C.sub.1 - C.sub.4 -alkyl or a mono- or di-C.sub.1 -C.sub.4 -alkylamino group,
• R.sub.1 represents hydrogen, C.sub.1 -C.sub.4 -alkyl optionally substituted by C.sub.1 -C.sub.4 -alkoxy, or phenyl,
• R represents hydrogen or a cation 1/n M.sup.n.sym., a C.sub.1 -C.sub.18 -alkyl group, which is unsubstituted or substituted by C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -alkylthio, carboxyl, C.sub.1 -C.sub.4 -alkoxycarbonyl, C.sub.3 -C.sub.12 -cycloalkyl, phenyl or a 5-6-membered heterocyclic ring, a C.sub.3 -C.sub.12 -cycloalkyl group, a C.sub.3 - C.sub.8 -alkenyl group or halogenolkenyl group, a C.sub.3 -C.sub.8 -alkynyl group, or a phenyl group which is unsubstituted or is mono- or polysubstituted by halogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -alkylthio, cyano or nitro,
• 1/n M.sup.n .sym. represents the ion equivalent of an alkali metal ion, an alkaline-earth metal ion, a copper ion or an iron ion, or a quaternary alkylammonium group or hydroxyalkylammonium group.