Phenoxy acids significantly increased the number of Sitobion avenae F. and Rhopalosiphum padi L.on wheat treated with Aminopielik D and Illoxan 36 EC. This herbicidal effect could be caused directly by derivatives ofphenoxy acid or indirectly by altered metabolism of wheat plant.

The influence of cinnamic acid, 1-tryptophane, 3,4-dihydroxyphenylalanine, 2,4-dichlorophenol modifying IAA-oxidase activity and indoleacetic acid on the development and reproduction of cereal aphids in laboratory conditions was tested. We observed that IAA and Try stimulated the reproduction of cereal aphids whereas CA, DOPA and DCP decreased it.