The Basis for Synergism between Barban and Flamprop on Wild Oat (Avena fatua)

Absorption, translocation, and metabolism of the methyl ester of 14 C-flamprop [ N -benzoyl- N -(3-chloro-4-fluorophenyl)- DL -alanine] (hereafter referred to as flamprop-methyl) and 14 C-barban (4-chloro-2-butynyl- m -chloro carbanilate) in wild oat ( Avena fatua L.) were investigated to determine the basis of the synergistic interaction between the two herbicides. The mutual effects of the two herbicides were studied when they were applied together to wild oat at the two- and four-leaf stage. The addition of the commercial formulation of barban, barban formulation additives, technical barban, or the nonionic surfactant polyoxyethylene-6-tridecylether resulted in varying degrees of increase in the absorption of 14 C-flamprop-methyl. Translocation of 14 C-flamprop-methyl following leaf application in wild oat was mainly acropetal. The addition of commercial barban to 14 C-flamprop-methyl did not influence the pattern of 14 C translocation. Metabolism of flamprop-methyl by wild oat at either leaf stage was not influenced by barban. Absorption of 14 C-barban was increased by the addition of the commercial formulation of flamprop-methyl and by polyoxyethylene-6-tridecylether. The addition of flamprop-methyl did not influence the pattern of translocation and metabolism of 14 C-barban in wild oat at either leaf stage. It is concluded that increased absorption of flamprop-methyl and barban by wild oat at the two- and four-leaf stages is the most important factor in the synergistic interaction between these herbicides. Translocation and metabolism of the herbicides do not seem to be important factors in the synergism observed.