Joint action of root‐absorbed mixtures of DPX‐4189* and linuron in Sinapis alba L. and barley

Abstract

SummaryThe joint action of DPX‐4189* (2 chloro‐N‐[(4‐methoxy‐6‐methyl‐1, 3, 5‐triazin‐2‐yl)‐aminocarbonyl] benzenesulfonamide) and linuron (N‐[3, 4‐dichlorophenyl]‐N‐methoxy‐N‐methylurea) mixtures, applied in fixed ratios of 1:15 and 1:30, was assessed using water culture experiments in growth chambers.The dose‐response curves of DPX‐4189 were fiat compared with these of linuron. At Gr50‐level (the dose required to reduce dry matter by 50% relative to the untreated control), DPX‐4189 was 12‐fold more potent in Sinapis alba than was linuron, whereas the potencies of the two compounds were almost similar in barley. The selectivity indices (Gr80[barley]/Gr20[S. alba]) of DPX‐4189 and linuron were 3.1 and 1.8.In both species the mixtures were less active than expected from an additive dose model, and the detracted efficacy of the mixtures was of almost similar magnitude. The results indicated that if S. alba is regarded a weed, the loss of bioactivity of the mixtures may be compensated by some increase in dose rate without injuring the barley crop.