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 inSinapis albathan was linuron, whereas the potencies of the two compounds were almost similar in barley. The selectivity indices (Gr80barley/Gr20S. 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 ifS. albais regarded a weed, the loss of bioactivity of the mixtures may be compensated by some increase
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