Cinmethylin controls multiple herbicide-resistant Lolium rigidum and its wheat selectivity is P450-based

Roberto Busi, Franck E. Dayan, Ian Francis, Danica Goggin, Jens Lerchl, Aimone Porri, Stephen B. Powles, Ci Sun, Hugh J. Beckie

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


BACKGROUND: Multiple-herbicide resistance in Lolium rigidum and other weed species is increasingly exerting pressure on herbicide discovery research for solutions against resistance-prone weeds. In this study we investigate: (i) the responses of L. rigidum populations and wheat to the new herbicide cinmethylin in comparison with other pre-emergence herbicides, (ii) the effect of seed burial depths on cinmethylin efficacy and crop selectivity, and (iii) the basis of cinmethylin selectivity in wheat. RESULTS: Cinmethylin at 400 g ha−1 controls herbicide-susceptible and multiple-resistant L. rigidum, with a reduction of >85% in plant emergence and 90% in aboveground biomass. Cinmethylin provides effective control of a large number of field populations of L. rigidum with evident resistance to trifluralin. When the wheat seed is buried ≥1 cm below the cinmethylin-treated soil surface, the emergence of crop seedlings is not different from the untreated control. The organophosphate insecticide phorate synergizes cinmethylin toxicity in wheat, with an LD50 of 682 g ha−1 in the absence of phorate versus 109 g ha−1 in the presence of phorate (84% reduction). The synergistic effect of phorate with cinmethylin on herbicide-susceptible L. rigidum appears smaller (a 44% reduction in the LD50 of cinmethylin). CONCLUSIONS: Cinmethylin is effective in controlling multiple-resistant L. rigidum and appears safe for wheat when the seed is separated at depth from the herbicide applied to the soil surface. The basis of this metabolism-based selectivity is likely regulated by cytochrome P450 monooxygenases.

Original languageEnglish
Pages (from-to)2601-2608
Number of pages8
JournalPest Management Science
Issue number8
Publication statusPublished - 1 Aug 2020


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