Dual mode of action herbicide rimisoxafen targets both phytoene desaturase and solanesyl diphosphate synthase

Abstract BACKGROUND The need for new, efficacious, and safe crop protection chemistries to control evolving pest populations is ever‐present to combat resistance derived from current crop protection offerings. Rimisoxafen is a novel pyrimidinyloxy benzene with herbicidal activity. Determination of mode of action (MoA) is key to de‐risking newly introduced crop protection chemistries with regards to toxicology and the potential for field resistance. RESULTS Weeds treated with rimisoxafen display a distinct bleaching phenotype, leading to investigation of multiple herbicidal targets surrounding carotenoid and plastoquinone biosynthesis and utilization. Here, we report rimisoxafen inhibits both solanesyl diphosphate synthase (SDPS) and phytoene desaturase (PDS). In vitro , rimisoxafen disrupts SDPS and PDS enzymatic activity at comparable levels to single‐target standards. Both MoAs are operable in vivo as rimisoxafen treatment within model systems results in a distinct metabolomic profile containing markers for both PDS and SDPS inhibition. In addition, rimisoxafen can control resistance mutations raised against SDPS or PDS standards in ultraviolet (UV)‐mutagenized Chlamydomonas reinhardtii strains, but only a strain containing both PDS and SDPS mutations is resistant to rimisoxafen. CONCLUSION Rimisoxafen inhibits SDPS and PDS both at the enzyme level and in vivo . Bringing two MoAs to the field within a single molecule promises to mitigate target site resistance risk for rimisoxafen, an outcome now achieved through mixtures and thereby could reduce the volume of weed control chemical residue applied to fields worldwide, especially in the corn and soybean markets. © 2025 Society of Chemical Industry.