Fendioxypyracil exhibits potent inhibition of PPO ‐resistant mutant enzymes and robust activity against PPO ‐resistant Amaranthus spp.

Abstract BACKGROUND Resistance to protoporphyrinogen oxidase (PPO)‐inhibiting herbicides is mainly driven by diverse target‐site mutations, reducing the effectiveness of this site of action in row‐crop systems. Fendioxypyracil is a newly developed PPO inhibitor with high intrinsic grass and broadleaf activity, but its performance against resistant populations and target‐site enzyme variants remains insufficiently characterized. RESULTS Enzyme assays using PPO2 from Amaranthus palmeri and Setaria viridis demonstrated that fendioxypyracil maintained low IC 50 values across a broad range of resistance‐associated mutations, including ΔG210 deletion and G210, R128 and G399 substitutions, whereas oxadiazon, tiafenacil, and saflufenacil showed substantial loss of potency. Greenhouse dose–response experiments confirmed strong fendioxypyracil efficacy, with susceptible and G399A populations controlled at the lowest tested rate, while ΔG210 and R128G populations were effectively controlled at the field recommended rate of 25 g ai ha −1 . Transgenic Arabidopsis thaliana expressing resistant PPX2 alleles exhibited faster and more severe injury with fendioxypyracil compared to saflufenacil. Field trials conducted in a PPO‐resistant Amaranthus palmeri population demonstrated that fendioxypyracil provided consistent weed control and density reduction, matching the performance of trifludimoxazin and saflufenacil while exceeding that of fomesafen. CONCLUSION Fendioxypyracil provides robust and broad‐spectrum activity against PPO‐resistant Amaranthus populations and target mutant enzymes, maintaining efficacy across diverse mutation backgrounds, highlighting its potential as an effective tool for managing PPO inhibitor resistance and sustaining weed control in row‐crop production systems. © 2026 BASF Agricultural Solutions Deutschland GmbH and The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.