Modernizing the economic threshold for true armyworm, Mythimna unipuncta, in wheat in Ontario, Canada

True armyworm (TAW; Mythimna unipuncta (Haworth; Lepidoptera: Noctuidae)) is a sporadic pest that causes significant injury in cereal crops including wheat (Triticum aestivum L.). TAW management in Ontario is based on research conducted >50 years ago; thus, the objective of this research was to develop modern economic thresholds. Field experiments were conducted in 2022 and 2023 to assess insecticide efficacy and application timing in response to TAW infestation densities in wheat in Ridgetown, ON Canada. Plots were infested with TAW (2022: 0, 4, 8, or 16 larvae per 30 cm², 2023: 0, 4, or 32 larvae per 30 cm²) at the boot, flowering, or milk growth stage and treated 24 h post-infestation with chlorantraniliprole (42 mL/ha or 83 mL/ha), lambda-cyhalothrin (83 mL/ha), spinetoram (100mL/ha), indoxacarb (791 mL/ha), or chlorantraniliprole + pydiflumetofen + propiconazole fungicides (83 mL/ha + 1000 mL/ha) in 2022 and chlorantraniliprole (83 mL/ha) or chlorantraniliprole + pydiflumetofen + propiconazole (83 mL/ha + 1000 mL/ha) in 2023. Plots were assessed for feeding incidence at 3, 7, 14, and 21 days post-infestation. Feeding incidence observed for eight and 16 larvae per 30 cm² were over two times greater than four larvae per 30 cm² at the boot and flowering stage; however, at the milk stage there was no significant difference. TAW total leaf defoliation was less than 10% across treatments but not significantly significant therefore, 2023 trials only included chlorantraniliprole. Revised economic thresholds for TAW relating to crop growth stages provides more precise application timing and reduces unnecessary insecticide applications.