Enhanced weed control in flooded rice through diversified pre-emergence programs integrating PROTOX-inhibiting herbicides

Rice (Oryza sativa L.) productivity in Brazil is increasingly threatened by herbicide-resistant weeds. We evaluated diversified pre-emergence programs in flooded Clearfield rice (Puitá INTA CL) through two field experiments conducted in southern Brazil during the 2016/2017 season. Programs were based on acetolactate synthase (ALS) inhibitors alone or combined with alternative modes of action, including protoporphyrinogen oxidase (PROTOX) inhibitors (saflufenacil and flumioxazin). Weed control of Aeschynomene spp. and Echinochloa spp. was high (≥80%) at 14 days after application (DAA) and remained satisfactory up to 21 DAA in most programs. Crop injury was treatment-dependent, with higher early phytotoxicity observed in mixtures containing mesotrione, but visual symptoms declined over time and did not compromise grain yield. All herbicide programs significantly increased productivity compared to the untreated control. These findings indicate that integrating PROTOX inhibitors into Clearfield-based pre-emergence programs is a feasible strategy to diversify modes of action while maintaining effective weed control and yield stability under flooded conditions.