Weed control in corn with diflufenican plus isoxaflutole

Abstract Diflufenican is a selective phenyl ether, Group 12 herbicide. Limited information exists on the weed control efficacy of diflufenican and the potential improvement in weed control when it is co-applied with isoxaflutole. Three field studies were conducted in Ontario to evaluate preemergence applications of isoxaflutole and diflufenican alone and in combinations for weed control in corn. Isoxaflutole applied at 52.5, 79, and 105 g ai ha −1 provided effective control of velvetleaf (83% to 89%, 91% to 98%, and 92% to 97%), green pigweed (73% to 85%, 85% to 91%, and 94% to 97%), common ragweed (81% to 86%, 93% to 97%, and 95% to 97%), and common lambsquarters (88% to 89%, 96% to 99%, and 98% to 100%), respectively when evaluated at 2, 4, and 8 wk after treatment (WAT). Diflufenican applied alone at 75 to 150 g ai ha −1 provided ≤3% control of velvetleaf, ≤38% of green pigweed, ≤7% of common ragweed, and ≤20% of common lambsquarters. Isoxaflutole applied alone provided 16% to 75% control of barnyardgrass, while diflufenican was ineffective (<3%). The co-application of isoxaflutole + diflufenican improved control to 34% to 86%, with synergistic effects of barnyardgrass control observed at several rates. Isoxaflutole and diflufenican, applied alone controlled green foxtail by 15% to 72% and 0% to 12%, respectively. The co-application of isoxaflutole + diflufenican improved green foxtail control to 25% to 89% with synergistic responses at some rates and evaluation timings. There was minimal corn injury with these treatments. Weed interference reduced corn yield by up to 69%. Weed interference with diflufenican applied alone resulted in corn yields of 4570 to 4750 kg ha −1 , which is similar to yields from the nontreated control (3.33 T ha −1 ). Reduced weed interference with isoxaflutole alone and in mixtures with diflufenican resulted in corn yields of 8.36 to 10.83 T ha −1 , which is higher than yields from both the nontreated control plots and those that received diflufenican treatments. Overall, isoxaflutole provided consistent broadleaf weed control, while synergistic interactions with diflufenican enhanced barnyardgrass and green foxtail suppression.