This field trial at Minnipa was undertaken to investigate factorial combinations of seed rate and herbicides on the management of annual ryegrass in wheat.

A field trial was undertaken at Minnipa in 2020 to investigate combinations of wheat seed rate and herbicide treatments to control annual ryegrass. The average seedbank of annual ryegrass (ARG) at the site was 2012 ± 461 seeds/m2. ARG plant density was significantly influenced by herbicide treatment (P=0.008). Boxer Gold and Sakura + Avadex controlled ARG plant density by 63% and 70% respectively. Consistent with the trends observed for ARG spike density, ARG seed production was also significantly influenced by herbicide treatments (P<0.001) and while not significant there was a trend towards suppression of ARG seed production when wheat seed rate was increased (P=0.096). When averaged across all the seed rate treatments, the untreated control produced 13,155 ARG seeds/m2. The Boxer Gold treatment reduced ARG seed set by 69% to 4,018 ARG seeds/m2, while the Sakura + Avadex treatment reduced it by 70% to 3,849 ARG seeds/m2. Such high ARG seed set even when using pre-emergent herbicides highlights the importance of an integrated weed management strategy that incorporates diverse crop options such as hay and includes other cultural methods such as harvest weed seed collection and improved crop competitiveness. Consistent with the level of ARG control, herbicide treatments had a significant effect on wheat grain yield with Boxer Gold (1.869 t/ha) and Sakura + Avadex (1.871 t/ha) both increasing grain yield by 35% compared to the control (1.384 t/ha).