Interference of wild oat (Avena fatua) and sterile oat (Avena sterilis ssp. ludoviciana) in wheat

Abstract Prevalence of wild oat ( Avena fatua L.) and sterile oat [ Avena sterilis ssp. ludoviciana (Durieu) Gillet & Magne; referred to as A. sterilis hereafter], winter-season weeds, is increasing in the eastern grain region of Australia. Biological attributes of these weeds enable them to survive in a wide range of environments and under different weed infestation levels. The interference of A. fatua and A. sterilis in a wheat ( Triticum aestivum L.) crop was examined in southeast Queensland, Australia, through field studies in 2019 and 2020. Different infestation levels (0, 3, 6, 12, 24, and 48 plants m −2 ) of A. fatua and A. sterilis were evaluated for their potential to cause yield losses in wheat. Based on a three-parameter logarithmic model, the A. fatua and A. sterilis infestation levels corresponding to 50% wheat yield loss were 15 and 16 plants m −2 , respectively. The yield reduction was due to a reduced spike number per unit area because of an increased weed infestation level. At the highest weed infestation level (48 plants m −2 ), A. fatua and A. sterilis produced a maximum of 4,800 and 3,970 seeds m −2 , respectively. Avena fatua exhibited lower seed retention (17% to 39%) than A. sterilis (64% to 80%) at wheat harvest, as most of the seeds of A. fatua had shattered at crop maturity. Our results implied that there is a good opportunity for harvest weed seed control if the paddock is infested with A. sterilis . This study suggests that in the absence of an integrated weed management strategy (using both chemical and nonchemical options), a high infestation of these weeds could cause a severe crop yield loss, increase weed seed production, and replenish the weed seedbank in the soil.