Herbicide options for sterile oats (Avena ludoviciana) control in winter-planted sorghum


 Australian grain growers are showing interest in winter-planted sorghum to avoid heat and water stress during the grain-filling stage. Winter-planted sorghum may face competition from winter weeds, including sterile oats, and there are no herbicides registered for controlling winter weeds in winter-planted sorghum. The objectives of this study were to (i) identify alternate herbicide options for sterile oats control in winter-sown imidazolinone (IMI)-resistant sorghum and (ii) assess the crop injury levels due to herbicides. Sterile oats control with pendimethalin at 0.59 kg ai ha-1, trifluralin at 0.38 kg ai ha-1, and prosulfocarb + S-metolachlor at 2.3 kg ai ha-1 was poor (<30%). Atrazine at 2.7 kg ai ha-1, imazamox + imazapyr at 0.048 kg ai ha-1, and atrazine at 2.7 kg ai ha-1 followed by imazamox + imazapyr at 0.048 kg ai ha-1 reduced the sterile oats biomass by 93, 96, and 100% and increased yields by 116, 136, and 140%, respectively, compared with nontreated control. Pendimethalin at 0.59 kg ai ha-1 and trifluralin at 0.38 kg ai ha-1 caused phytotoxicity to the crop and gave similar yields to nontreated control. Triallate at 0.8 kg ai ha-1, pyroxasulfone at 0.1 kg ai ha-1, and terbuthylazine at 1.0 kg ai ha-1 provided moderate weed control (44 to 65%) and increased yields by 68, 108, and 80%, respectively, compared with nontreated control. This research identified herbicide treatments for the effective control of sterile oats in winter-sown IMI-resistant sorghum that could be used in rotations to reduce the reliance on single herbicide treatments.