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 no herbicides are registered for controlling winter weeds in winter-planted sorghum. The objectives of this study were to (1) identify alternate herbicide options for sterile oats control in winter-sown imidazolinone (IMI)-resistant sorghum and (2) 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.

Nomenclature: atrazine; imazamox + imazapyr; pendimethalin; prosulfocarb + S-metolachlor; pyroxasulfone; triallate; trifluralin; terbuthylazine; sterile oats, Avena sterilis L. ssp. ludoviciana (Durieu) Gillet & Magne; sorghum, Sorghum bicolor (L.) Moench