Multiple herbicide-resistant kochia (Bassia scoparia) control in glufosinate-resistant canola

Abstract

Multiple herbicide-resistant kochia [Bassia scoparia (L.) A.J. Scott] has grown in prevalence in the canola (Brassica napus L.) production region of North America. Glufosinate-resistant canola facilitates kochia management since glufosinate-resistant kochia is not known to occur. Field experiments were conducted from 2013 to 2015 in five environments near Lethbridge and Coalhurst, Alberta, to identify herbicide strategies targeting acetolactate synthase inhibitor-resistant kochia with and without glyphosate resistance in glufosinate-resistant canola. Sequential glufosinate treatments (500 g ai ha-1) postemergence caused excellent (≥90%) kochia control and biomass reduction across environments. Preplant (PP) carfentrazone + sulfentrazone (9 + 105 g ai ha-1) alone or followed by (fb) postemergence glufosinate (9 + 27 fb 500 or 9 + 105 fb 500 g ai ha-1) resulted in excellent kochia control in all environments tested. PP carfentrazone + sulfentrazone (9 + 53 g ai ha-1) alone, and a single postemergence treatment with glufosinate (500 or 590 g ai ha-1) alone or preceded by fall-applied ethalfluralin (1100 fb 500 g ai ha-1) with or without preplant carfentrazone (1100 fb 9 fb 500 g ai ha-1) caused ≥80% kochia control and biomass reduction in all environments tested. However, treatments containing preplant carfentrazone + sulfentrazone caused unacceptable canola injury or yield loss in at least one environment. In conclusion, single or sequential treatments of glufosinate postemergence managed multiple herbicide-resistant kochia effectively in canola. Layering fall-applied/preplant ethalfluralin and/or preplant carfentrazone with glufosinate postemergence may help alleviate resistance selection pressure placed on glufosinate in canola.