Utilising the double knock to increase efficacy of weed control on major weeds in Xtendflex co on systems.

Abstract

Cotton with resistance to dicamba and glufosinate and glyphosate (XtendFlexTM) will be released this season. The addition of glufosinate and dicamba will result in two additional modes of action to be applied in crop. The double knock has proven successful in managing glyphosate resistant weeds in fallow. Substituting glufosinate for paraquat as the follow-up herbicide should be an effective way to increase weed efficacy and manage herbicide resistance.

In a glasshouse experiment, treatments containing glyphosate, dicamba and clethodim (grasses) and glyphosate mixtures with dicamba or clethodim were applied with follow-up glufosinate applied at 1, 3, 7 and 10 days later. These combinations were applied to glyphosate-resistant and -susceptible populations of Conyza bonariensis, Sonchus oleraceus, Chloris virgata, Chloris truncata and Echinochloa colona.

Total control of C. bonariensis was achieved with dicamba and glyphosate+dicamba followed by glufosinate at all timing intervals. Effective control of S. oleraceus was achieved with dicamba and glyphosate+dicamba glufosinate at all timing intervals. Control of C. virgata was achieved with glyphosate, clethodim or glyphosate+clethodim glufosinate 7 and 10 days later. Control of C. truncata was inconsistent, with the most effective treatment being glyphosate+clethodim glufosinate 10 days later. E. colona was controlled with all treatments apart from glyphosate alone on the glyphosate-resistant population.