Integrated Management of Wild Oat (Avena fatua) and Feather Fingergrass (Chloris virgata) Using Simulated Grazing and Herbicides

Abstract

Wild oat (Avena fatua L.) and feather fingergrass (Chloris virgata Sw.) are among the most problematic weed species in Australian winter and summer cropping systems, respectively. Pot trials were conducted in respective seasons to evaluate the integrated effect of simulated grazing and foliar-applied herbicides on the control of these weed species. Different herbicides were applied 1, 5, and 12 d after grazing on A. fatua plants and 1, 3, 7, 10, and 14 d after grazing on C. virgata. In general, the efficacy of herbicides was better on A. fatua when applied 5 or 12 d after grazing (i.e., 7–20 cm tall plants) and 7 to 14 d (i.e., 10–22 cm tall plants) after grazing on C. virgata. Clethodim 90 g a.i.·ha−1, and haloxyfop 52 and 78 g a.i.·ha−1 resulted in 100% mortality of A. fatua seedlings, irrespective of their application timings. Delayed application (5 or 12 d after grazing) of clethodim 60 g a.i.·ha−1 and pinoxaden 20 and 30 g a.i.·ha−1 resulted in 100% mortality of A. fatua. Glyphosate at the field rate (370 g a.e. ha−1) was the least effective herbicide to control A. fatua plants after grazing. Glufosinate application after grazing resulted in the greatest mortality (69 to 81%) of C. virgata. Depending on application timing, only glufosinate was able to provide complete control of C. virgata seed production. Butroxydim, clethodim, and haloxyfop were found to be promising herbicides to manage C. virgata after grazing but their applications had to be delayed by 7 to 14 d after grazing. This study identified several successful herbicide treatments that could be applied after grazing or mowing for integrated control of A. fatua and C. virgata. However, to achieve complete control of C. virgata, the application of these herbicides needs to be followed by other tools, including additional herbicide applications.