Sequential application of soil-incorporated and post-emergence herbicides for controlling wild oat ( Avena fatua L.) and green foxtail ( Setaria viridis (L.) Beauv.) in spring wheat

Abstract

The effects of shallow-soil-incorporated tri-allate or trifluralin, applied alone or in sequence with three post-emergence herbicides (barban, difenzoquat or flamprop-methyl), for controlling wild oat ( Avena fatua L.) and green foxtail ( Setaria viridis (L.) Beauv.) in spring wheat ( Triticum aestivum L., cv. Neepawa) were investigated at Brandon, Manitoba in 1977, 1978, 1979 and 1981. All herbicide treatments, except trifluralin alone in 1981, gave good wild-oat control compared with the untreated control. Tri-allate applied alone did not control green foxtail. With tri-allate, subsequent applications of post-emergence herbicides did not further improve wild-oat control and produced a wheat yield similar to that of tri-allate applied alone. The addition of barban in 1981 did provide a significant yield increase. All treatments involving trifluralin gave equal foxtail control superior to that of tri-allate, but the post-emergence herbicides had no activity on green foxtail. Subsequent applications of barban and flamprop-methyl to trifluralin in 4 years and difenzoquat in 3 years improved wild-oat control. As a result, significant increases in yield were recorded from the addition of barban, difenzoquat, and flamprop-methyl in 1981 and in the mean values for 4 years. In one (1979) of the four years, difenzoquat application to tri-allate or trifluralin tended to reduce wheat tolerance based on visual ratings of plant height and growth vigour, but this did not affect wheat yield. Overall, herbicide treatments in 4 years resulted in significant wheat yield increases over the untreated control.