Woolly cupgrass (Eriochloa villosa) management in corn (Zea mays) by sequential herbicide applications and cultivation

Field experiments were conducted in southern Wisconsin from 1996 to 1998 to evaluate the effects of acetochlor applied preemergence (PRE) followed by nicosulfuron or sethoxydim applied postemergence (POST) and of cultivation on woolly cupgrass control, corn grain yield, and woolly cupgrass seed prod uction. Sethoxydim treatments provided greater woolly cupgrass control than nicosulfuron treatments in 1997 and similar control to nicosulfuron treatm ents in 1996 and 1998. However, neither herbicide killed all emerged woolly cupgrass plants, regardless of herbicide rate or POST application timing. Late postemergence treatments provided greater season-long control than ear ly postemergence treatments in 1996 and 1998, but there was no difference i n control between timings in 1997. Acetochlor applied PRE at 1,800 g ai/ha (1x) followed by nicosulfuron (35 g ail ha) or sethoxydim (213 g ai/ha) at the registered rate (1x) or at one half of the registered rate (0.5x) consi stently provided sufficient woolly cupgrass control to maximize corn yield, regardless of cultivation or POST herbicide application timing. Acetochlor PRE treatments, cultivated and noncultivated, followed by sethoxydim POST and cultivated acetochlor PRE treatments followed by nicosulfuron POST trea tments provided sufficient control in each year to limit woolly cupgrass se ed production to a level that decreased the predicted future seedbank densi ty, regardless of herbicide rate or POST herbicide application timing. Howe ver, noncultivated acetochlor treatments followed by nicosulfuron applied a t IX followed by 0.5x or at 0.5x followed by 0.5x did not consistently redu ce seed production to a level that decreased the predicted future seedbank density. These results suggest that the rate of sethoxydim can be reduced t o 0.5x if a full rate of acetochlor is applied PRE with little effect on co rn yield or woolly cupgrass seedbank density. However, reducing the rate of nicosulfuron to 0.5x following an application of acetochlor at the full ra te or reducing both the acetochlor and nicosulfuron or sethoxydim rate to 0 .5x is recommended only if a cultivation is planned.