Postemergence-Directed Herbicides Control Wild-Proso Millet (Panicum miliaceum) in Sweet Corn (Zea mays)

Thirty-six postemergence-directed (PDIR) herbicide treatments, applied with a precision PDIR sprayer, were evaluated for wild-proso millet (PANMI) control in sweet corn field trials in Wisconsin from 1987 to 1990. The performance of butylate and cyanazine (B + C), applied to suppress PANMI early in the season and to provide a height differential between corn and PANMI, greatly influenced PANMI control with PDIR treatments. PDIR treatments controlled PANMI greater than 90% when PANMI was effectively suppressed by B + C, but poor PANMI suppression reduced PDIR herbicide efficacy. Generally, PDIR treatments of paraquat or sethoxydim most effectively controlled PANMI. Paraquat alone at 545 g ha–1or combined with simazine or sethoxydim at 57 and 114 g ha–1, and sethoxydim at 170 and 227 g ha–1plus an adjuvant controlled PANMI greater than 95%. PDIR applications of ametryn, linuron, sethoxydim at 57 to 227 g ha–1alone, sethoxydim at less than 114 g ha–1plus an adjuvant, and sethoxydim at 114 g ha–1tank mixed with either of four other herbicides controlled less than 86% of PANMI. Tank mixing a photosynthetic inhibitor or sethoxydim with paraquat did not improve PANMI control compared with paraquat alone. PANMI control with sethoxydim plus an adjuvant at 114 g ha–1was similar to 227 g ha–1. There was no difference in PANMI control with sethoxydim applied with crop oil concentrate or BCH-815. With the exception of glyphosate at 318 g ha–1and sethoxydim at 227 g ha–1plus an adjuvant, PDIR treatments did not injure sweet corn in 1987, 1988, or 1990. However, sethoxydim in 1989 at all rates severely injured corn.