Effect of Nicosulfuron Timing on Wild-Proso Millet (Panicum miliaceum) Control in Sweet Corn (Zea mays)1

Abstract

The effect of nicosulfuron application timing on wild-proso millet (Panicum miliaceum) control and sweet corn (Zea mays) yield was evaluated in the field during 1991, 1992, and 1993. Sweet corn yields were equal to hand weeded controls when nicosulfuron was applied to wild-proso millet shorter than 9 cm, but the best (> 95%) wild-proso millet control occurred when nicosulfuron was applied to wild-proso millet plants between 11 and 19 cm tall. However, nicosulfuron controlled wild-proso millet 90 to 95%, 13 wk after planting, when nicosulfuron was applied to plants 8 to 10 cm tall. Nicosulfuron applications made to wild-proso millet plants less than 8 cm were made early in the season and failed to control subsequent wild-proso millet flushes. Additionally, nicosulfuron failed to control completely wild-proso millet plants larger than 20 cm. Consequently, nicosulfuron applied to wild-proso millet plants shorter than 8 cm or taller than 20 cm resulted in a rapid decline in wild-proso millet control 13 wk after planting. Nicosulfuron applied following 6.7 kg ai/ha EPTC plus 2.2 kg ai/ha cyanazine PPI in 1991, could be applied to wild-proso millet 25 cm tall without subsequent losses in wild-proso millet control or sweet corn yield. Wild-proso millet control was 93% and sweet corn yields were equal to hand-weeded controls when nicosulfuron was applied to wild-proso millet 4 cm tall and followed by one cultivation 14 d after application.Nomenclature: Cyanazine, 2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino]-2-methylpropanenitrile; EPTC, S-ethyl dipropyl carbamothioate; nicosulfuron, 2-[[[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]-N,N-dimethyl-3-pyridinecarboxamide; wild-proso millet, Panicum miliaceum L. #3 PANMI; sweet corn, Zea mays L.Additional index words: Cultivation, PANMI, yield loss.Abbreviations: DAA, days after application; OEM, oil emulsifier concentrate; PDIR, directed postemergence; POST, postemergence; PPI, preplant incorporated; PRE, preemergence; UAN, urea ammonium nitrate; WAP, weeks after planting.