Selectivity and efficacy of sulfonylurea herbicides and wild-proso millet competition in field and sweet corn

Wild-proso millet (Panicum miliaceum) can compete with field and sweet corn (Zea mays) in the field. Millet density was higher and emergence was earlier in 1991 than in 1990. Millet reduced corn biomass and yield in 1991 but not in 1990.;Millet control from nicosulfuron at 35 g/ha was similar when applied with nonionic surfactant (NIS), crop oil concentrate (COC), or methylated seed oil adjuvants; however, 28% nitrogen fertilizer solution (28% N) added to nicosulfuron plus COC or NIS occasionally increased millet control. Nicosulfuron plus COC and 28% N controlled millet better postemergence than early postemergence; however, the best millet control for the eight locations resulted from two sequential applications of nicosulfuron.;Primisulfuron injured giant foxtail (Setaria faberi) and quackgrass (Elytrigia repens) more in a simulated cool-moist than a hot-dry environment. Foxtail control 3 weeks after treatment was unaffected by primisulfuron rates or adjuvants. Adding 28% N frequently improved quackgrass control with primisulfuron plus NIS or COC. Absorbed ;Field corn response to nicosulfuron and terbufos was similar at all locations in 1990. Nicosulfuron applied at the V4 stage injured field corn more than at the V3 stage. Sweet corn injury was observed at all locations and was most severe at Hancock, WI. Corn injury increased with nicosulfuron rate and terbufos application. Nicosulfuron at 140 g/ha or less did not reduce field or sweet corn yield, unless corn was previously treated with terbufos.;Field corn injury as a result of nicosulfuron and terbufos applications was more severe in Wisconsin than in Michigan, while no injury was observed in Minnesota in 1991. Grain yield was not reduced by nicosulfuron at 70 g/ha or less without terbufos. Nicosulfuron at 70 g/ha reduced corn vigor 2 weeks after treatment 45 and 13% following T-band applications of granular or controlled release granular formulations of terbufos in Wisconsin, respectively. Slight nicosulfuron injury was noted following T-band applications of phorate, fonofos, chlorpyrifos, chlorethoxyfos, tefluthrin, and carbofuran.