ACTIVITY OF NICOSULFURON, RIMSULFURON, AND THEIR MIXTURE ON FIELD CORN (ZEA-MAYS), SOYBEAN (GLYCINE-MAX), AND 7 WEED SPECIES

Seven annual weed species were treated under greenhouse conditions with six rates of either nicosulfuron, rimsulfuron, or a 1:1 mixture (DPX-79406). Herbicide rates in g ai/ha producing 90% dry biomass reduction (GR90) were calculated for each weed species. Accordingly, weeds were classified as very susceptible when GR90 less-than-or-equal-to 9, susceptible when 9 < GR90 less-than-or-equal-to 18, moderately susceptible when 18 < GR90 less-than-or-equal-to 27, and tolerant when GR90 > 27. Giant and green foxtails were very susceptible to the three herbicides. Proso millet was very susceptible to rimsulfuron and DPX-79406, and susceptible to nicosulfuron. Wild oat was susceptible to nicosulfuron and DPX-79406, and moderately susceptible to rimsulfuron. Redroot pigweed was very susceptible to nicosulfuron; whereas, it was susceptible to rimsulfuron and DPX-79406. Common ragweed and smooth crabgrass were tolerant to the three herbicides. In a second experiment, we used regression estimate analysis with an additive reference model to evaluate nicosulfuron and rimsulfuron interaction on corn, soybean, common ragweed, and smooth crabgrass. We found these herbicides synergistic on smooth crabgrass, antagonistic on soybean, less than additive on common ragweed, and additive on corn. Nomenclature: Nicosulfuron, 2-[[[4,6-dimethoxy-2-pyrimidinyl)amino]sulfonyl]-N-N-dimethyl-3-pyridinecarboxamide; rimsulfuron, N-[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]-3-(ethylsulfonyl)-2-pyridinesulfonamide; common ragweed, Ambrosia artemisiifolia L. #3 AMBEL; giant foxtail, Setaria faberi Herrm. # SETFA; green foxtail, Setaria viridis L. Beauv. # SETVI; proso millet, Panicum miliaceum L. # PANMI; redroot pigweed, Amaranthus retroflexus L. # AMARE; smooth crabgrass, Digitaria ischaemum (Schreb. ex Schweig.) Schreb. ex Muhl. # DIGIS; wild oat, Avena fatua L. # AVEFA); corn, Zea mays L. 'Pioneer 3971'; soybean, Glycine max L. 'Maple Glen.'