Experiments were conducted to determine the efficacy, absorption, and translocation of nicosulfuron, rimsulfuron, and nicosulfuron rimsulfuron on barnyardgrass, green foxtail, longspine sandbur, and large crabgrass. In the greenhouse, nicosulfuron, rimsulfuron, and nicosulfuron rimsulfuron were applied at 0.0625, 0.125, 0.25, 0.5, 0.75, 1, and 2 times their label rates of 35, 13, and 26 13 g ai ha−1, respectively, on 5- to 10-cm plants. Three weeks after treatment (WAT), barnyardgrass was the most susceptible species to all three herbicides, and large crabgrass was the least susceptible. The nicosulfuron, rimsulfuron, or nicosulfuron rimsulfuron rates causing 50% visible injury (GR50) for barnyardgrass were 10.9, 4.8, and 6 3 g ai ha−1, respectively. Similarly, the GR50 for large crabgrass were 25.6, 9.9, and 14.3 7.2 g ai ha−1, respectively, 3 WAT. Absorption of nicosulfuron, rimsulfuron, and nicosulfuron rimsulfuron was greater in barnyardgrass than in large crabgrass. Absorption of nicosulfuron rimsulfuron in barnyardgrass and large crabgrass was 74% and 57%, respectively, 7 d after treatment (DAT). In addition, translocation of nicosulfuron, rimsulfuron, and nicosulfuron rimsulfuron out of the treated leaf was 14, 12, and 14% higher, respectively, in barnyardgrass than in large crabgrass. The differential response of these weed species to nicosulfuron, rimsulfuron, and nicosulfuron rimsulfuron might be due to differences in herbicide absorption and translocation.
Nomenclature: Nicosulfuron; rimsulfuron; barnyardgrass, Echinochloa crus-galli (L.) P. Beauv.; green foxtail, Setaria virdis (L.) Beauv.; large crabgrass, Digitaria sanguinalis (L.) Scop.; longspine sandbur, Cenchrus longispinus (Hack.) Fernald.