| Abstract/Contents: | "Field studies were conducted from 1989 to 1992 to determine turf tolerance (phytotoxicity) and control of crabgrass species (Digitaria ciliaris and D. serotina) with experimental and registered postemergence herbicides (POST). Research was conducted on established 'Floratam' St. Augustinegrass and consisted of 3.3 x 3.3 m plots arranged in a RCBD, with 4 replicates. Treatments and rates (kg ai/ha) included asulam 3.3EC at 0.56 and 2.24; atrazine 4.0EC at 1.12 and 2.24; clethodim 2.0EC at 0.14 and 0.28; clethodim 0.94EC at 0.052 and 0.10; cyanazine 90DF at 1.12 and 2.24; diclofop 3.0EC at 1.12 and 2.24; dithiopyr 1.0EC at 0.56; fenoxaprop 1.0EC at 0.14, 0.20, 0.28, and 0.56; fenoxaprop ethyl 0.79 EC at 0.054 and 0.10; fluazifop 1.0EC at 0.035, 0.068, 0.14, 0.28, and 0.56; fluazifop -P- butyl 2.66EC at 0.18 and 0.23; haloxyfop 2.0EC at 0.035, 0.068, 0.14, 0.28, and 0.56; imazaquin 1.5SC at 0.42; imazquin + pendimethalin 65DF at 2.1; MSMA 6SC at 2.24; nicosulfuron 75DF at 0.035, 0.070, 0.14 and 0.28; quinclorac 75DF 0.14, 0.28, and 1.12; quizalofop 0.8EC 0.030, 0.061, 0.14, 0.28, and 0.56; isomer of quizalofp 0.88EC at 0.030 and 0.61; sethoxydim 1.5 EC at 0.035, 0.056, 0.068, 0.112, 0.14, 0.28, and 0.56; sulfometuron 75DF at 0.14 and 0.28; tridiphane 4.0EC at 0.14 and 0.28; ASC-67040 10WP at 0.049, 0.098, and 0.197; and 360-14H 0.460EC at 0.067, 0.10, 0.14, and 0.20. Crop oil, X-77, or surfactant were mixed with appropriate herbicides as recommended by manufacturers. Treatments were applied at the 2-4 leaf growth stage with a CO2 back-pack sprayer calibrated at 187 L/ha. POST phytotoxicity was visually rated from 1 to 10 where 5.0 = minimally acceptable and 10 = best turfgrass color. Crabgrass control also was visually determined on a 0 to 100 scale, where 0 = no control and 100 complete control. Data was collected every two weeks and subjected to statistical analysis. Imazquin + pendimethalin at 2.1, quinclorac at 1.0, sthoxydim at 0.56, and fluazifop -P- butyl at 0.23 kg/ha provided good (> or = 80%) crabgrass control 6 to 9 weeks after initial treatment (WAIT). Sethoxydim rates lower than 0.56 kg/ha provided 60 to 80% less crabgrass control than the highest rate. Generally, these chemicals provided acceptable turf color 6 WAIT, however, unacceptable turf color lasted from 3 to 4 weeks with quinclorac and up to 9 weeks for sethoxydim. Poor (< or = 70%) crabgrass control followed atrazine, clethodim, cyanazine, diclofop, dithiopyr, fenoxaprop, fenoxaprop ethyl, fluazifop, haloxyfop, imazaquin, MSMA, nicosulfuron, quizalofop, isomer of quizalofop, sulfometuron, tridiphane, fenoxaprop ethyl, ASC-67040, and 360-14H treatments. Unacceptable turf color also was associated with most of these treatments up to 9 WAIT when compared to both untreated and asulam plots. Acceptable turf color however, was observed in plots treated with quizalofop at 0.030 and 0.061 kg/ha. Tank mix of asulam 0.56 kg/ha + haloxyfop 0.068 provided > or = 80% crabgrass control when compared to either asulam 2.24 or haloxyfop at 0.035 or 0.068 kg/ha alone. Excellent (> or = 90%) crabgrass control was provided by tank mixing fluazifop 0.035 + asulam 1.12 kg/ha or haloxyfop 0.068 + asulam 1.12 kg/ha. Acceptable turf color was obtained with these tank mixtures when compared to both untreated and asulam plots. Similarly, these tank mixtures were better than mixing atrazine 1.12 + ASC 0.049 kg/ha; dithiopyr 0.56 + MSMA 2.24 kg/ha, or sethoxydim 0.035/0.068 kg/ha + asulam 0.56/0.56; which resulted in poor crabgrass control and unacceptable turf color for up to 6 WAIT. In general, imazquin + pendimethalin 2.1 kg/ha, quinclorac 1.0 kg/ha, fluazifop -P- butyl 0.23 kg/ha and sethoxydim 0.56 kg/ha; and tank mixing asulam 0.56 + haloxyfop 0.068; fluazifop 0.035 + asulam 1.12 kg/ha or haloxyfop 0.068 + asulam 1.12 kg/ha were the best treatments in that they provided good or excellent crabgrass control and acceptable turf color after an initial 6 to 9 week period of phytotoxicity." |
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