Chemical Control Options for Juncus Species in Maintained Turfgrass.

Path rush (Juncus tenuis) and toad rush (J. bufonius) are troublesome weeds in maintained turfgrass throughout the southeastern United States. Chemical control options are limited. Historically, turfgrass managers have used auxin mimicking herbicides to control Juncus species with varied success. An ongoing research study is being conducted in Mississippi and Tennessee to determine potential chemical control options with the hypothesis that several common herbicides may provide acceptable control of Juncus species. Treatments include: halosulfuron (70.0 g ai/ha) flazasulfuron (52.7 g ai/ha), trifloxysulfuron (29.5 g ai/ha), Speedzone (carfentrazone, 2,4-D, mecoprop, dicamba; 1,230 g ai/ha), Strike 3 (2,4-D, MCPA, dicamba; 1,520 g ai/ha), Celsius (thiencarbazone, iodosulfuron, dicamba; 233 g ai/ha), Tribute Total (thiencarbazone, foramsulfuron, halosulfuron; 136 g ai/ha), foramsulfuron (58.6 g ai/ha), Fahrenheit (dicamba and metsulfuron; 320 g ai/ha), SwitchBlade (halauxifen-methyl, fluroxypyr, dicamba; 310 g ai/ha), and the experimental herbicide EH1580 (pyrimisulfan and penoxulam; 90 and 180 g ai/ha). Treatments were applied using a CO₂-pressurised backpack sprayer in a water carrier volume of 374 L/ha. Control was evaluated visually 2, 5, 9 and 12 weeks after treatment. Data were subjected to analysis of variance (α = 0.05). Control varied due to species and location. Trials (two per species) are presented separately. Means were separated using Student-Newman-Keuls LSD (α = 0.05). In general, none of the treatments provided commercially acceptable control of either toad or path rush. However, in several instances greater than 50% control was achieved with Tribute Total, halosulfuron, EH1580, and Celsius. Almost all herbicides failed to adequately control toad rush, possibly due to maturity of the stands tested. Both species appear to be easier to control when herbicides are applied prior to flowering. Sequential applications will likely be needed in order to adequately control these two rush species. Future research should evaluate differential herbicide response and application timing.