Perennial Ryegrass Control in Bermudagrass and Zoysiagrass

Abstract

Pronamide [3,5-dichloro-N-(l-dimethyl-2-propynyl) benzamide] is commonly used in spring to suppress or selectively control perennial ryegrass (Lolium perenne L.) (PRG), which had been overseeded into bermudagrass (Cynodon spp.) turf the previous fall. Some turfgrass managers have observed either slow or unacceptable PRG control with pronamide, and this herbicide can move in water to severely injure cool-season turf grown adjacent to treated areas. The objectives of these field studies were to compare the safety and PRG control efficacy of diclofop [methyl (±)-2-[4[(2,4-dichlorophenoxy) phenoxy]propanoate], chlorsulfuron [2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-y1)amino]carbonyl]benzenesulfonamide], metsulfuron [2-[[[[(4-methoxy-6-methyl-l,3,5-triazin-2y1)amino]carbony] amino]sulfonyl]benzoic acid], and pronamide applied to Midiron or Tufcote bermudagrass (Cynodon dactylon [L.] Pers.) and Meyer zoysiagrass (Zoysia japonica Steud). In bemudagrass, diclofop (1.12 and 2.24 kg ha¯¹), chlorsulfuron (0.07 and 0.14 kg ha¯¹), and metsulfuron (0.07 and 0.14 kg ha¯¹) provided more rapid, and sometimes improved PRG control, when compared to pronamide (1.12 kg ha¯¹). None of the herbicides were phytotoxic to Midiron or Tufcote, and herbicide use was associated with a more rapid transition to a bermudagrass monostand. Chlorsulfuron (0.07 or 0.14 kg ha¯¹) and metsulfuron (0.035, 0.070 or 0.140 kg ha¯¹) were either too phytotoxic or induced unacceptable levels of chlorosis in Meyer zoysiagrass. Diclofop effectively controlled PRG in a single application at rates ranging from 1.12 to 3.36 kg ha¯¹. These rates generally elicited an objectionable chlorosis in Meyer, which persisted for 2 to 3 weeks. A single spring or fall application of pronamide (1.12 kg ha¯¹) provided poor 'Palmer' + 'Prelude' PRG control, but caused only a slight amount of chlorosis in zoysiagrass.