Tropical signalgrass control in hybrid bermudagrass with glufosinate and imazapic tank‐mixes

Abstract Tropical signalgrass (TSG [ Urochloa distachya (L.) T.Q. Nguyen]) is difficult to control in Florida turfgrass due to limited herbicide options, perennial life cycle, aggressive growth, and ability to reestablish from stolons and seeds. Field studies in central Florida were conducted in 2022 and 2023–2024 to identify effective herbicide combinations for controlling severe (i.e., ≥50% cover) TSG infestations in a hybrid bermudagrass [BGR Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] athletic field. Application timing (spring/summer [S/S Seq.] vs. fall/winter [F/W Seq.]) and turfgrass recovery were also assessed. Herbicide treatments (topramezone [TPZ; 12 or 18 g ha −1 ], quinclorac [QNC; 841 g ha −1 ], amicarbazone [AMC; 175 or 254 g ha −1 ], imazapic [IMC; 70 g ha −1 ], glyphosate [GLY; 140 or 280 g ha −1 ], glufosinate [GLU; 553 or 840 g ha −1 ], pinoxaden [PNX; 154 g ha −1 ], thiencarbazone + foramsulfuron + halosulfuron [TFH; 355 + 710 + 1105 g ha −1 ]) were applied alone or combined every 2 weeks for a total of two applications, starting from August 3, 2022 (Study 1) and May 18, 2023, or October 11, 2023 (Study 2; PNX, IMC, and GLU only). In Study 1, only PNX and GLU‐based treatments effectively controlled TSG. Study 2 showed similar results, with IMC plus a low rate of GLU providing similar control to the higher rate of GLU alone. TSG removal was faster in the S/S Seq., but only the F/W Seq. consistently prevented reestablishment. GLU‐based treatments caused rapid, severe BGR injury, though complete regeneration followed within 6–8 weeks after initial treatment (WAIT). Recovery was slower with F/W Seq. in Study 2 compared to Study 1.