Prostrate knotweed (Polygonum aviculare L.) is a mat-forming, summer annual that overruns compacted areas. On golf courses, areas adjacent to cart paths can sometimes become compacted allowing for infestation by prostrate knotweed. Control options for prostrate knotweed in warm-season turf have not been reported. Two experiments were conducted in May 2002 at Hanover Country Club, in Hanover, VA to determine control options for prostrate knotweed in bermudagrass (Cynodon dactylon (L.) Pers.). The first study consisted of acetolactate synthase (ALS) inhibiting herbicides which included metsulfuron at 0.04 lb ai/A, chlorsulfuron at 0.13 lb ai/A, rimsulfuron at 0.05 lb ai/A, imazaquin at 0.44 lb ai/A, foramsulfuron at 0.04 lb ai/A, flazasulfuron at 0.05 lb ai/A, trifloxysulfuron at 0.02 lb ai/A, and sulfosulfuron at 0.02 lb ai/A and included a non-ionic surfactant (NIS) at 0.25% (v/v). The other study evaluated bromoxynil at 0.50 lb ai/A + NIS, bromoxynil + dicamba at 0.50 + 0.25 lb ai/A + NIS, dicamba at 0.25 lb ai/A, triclopyr at 0.56 lb ai/A, triclopyr +clopyralid at 0.75 lb ai/A, 2,4-D + triclopyr at 1.69 lb ai/A, 2,4-D + dicamba at 0.97 lb ai/A, 2,4-D + dicamba + MCPP at 1.66 lb ai/A, quinclorac at 1.50 lb ai/A+ COC at 1% (v/v), and metribuzin at 0.50 lb ai/A. Both experiments were conducted as randomized complete block designs with three replications, in bermudagrass roughs with natural infestations of prostrate knotweed. Bermudagrass injury and prostrate knotweed control were rated 2, 4, and 7 week after treatment (WAT).
In the ALS-inhibiting herbicide experiment, metsulfuron and chlorsulfuron controlled prostrate knotweed at least 90% 7 WAT. Flazasulfuron controlled prostrate knotweed 65% 7 WAT. Imazaquin, rimsulfuron, trifloxysulfuron, foramsulfuron, and sulfosulfuron controlled prostrate knotweed less than 35% 7 WAT. Imazaquin injured bermudagrass 30% 2 WAT, injury lessened with time. In the other experiment, 2,4-D + triclopyr, 2,4-D + dicamba, 2,4-D + dicamba + MCPP, and dicamba controlled prostrated knotweed at least 90% 7 WAT. Bromoxynil + dicamba, triclopyr, and triclopyr + clopyralid controlled prostate knotweed 70, 58, and 50%, respectively 7 WAT. Bromoxynil, quinclorac, and metribuzin controlled prostrate knotweed less than 25% 7 WAT. Quinclorac injured bermudagrass 27% 2 WAT, injury lessened with time. Results indicate metsulfuron, chlorsulfuron, 2,4-D + triclopyr, 2,4-D + dicamba, and 2,4-D + dicamba + MCPP control prostrate knotweed in bermudagrass roughs.