Abstract/Contents: | "Glyphosate resistant creeping bentgrass may soon be available for commercial use on golf courses. In other agricultural areas, transgenic crops have provided a comprehensive weed management solution; however, there are potential management challenges. A specific concern with glyphosate resistant creeping bentgrass is control in the event it escapes a managed environment. The objective of this research was to evaluate various herbicides for bentgrass control. Replicated research trials were initiated on non-transgenic 'Penncross' creeping bentgrass on 10 April or 22 May 2002 at Jackson Springs, NC. Evaluated treatments included: glyphosate as a standard (1.7 kg/ha), fluazifop (0.4 kg/ha), glyphosate + fluazifop (1.7 + 0.4 kg/ha), clethodim (0.3 kg/ha), sethoxydim (0.4 kg/ha), sulfometuron (0.05 kg/ha), imazaquin (0.06 kg/ha), imazaquin + MSMA (0.06 kg/ha + 2.2 kg/ha), atrazine (2.2 kg/ha), metribuzin + MSMA (0.3 + 2.2 kg/ha), isoxaflutole (0.1 fb 0.1 or 0.2 kg/ha), rimsulfuron (0.05 or 0.1 kg/ha), and sulfosulfuron (0.1 kg/ha). Glyphosate and fluazifop applied alone or as a tank-mix as well as clethodim and sethoxydim were evaluated as single applications or with one sequential applied four weeks after initial treatment. Fluazifop, clethodim, sethoxydim, and atrazine were applied with a crop oil concentrate (1% v/v) while imazaquin, MSMA, rimsulfuron, sulfometuron, and sulfosulfuron were applied with a non-ionic surfactant (0.25% v/v). All treatments were applied with a backpack sprayer calibrated to deliver 304 l/ha. Visual estimates of bentgrass control were taken at four and eight weeks after initial treatment and were subjected to ANOVA and means were separated according to Fisher's protected LSD (P=0.05). At four weeks after initial treatment, one or two applications of glyphosate provided excellent bentgrass control when initiated in April but only fair control when initiated in May. Similarly, one or two applications of glyphosate plus fluazifop provided excellent control when initiated in April but only good control when initiated in May. Additionally, atrazine provided excellent bentgrass control, while fluazifop, clethodim, sethoxydim, sulfometuron, imazaquin, imazaquin + MSMA, metribuzin + MSMA, isoxaflutole, rimsulfuron, or sulfosulfuron provided poor control at four weeks after initial treatment. At eight weeks after initial treatment, single applications of glyphosate provided good to excellent bentgrass control, dependent upon initiation time, while two applications provided excellent bentgrass control. One or two applications of glyphosate + fluazifop provided excellent bentgrass control. Two applications of fluazifop provided good to excellent bentgrass control while single applications provided poor control. Additionally, two applications of clethodim provided excellent control while two applications of sethoxydim ranged from good to excellent, dependent upon initiation time. Atrazine provided excellent control while sulfosulfuron control ranged from good to excellent. Sulfometuron, imazaquin, imazaquin + MSMA, metribuzin + MSMA, isoxaflutole, and rimsulfuron provided poor control. In conclusion, atrazine, fluazifop, clethodim, or sethoxydim offer non-glyphosate options for bentgrass control; however, it is likely repeat applications will be needed." |