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Research was conducted to evaluate the tolerance of tall fescue to mesotrione applied during establishment from seed. Nine field studies were conducted over a 3-year period (2004–2006) near Knoxville, Tenn., to evaluate the tolerance of seedling tall fescue [Schedonorus phoenix (Scop.) Holub] to mesotrione and quinclorac. The first evaluated tall fescue tolerance to single and sequential applications of mesotrione compared with quinclorac (multiple application study). The second evaluated the timing of mesotrione application on tall fescue injury and establishment (timing study). In the multiple application study, all treatments injured tall fescue 23% or less. Quinclorac reduced tall fescue groundcover up to 17% 63 days after emergence (DAE). Mesotrione at 0.28 kg·ha−1 applied 28 and 42 DAE or 14, 28, and 42 DAE decreased groundcover only 4% and 6% 63 DAE. In the timing study, mesotrione at 0.28 kg·ha−1 applied at 7 and 28 DAE injured tall fescue 17% to 21% 7 and 14 days after application; however, injury subsided to less than 10% by 28 days after application. Only mesotrione at 0.28 kg·ha−1 applied 7 DAE resulted in delayed tall fescue groundcover at 70 DAE. Variation was observed in Fall 2005 evaluations compared with other evaluations, which may be attributable to delayed seeding date and cool, wet conditions.
Siduron and quinclorac provide limited broadleaf weed control during seeded establishment of tall fescue. Carfentrazone and bromoxynil are contact herbicides that act primarily on broadleaf, dicot species. Research was conducted to evaluate tall fescue tolerance to carfentrazone or bromoxynil when integrated into traditional siduron and quinclorac weed control programs. Quinclorac at 0.84 kg·ha–1 applied at seeding followed by quinclorac at 0.84 kg·ha–1 35 days after emergence (DAE) and quinclorac at 1.68 kg·ha–1 plus carfentrazone at 0.034 kg·ha–1 applied DAE were the most injurious to tall fescue 42 and 49 DAE. While quinclorac sequential applications reduced turfgrass groundcover 42 DAE, tall fescue recovered by 49 DAE. Injury from all quinclorac treatments persisted until 63 DAE. Bromoxynil (0.28 or 0.56 kg·ha–1) or carfentrazone (0.017 or 0.034 kg·ha–1) caused minimal injury and no decrease in turfgrass groundcover when applied 35 DAE. While siduron applied at seeding followed by (fb) bromoxynil applied 35 DAE (6.7 fb 0.56 kg·ha–1) caused minimal tall fescue injury, a decrease in groundcover was observed at 49 DAE. No tall fescue cover reduction was observed for any treatment by 63 DAE. These data indicate that bromoxynil and carfentrazone can be safely used during seeded establishment of tall fescue beginning 35 DAE with no long-term effects on turfgrass stand development.
Carfentrazone is a broadleaf weed control herbicide that is also used for control of silvery-thread moss (Bryum argenteum) in creeping bentgrass (Agrostis stolonifera) putting greens. Field studies were initiated in June 2006 and May 2007 to evaluate silvery-thread moss control with carfentrazone alone, carfentrazone applied with nitrogen (N) and/or topdressing (TD), N alone, TD alone, and mancozeb plus copper hydroxide. All treatments except for mancozeb plus copper hydroxide and the non-treated control reduced silvery-thread moss populations 16 weeks after initial treatment. Carfentrazone applied alone and carfentrazone followed by N decreased silvery-thread moss populations by 39%. Carfentrazone followed by TD and carfentrazone followed by N + TD decreased silvery-thread moss populations by 73% and 66%, respectively. These data indicate the importance of using cultural practices to control silvery-thread moss on creeping bentgrass putting greens.
Indaziflam is an alkylazine herbicide that controls winter and summer annual weeds in bermudagrass (Cynodon sp.) turf by inhibiting cellulose biosynthesis. Research was conducted in Tennessee and Texas during 2010 and 2011 to evaluate the effects of indaziflam applications on overseeded perennial ryegrass (Lolium perenne) establishment and summer annual weed control. In Texas, perennial ryegrass cover on plots treated with indaziflam at 0.75 and 1.0 oz/acre measured 37% to 48% compared with 88% for the untreated control 257 days after initial treatment (DAIT). Perennial ryegrass cover following applications of indaziflam at 0.5 oz/acre measured 84% 257 DAIT and did not differ from the untreated control on any evaluation date. Inconsistent responses in crabgrass (Digitaria sp.) control with indaziflam at 0.5 oz/acre were observed in Tennessee and Texas. However, control was similar to the 0.75-oz/acre rate and prodiamine at 7.8 oz/acre at each location. A September application of indaziflam at 0.75 oz/acre followed by a sequential treatment at 0.5 oz/acre in March of the following year provided >90% control by June 2011. Indaziflam application regimes of this nature would allow for successful fall overseeding of perennial ryegrass every two years and control winter annual weed species such as annual bluegrass (Poa annua).