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Little documentation exists on the success of seeding cool-season turfgrasses in the late fall, winter and spring. The objectives of these two studies were to document the success of seeding Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), and tall fescue (Festuca arundinacea Schreb.) at less-than-optimum times of the year, and to determine if N and P fertilizer requirements vary with seeding date of Kentucky bluegrass. `Ram I' Kentucky bluegrass, `Fiesta' perennial ryegrass, and `Mustang' tall fescue were seeded on 1 Sept., 1 Oct., 1 Nov., 1 Dec., 1 Mar., 1 Apr., and 1 May ± 2 days beginning in 1989 and 1990. As expected, the September seeding date produced the best establishment, regardless of species. Dormant-seeding Kentucky bluegrass and tall fescue in November, December, or March reduced the establishment time compared with seeding in April or May. Seeding perennial ryegrass in November, December, or March may not be justified because of winterkill potential. To determine the effect of starter fertilizer on seedings made at different times of the year, `Ram 1' Kentucky bluegrass was seeded 1 Sept., 1 Nov., 1 Mar., and 1 May ± 2 days in 1989 and 1990, and the seedbed was fertilized with all combinations of rates of N (0, 24, and 48 kg·ha^-1) and P (0, 21, and 42 kg·ha^-1). Fertilizer rate had no effect on establishment regardless of seeding date, possibly because of the fertile soil on the experimental site.

Controlling mature roughstalk bluegrass (Poa trivialis L.; RSBG) using bispyribac–sodium (BYS) or sulfosulfuron (SUL) often yields inconsistent results. Attempting to control RSBG shortly after emergence may eliminate or reduce it with fewer inputs and less noticeable creeping bentgrass (Agrostis stolonifera L.; CBG) phytotoxicity than if treated at maturity. The objective of these studies was to determine whether BYS or SUL controls seedling RSBG with only minimal seedling CBG cover reduction. Four separate studies on either CBG or RSBG were conducted in spring or fall of 2007 and repeated in 2008 to simulate spring or fall fairway establishment. Studies were arranged as split plots with application timing (7, 14, 21, or 28 days after CBG emergence) as main plots and subplots were herbicide treatments in a 2 × 5 factorial with BYS or SUL applied once at five uniformly increasing rates of 0, 18, 37, 55, and 74 g·ha⁻¹ a.i. and 0, 6, 13, 19, and 26 g·ha⁻¹ a.i., respectively. Plots were maintained at 1.3 cm and emergence was defined as ≈50% of the study area being populated with one- to two-leaf CBG seedlings. Spring-seeded stands of CBG were safely treated with BYS 14 or more days after emergence (DAE) at 55 g·ha⁻¹ a.i. or less, whereas SUL was not safe by 28 DAE at any tested rate. Fall-seeded CBG was generally less sensitive to BYS and SUL. Sulfosulfuron resulted in excessive damage if applied to seedling CBG before 14 DAE at rates greater than 6 g·ha⁻¹ a.i. and if applied before 21 DAE at rates greater than 26 g·ha⁻¹. Bispyribac–sodium was safely applied as soon as 7 DAE at rates of 74 g·ha⁻¹ a.i. or less. Chemical names used: {2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy] benzoic acid} (bispyribac–sodium); {1-[4,6-dimethoxypyrimidin-2-yl]-3-[2-ethanesulfonyl-imidazo(1,2-a)pyridine-3-yl) sulfonyl]urea} (sulfosulfuron).

Mixtures of turfgrass seed are commonly used to establish lawns, with kentucky bluegrass (KBG) and perennial ryegrass (PRG) comprising two of the more commonly used species. In the humid regions of the Midwest United States, KBG is a desirable species, but slow germination makes it difficult to establish compared with PRG. The objective of our study was to evaluate establishment rate and species composition over 3 years of a turf stand seeded with different ratios of KBG and PRG (wt:wt) maintained as a lawn. Repeat experiments were initiated in 2007 and 2008 and conducted for 3 years in West Lafayette, IN, with seed mixtures of KBG:PRG of 100:0, 90:10, 80:20, 70:30, 50:50, and 0:100 wt:wt of pure live seed. Plots were seeded late August each year and percent turfgrass cover was rated up to 6 weeks after seeding (WAS). To evaluate stand composition after establishment, percent KBG cover was rated annually in August for 3 years using transect counts after selective removal of PRG with the herbicide chlorsulfuron. Likely as a result of greater crabgrass (Digiaria sp.) competition during establishment in 2007, 100% PRG, 50:50, 70:30, or 80:20 KBG:PRG ratio had the highest percentage turf cover at 6 WAS, whereas there was no difference between treatments at 6 WAS in 2008 when crabgrass competition was lower. Regardless of turf cover during establishment, all treatments except 100% PRG shifted to greater than 95% KBG cover by 3 years after establishment. For the region in which our study was conducted, it may be desirable to seed with a higher proportion (greater than 50%) of PRG to speed initial establishment for customer satisfaction, erosion control, and/or to offset years with high weed pressure. Under lawn conditions similar to our study, seeding ratios with high KBG (80:20 or 90:10 KBG:PRG) will likely shift to a stand composition of greater than 95% KBG within 2 years, whereas all other ratios lower in KBG will likely shift similarly within 3 years. Chemical names used: 2-chloro-N-{[(4-methoxy-6-methyl-1,3,5-triazin-2 yl)amino]carbonyl}benzenesulfonamide (chlorsulfuron)

Creeping bentgrass (Agrostis stolonifera L.) is well adapted to golf course greens, tees, and fairways but may become a weed in Kentucky bluegrass (Poa pratensis L.) roughs and lawns. The objectives of this study were to determine effects of sulfosulfuron rate and application date on control of creeping bentgrass and safety on Kentucky bluegrass. Field experiments were initiated in 2003 and 2004 in Ames, IA, and West Lafayette, IN. Single applications of sulfosulfuron at 0.011 or 0.022 kg·ha⁻¹ were applied over a 9-week period during the fall of each year. Phytotoxicity on Kentucky bluegrass was recorded weekly and control of creeping bentgrass was determined in the spring after fall treatments. No treatment provided greater than 31% control, and there were few differences in control between the two rates of sulfosulfuron. In West Lafayette, late fall applications were the most effective providing up to 31% control of creeping bentgrass. Sulfosulfuron provided less than 18% control in Ames in either year. Kentucky bluegrass was tolerant of all sulfosulfuron applications. Late fall applications of sulfosulfuron may be useful in partially removing creeping bentgrass from a heavily contaminated sward of Kentucky bluegrass.

Chemical names used: 1-(4,6-dimethoxypyrimidin-2-yl)-3-(2-ethylsulfonylimidazo[1,2-a]pyridin-3-ylsulfonyl)urea (sulfosulfuron)

Preemergence (PRE) herbicides are used to control crabgrass (Digitaria spp.). Single spring applications are common in areas with relatively low crabgrass pressure, whereas sequential applications often are used to extend control in locations with high crabgrass pressure. Our objectives were to determine if changing a.i. in initial and sequential applications affects crabgrass control and if single spring applications of tank-mixed PRE herbicides provide season-long crabgrass control. Studies were conducted 2009, 2010, and 2011 in West Lafayette, IN, and 2011 in Wymore, NE. The PRE herbicides prodiamine, pendimethalin, and dithiopyr were tested using different application strategies. Sequential applications were applied mid-April and mid-June using all possible combinations of the three herbicides and untreated for the initial and sequential application. These herbicides also were applied mid-April as single full-rate PRE application or as a tank mixture of two PRE herbicides at half-plus-half or half-plus-quarter rate. Season-long crabgrass control was consistently achieved using sequential applications regardless which of the three herbicides was used for initial or sequential applications. Single applications of tank mixtures also provided consistent crabgrass control, equivalent to single full-rate applications of the individual PRE herbicides. Tank mixtures of half-plus-quarter rate and single half-rate applications resulted in more crabgrass cover than single full-rate or half-plus-half rate applications regardless of the herbicide applied.

Roughstalk bluegrass (Poa trivialis L.) is a troublesome weed on golf courses, home lawns, and athletic fields from the Midwest to the mid-Atlantic states. Bispyribac-sodium and sulfosulfuron have recently been labeled for roughstalk bluegrass control, but their use needs to be refined. Our objective was to determine the most effective herbicide strategies for control of roughstalk bluegrass. Initial studies were conducted during 2005 in Illinois and Indiana and follow-up studies in 2006 in Indiana, Illinois, South Dakota (partial shade and full sun), and Wisconsin. Applications starting in the warmer temperatures of late May and June 2005 were more effective than those starting in mid-May. Bispyribac-sodium (a.i.) was applied at 74 or 114 g·ha⁻¹ four times at 2-week intervals decreased roughstalk bluegrass cover to 1% and 0% 12 weeks after initial treatment (WAIT) in Illinois and Indiana in 2005, respectively, whereas sulfosulfuron (a.i.) at 13 or 27 g·ha⁻¹ applied twice at 2-week intervals decreased cover to no less than 18%. In 2006, bispyribac-sodium was most effective in Indiana and Illinois decreasing cover to as low as 4%, whereas sulfosulfuron was most effective in South Dakota resulting in a decrease in cover to as low as 7%, and both herbicides performed similarly in Wisconsin. Three applications of sulfosulfuron (a.i.) at 27 g·ha⁻¹ at 2-week intervals or four applications of bispyribac-sodium (a.i.) at 56 or 74 g·ha⁻¹ at 2-week intervals were most effective for roughstalk bluegrass control.

Roughstalk bluegrass (Poa trivialis L.) contamination is problematic on golf course fairways from the Midwest to the mid-Atlantic regions of the United States. Bispyribac–sodium and sulfosulfuron have potential to selectively control roughstalk bluegrass. Our objectives were to determine the most effective herbicide treatments for short- and long-term roughstalk bluegrass control and to determine if interseeding with creeping bentgrass (Agrostis stolonifera L.) after herbicide treatments will improve long-term control of roughstalk bluegrass or conversion to creeping bentgrass. Plots were treated with bispyribac–sodium or sulfosulfuron and then half of each plot was interseeded with creeping bentgrass in early August, 2 weeks after the final herbicide application in 2006, 2007, and 2008 in Indiana. Roughstalk bluegrass cover reduction was highest when treated with bispyribac–sodium at 56 or 74 g·ha⁻¹ a.i. applied four times or sulfosulfuron at 27 g·ha⁻¹ a.i. applied three times. Interseeding with creeping bentgrass improved long-term roughstalk bluegrass control and quickened conversion to creeping bentgrass. Furthermore, bispyribac–sodium and sulfosulfuron appeared to be more effective in the first 2 years of the study when seasonal heat stress was greater, which appeared to improve long-term roughstalk bluegrass control and promoted creeping bentgrass establishment. Chemical names used: {2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy] benzoic acid} (bispyribac–sodium), {1-[4,6-dimethoxypyrimidin-2-yl]-3-[2-ethanesulfonyl-imidazo(1,2-a)pyridine-3-yl) sulfonyl]urea} (sulfosulfuron).