seeded earlier. Further research confirmed that seeded bermudagrass should be established as early as possible Bermudagrass [Cynodon dactylon var. dactylon (L.) Pers.] and in late spring to increase winter survival (Munshaw et zoysiagrass (Zoysia japonica Steud.) cultivars established by seed are Hensler et al., 1999). However, Ahring et al. desirable for golf and athletic turfs because of minimum establishment (1975) reported an experimental strain of bermudagrass costs, but little is known about their management during establishment. Seeding dates, seeding rates, post-seeding N fertility, and herbi-was not affected by freezing when seeded as late as 21 cide safety on seedling 'Mirage' bermudagrass and 'Zenith' zoysiagrass July in Oklahoma, indicating potential improvements were investigated in Indiana and Kentucky. Under the conditions in cold hardiness through plant breeding. Portz et al. of our studies, optimum bermudagrass establishment occurred when (1981) reported that zoysiagrass could be successfully seeded 1 June to 15 July at 12 to 49 kg ha Ϫ1 , when Ͼ950 growing established in Southern Illinois when seeded 1 July. degree days (GDD, 5؇C base) accumulated by first frost and when Although seeded zoysiagrass cultivars are generally tol-49 kg ha Ϫ1 N mo Ϫ1 was applied. Earlier seeding dates provided more erant of winters in the transition zone (NTEP, 2001), bermudagrass cover after the first winter. Optimum zoysiagrass estabno information exists on the effect of seeding date on lishment occurred when seeded from 1 to 15 June at 49 to 98 kg ha Ϫ1 , establishment and winter survival. Thus, defining the when Ͼ 1750 GDD accumulated by first frost, and when 49 kg ha Ϫ1optimum seeding dates for bermudagrass and zoysia-N mo Ϫ1 was applied. Increasing N from 49 kg ha Ϫ1 mo Ϫ1 to 98 kg ha Ϫ1 mo Ϫ1 did not hasten establishment of either species. Quinclorac

Improved cultivars of zoysiagrass established by seed are now available, but little is known about the safety of herbicides on zoysiagrass seedlings. Our objective was to determine the turf safety of various herbicides when applied from emergence to 4 wk after emergence (WAE) of ‘Zenith’ zoysiagrass. Oxadiazon (3.4 kg ai/ha), MSMA (2.3 kg ai/ha), and pronamide (1.1 kg ai/ha) did not reduce coverage 7 WAE when applied at emergence or later and caused only temporary discoloration of seedlings. Foramsulfuron (0.03 kg ai/ha) injured seedling zoysiagrass both years of testing and reduced cover in the final year. Fluazifop (0.07 kg ai/ha) caused significant injury in all 3 yr of the study and reduced coverage in the final year. Fenoxaprop (0.14 kg ai/ha) caused visible injury and reduction in zoysiagrass coverage in all 3 yr of the study. Our studies indicate pronamide, MSMA, or oxadiazon are the safest herbicides to use over Zenith zoysiagrass seedlings, and selection among these three depends on the primary weed species present.

Annual bluegrass (Poa annua L.) is an invasive weed producing copious amounts of viable seed that compete with seedling turfgrasses during renovation. These field studies were conducted to determine the effectiveness of dazomet (tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione), a granular soil sterilant that breaks down in soil to release methyl isothiocyanate (MITC), for controlling the soil seed bank of annual bluegrass during turfgrass renovation. Field trials in Urbana, Ill., and West Lafayette, Ind., in Spring and Fall 2000 and 2001 evaluated dazomet rate from 0 to 504 kg·ha-1 and soil preparation techniques to determine the most effective practices to reduce annual bluegrass reestablishment into a creeping bentgrass (Agrostis stolonifera L.) seeding. The interval, in days, between dazomet application and creeping bentgrass planting was also examined to determine the optimal seeding time as measured by the level of annual bluegrass reestablishment. Spring trials generally gave poor results that were attributed to windy conditions resulting in rapid loss of MITC. The annual bluegrass soil seed bank was reduced 46% in spring trials compared to 78% in fall trials. Increasing dazomet rates reduced the absolute number of viable annual bluegrass seeds remaining in the soil. However, significant quantities of viable seed remained, regardless of dazomet rate. Annual bluegrass infested the renovated turf in all trials to varying degrees. Dazomet rates of 420 or 504 kg·ha-1 yielded the lowest rates of annual bluegrass reestablishment. Trials conducted in the fall at these rates resulted in annual bluegrass cover of 1% to 20% in the resulting turf. Creeping bentgrass planted at 1 day after dazomet application had significantly less annual bluegrass than when seeded at 7 or 9 days after dazomet application. Dazomet is a tool that can help reestablish a new turf with lower levels of annual bluegrass. However, eradication of annual bluegrass with dazomet is not likely and environmental conditions will dramatically affect the success of the sterilization.

Annual bluegrass (Poa annua L.) (ABG) is an invasive weed in creeping bentgrass (Agrostis stolonifera L.) (CBG) golf course fairways and tees. Plant growth regulators (PGRs) like flurprimidol (FL) are often applied to these areas to manage shoot growth and minimize ABG encroachment. This two‐year field study evaluated the effects of various FL, trinexepac‐ethyl (TE), and FL + TE tank‐mix combinations applied monthly from May through October to a mature CBG research fairway containing > 30% ABG prior to PGR initiation. After two consecutive years of PGR applications the most effective treatments for reducing ABG populations were FL alone (0.28, or 0.56 kg a.i./ha) or the FL + TE (0.56 + 0.06 kg a.i./ha) tank‐mix which reduced the ABG populations from initial levels by 78, 74, and 87% respectively. PGR effects on visual color and quality were not significant when averaged across both study years. These results demonstrate that even where rather large, > 30%, ABG populations exist, monthly FL applications throughout the growing season can gradually reduce ABG to tolerable, <10%, levels without the risk for rapid turf cover losses which can result in substantial turf voids.

Converting cool-season golf course fairways to creeping bentgrass (Agrostis palustris Huds.) is desirable because it affords excellent playability, enhanced recuperative potential, and enhanced disease tolerance compared to annual bluegrass (Poa annua sp. Timm.) or perennial ryegrass (Lolium perenne), which are common species in fairways. However, converting current golf course fairways to creeping bentgrass with nonselective herbicides is problematic because it disrupts play and decreases revenue, as fairways must be closed for an extended period of time. The objective of our study was to quantify the effect of trinexapac-ethyl (TE), overseeding date, and overseeding rate on the success on the gradual conversion of cool-season fairways to creeping bentgrass over 3 years. `Penneagle' creeping bentgrass was overseeded at 0, 49, or 98 kg·ha-1 in fall, spring, or fall+spring after aerification, and application of TE at 0.0, 0.2, or 0.4 kg·ha-1. Gradual conversion to creeping bentgrass was effective, on perennial ryegrass fairways, with up to 36% cover of creeping bentgrass after 3 years of overseeding. However, only a maximum of 3% creeping bentgrass cover was obtained after the third year of overseeding into primarily annual bluegrass fairways. Fall overseeding with bentgrass at 49 or 98 kg·ha-1 was equally effective and additional spring overseeding did not improve establishment. Applications of TE prior to overseeding did not enhance the conversion. Chemical name used: 4-cyclopropyl-a-hydroxy-methylene-3,5-dioxocyclohexanecarboxylic acid ethyl ester (trinexapac-ethyl).