Applied Turfgrass Science最新文献

Creeping bentgrass (Agrostis stolonifera L.) is a highly desirable cool-season turfgrass that produces a quality golf playing surface. Golf courses that are established with creeping bentgrass are often invaded by annual bluegrass (Poa annua L.) and other turfgrass species over a relatively short period of time. Interseeding and non-selective herbicides, like glyphosate, have often been used to increase creeping bentgrass on golf course fairways. The objective of this research was to determine the most effective glyphosate rate and application timing necessary to quickly increase creeping bentgrass populations through interseeding into predominantly annual bluegrass fairways, while keeping the golf course open for play. This study was conducted from July to October 2010 at the University of Minnesota Les Bolstad Golf Course (St. Paul, MN) and Michigan State University Hancock Turfgrass Research Center (East Lansing, MI). Glyphosate was applied to plots at 14, 7, or 0 days before seeding (DBS) at rates of 0, 0.28, 0.42, 0.84, 1.68, or 5.62 kg ai/ha (0, 0.25, 0.37, 0.75, 1.5, or 5.0 lb ai/acre). ‘T-1’ creeping bentgrass was slit-seeded into the entire plot area in two directions at a total rate of 73.2 kg/ha. Higher glyphosate rates provided the greatest increase in bentgrass abundance at both locations. The greatest bentgrass population increase (54%) was observed in Michigan for the 5.62 kg ai/ha (5.0 lb ai/acre) treated plots at 8 weeks after seeding (WAS). The glyphosate applications at 7 and 0 DBS had the longest duration of acceptable turf quality and the greatest increase in creeping bentgrass. Our results suggest optimal bentgrass conversion during mid-summer stress periods when interseeded at a rate of 73 kg/ha in combination with glyphosate applied between 0 and 7 DBS at 1.68 kg ai/ha (1.5 lb ai/acre) or greater.

Sand topdressing and crumb rubber can be used to improve native soil athletic field playability. However, there is a wide range in the physical properties, price, and availability of these materials. The objective of this field research was to evaluate the effects of various topdressing materials on the autumn wear tolerance and surface stability of a well established Kentucky bluegrass (Poa pratensis L.) stand. Research was conducted on a sandy loam in East Lansing, MI, to evaluate the effects of four different sand-based materials with a range of physical properties, crumb rubber, a treatment that received sand then crumb rubber and a non-topdressed control. In the first summer, 4.8 cm of sand-based topdressing material, 2.4 cm of crumb rubber, and 2.4 cm of sand then 2.4 cm of crumb rubber was accumulated over their respective plots. Turf was subjected to simulated traffic using the Cady traffic simulator from mid-October through mid-November. In 2009, topdressing applications and subsequent traffic were repeated on the same experimental plots. Visual percent living ground cover (0 to 100%) and Clegg turf shear tester (TST) strength were measured. The control, while producing some of the greatest turf shear tester strength, provided the lowest turfgrass cover: 46.7% in 2008 and 35.0% in 2009. Crumb rubber, while being the most expensive topdressing material, provided the greatest turfgrass cover: 85.0% in 2008 and 90.0% in 2009. All sands provided comparable living ground cover and turf shear tester strength with the exception of a poorly-graded sand, which produced the lowest shear tester strength values in 2008.

Dollar spot (Sclerotinia homoeocarpa F.T. Bennett) injury can be suppressed by applications of nitrogen fertilizer to creeping bentgrass (Agrostis stolonifera L.). Previous studies evaluated applications of relatively high rates of nitrogen (≥ 24 kg N/ha) for dollar spot suppression. In this study, ammonium nitrate, ammonium sulfate, urea, potassium nitrate, calcium nitrate, and 20-20-20 were applied to fairway height creeping bentgrass on two week intervals at 7.3 kg N/ha in 2008 and 2009. The N sources were applied alone or tank-mixed with a low rate of the contact fungicide chlorothalonil (1.6 kg a.i./ha in 2008 and 3.2 kg a.i./ha in 2009). It was hypothesized that N + chlorothalonil would improve the level or longevity of dollar spot control compared to chlorothalonil alone. Treatments were initiated prior to the onset of dollar spot symptoms. Area under the disease progress curve data revealed that only ammonium sulfate had reduced dollar spot in both years, whereas ammonium nitrate and 20-20-20 did not reduce dollar spot over the season in any year. There was a trend for less dollar spot control in plots treated with N + chlorothalonil versus the low chlorothalonil rate alone in 2008, but in 2009 the deleterious effect was significant. It is likely that N stimulated plant growth and thus the contact fungicide was more rapidly removed from plants by mowing or there was more unprotected tissue for a longer period compared to plots treated with chlorothalonil alone. Ammonium nitrate, urea and 20-20-20 were not injurious. Potassium nitrate and calcium nitrate caused a short-lived tip burn, but ammonium sulfate elicited a severe burn since the N sources were not watered-in immediately.

Thatch accumulation is a serious management problem of bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis (Burtt-Davy)] putting greens. Excessive thatch can lead to increased disease incidence, reduced tolerance to environmental stress, and water management difficulties. Cultivation is a necessary aspect of moderating thatch accumulation in turf systems. Traditional cultivation techniques such as hollow-tine core aeration often lead to substantial damage to the turf playing surface. A field study was conducted at the Texas A&M Turfgrass Field Laboratory in College Station, TX, on a thatchy mature ‘Tifeagle,’ ‘Tifdwarf,’ and ‘Mini-Verde’ bermudagrass putting green having a USGA specified rootzone. Treatments compared effects of small diameter tine core aeration to venting aeration at three frequencies on thatch-mat accumulation, organic matter content, turf quality, and soil-water relationships. After two years, no treatments consistently reduced thatch accumulation compared to the non-cultivated control. Individual venting events were minimally disruptive to the putting surface, but frequent application reduced turf quality and saturated hydraulic conductivity over time. Results suggest venting aeration alone may not be an effective practice for thatch management or improving water infiltration if substantial undiluted organic matter layers exist.

Golf course fairways may be renovated to replace different species or older cultivars of creeping bentgrass (Agrostis stolonifera L.) (CBG) with improved bentgrass cultivars. Older cultivars are often infested with annual bluegrass (Poa annua L.) (ABG), and a primary goal of the renovation is to remove ABG from the turf. A series of trials were conducted from 2004 to 2007 to determine optimum bispyribac-sodium (BPS) application regimes to control ABG without excessive injury to establishing CBG. Bispyribac-sodium applications were initiated as soon as one week after CBG seedling emergence and continued at various rates and timings up to seven weeks after seedling emergence. Bispyribac-sodium treatments generally caused CBG seedling injury that was manifested as a reduction in growth and color. All treatment regimes provided significant reductions in ABG populations in some years. Several treatment regimes provided outstanding ABG control in all years. When balancing ABG control with CBG injury, applying 74 g ai/ha at 3 and 5 weeks after seedling emergence (WAE) gave excellent ABG control with moderate, but temporary, CBG injury. Applying 74 g only at 3 WAE provided moderate ABG control and minimal CBG injury with minimized application labor.

Several approaches for timing curative fungicide applications for control of dollar spot were compared on creeping bentgrass managed under fairway conditions. The efficacy of curative control of dollar spot depended on the action threshold selected. The “≥1%” curative treatment, in which applications were made when dollar spot severity in those plots averaged ≥1% (minimum spray interval 14 days), reduced fungicide usage by 30+% and generally provided equivalent or nearly equivalent disease control, as compared to a biweekly preventive program. The use of an action threshold of ≥10% disease severity reduced fungicide usage further but resulted in substantially less disease control than the preventive program. Based on our results, on creeping bentgrass fairways, golf course superintendents may be able to reduce fungicide usage by applying an effective fungicide when an early curative action threshold (such as 0.5% or 1%) is reached, with a minimum of two weeks between applications. The growth regulator trinexapac-ethyl had little impact on disease severity and minimal effect on the number of fungicide applications called for in the different curative programs tested.

Silvery-thread moss (Bryum argenteum Hedw.) is a common weed in creeping bentgrass (Agrostis stolonifera L.) putting greens, and control strategies alternative to the conventional use of synthetic pesticides may be useful. Spot-spray treatments of sodium bicarbonate (SB, 22.5 and 45 g ai/liter), potassium bicarbonate (PB, 22.5 and 45 g ai/liter), and essential oil (Moss Buster, 1% essential oil of oregano, ready-to-use), as well as broadcast treatments of SB (55 and 110 kg ai/ha), PB (4.8, 11.4, and 93.5 kg ai/ha), and carfentrazone-ethyl (CE, Quicksilver, 0.09 kg ai/ha) were applied twice in the spring and fall of 2009 and 2010 (4 applications each year). Moss severity and creeping bentgrass color were assessed biweekly. Spot application of SB or PB (45 g ai/liter), essential oil, and broadcast treatment with CE suppressed moss 39% to 55% in 2009. Broadcast applications of SB or PB were not effective either year. Creeping bentgrass treated with spot application of SB or PB (45 g ai/liter) required up to 8 days to recover to acceptable color, whereas bentgrass treated with essential oil required up to 18 days. Bicarbonate and essential oil products can reduce moss severity at a similar level to CE, but rates and/or application methods may need to be adjusted to avoid injury to creeping bentgrass putting greens.

Silvery-thread moss (Bryum argenteum Hedw.) is a common weed in creeping bentgrass (Agrostis stolonifera L.) putting greens. Low N fertility has been associated with increased moss severity, though the effect of N source on moss is unknown. Recent studies suggest that N source may be important in influencing moss encroachment. Our objective was to evaluate the response of silvery-thread moss to differing N sources on a ‘Penncross’ creeping bentgrass putting green. In 2009 and 2010, liquid urea (i.e., urea dissolved in water), granular urea, isobutylidene diurea (IBDU), and organic N were used to deliver N at 0.3 lb/1,000 ft² biweekly for a total of 4.3 lbs/1,000 ft² annually. According to mean area under the curve (AUC) values over 2009 and 2010, fertilizing the green with liquid urea resulted in a 147% to 155% increase in moss coverage compared to all other N sources. Application of liquid urea on creeping bentgrass infested with silvery-thread moss has the potential to increase its spread.

Bermudagrass [Cynodon spp. (L.) Rich.] is one of the most widely used turfgrass species for golf courses and sports fields in the southern United States and in the transitional climatic zone. Continuous trafficking from play or equipment can reduce bermudagrass coverage and turf quality. This study evaluated 42 bermudagrass cultivars for their response to traffic. Traffic was applied in summer and fall of 2007 and 2008 with a Cady Traffic Simulator. There were several commercially available cultivars that had the highest coverage in both summers when trafficked including Barbados, Celebration, Contessa, Dune, Midlawn, Mirage II, Panama, Premier, Princess 77, Patriot, Riviera, Southern Star, Sovereign, Sundevil II, Sunsport, TifGrand, Tifsport, Tifway, Transcontinental, Veracruz, and Yukon. However, only the cultivars Barbados, Celebration, Contesssa, and Premier and the experimental genotypes SWI-1003, SWI-1046, Tift No. 1, and Tift. No. 2 were in the top statistical grouping for green turf coverage in both summer and fall of both years. These results demonstrate that bermudagrass cultivars vary in their response to traffic. Selecting improved, traffic-tolerant bermudagrasses will help reduce maintenance inputs and increase sustainability of golf courses and athletic fields while also producing a better-quality and safer surface for sports.