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Frequent vs. infrequent irrigation are two common irrigation practices. This field study was conducted on 'Providence' creeping bentgrass (Agrostis stolonifera L.) grown on a sand-based rootzone and maintained as a putting green. The objectives of this study were to measure several creeping bentgrass performance and physiological factors as influenced by light and frequent (LF) vs. deep and infrequent (DI) irrigation. The LF plots were irrigated daily to moisten the upper 4 to 6 cm of soil, while DI plots were irrigated at leaf wilt to wet soil to a depth of [greater than or equal to] 24 cm. The LF-irrigated creeping bentgrass exhibited very good color and quality throughout most of 2006 and 2007, whereas DI-irrigated bentgrass exhibited acceptable quality in 2007 but not in 2006. The DI-irrigated bentgrass had lower chlorophyll levels in leaf and sheath tissue in 2006, but developed better color and quality and had higher chlorophyll levels in late summer of 2007 vs. LF-irrigated bentgrass. Creeping bentgrass subjected to DI irrigation developed a less thick thatch--mat layer that contained less organic matter than that found in LF-irrigated plots. Twice the amount of water was applied to the LF-vs. the DI-irrigated plots.

Coring is a common cultural practice used on golf courses. The reported effects of coring alone on thatch--mat accumulation have been mixed. The objectives of this field study were to examine the effects of spring and summer coring on thatch-mat thickness and organic matter accumulation in creeping bentgrass (Agrostis stolonifera L.). Turfgrass color and quality and chlorophyll content were also monitored. The study site was 'Providence' creeping bentgrass grown on a sand-based rootzone maintained as a putting green. Three coring regimes were assessed as follows: spring-only coring (1.27-cm-diam. tines), spring plus three summer corings (0.64-cm-diam. tines), and a noncored control. At the end of the second year, spring-only and spring-plus-summer cored plots had developed a 66 and 89%, respectively, thicker thatch-mat layer compared with noncored bentgrass. The total organic matter content (weight loss-on-ignition) in thatch--mat layers, however, generally was similar among all three regimes in both years. This indicated that the organic matter was diluted by inclusion of sand from topdressing or reincorporation of cores. Thus, organic matter concentration (i.e., gravimetric organic: dry weight of the cores) in the thatch--mat layer was much lower in plots of both coring regimes vs. noncored plots. Both spring-only and especially spring-plus-summer coring caused substantial reductions in turf quality for a 2-wk period. Spring-plus-summer coring resulted in increased chlorophyll levels as well as improved turf color and quality in late summer.

Light and frequent (LF) and deep and infrequent (DI) irrigation are two common practices for golf course managers. Few studies have compared the effects of these two opposing irrigation practices on summer root performance in creeping bentgrass (Agrostis stolonifera L.). The objectives of this field study were to quantify summer root development and longevity in response to LF vs. DI irrigation in 'Providence' creeping bentgrass grown on a sand-based rootzone. The LF plots were irrigated daily to moisten the upper 4 to 6 cm of soil, whereas DI plots were irrigated at leaf wilt to wet soil to a depth [greater than or equal to] 24 cm. Root measurements were obtained using the minirhizotron imaging technique and included total root count, total root length (TRL), total root surface area (TRSA), and average root diameter. When averaged over the entire 0-to 24-cm rootzone depth, DI-irrigated creeping bentgrass produced a greater number of roots, longer root lengths, and a larger root surface area than LF-irrigated turf. Average root diameters were smaller in DI-irrigated creeping bentgrass in the summer of 2007. Compared with data collected in 2006, the 2-yr-old turf had 55 and 32% fewer roots in LF-and DI-irrigated bentgrass by September 2007, respectively. There were similar reductions in TRL and TRSA between years in both irrigation regimes. Deep and infrequent irrigation stimulated root growth throughout the 0-to 24-cm rootzone in May and June and promoted root longevity in summer.

Annual bluegrass (Poa annua L.; ABG) can be a major weed problem in golf course turf, Research-based information on the seasonal emergence patterns of ABG is limited. The objectives of this four-year field study were (i) to determine seasonal ABG emergence patterns in Maryland, (ii) to determine peak period(s) of ABG emergence, and (iii) to determine the date and estimated percentage of seedlings emerged when the rate of emergence declines. Annual bluegrass seedlings were found to emerge between August and May in two Maryland golf course roughs. A majority (50-70%) of seedling emergence occurred between late September and mid-October, and peak germination generally was observed in early October. The linear increase in ABG seedling emergence generally ended by early November; however, 24% of all seedlings emerged between November and May. No major ABG emergence cycles were observed during the spring in any year. Mean daily temperatures generally were [less than or equal to] 20[degrees]C during peak ABG emergence periods, and germination was stimulated by precipitation. Since the genetic diversity of ABG is well known, these findings may only be applicable to Maryland and regions with similar environmental conditions.

Creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds.) Farw.] and perennial ryegrass (Lolium perenne L.) are commonly grown fairway grasses that are susceptible to dollar spot (Sclerotinia homoeocarpa F. T. Bennett; DS) and gray leaf spot [Pyricularia grisea (Cooke) Sacc; GLS.] diseases, respectively. This field study assessed the influence of two irrigation regimes (light and frequent nighttime versus deep and infrequent morning irrigation) and six chemical treatments including: chlorothalonil (tetrachloroisophthalonitrile), paclobutrazol [(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl) pentan-3-ol; PB], wetting agent (polymeric polyoxyalkylene 95% oxoalkonyl hydroxyl polyoxlalkane diyl 5%; WA), chlorothalonil + PB, chlorothalonil + WA and chlorothalonil + PB + WA on DS and GLS severity over a 3-yr period. Dollar spot was more severe in late summer in creeping bentgrass that received deep and infrequent versus light and frequent irrigation in 2002 and 2004 and disease severity was negatively correlated with volumetric soil moisture (r = -0.77 to -0.96). Soil moisture levels above 0.25 [cm.sup.3] [cm.sup.-3] were associated with an improved ability of chlorothalonil, PB, and WA to suppress DS, but they had no effect on GLS. In 2002, GLS rapidly and severely damaged even fungicide-treated plots, and there was no irrigation effect. In 2004, gray leaf spot was more severe in light and frequent nighttime irrigated blocks versus deep and infrequent morning irrigated blocks. Chlorothalonil (8.0 kg a.i. [ha.sup.-1]) provided effective GLS control when applied on an 8-d interval in 2004 but only in infrequently irrigated blocks where disease pressure was less.

There is increasing interest in the use of bio-organic nitrogen (N) sources to suppress turfgrass diseases. The objectives of this field study were to evaluate nine N-sources for their effects on dollar spot (caused by Sclerotinia homoeocarpa F. T. Bennett) severity; to elucidate the relationship among N-sources, tissue N, soil microbial activity, and the severity of dollar spot; and to evaluate N-source effects on thatch and soil organic matter levels, and plant parasitic nematodes. Nitrogen sources included urea, sulfur-coated urea (SCU), Milorganite (Milwaukee Metropolitan Sewerage District, Milwaukee, WI), Sustane Medium (Sustane Corporation, Chaska, MN), Earthgro 1881 Select (Earthgro Inc., Lebanon, CT), Earthgro Dehydrated Manure, Ringer Lawn Restore (Ringer LR, Ringer Corporation, Minneapolis, MN), Com-Pro (Blue Plains Sanitation Commission, Silver Spring, MD), and Scotts All Natural Turf Builder (Scotts ANTB, Scotts Company, Marysville, OH). The N was applied annually at a rate of 200 kg N [ha.sup.-1] [yr.sup.-1] between 1994 and 2000 to a stand of fairway height `Southshore' creeping bentgrass (Agrostis stolonifera L.). Data were collected between 1998 and 2000. Ringer Lawn Restore (all 3 yr) and urea (1999 and 2000) delayed dollar spot to within an acceptable threshold from May to early or mid-June, when disease pressure was low to moderately severe. Com-Pro (all 3 yr), however, enhanced dollar spot. No N-source reduced dollar spot when data were averaged over-the-season. No N-source was consistently associated with higher levels of soil microbial activity. There was a weak negative correlation between soil microbial activity and dollar spot on one date in 2000, when disease pressure was low. When disease pressure was moderately severe, there was a strong negative correlation between the amount of foliar N and dollar spot severity in June 1999, but no correlation was found in 2000. Only Sustane Medium-treated plots had higher organic matter levels in the upper 2.5 cm of soil on all rating dates, but there was no increase in soil organic matter in the 2.6 to 5.0 cm soil zone with any N-source., THERE IS INCREASING INTEREST in the use of natural or bio-organic nitrogen (N) sources and soil amendments for use on turfgrasses. Several natural fertilizers are good N sources and their [...]

Understanding root growth response of creeping bentgrass {Agrostis stolonifera L.) to coring will help golf course superintendents maintain high quality putting green turf. The objective of this field study was to examine the effects of coring on summer rooting in young creeping bentgrass grown on a sand-based root zone and maintained as a putting green. The study was initiated on 7-mo-old 'Providence' creeping bentgrass in 2006 and compared spring (SP) only coring, spring plus three summer (SU) corings (SP + SU) and a noncored control through 2007. The minirhizotron imagining technique was used to measure total root count (TRC) and total root length (TRL) from late spring to late summer. The percentage of the TRC in the surface 0- to 6-cm root zone depth averaged over measurement dates was 48 to 53% and 33 to 44% among all treatments in 2006 and 2007, respectively. Greater TRC were observed in 2006 with 28, 51, and 50% lower TRC's found in SP + SU, SP only, and noncored plots in 2007, respectively. Spring + SU coring generally reduced TRC and TRL at various root zone depths and dates during the first year of establishment. In 2007, greater TRC and TRL were observed throughout the 0- to 24-cm root zone in SP + SU cored compared to SP only and noncored plots. Thus, SP + SU coring in the second study year promoted creeping bentgrass root growth and/or longevity, but coring during the first summer of establishment reduced rooting. [ABSTRACT FROM AUTHOR]

This 3-year field study evaluated the incidence and severity of dollar spot (Sclerotinia homoeocarpa F.T. Bennett) in six creeping bentgrass (Agrostis stolonifera L.) cultivars maintained as a golf course fairway. Comparison of area under the disease progress curve (AUDPC) data clearly indicted two resistance groups among the six cultivars. 'Crenshaw' and 'Backspin' were classified as highly susceptible (HS) and the other four cultivars (i.e., 'Penncross', 'Providence', 'L-93', and '007') were classified a moderately susceptible (MS) to dollar spot. in all three study years, there were three epidemics that began in May. Data could not be collected in HS cultivars after the first epidemic in each year as a result of severe damage. In MS cultivars, the first epidemic ended and a second began between early July and late August. The second epidemic ended approximately mid-October and a third epidemic appeared in MS cultivars between late October and early December. The second epidemic was longest and most severe, and the third fall epidemic was least severe and of shortest duration. The first epidemic in HS cultivars developed up to two weeks earlier and progressed more rapidly and severely than in MS cultivars. A growing degree-day (GDD) model, using a base air temperature of 15 °C and a start date of I Apr., was accurate in predicting the onset of the first epidemic in HS (60 to 70 GDD) and MS (105 to 115 GDD) cultivars during each of the three study years. Growing degree-day models are greatly influenced by the many microclimates found on golf courses and need to be evaluated for accuracy in diverse environments. [ABSTRACT FROM AUTHOR]

Frequent vs. infrequent irrigation are two common irrigation practices. This field study was conducted on 'Providence' creeping bentgrass (Agrostis stolonifera L.) grown on a sand-based rootzone and maintained as a putting green. The objectives of this study were to measure several creeping bentgrass performance and physiological factors as influenced by light and frequent (LF) vs. deep and infrequent (DI) irrigation. The LF plots were irrigated daily to moisten the upper 4 to 6 cm of soil, while DI plots were irrigated at leaf wilt to wet soil to a depth of ≥24 cm. The LF-irrigated creeping bentgrass exhibited very good color and quality throughout most of 2006 and 2007, whereas DI-irrigated bentgrass exhibited acceptable quality in 2007 but not in 2006. The DI-irrigated bentgrass had lower chlorophyll levels in leaf and sheath tissue in 2006, but developed better color and quality and had higher chlorophyll levels in late summer of 2007 vs. LF-irrigated bentgrass. Creeping bentgrass subjected to DI irrigation developed a less thick thatch-mat layer that contained less organic matter than that found in LF-irrigated plots. Twice the amount of water was applied to the LF- vs. the DI-irrigated plots. [ABSTRACT FROM AUTHOR]

Light and frequent (LF) and deep and infrequent (DI) irrigation are two common practices for golf course managers. Few studies have compared the effects of these two opposing irrigation practices on summer root performance in creeping bentgrass (Agrostis stolonifera L.). The objectives of this field study were to quantify summer root development and longevity in response to LF vs. DI irrigation in 'Providence' creeping bentgrass grown on a sand-based rootzone. The LF plots were irrigated daily to moisten the upper 4 to 6 cm of soil, whereas DI plots were irrigated at leaf wilt to wet soil to a depth ≥24 cm. Root measurements were obtained using the minirhizotron imaging technique and included total root count, total root length (TRL), total root surface area (TRSA), and average root diameter. When averaged over the entire 0- to 24-cm rootzone depth, DI-irrigated creeping bentgrass produced a greater number of roots, longer root lengths, and a larger root surface area than LF-irrigated turf. Average root diameters were smaller in DI-irrigated creeping bentgrass in the summer of 2007. Compared with data collected in 2006, the 2-yr-old turf had 55 and 32% fewer roots in LF- and DI-irrigated bentgrass by September 2007, respectively. There were similar reductions in TRL and TRSA between years in both irrigation regimes. Deep and infrequent irrigation stimulated root growth throughout the 0- to 24-cm rootzone in May and June and promoted root longevity in summer. [ABSTRACT FROM AUTHOR]

Coring is a common cultural practice used on golf courses. The reported effects of coring alone on thatch-mat accumulation have been mixed. The objectives of this field study were to examine the effects of spring and summer coring on thatch- mat thickness and organic matter accumulation in creeping bentgrass (Agrostis stolonifera L.). Turfgrass color and quality and chlorophyll content were also monitored. The study site was 'Providence' creeping bentgrass grown on a sand-based rootzone maintained as a putting green. Three coring regimes were assessed as follows: spring-only coring (1.27-cm-diam. tines), spring plus three summer corings (0.64-cm-diam. tines), and a noncored control. At the end of the second year, spring-only and spring-plus-summer cored plots had developed a 66 and 89%, respectively, thicker thatch-mat layer compared with noncored bentgrass. The total organic matter content (weight loss-on-ignition) in thatch- mat layers, however, generally was similar among all three regimes in both years. This indicated that the organic matter was diluted by inclusion of sand from topdressing or reincorporation of cores. Thus, organic matter concentration (i.e., gravimetric organic: dry weight of the cores) in the thatch-mat layer was much lower in plots of both coring regimes vs. noncored plots. Both spring-only and especially spring-plus-summer coring caused substantial reductions in turf quality for a 2-wk period. Spring-plus-summer coring resulted in increased chlorophyll levels as well as improved turf color and quality in late summer. [ABSTRACT FROM AUTHOR]

Establishing creeping bentgrass [Agrostis stolonifera L. (CBG)] and perennial ryegrass [Lolium perenne L. (PRG)] from seed can be hampered by competition from annual bluegrass (Poa annua L.). Bispyribac-sodium (BPS) is a postemergence annual bluegrass herbicide that may have applications for use when establishing these grasses. This field study was undertaken to determine if BPS could be applied safely to CBG and PRG seedlings. Ethofumesate (ETHO) was applied sequentially (840 + 840 g·ha-1 a.i.) and served as a standard. In 2004, BPS was applied once (49, 74, 111, and 148 g·ha-1 a.i.) or sequentially (49 + 49 and 74 + 74 g·ha-1 a.i.) to CBG and PRG seedlings 4 weeks after emergence in Maryland. In 2004, BPS discolored CBG and PRG and reduced PRG cover, whereas ETHO reduced CBG cover but was not injurious to PRG. In 2005, a single (148 g·ha-1 a.i.) and sequential (25 + 25, 49 + 49 and 74 + 74 g·ha-1 a.i.) applications of BPS were made to CBG and PRG 2 and 4 weeks after seedling emergence (WASE) in Maryland and Connecticut. Treatments applied 2 WASE generally resulted in more injury when compared with applications made 4 WASE. in Maryland in 2005, CBG only sustained long-term loss of cover when treated 2 WASE with 148 g·ha -1 a.i. of BPS. The PRG was more sensitive to BPS and 148 g·ha-1 a.i. applied once and sequential treatments 49 g·ha-1 a.i. or greater applied 2 and 4 WASE generally caused the greatest loss in PRG cover. Conversely, CBG was severely injured by all BPS treatments and ETHO in Connecticut. In PRG, only 25 + 25 g·ha-1 a.i. of BPS and ETHO in both timings did not cause a loss in cover in Connecticut or Maryland. High levels of precipitation and probably other unknown factors may have enhanced the phytotoxicity observed in Connecticut. Ethofumesate generally was safer than BPS for use on PRG seedlings. [ABSTRACT FROM AUTHOR]

Creeping bentgrass (Agrostis stolonifera L.; CBG) is a common weed in home lawns and golf course roughs in many regions of the United States. Currently, no herbicides are registered for selective control of CBG in cool-season grasses. The objective of this field study was to evaluate the ability of mesotrione and triclopyr ester to selectively remove CBG from Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.). Mesotrione (0.14 and 0.21 kg⋅ha-1 a.i.) and triclopyr ester (0.56 and 1.12 kg⋅ha-1 a.i.) were applied on a 2-week interval two, three, or four times in Connecticut and Maryland in 2005, and three or four times in Maryland in 2006. Two applications of mesotrione at 0.21 kg⋅ha-1 a.i. provided marginally acceptable CBG control, but three or four applications at 0.14 or 0.21 kg⋅ha-1 a.i. provided excellent CBG control. Mesotrione elicited little or no injury to Kentucky bluegrass, but generally caused objectionable injury in tall fescue for about 7 to 14 d after each application. Triclopyr applied at 0.56 kg⋅ha-1 a.i. reduced CBG cover, but the level of control generally was unacceptable, regardless of application frequency. Three or four applications of triclopyr (1.12 kg⋅ha-1 a.i.) effectively controlled CBG in Connecticut in 2005 and Maryland in 2006. Triclopyr caused no visual injury to tall fescue, regardless of rate or application frequency. Four triclopyr applications to Kentucky bluegrass, however, were phytotoxic and reduced stand density, especially at the high rate (1.12 kg⋅ha-1 a.i.). Three summer applications of mesotrione (0.14 kg⋅ha-1 a.i.) or triclopyr (1.12 kg⋅ha-1 a.i.) provided the best combination of turfgrass safety and CBG control. Chemical names used: [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid (triclopyr ester); 2-[4-(methylsulfonyl)-2-nitrobenzoyl]-l,3-cycilohexanedione (mesotrione) [ABSTRACT FROM AUTHOR]

Dead spot of creeping bentgrass is incited by Ophiosphaerella agrostis. The objectives of this 3-year field study were to: (i) elucidate environmental conditions associated with the expression of dead spot symptoms, (ii) develop a model to assist in predicting the appearance of dead spot symptoms and epidemics in creeping bentgrass, and (iii) elucidate the association between ascospore release and the appearance of new dead spot symptoms. Environmental parameters measured included relative humidity (RH), air (AT) and soil (ST) temperatures, solar irradiance (SOL), precipitation and irrigation (RAIN), and leaf wetness duration (LWD). Dead spot symptoms generally did not occur at temperatures (air or soil) below 15°C. Two descriptive models were developed that predicted the appearance of dead spot symptoms with an accuracy of 74 to 80%. Between 1 May and 31 October 2000 to 2002, the appearance of new dead spot infection centers was most accurately predicted (80%) by the single parameter of STMean ≥ 20°C. In years with severe levels of dead spot, the occurrence of major infection events was predicted on 37 of 40 days (93%). A combination of elevated air (ATMax ≥ 27°C) and soil (STMean ≥ 18°C) temperatures, low relative humidity (RHMean ≤ 80%), shortened periods of leaf wetness (LWD ≤ 14 h), and high levels of solar radiation (SOLMean ≥ 230 W m-2) were associated with the development of major dead spot epidemics. Ascospore discharge and the appearance of new infection centers occurred in a cyclic pattern that peaked about every 12 days. New infection centers appeared 3 to 10 days after the release of a large number of ascospores. [ABSTRACT FROM AUTHOR]

Dead spot (Ophiosphaerella agrostis) is a damaging disease of young (≤6 years old) creeping bentgrass (Agrostis stolonifera) golf greens. The objectives of this 3-year field study were to determine the peak periods of dead spot activity based on increasing patch diameter and pseudothecia development, and to determine where O. agrostis overwinters. Patch diameter generally increased at a linear rate between mid-June and early August. Increases in pseudothecia production closely followed increasing patch diameter. Pseudothecia could be found within necrotic tissue as early as the first day of symptom expression and as many as 478 pseudothecia were found in a single patch. Periods of rapid dead spot development coincided with air and soil temperatures ranging from 22 to 26°C. Increases in patch diameter and pseudothecia development were negligible after late August. Dead spot severity was highest in the year following green construction or fumigation, but then rapidly declined in severity in subsequent years. O. agrostis was capable of overwintering as pseudothecia or as hyphae within or on bentgrass leaf sheaths, crowns, roots, and especially the nodes of stolons. [ABSTRACT FROM AUTHOR]

Dead spot (Ophiosphaerella agrostis) is a relatively new disease of young creeping bentgrass and hybrid bermudagrass putting greens in the United States. Little is known about the biology or genetic diversity of the pathogen. O. agrostis is unusual in that it produces prodigious numbers of pseudothecia in the field throughout the summer months and has no known asexual state. A total of 77 O. agrostis isolates were collected from 21 different bentgrass putting greens and one hybrid bermudagrass green in 11 states. DNA fingerprint analysis revealed that 78 out of 97 markers were polymorphic (80.4%), providing 57 unique profiles. Genetic variation of O. agrostis was diverse, and isolates separated into three distinct clades with ≥69% similarity. Analysis of molecular variance indicated that the geographic origins of the isolates and the ability to produce pseudothecia were the best indicators for genetic similarity among O. agrostis isolates. Colony color varied among the isolates, but generally was similar for isolates residing within two clades (B and C). Colony color of isolates within clade A appeared to be a mixture of the colony colors exhibited by clades B and C. Isolates examined within each clade generally had varying levels of pseudothecia production and varying colony colors when grown on PDA. Although O. agrostis is a homothallic species, it is unclear if outcrossing among strains occurs. [ABSTRACT FROM AUTHOR]

Ophiosphaerella agrostis, the causal agent of dead spot of creeping bentgrass (Agrostis stolonifera), can produce prodigious numbers of pseudothecia and ascospores throughout the summer. The environmental conditions and seasonal timings associated with O. agrostis ascospore release are unknown. The objectives of this research were to (i) determine the influence of light and relative humidity on ascospore release in a controlled environment, (ii) document the seasonal and daily discharge patterns of ascospores in the field, and (iii) elucidate environmental conditions that promote ascospore release under field conditions. In a growth chamber, a sharp decrease (100 to ≈50%; 25°C) in relative humidity resulted in a rapid (1- to 3-h) discharge of ascospores, regardless of whether pseudothecia were incubated in constant light or dark. In the field, daily ascospore release increased between 1900 and 2300 h and again between 0700 and 1000 h local time. The release of ascospores occurred primarily during the early morning hours when relative humidity was decreasing and the canopy began to dry, or during evening hours when relative humidity was low and dew began to form. Few ascospores were released between 1100 and 1800 h when the bentgrass canopy was dry. The release of ascospores also was triggered by precipitation. Of the ascospores collected during precipitation events, 87% occurred within 10 h of the beginning of each event. [ABSTRACT FROM AUTHOR]

Dead spot is a relatively new disease of creeping bentgrass and hybrid bermudagrass that is incited by Ophiosphaerella agrostis. Initial symptoms are difficult to diagnose and clinicians generally rely on the presence of pseudothecia within infected tissue or isolation of O. agrostis on an artificial medium. The main goal of this study was to develop a polymerase chain reaction based technique capable of quickly identifying O. agrostis within infected creeping bentgrass tissues. Oligonucleotide primers specific for O. agrostis were developed based on the internal transcribed spacer (ITS) rDNA regions (ITS1 and ITS2) of three previously sequenced isolates of O. agrostis. The 22-bp primers amplified a 445 or 446-bp region of 80 O. agrostis isolates collected from creeping bentgrass and bermudagrass in 11 states. Primers did not amplify DNA from other common turfgrass pathogens, including three closely related species of Ophiosphaerella. Selective amplification of O. agrostis was successful from field-infected creeping bentgrass samples and primers did not amplify the DNA of noninfected, field grown creeping bentgrass or hybrid bermudagrass plants. Amplification of purified O. agrostis DNA was successful at quantities between 50 ng and 5 pg. The entire process, including DNA isolation, amplification, and amplicon visualization, may be completed within 4 h. These results indicate the specificity of these primers for assisting in the accurate and timely identification of O. agrostis and the diagnosis of dead spot in both bentgrass and bermudagrass hosts. [ABSTRACT FROM AUTHOR]

The tolerance of creeping bentgrass (Agrostis stolonifera L.) seedlings to many herbicides has not been evaluated. Three field studies were conducted between fall and spring from 1998 to 2002 to assess creeping bentgrass seedling tolerance to five herbicides and paelobutrazol. The primary objectives of this investigation were to assess bentgrass tolerance to these chemicals when applied at various timings following seedling emergence, and establishment of new seedlings as influenced by potential soil residues in the spring following a fall application of the chemicals. Treatments were applied 2, 4, or 7 weeks after either 'Crenshaw' or 'L-93' creeping bentgrass seedlings had emerged. Siduron (6.7 and 9.0 kg⋅ha-1) and bensulide (8.4 kg⋅ha-1) were noninjurious when applied two weeks after seedling emergence (2 WASE). Bensulide (14 kg⋅ha-1), ethofumesate (0.84 kg⋅ha-1), prodiamine (0.36 kg⋅ha-1) and paelobutrazol (0.14 kg⋅ha-1) were too injurious to apply 2 WASE, but they were generally safe to apply at 4 WASE. Chlorsulfuron (0.14 kg⋅ha-1) was extremely phytotoxic to seedlings when applied 2 WASE. Plots were treated with glyphosate and overseeded the following spring. The overwintering soil residuals of prodiamine and bensulide (14.0 kg⋅ha-1) unacceptably reduced spring establishment. All other herbicides and paelobutrazol had little or no adverse residual effects on spring establishment. Chemical names used: N-(phosphonomethyl)gyeline (glyphosate); (±)-(R*,R*)-beta[(4-chlorophenyl)methyl]- alpha-(1,1-dimethylethyl)-1H-1,2,4-triazole.1.ethanol (paclobutrazol); 2-ethoxy-2,3-dihydro-3,3-dimetbyl-5-benzofuranyl methanesulfonate (ethofumesate); S-(0,0-diisopropyl phosphorodithioate) ester of N-(2-mereaptoethyl) benzenesulfonamide (bensulide); [1-(2-methyleyelohexyl)-3-phenylurea] (siduron); N3,N3... [ABSTRACT FROM AUTHOR]

Natural organic fertilizers require microbial degradation for nitrogen (N) release, but their ability to promote rapid turfgrass establishment has not been well documented in newly constructed sand-based rootzones. This 2-year field study evaluated the influence of two general fertilizer and soil amendment programs for their effect on establishment and quality of three creeping bentgrass (Agrostis stolonifera L.) cultivars--'Crenshaw', 'Penn G-2', and 'Providence'. Turf was grown on a 4 sand : 1 sphagnum peat (by volume) rootzone mixture. Four treatments consisting of surface-applied synthetic fertilizer (SF; mostly water-soluble N in 1999 and methylene urea thereafter); surface-applied hydrolyzed poultry meal (PM); preplant-incorporated granular humate (GH) with surface-applied SF; and preplant-incorporated PM with surface-applied PM. Tuff cover data collected 42 days after seeding (DAS) showed that the rate of establishment was SF+GH incorporated = SF surface-applied >PM surface-applied + PM incorporated >PM surface-applied. Turf cover was ≥96% among all treatments 90 DAS. Rootmass density was greater (18% to 29%) at 103 DAS in GH incorporated plots combined with SF, when compared to all other treatments, but no rootmass differences subsequently were observed. Soil microbial activity generally was highest in PM-treated plots during the first 14 months following seeding, but not thereafter. Turf treated with SF had less microdochium patch (Microdochium nivale (Fr.) Samuels and I.C. Hallett) and more bentgrass dead spot (Ophiosphaerella agrostis Dernoeden, M.P.S. Camara, N.R. O'Neill, van Berkum et M.E. Palm), when compared to PM-treated plots. Slightly less thatch developed in PM-treated turf when compared to plots receiving SF alone by the end of the second year. Penn G-2 and SF generally provided the best overall turf quality. This study demonstrated the beneficial effects of readily available N from SF for rapid establishment and... [ABSTRACT FROM AUTHOR]

Presents a study which assessed the effects of quinclorac rates applied in three timings for postemergence crabgrass control in perennial ryegrass and evaluated the creeping bentgrass injury in response to quinclorac. Materials and methods; Results and discussion; Conclusions.

Examines the usability of bio-organic nitrogen on suppressing turfgrass diseases. Effect of nitrogen on thatch and soil organic matter level; Correlation between dollar spot and soil microbial activity; Comparison on the effectivity between synthetic and non-synthetic sources of nitrogen.

Analyzes the influence of irrigation, fungicide and fertilizer on brown patch severity in perennial ryegrass. Shortage of information on the cultural management practices; Importance of the slow nitrogen release characteristics of sulfur-coated urea in disease reduction; Effect of the extended fungicide application interval.

Analyzes the influence of mowing height on brown patch severity in perennial ryegrass. Effect of nitrogen source; Effect of iprodione; Absence of relationship between brown patch severity and soil pH or crown tissue carbohydrates.

With the potential introduction of glyphosate-resistant kentucky bluegrass (GRKB) (Poapratensis L.), postemergence herbicides must be identified for renovation from glyphosate-resistant stands or control escaped GRKB. Field experiments were conducted in Indiana, Maryland, New Jersey, and Virginia from July to September 2004 to investigate efficacy of postemergence herbicides for kentucky bluegrass control. Herbicides tested included clethodim at 0.28 kg⋅ha-1 (a.i.), fluazifop-p at 0.43 kg⋅ha-1 (a.i.), formasulfuron at 0.03 kg⋅ha-1 (a.i.), glufosinate at 1.12 kg⋅ha-1 (a.i.), glyphosate at 1.68 kg⋅ha-1 (a.i.), rimsulfuron at 0.03 kg⋅ha-1 (a.i.), sethoxydim at 0.53 kg⋅ha-1 (a.i.), and trifloxysulfuron at 0.03 kg⋅ha-1 (a.i.). One and two applications of each herbicide were applied to separate plots with the sequential applied 4 weeks after initial treatments (WAIT). Single applications of glyphosate completely controlled kentucky bluegrass 4 WAIT in Maryland, New Jersey, and Virginia. Glufosinate completely controlled kentucky bluegrass with one application in Maryland and New Jersey but single and sequential applications provided only 80% to 88% control in Indiana and Virginia. Foramsulfuron and rimsulfuron required sequential applications for complete kentucky bluegrass control 8 WAIT in New Jersey and Maryland but <82% control was obtained in Indiana and Virginia. Trifloxysulfuron controlled kentucky bluegrass 95% to 100% with single applications in Maryland, New Jersey, and Virginia. Single applications of clethodim, fluazifop, and sethoxydim provided minimal stand reductions but sequential applications controlled kentucky bluegrass 65% to 100%. Results suggest glufosinate and trifloxysulfuron have the greatest potential for controlling GRKB while other herbicides provided erratic control and require sequential applications. [ABSTRACT FROM AUTHOR]

Bentgrass dead spot (BDS) is a disease of creeping bentgrass incited by Ophiosphaerella agrostis. This project was designed to determine the susceptibility of field-grown bentgrass cultivars to BDS and to gather information regarding the geographic distribution and field conditions favoring the disease. In a field cultivar evaluation trial, all major Agrostis spp. used on golf courses, including colonial, creeping, and velvet bentgrasses, were shown to be susceptible to an isolate of O. agrostis. Velvet bentgrass cvs. SR7200 and Bavaria were among the most and least susceptible cultivars, respectively. Among creeping bentgrass cultivars, L-93 generally was the most susceptible and Pennlinks, Penncross, and Crenshaw were among the least susceptible. Although recovery of BDS patches in the autumn was slow, Bardot colonial bentgrass and Crenshaw, Imperial, L-93, and Penn G-6 creeping bentgrasses showed the most rapid recovery prior to winter. Variation in the virulence of isolates and the potential for races of the pathogen, however, may affect cultivar susceptibility. The disease was most commonly found on 1- to 4-year-old golf greens and disease severity declined 1 to 3 years after it first appeared. BDS only was found on sand-based greens, collars, and tees and has not been observed in bentgrass grown on native soil. Between 1998 and 2001, O. agrostis was isolated from diseased leaves, roots, crowns, and stolons of creeping bentgrass and hybrid bermudagrass turf samples received from 13 states. The disease was most severe in sunny and exposed locations, especially on ridges, mounds, and slopes. In the mid-Atlantic region, BDS appeared as early as May and remained active as late as December. The disease was most active in July and August, and usually became inactive with the advent of frost in October.

Putting green samples (n = 109) were inspected for the presence of Pythium oospores in roots of plants from golf courses (n = 39) in Maryland and adjacent states. Twenty-eight Pythium isolates were recovered from creeping bentgrass (Agrostis palustris) (n = 25) and annual bluegrass (Poa annua) (n = 3) plants. Most isolates associated with Pythium-induced root dysfunction were from greens less than 3 years of age and were obtained primarily between March and June, 1995 to 1997. Eight Pythium species (P. aristosporum, P. aphanidermatum, P. catenulatum, P. graminicola, P. torulosum, P. vanterpoolii, P. volutum, and P. ultimum var. ultimum) were isolated from creeping bentgrass and two species (P. graminicola and P. torulosum) were from annual bluegrass. All species, except P. catenulatum, were pathogenic to 'Crenshaw' creeping bentgrass seedlings in postemergence pathogenicity tests. P. aristosporum (n = 3) and P. aphanidermatum (n = 1) were highly aggressive at a low (18°C) and a high temperature (28°C). P. graminicola (n = 1) was low to moderately aggressive. P. torulosum (n = 12) was the most frequently isolated species, but most isolates were either nonpathogenic or caused very little disease. P. aristosporum (n = 3) and P. aphanidermatum (n = 1) were highly aggressive and were associated with rapid growth at 18 and 28°C on cornmeal agar. P. volutum (n = 1) was highly aggressive at 18°C, but was one of slowest growing isolates. Infected roots were generally symptomless, and the number of oospores observed in roots was not always a good indicator of disease or of the aggressiveness of an isolate. Large numbers of oospores of low or even nonpathogenic species may cause dysfunction of creeping bentgrass roots.