Low Mowing Research Articles

Best Management Practices Effects on Anthracnose Disease of Annual Bluegrass

Increased N fertilization, mowing height, and sand topdressing are management practices that can suppress anthracnose disease of annual bluegrass [Poa annua L. f. reptans (Hausskn) T. Koyama; ABG] caused by Colletotrichum cereale Manns. A 3‐yr field study evaluated the relative importance and interactions of these factors on anthracnose severity, turfgrass quality, and ball roll distance (BRD) on ABG turf in North Brunswick, NJ. A factorial combination of mowing height (2.3 and 3.2 mm), N fertilization (100 and 200 kg ha−1 yr−1), and sand topdressing (46 and 98 Mg ha−1 yr−1 in 2012; 37 and 81 Mg ha−1 yr−1 during 2013 and 2014) was arranged in a split‐split‐plot design with four replications. The practice of applying greater N fertilization (200 kg ha−1) provided the greatest reduction in disease severity and improvement in quality than the practices of higher mowing (3.2 mm) or greater sand topdressing (98 or 81 Mg ha−1). Combining greater N with higher mowing and greater sand topdressing provided acceptable disease suppression without the use of fungicides during moderate but not severe anthracnose epidemics. Higher mowing often produced unacceptable BRD (<2.9 m) especially when combined with greater N fertilization; whereas, under lower mowing, BRD was acceptable on most observation dates (91–96%) and less influenced by greater N fertilization. Thus, when adjustments in best practices for anthracnose management are needed to enhance BRD; lowering the mowing height will provide that enhancement while not greatly increasing the risk for anthracnose especially when greater N and increased topdressing practices are also employed.

Potassium Rate and Mowing Height for Kentucky Bluegrass Growth

Potassium is well-known to improve turfgrass tolerance to environmental stresses such as low temperature and drought stress. Low mowing height reduces leaf area of turfgrass that is main place for photosynthesis and carbohydrate production. Closely-mowed turf would suffer from summer decline by low level of carbohydrate resulted from low photosynthesis of reduced leaf area. The objective of the study is to investigate K rate and mowing height for Kentucky bluegrass. The K rate treatments were 5, 10, and 20 g K2O m −2 for the low, medium and high K rates, respectively. The bi-weekly mowing treatment was made for treatments. Mowing was implemented at 40 and 100 mm using a rotary mower. Regardless K rates, the high mowing height would be required when the air temperature is higher than 28.5℃ and high turfgrass quality of Kentucky bluegrass is needed. When the air temperature is optimal for cool-season grass, the high mowing height and the low K rate is needed for the root length of Kentucky bluegrass.

Nitrogen, Phosphorus, Mowing Height, and Arbuscular Mycorrhiza Effects on Red Fescue and Mixed Fescue–Bentgrass Putting Greens

Red fescue (RF, Festuca rubra L.) is used on golf putting greens in the Nordic region due to its high disease resistance and low requirements for nitrogen (N) and water, but low density and growth rate makes RF susceptible to annual bluegrass (AB, Poa annua L.) invasion. Putting greens seeded with RF + bentgrass (Agrostis sp.) may be more competitive with AB but also have different playing characteristics. Our objective was to compare RF, RF + colonial bentgrass (CB, Agrostis capillaris L.), and RF + velvet bentgrass (VB, Agrostis canina L.) putting greens at two mowing heights (4.0 or 5.5 mm), three N rates (5, 10, or 15 g N m−2 yr−1), and three phosphorus (P)–arbuscular mycorrhizal fungi treatments (0 and 1.8 g P m−2yr−1 without inoculation and 0 g P m−2yr−1 with inoculation). The four‐factorial experiment was conducted in 2011 and 2012 at Landvik, Norway. Red fescue provided lower visual quality and density and less competition against AB than RF + bentgrass combinations. Increasing the N rate from 5 to 15 g N m−2yr−1 increased the proportion of bentgrass tillers from 53 to 64% in RF + CB and from 86 to 92% in RF + VB. Surface hardness increased in the order RF + VB < RF + CB < RF turfs. Ball‐roll distance decreased with increasing N rate and was longer with RF and RF + VB than with RF + CB. The main effects of N and mowing height on AB invasion were not significant, but lower mowing increased AB competition in RF. Mycorrhiza colonization of roots was not significantly affected by any practice, and neither P nor arbuscular mycorrhizal fungi influenced the competition against AB.

Isolation of prostrate turfgrass mutants via screening of dwarf phenotype and characterization of a perennial ryegrass prostrate mutant.

Prostrate turf varieties are desirable because of their increased low mowing tolerance, heat resistance, traffic resistance and ground coverage compared with upright varieties. Mutation breeding may provide a powerful tool to create prostrate varieties, but there are no simple, straightforward methods to screen for such mutants. Elucidation of the molecular basis of the major ‘green revolution’ traits, dwarfism and semi-dwarfism, guided us to design a simple strategy for isolating dwarf mutants of perennial ryegrass (Lolium perenne L.). We have shown that gamma-ray-mediated dominant dwarf mutants can be easily screened for at the three-leaf stage. About 10% of dwarf mutant lines also displayed a prostrate phenotype at mature stages (>10 tillers). One prostrate line, Lowboy I, has been characterized in detail. Lowboy I had significantly shorter canopy, leaf blade and internode lengths compared with wild type. Lowboy I also exhibited greater tolerance to low mowing stress than wild type. Exogenous gibberellic acid (GA) restored Lowboy I to a wild-type phenotype, indicating that the dwarf and prostrate phenotypes were both due to GA deficiency. We further showed that phenotypes of Lowboy I were dominant and stably inherited through sexual reproduction. Prostrate turfgrass mutants are difficult to screen for because the phenotype is not observed at young seedling stages, therefore our method represents a simple strategy for easily isolating prostrate mutants. Furthermore, Lowboy I may provide an outstanding germplasm for breeding novel prostrate perennial ryegrass cultivars.

Carbon Balance of Turfgrass Systems in Response to Seasonal Temperature Changes Under Different Mowing Heights

Turfgrass growth and physiological activities are sensitive to temperatures and are affected by mowing height. Increasing temperatures associated with global climate change may limit photosynthetic capacity of established turfgrass stands. The objective of this study was to determine the effects of mowing height on carbon exchange of a turfgrass system and consequential effects on turfgrass growth in response to temperature variations across the growing season in kentucky bluegrass (Poa pratensis cv. Baron) stands. Mature (8 years old) turfgrass was mowed at 7.6 cm [high mowing height (HM)] or 3.8 cm [low mowing height (LM)] during 2012 and 2013. Both LM and HM plots displayed significant decline in turf quality (TQ), shoot biomass, and canopy photosynthetic rate (Pn) with increasing air temperature above 23–24 °C in both years and the decline was more pronounced for LM plots. Turf plots were carbon emitters when total respiration rate of shoots, roots, and soil (Rtotal) exceeded canopy Pn under high temperatures during July–September but maintained net carbon gain during cooler seasons (May and June) due to greater Pn to Rtotal ratio (Pn:Rtotal). Lowering mowing height accelerated carbon loss by reducing canopy Pn, particularly under high temperatures. Our results suggested that whether mature turfgrass stands fix or emit carbon is heavily dependent on interaction between seasonal temperatures and mowing height gauging whole-stand photosynthetic capacity. Furthermore, increasing mowing height during summer months may offset the deleterious effects of high temperature by maintaining positive carbon balance within the turfgrass system.

Species Succession and Turf Quality of Tall Fescue and Kentucky Bluegrass Mixtures as Affected By Mowing Height

ABSTRACTMixtures of turfgrass species are commonly used throughout the world when establishing cool‐season grasses from seed. However, there have been limited studies investigating how various species compete with each other as the turf matures. A study was conducted in Padova, Italy, to investigate the performance and species composition of four mixtures that contained a single cultivar of Kentucky bluegrass (KB; Poa pratensis L.) and two rhizomatous or two nonrhizomatous tall fescue (TF; Festuca arundinacea Schreb.) cultivars. The trial was seeded in September 2010. Three mowing heights (20, 32, and 62 mm) were also applied to all the mixtures. General turfgrass performance of the mixtures was monitored through the 2011 growing season, and species composition was measured regularly to determine the abundance of both species in the mixture. Throughout the study, the mixtures containing the rhizomatous TF consistently had higher turfgrass quality and turfgrass density than mixtures containing the nonrhizomatous types. Mowing height had less effect on the performance of the mixtures, but the lower mowing heights (20 and 32 mm) performed more consistently than the plots mowed at the highest (62 mm) mowing height. Species composition of the mixtures was significantly influenced by the different TF cultivars, in that KB was less abundant in mixtures containing rhizomatous TF cultivars compared to nonrhizomatous cultivars, suggesting an increased competitive ability of rhizomatous TF lines. Mowing height also influenced the species composition, in that KB was significantly more abundant at lower mowing heights.

Impacts of Mowing, Grazing and Edge Effect on Orthoptera of Submontane Grasslands: Perspectives for Biodiversity Protection

Semi-natural grasslands managed by mowing and grazing are an important part of European landscape. Orthopterans are considered to be an appropriate indicator to assess the impact of agricultural management on grassland ecosystems. We studied effects of mowing, grazing and two kinds of edges on Orthoptera of submontane hay meadows and pastures in the Hrubý Jeseník Mts. (Czech Republic). Using sweep netting and pan trapping, we sampled orthopteran assemblages associated with the farmland managed for at least five years under Czech agri-environmental schemes. In total we collected 2253 individuals of orthopterans representing 14 species. The short-term impacts of mowing and grazing were tested by multivariate ordination analyses. The results indicate that mowing significantly decreased Orthoptera species abundance. Conversely, the response of orthopterans to grazing was not statistically significant and appeared to be species-specific. The abundance of acridid Gomphocerippus rufus increased substantially with grazing, which is in contrast with its negative response to mowing. The negative influence of mowing on grassland inhabitants can be mitigated by lower mowing frequency and by providing temporary uncut refuges. The results of generalized linear models showed significant increase of both species richness and total abundance of Orthoptera towards the baulks. Therefore, the refuges should be established primarily along grass baulks or similar types of permanent grassy edges. As a general rule an effort should be made when managing grasslands to ensure the highest habitat heterogeneity.

Comparative Genome Analysis between Agrostis stolonifera and Members of the Pooideae Subfamily, including Brachypodium distachyon

Creeping bentgrass (Agrostis stolonifera, allotetraploid 2n = 4x = 28) is one of the major cool-season turfgrasses. It is widely used on golf courses due to its tolerance to low mowing and aggressive growth habit. In this study, we investigated genome relationships of creeping bentgrass relative to the Triticeae (a consensus map of Triticum aestivum, T. tauschii, Hordeum vulgare, and H. spontaneum), oat, rice, and ryegrass maps using a common set of 229 EST-RFLP markers. The genome comparisons based on the RFLP markers revealed large-scale chromosomal rearrangements on different numbers of linkage groups (LGs) of creeping bentgrass relative to the Triticeae (3 LGs), oat (4 LGs), and rice (8 LGs). However, we detected no chromosomal rearrangement between creeping bentgrass and ryegrass, suggesting that these recently domesticated species might be closely related, despite their memberships to different Pooideae tribes. In addition, the genome of creeping bentgrass was compared with the complete genome sequence of Brachypodium distachyon in Pooideae subfamily using both sequences of the above-mentioned mapped EST-RFLP markers and sequences of 8,470 publicly available A. stolonifera ESTs (AgEST). We discovered large-scale chromosomal rearrangements on six LGs of creeping bentgrass relative to B. distachyon. Also, a total of 24 syntenic blocks based on 678 orthologus loci were identified between these two grass species. The EST orthologs can be utilized in further comparative mapping of Pooideae species. These results will be useful for genetic improvement of Agrostis species and will provide a better understanding of evolution within Pooideae species.

한국잔디 신품종 '세밀(Semil)' 개발

This study was carried out to develope new zoysiagrass cultivar ‘Semil’ (Registration no. 1749). Artificial crossing between the collected lines of typical Z. matrella, NM1 (collected in South Korea) and the different ecotype of Z. matrella, ASm (collected in South Korea) was made to develop a F1 hybrid plant (NM1 x ASm). Among the 30 progenies, (NM1 x ASm)-1 (Semil) showed superior performance in density rating. ‘Semil’ showed genetically light green color, with narrow leaf width (2.7±0.12 mm), and low plant height (10.3±3.7 cm), Length to lowest leaf blade of this cultivar was 1.8±0.15 cm, which may allow low mowing height upto 12 mm.

Annual Bluegrass의 생물학적 특성과 방제

Annual bluegrass는 종자 생산능력이 뛰어나고 한번 조성이 되었을 때 그 분얼경과 지상부 생육이 뛰어나, 전 세계에 가장 널리 퍼져 서식하는 잔디 초종중의 하나이다. 또한 낮은 예초에 적응하는 능력과 조성이 되었을 때 균일성이 좋은 것으로 알려져 있다. Annual bluegrass의 지상부가 성장하기 가장 좋은 온도 범위가 <TEX>$16-21^{\circ}C$</TEX>이며 지하부 성장을 위한 최적의 온도범위는 <TEX>$13-18^{\circ}C$</TEX>로 고온과 저온에 취약한 초종이다. Annual bluegrass를 관리하기 위해서는 질소와 인산의 비교적 높은 시비량은 annual bluegrass의 확산을 촉진하며 반대로 낮은 시비량은 방제에 도움이 된다. 질소원으로 ammonium sulfate를 사용했을때 sulfate에 의해서 낮아진 토양 pH는 토양속에 존재하는 인이 용해되는 것을 감소시키고 annual bluegrass에 피해를 주는 aluminum의 양을 증가시켜 방제에 효과적이다. 관수는 light and frequent 보다는 deep and infrequent 관수방법이 방제에 도움이 되며 예초높이는 낮추고 예지물은 회수 하는 것이 annual bluegrass의 방제에 도움이 된다. 우리나라에서는 화학적 방제가 주를 이루고 있는데 발아전 처리제로서 prodiamine, bensulide, dithiopyr등이 있으며 발아후 처리제로는 ethofumesate, bisbyribac-sodium 그리고 최근에 연구가 되고 있는 mesotrione등이 있다. 발아전 혹은 발아후 처리제 이외에 생장조절제가 annual bluegrass 방제에 이용이 되고 있는데 paclobutrazol, flurprimidol 등이 있다. 우리나라에서 많이 사용이 되고 있는 생장조절제인 trinexapac은 오히려 여름철 annual bluegrass에 좋은 효과를 나타내고 있어 방제에 적합하지 않다. Annual bluegrass의 방제 효과를 극대화 하기 위해서는 관리적 방제와 화학적 방제의 두 가지 방법이 동시에 고려되어야 할 것이다. The object of this study is to review the current states of the characteristics and strategies to control annual bluegrass to apply information to the circumstance of South Korea. Annual bluegrass is one of the most widespread turfgrass species which has great ability to produce seedhead and shoot growth. It also has ability to tolerate low mowing height and to form uniformity of turfgrass when it is established. Annual bluegrass is well-known as weak turfgrass for high and low temperature. High rate of nitrogen and phosphorus improves growth of annual bluegrass. To control annual bluegrass, deep and infrequent irrigation is more effective than light and frequent irrigation. Clipping removal is more effective than clipping return to control annual bluegrass. Prodiamine, bensulide, and dithiopyr are applied as pre-emergence herbicide, and ethofumesate and bisbyribac-sodium are used as post-emergence herbicide. Paclobutrazol and flurprimidol are used as plant growth regulator. Trinexapac which is one of the most popular plant growth regulators (PGRs) in South Korea is not proper to control annual bluegrass because it accelerates improve growth of annual bluegrass in summer. Although chemical control is mainly used in South Korea, combination of cultural and chemical control may be the strategy to maximize effectiveness to control annual bluegrass.

Grassland resistance and resilience after drought depends on management intensity and species richness.

The degree to which biodiversity may promote the stability of grasslands in the light of climatic variability, such as prolonged summer drought, has attracted considerable interest. Studies so far yielded inconsistent results and in addition, the effect of different grassland management practices on their response to drought remains an open question. We experimentally combined the manipulation of prolonged summer drought (sheltered vs. unsheltered sites), plant species loss (6 levels of 60 down to 1 species) and management intensity (4 levels varying in mowing frequency and amount of fertilizer application). Stability was measured as resistance and resilience of aboveground biomass production in grasslands against decreased summer precipitation, where resistance is the difference between drought treatments directly after drought induction and resilience is the difference between drought treatments in spring of the following year. We hypothesized that (i) management intensification amplifies biomass decrease under drought, (ii) resistance decreases with increasing species richness and with management intensification and (iii) resilience increases with increasing species richness and with management intensification.We found that resistance and resilience of grasslands to summer drought are highly dependent on management intensity and partly on species richness. Frequent mowing reduced the resistance of grasslands against drought and increasing species richness decreased resistance in one of our two study years. Resilience was positively related to species richness only under the highest management treatment. We conclude that low mowing frequency is more important for high resistance against drought than species richness. Nevertheless, species richness increased aboveground productivity in all management treatments both under drought and ambient conditions and should therefore be maintained under future climates.

The Effect of PcGA2ox Overexpression on Creeping Bentgrass (Agrostis stolonifera L.): Performance under Various Light Environments

Turf grown in shade exhibits increased stem elongation. Dwarfism could improve turfgrass quality by reducing elongation. The purpose of this study was to examine the effect of GA2-oxidase (GA2ox) overexpression on creeping bentgrass (Agrostis stolonifera L.) performance under restricted light conditions and low mowing heights. Greenhouse studies were conducted at The Ohio State University, Columbus, OH, from 1 Sept. to 31 Oct. in both 2008 and 2009. Two experimental lines, Ax6548 and Ax6549, transformed with CP4 EPSPS and PcGA2ox gene; and a nontransformed control (NTC) was subjected to four light environments: full sun, reduced red to far red light ratio (R:FR), neutral shade [reduced photosynthetic photon flux (PPF)], and canopy shade (reduced PPF and R:FR). Turf was evaluated every 10 days for color and percent coverage. GA2ox overexpression resulted in darker green color in both transgenic lines under all light treatments as compared with NTC plants. No differences in overall turfgrass coverage were noted in full sun conditions among the lines. A significant decrease in turf coverage occurred for all shade treatments regardless of line. However, Ax6549 decreased the least. Overall data indicated that GA2ox overexpression can improve quality of turfgrass under reduced light conditions.

잔디(Zoysia japonica Steud.) 육묘 이식재배법에 관한 연구 VI. 예초고에 따른 월년생 잡초종의 억제효과

잔디 실생묘를 이식하여 조성된 잔디밭에서 초봄의 생육 초기에 많은 피해를 주고 있는 월년생(동생) 잡초를 방제하고자 예초실험을 실시한 결과 요지는 다음과 같다. (1) 전체 예초 시험구별 잡초발생율은 평균 17.9%였다. (2) 저 예초 시험구인 12.5 mm 구에서 잡초발생율은 24.7%로 높게 나타나, 4개의 예초 시험구 가운데 잡초억제효과가 가장 낮은 것으로 나타났다. (3) 22.5 mm 구에서는 10.6%의 잡초발생율을 보여 가장 높은 잡초억제효과를 나타내고 있다. (4) 고 예초 시험구인 32.5 mm 구와 42.5 mm 구에선 각각 평균보다 다소 높은 18.2%와 18.3%의 잡초발생율을 나타냈다. This study was carried out to control biennial weed which gives a lot of damage to landscaped and early growth of lawns in early spring. The results obtained from the mowing experiment are as follows. (1) Average of occurrence rate of weed species of the total treatments was 17.9%, (2) Occurrence rate of weed species was as 24.7% at 12.5 mm low mowing section. The rate indicates that the lowest weed depression effect was appeared at the lowest mowing among 4 mowing sections. (3) Occurrence rate of weed species was 10.6% at 22.5 mm mowing section. The highest weed depression effect among the 4 mowing sections was observed at the 22.5 mm mowing section. (4) Occurrence rates of weed species were 18.2% and 18.3% at 32.5 mm and 42.5 mm high mowing section, respectively.

Explaining grassland biomass – the contribution of climate, species and functional diversity depends on fertilization and mowing frequency

Summary1. Grassland ecosystems are often used to generate biomass in temperate regions of the world. It is well known that biomass is influenced by climate and biodiversity, but the relative importance of these two factors in relation to management has not been widely studied. To recommend management treatments maximizing biomass yields we aim to quantify the relative effects of climate species and functional diversity on biomass in differently managed grasslands.2. We studied the development of biomass yields over the last 37 years on a grassland site in Germany, with mowing at five frequencies (one to eight times per year), each with and without fertilization. We measured plant species richness (SR) and functional richness (FR) (the diversity of functional species properties) using presence–absence indices. We also measured species evenness (SE), functional evenness and functional divergence (FD) using abundance weighted indices. Climate was included as the mean temperature and sum of precipitation during the growing period. By relating biomass to the above‐mentioned climatic and biodiversity parameters, we extracted the contribution of these to biomass yields.3. Biomass changed over time for all treatments and was maximal at intermediate mowing frequencies. Temporal changes in biomass were partly explained by climate and different aspects of biodiversity, although this differed significantly between treatments. The relative importance of precipitation was highest at high mowing frequencies; the contribution of temperature was highest on less disturbed, unfertilized plots. FR and SR influenced biomass changes in the most intensive disturbance regimes on unfertilized and fertilized plots respectively. FD was most important on intensively disturbed, fertilized plots. SE influenced biomass at low mowing frequencies.4. Synthesis and applications. Climate, species and functional diversity influence annual grassland biomass yields but their importance depends on nutrient status and management frequency. Our results indicate that management treatments with intermediate disturbance regimes will maximize biomass yields in temperate environments. This recommendation may become even more important in the context of climate change: at intermediate mowing frequencies the influence of climatic variables on biomass is less important by comparison to different aspects of biodiversity.

Registration of Turf‐Type Kentucky Bluegrass Cultivars ‘Awesome’, ‘Blue Velvet’, ‘Courtyard’, ‘Ginney’, and ‘Perfection’

Kentucky bluegrass (Poa pratensis L.) is typically grown in multiple‐cultivar blends for golf‐course, sports‐field, lawn, and landscape surfaces. This article describes the breeding and development of five cultivars, all sharing the common trait of tolerance to low mowing heights. ‘Awesome’ (Reg. No. CV‐96, PI 632299), ‘Blue Velvet’ (Reg. No. CV‐98, PI 635049), ‘Courtyard’ (Reg. No. CV‐97, PI 635048), ‘Ginney’(Reg. No. CV‐99, PI 634980), and ‘Perfection’ (Reg. No. CV‐95, PI 632298) are seed‐propagated, single‐clone, apomictic cultivars with minor, but measurable, differences in morphology. Awesome, Blue Velvet, Courtyard, and Perfection were developed from a hybrid cross between ‘Limousine’ and ‘Midnight’ Kentucky bluegrass. Ginney was developed from a hybrid cross between ‘Julia’ and Limousine. All five cultivars are classified as late in reproductive maturity. They are resistant to dollar spot (caused by Sclerotinia homoeocarpa F.T. Bennett), warm‐weather brown patch (caused by Rhizoctonia solani Kühn), and summer patch (caused by Magnaporthe poae Landschoot &amp; Jackson). Awesome, Blue Velvet, Courtyard, Ginney, and Perfection are recommended for golf‐course tees, fairways, and roughs and for lawns, parks, and sports turf, in full sun or partial shade, and in areas where Kentucky bluegrass is well adapted for turf. They are compatible in blends and mixtures with other cool‐season turfgrasses at mowing heights as low as 13 mm.

Relationships between Normalized Difference Vegetation Index and Visual Quality in Turfgrasses: Effects of Mowing Height

Canopy spectral reflectance may provide an objective means to evaluate visual quality of turfgrass, but evaluations of quality may be confounded by cultural practices that affect reflectance, such as mowing height. In this 2‐yr study near Manhattan, KS, we examined effects of mowing height on relationships between normalized difference vegetation index (NDVI) and visual quality ratings in Kentucky bluegrass (KBG; Poa pratensis L., ‘Apollo’) and in a KBG × Texas bluegrass (Poa arachnifera Torr.) hybrid (HBG; ‘Thermal Blue’). Mowing heights were 7.62 cm (high) and 3.81 cm (low). The NDVI averaged 4.5 to 7% greater in high‐ than in low‐mown plots. Distinct regression models of visual quality were found at each mowing height and in each species (r2 from 0.40 to 0.81); separate relationships between NDVI and visual quality were also found between years in the same plots. Correlations between NDVI and visual quality were stronger at high than at low mowing heights, possibly because of greater green biomass at high mowing heights. The 95% confidence intervals surrounding predictions of visual quality from NDVI ranged from ±1.34 to 2.75 (on a 1‐to‐9 scale). Thus, lack of precision is a concern when using these models for detection of differences between treatments. Results indicate that when using NDVI to evaluate turfgrass quality, evaluations should be limited to plots maintained at the same mowing height and with the same species to reduce variability in NDVI.

First Report of Dollar Spot of Seashore Paspalum (Paspalum vaginatum) Caused by Sclerotinia homoeocarpa in South China.

Seashore paspalum (Paspalum vaginatum Swartz), a warm-season perennial grass, is native to tropical and subtropical regions of North and South America (1). Its fine texture and tolerance to low mowing and hypersaline environments make it a commercially promising turfgrass species for coastal regions of south China. In late March 2009, disease symptoms were observed from two golf course fairways in Shenzhen and Foshan, Guangdong Province, China. Small, round patches from 25 to 75 mm in diameter were found to be consisting of bleached, straw color leaf lesions bounded by reddish brown margins. Similar patches had previously been observed on seashore paspalum since 1997 in Guangdong Province, but this turf species has been grown in southern China only since the early 1990s. These symptoms were observed when daytime temperatures were above 25°C and with heavy dew formation at night. Greatest severity was seen in the spring and fall. Several contact and systemic fungicides were applied after first symptoms were observed and they were usually successful in suppressing disease. To confirm the disease as dollar spot, isolates from Shenzhen and Foshan were obtained by plating diseased leaf blades of P. vaginatum (cv. Salam) on potato dextrose agar media. Isolates produced white, fluffy, aerial mycelium, columnar when mature, and usually with a cinnamon base and dark brown or black substratal stroma on and in the agar. One representative isolate from each location was chosen for pathogenicity testing. Six-week-old P. vaginatum (cv. Salam) grown from seed in pots was inoculated, with 5-mm-diameter agar plugs with hyphae from 5-day-old cultures, by direct placement onto leaves and with three replicate pots per isolate. Plants treated with sterile agar plugs served as controls. Inoculated turf was incubated at 25°C with 12-h light/dark conditions. A plastic film was also placed over the pots to retain moisture. Chlorotic leaf lesions started to develop 4 days after inoculation and became a bleached straw color. The same fluffy, white fungus was reisolated from lesions, while no disease was observed on controls, thus completing Koch's postulates. The internal transcribed spacer (ITS) region of the ribosomal DNA was amplified from DNA extracted from two isolates using primers ITS5 and ITS4 (2), and the 610-bp sequences showed 98% similarity with Sclerotinia homoeocarpa F.T. Bennett in GenBank and have been deposited as Accessions GQ386985 and GU002301. Dollar spot on P. vaginatum has been commonly observed in the United States (1). To our knowledge, this is the first confirmed report of dollar spot on P. vaginatum in China or from any host plant in China.

Creeping Bentgrass (Agrostis stolonifera) Putting Green Tolerance to Bispyribac-Sodium

Bispyribac-sodium is an efficacious herbicide for annual bluegrass control in creeping bentgrass fairways, but turf tolerance and growth inhibition may be exacerbated by low mowing heights on putting greens. We conducted field and greenhouse experiments to investigate creeping bentgrass putting green tolerance to bispyribac-sodium. In greenhouse experiments, creeping bentgrass discoloration from bispyribac-sodium was exacerbated by reductions in mowing height from 24 to 3 mm, but mowing height did not influence clipping yields or root weight. In field experiments, discoloration of creeping bentgrass putting greens was greatest from applications of 37 g/ha every 10 d, compared to 74, 111, or 222 g/ha applied less frequently. Chelated iron effectively reduced discoloration of creeping bentgrass putting greens from bispyribac-sodium while trinexapac-ethyl inconsistently reduced these effects. Overall, creeping bentgrass putting greens appear more sensitive to bispyribac-sodium than higher mowed turf, but chelated iron and trinexapac-ethyl could reduce discoloration.

Impact of land use on vegetation composition, diversity and potentially invasive, nitrophilous clonal species in a wetland region in Flanders

In the framework of a nature conservation project in a wetland region of Meetkerke, Belgium, a comprehensive study was conducted to analyse and to compare species composition and diversity among wet grasslands under the six following types of agricultural land use: pastures used at high or low stocking rate, hayfields used at high or low mowing frequency, abandoned hayfields and hay pastures. The focus of the study was on the effects of grassland management on species diversity and on the restriction of occurrence of invasive clonal species. The results show that species importance was strongly related to grassland exploitation parameters and soil hydrological parameters, as shown by the ordination diagram drawn by canonical correspondence analysis (CCA). Species number and importance of non-leguminous dicotyledons were negatively correlated to intensity of use, N supply, water table depth and soil drainage. Phalaris arundinacea, an invasive species which might reduce species diversity, was better suppressed in grazed grassland than in mown grassland. Phalaris arundinacea and Cirsium arvense were most prevalent in abandoned hayfields. Grazing at low stocking rate was the best management technique to maximise plant diversity while restricting invasion by nitrophilous clonal species. Although species-rich and of high complementary value on a landscape scale, haylands mown at low frequency are at higher risk of invasion by clonal species.

EVALUATING BENTGRASSES FOR QUALITY, BALL-ROLL DISTANCE, THATCH/MAT DEVELOPMENT AND ANNUAL BLUEGRASS INVASION

The industry trend to golf putting greens which produce greater ball-roll distances has led to development of high density creeping bentgrass (Agrostis palustris, Huds.) cultivars that tolerate very low mowing heights. These cultivars also have a finer leaf texture and improved competitiveness with the invasive weed, annual bluegrass (Poa annua L.). In this multi-year field study, newer cultivars showed superior quality, color, leaf texture, density and resistance to P. annua invasion than older cultivars; however, there were no significant differences among cultivars in ball roll distance (as determined by a Stimpmeter) or thatch/mat depth.