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Fungicides (azoxystrobin, propiconazole, pyraclostrobin, and thiophanatemethyl) were applied to field plots of creeping bentgrass established on a sand-based root zone substrate and maintained at a cutting height of 0.34 cm. The wetting agent, a modified alkylated polyol, was applied 24 h prior to fungicide application. Irrigation (0.51 cm) was applied to plots immediately after the fungicide spray. Turf was sampled nine times over 42 days to examine fungicide residues in three components of the turf profile: verdure/thatch. roots, and soil. Residues were extracted from samples and then quantified using a liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) procedure. The experiment was run twice. Wetting agent had little or no effect on fungicide distribution in any of the turf components. Postapplication irrigation had little effect on residues observed in the verdure/thatch component. Significant irrigation treatment effects were observed in root and soil components, but results varied among fungicides and sampling dates. Where significant effects were observed for the irrigation plus wetting agent treatment, results generally mirrored outcomes for irrigation treatment. [ABSTRACT FROM AUTHOR]

Creeping bentgrass (Agrostis stolonifera L.), is one of the major cool-season turfgrass species, which is widely planted in putting greens at golf courses in China (Zhou et al. 2022). In June 2022, an unknown disease with reddish-brown spots (2-5 cm in diameter) were observed on 'A4' creeping bentgrass putting greens at Longxi golf course in Bejing. As the disease progressed, the spots coalesced and formed irregular patches (15-30 cm in diameter). When looking closely, the leaves were wilting, yellowing and melting out from the foliar tips to the crowns. The disease incidence was estimated up to 10-20 % of each putting green and a total of five putting greens had similar symptoms as described above. Three to five symptomatic samples were collected from each green. Diseased leaves were cut into pieces, surface sterilized in 0.6% sodium hypochlorite (NaClO) for 1 min, washed three times with sterilized water, air dried and placed on potato dextrose agar (PDA) containing 50 mg L-1 streptomycin sulfate and tetracycline. Plates were incubated in the dark at 25 °C for 3 days, and fungal isolates with similar morphology (irregular cultures with dark-brown back and light-brown to white surface) was consistently recovered. Pure cultures were obtained by repeat hyphal-tip transfer. The fungus did not grow well on PDA medium, radial growth was estimated 1.5 mm/d, and dark-brown colony was surrounded by light-white margin. However, it grew fast on creeping bentgrass leaf extract (CBLE) medium, CBLE medium was produced by adding 0.75 g potato powder, 5 g agar and 20 mL creeping bentgrass leaf juice (with 1 g fresh creeping bentgrass leaf) into 250 mL sterile water. The colony was sparse and light-white, and radial growth was roughly 9 mm/d on CBLE medium. Conidia were spindle-shaped, olive to brown in color, pointy or obtuse at both ends, 4 to 8 septa, and a size range of 9.85 to 20.20 × 26.26 to 45.64 μm (14.85 μm × 40.62 μm average, n = 30). Genomic DNA of two representative isolates (HH2 and HH3) was extracted, the nuclear ribosomal internal transcribed spacer (ITS) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) region were amplified with primers ITS1/ITS4 (White et al. 1990) and gpd1/gpd2 (Berbee et al. 1999), respectively. The ITS (OQ363182 and OQ363183) and GAPDH (OQ378336 and OQ378337) sequences were deposited in GenBank. BLAST analyses revealed that the sequences shared 100% and 99% similarity with the published ITS (CP102792) and GAPDH (CP102794) of B. sorokiniana strain LK93, respectively. To complete Koch's postulates, 3 plastic pots (15 cm height × 10 cm top diameter × 5 cm bottom diameter, three replicates for the isolate HH2) were seeded with creeping bentgrass and inoculated with a spore suspension (1×105 conidia/mL) after two months of plant growths. Healthy creeping bentgrass inoculated with distilled water served as controls. All pots were covered with plastic bags, placed in a growth chamber with a 12-h day/night cycle at 30/25°C and 90% relative humidity. Disease symptoms (yellowing and melting out leaf) were noted after 7 days. B. sorokiniana was recovered from the diseased leaves and identified morphologically and molecularly as described above. To our knowledge, this is the first report of melting out on creeping bentgrass caused by B. sorokiniana in China. The report here will provide a scientific basis for developing management strategies on this disease in the future. Additional study is needed to investigate the prevalence of the disease on putting greens from golf courses in larger regions of China.

Residual efficacy of five fungicides (azoxystrobin, flutolanil, metcona-zole, polyoxin D, and pyraclostrobin) applied to creeping bentgrass (Agrostis stolonifera) maintained under golf course fairway conditions was determined using a bioassay method. During 2010 and 2011, six different field experiments were conducted. Each consisted of a single fungicide application followed by periodic (0, 3, 7, 10, 14, 17, and 21 days after application) turf sampling, inoculation of samples with an isolate of Rhizoctonia solani, and incubation in a controlled environment chamber for 48 h. For each sample date, fungicide efficacy was determined by measuring the extent of symptom expansion on fungicide treated and nontreated samples. Efficacy half-life values based on a two-parameter Weibull function were 3.1 to 14.0 days for the fungicides used in this study. Residual efficacy was further examined in 2011 by analyzing residues from creeping bentgrass verdure using liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS). Quantitative analysis from LC/TOF-MS revealed that fungicide residues were depleted rapidly following application to turfgrass and reinforced the precipitous decline in fungicide efficacy demonstrated by the bioassays. Regardless of fungicide, more than 90% of active ingredient applied was depleted from the verdure between 3 and 8 days after application, and more than 99% of fungicide was depleted at 17 days after application. This research provides a quantitative description of the temporal nature of loss of fungicide and fungicide protection from turf. [ABSTRACT FROM AUTHOR]

Bacterial etiolation and decline caused by Acidovorax avenae subsp. avenae is an emerging disease of creeping bentgrass (Agrostis stolonif-era) in and around the transition zone, a unique area of turfgrass cul-ture between cool and warm regions of the United States. It is sus-pected that the disease has been present for many years, although diagnosis of the first occurrence was not reported until 2010. Solicita-tion of samples from golf courses in 2010 and 2011 was undertaken to investigate the prevalence and dissemination of Acidovorax avenae subsp. avenae on creeping bentgrass. At least 21 isolates from 13 states associated with these outbreaks on golf courses were confirmed as A. avenae subsp. avenae by pathogenicity assays and 16S rDNA sequenceanalysis at two independent locations. Pathogenicity testing of bacte-rial isolates from creeping bentgrass samples exhibiting heavy bacterial streaming confirmed A. avenae subsp. avenae as the only bacterium to cause significant disease symptoms and turfgrass decline. Host range inoculations revealed isolates of A. avenae subsp. avenae to be patho-genic on all Agrostis stolonifera cultivars tested, with slight but signifi-cant differences in disease severity on particular cultivars. Other turfgrass hosts tested were only mildly susceptible to Acidovorax avenae subsp. avenae infection. This study initiated research on A. avenae subsp. avenae pathogenicity causing a previously uncharacter-ized disease of creeping bentgrass putting greens in the United States [ABSTRACT FROM AUTHOR]

Management of dollar spot (incited by Sclerotinic, homoeocarpa) on golf course fairways is increasingly challenging. The objectives of this study were to determine the influence of mowing frequency and plant growth regulators (PGR5) on dollar spot severity and on the residual efficacy of fungicides for control of dollar spot. Two 4-month-long studies were conducted on 'Putter' creeping benlgrass (Agrostis stolonifera) maintained as a fairway at the University of Connecticut. Treatments were arranged itt a three-by-three-by-five factorial that assessed the influence of mowing Irequency (2, 4, or 6 days week) and PGRs (paclobutrazol, trinexapac-ethyl, or none) on dollar spot coistrol by five fungicide Ireatlsseuts (boscalid, chlorolbalonil, iprodione, propiconazo!e, or none). Turf was mowed in the afternoon hours In minimize the confounding effect of mowing frequency on leaf wetness duration. Treatments were initiated in the late spring of 2007 and 2008, and each fungicide treatment was reapplied only when dollar spol exceeded a threshold of five infection centers plor'. to the absence of fungicides, dollar spot ses'erity was reduced by 63 to 90% in plots treated with paclobotrazo! and by 13 to 55% in plots treated with trinexapac-cthyl. Dollar spot severity was 23 to 50% lower in plots mown 2 clays week1 compared with those mown 6 days week-1 In cases where a significant interaction was observed between mowing frequency and PGRs. dollar spot was reduced on most rating dates in plots treated with trittenapaeethyl that wets mown 2 days weeld contpared wilit those tttown 6 clays weekL Survival aoatysis of days tintit threshold was met resealed that duration of control of fungicides in plots receiving paclobuttrazol were 28 to 84% longer compared with plots not receiving POR. Duration of control by fungicides was getterally similar between plots treated with trinexupuc-ethyl and no PGR. In general. ntowing frequency did not influence duration of control. Results from this study indicate that paclobutrazol could be nsed to increase the treatment interval of fungicides and that mowing freqttency in the absence of dew is likely to have little influence on fungicide residual efficacy. When used without fungicides, PORs and less frequent mowing niay reduce dollar spot in situations where fungicide use is limited. [ABSTRACT FROM AUTHOR]

Dollar spot (Sclerotinia homoeocarpa) is a severe disease problem on creeping bentgrass (Agrostis stolonifera) fairways. The objective of this study was to evaluate the effects of dew removal and mowing feequency on fungicide performance for dollar spot control. In 2009 and 2010, an experiment involving daily dew removal or no dew removal, mowing frequency (2. 4. and 6 days week-1), and fungicides (chlorothalonil, propiconazole, and iprodine) was condutsed on creeping bentgrass maintained as a fairway. Daily dew removal resulted in fewer dollar spot infection center (IC) cowpared with not removing dew during late summer 2009 and 2010 for all mowing-frequncy and fungicide treatments. As mowing frequency inceeaced from 2 sob days week', dollar spot IC decreased when averaged across all fungicide treatments. For all fungicides, daily dew removal increased the october of days seeded to wach a 15-IC plot' point of reference when compared with fungicide treatments in which dew scus not removed. The eunthee of days required to reach 15 IC varied with fungicide. mowing frequency, und year the teat was conducted. Results demonstrate that dollar spot control with fungicides can beextcnded when daily dew removal employed anti, insomocanes, when wowiog frequency in iecreared on dew counted surf. Benefits of dew-removal practices on dollar spot and fungicide performance can vary with weather conditions, fungicide, threshold level, and possibly other factors. [ABSTRACT FROM AUTHOR]

In this 2-year field study, four chemically diverse fungicides (i.e., chlorothalonil, boscalid, iprodione, and propiconazole) were evaluated for their ability to control dollar spot (Scierotinia homoeocarpa) in creeping bentgrass (Agrostis stolonifera) as affected by simulated rain and mowing timing. Simulated rain (25 to 32 mm) was imposed about 30 mm after fungicide application and was compared to rain-free plots. One set of plots was mowed in the morning when the canopy was wet with dew and compared to plots that were mowed when the canopy was dry in the afternoon. The percent reduction in dollar spot control associated with simulated-rain versus rain-free treatments in 2007 and 2008, respectively, was as follows: chlorothalonil 67 and 83%; propiconazole 42 and 79%; boscalid 48 and 70%; and iprodione 33 and 66%. When disease pressure was low, all fungicides subjected to simulated rain provided effective dollar spot control for 7 or more days following the initial application in each year. Across all fungicidetreated plots over 2 years, the average percent reduction in dollar spot associated with morning mowing ranged from 54 to 65%. The reduction in dollar spot severity in morning-mowed plots improved the performance of all fungicides. [ABSTRACT FROM AUTHOR]

Pythium root dysfunction (PRD), caused by Pythium volutum, has been observed on golf course putting greens established with creeping bentgrass in the southeastern United States since 2002. To evaluate preventative strategies for management of this disease, a 3-year field experiment was conducted in Pinehurst, NC on a `G-2' creeping bentgrass putting green. Fungicide treatments were applied twice in the fall (September and October) and three times in the spring (March, April, and May) in each of the 3 years. Applications of pyraclostrobin provided superior preventative control compared with the other fungicides tested. Azoxystrobin and cyazofamid provided moderate control of PRD in two of three seasons. Experiments were conducted to determine whether the disease suppression provided by pyraclostrobin was due to fungicidal activity or physiological effects on the host. In vitro sensitivity to pyraclostrobin, azoxystrobin, fluoxastrobin, cyazofamid, mefenoxam, propamocarb, and fluopicolide was determined for 11 P volutuin isolates and 1 P aphanidermatum isolate. Isolates of P volutum were most sensitive to pyraclostrobin (50% effective concentration [EC50] value = 0.005), cyazofamid (EC50 = 0.004), and fluoxastrobin (EC50= 0.0 10), followed by azoxystrobin (EC50 = 0.052), and mefenoxam (EC50 = 0.139). P volutum isolates were not sensitive to fluopicolide or propamocarb. Applications of pyraclostrobin did not increase the foliar growth rate or visual quality of creeping bentgrass in growth-chamber experiments. This work demonstrates that fall and spring applications of pyraclostrobin, azoxystrobin, and cyazofamid suppress the expression of PRO symptoms during summer and that field efficacy is related to the sensitivity of P volutum to these fungicides. [ABSTRACT FROM AUTHOR]

Colletotrichum cereale is the causal agent of turfgrass anthracnose, which has become a serious problem on annual bluegrass (Poa annua) and creeping bentgrass (Agrostis palustris) golf course putting greens. Thiophanate-methyl is a benzimidazole (methyl benzimidazole carbamate [MBC]) fungicide used for the management of anthracnose. In this study, we examined 481 isolates from 10 California populations to determine the presence and frequency of MBC resistance. An in vitro methodology was developed to construct a baseline sensitivity distribution using 60 isolates from an unexposed population (TCGC). The 50% effective dose (ED50) values for the baseline sensitivity distribution for thiophanate-methyl ranged from 0.14 to 2.3 μ/mI with a mean of 0.75 μ/mI. For 60 isolates assayed from an exposed population (AHCC), 57 isolates were not responsive to in vitro concentrations of thiophanate-methyl of up to 30 μ/mI. Isolates nonresponsive to thiophanate-methyl were not responsive to benomyl in vitro. Two isolates nonresponsive in vitro to thiophanate-methyl or benomyl were not controlled in vivo on annual bluegrass plants treated preventively with either fungicide at 11 mg/ml, confirming the results of the in vitro testing. The remaining 361 isolates from eight populations were tested using the single discriminatory dose of thiophanate-methyl at 10 μ/mI. A high proportion (>90%) of isolates from six of the populations were resistant to thiophanate-methyl, indicating the presence of practical resistance at these locations. To determine the molecular mechanism of MBC resistance, the two β-tubuIin genes, TUB1 and TUB2, of 12 resistant and 6 sensitive isolates were amplified and sequenced, revealing a glutamic acid to lysine substitution at position 198 of TUB2 that was present in all resistant isolates. This work confirms the presence of MBC resistance in C. cereale populations from California and presents methods and information that can be used to manage resistance to the MBC fungicides and improve anthracnose management programs. [ABSTRACT FROM AUTHOR]

The duration of effective concentrations of fungicides for control of dollar spot on creeping bentgrass fairways was investigated using a bioassay technique. In each of three runs of the experiment, fungicide treatments were applied once to turf in replicated field plots; then, the plots were sampled periodically over 3 weeks by removing turf plugs from the field. The sampled plugs were placed in incubation containers and inoculated with sections from a 4-day-old colony of Sclerotinia homoeocarpa growing on potato dextrose agar. After a 96-h incubation period, the extent of pathogen growth on the turf plugs was measured. Results described a precipitous decline in effective concentration for all fungicide treatments beginning 7 to 10 days after application. The fungicides were only marginally effective at 14 days after application, and none provided any disease suppression at 21 days after application. The efficacy half-life (EHL) associated with four of the fungicides (chlorothalonil, iprodione, propiconazole, and thiophanate methyl) was estimated with two models. EHL estimates ranged from 6.1 to 15.2 days depending on the fungicide and the model. This research contributes to our knowledge of the duration of effective fungicide concentrations on creeping bentgrass and can provide insight for scheduling fungicide sprays for golf course fairways. [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]

The effects of management practices and nematode population density on the seasonal fluctuations in lance nematode (Hoplolaimus galeatus) populations in creeping bentgrass were studied in a naturally infested experimental putting green and in artificially infested microplots. In general, H. galea (us populations increased from late spring through midsummer, declined in August, and increased again in the fall. Population increase in microplots was strongly density dependent, with final population densities inversely proportional to inoculum levels. Ectoparasitic populations of H. galeatus in both studies were composed of adults and juveniles, whereas endoparasitic populations were almost exclusively juveniles. H. galeatus populations in the naturally infested site were aggregated spatially, but the aggregation was not temporally stable. Nematode populations were not affected by bentgrass cultivar selection or irrigation frequency. [ABSTRACT FROM AUTHOR]

Avenacinase activity has been shown to be a key factor determining the host range of Gaeumannomyces graminis on oats (Avena saliva). G. graminis var. avenae produces avenacinase, which detoxifies the oat root saponin avenacin, enabling it to infect oats. G. graminis var. tritici does not produce avenacinase and is unable to infect oats. G. graminis var. avenae is also reported to incite take-all patch on creeping bentgrass (Agrostis stolonifera). It is unknown whether creeping bentgrass produces avenacin and if the avenacin-avenacinase interaction influences G. graminis pathogenicity on creeping bentgrass. The root extracts of six creeping bentgrass cultivars were analyzed by fluorimetry, thin-layer chromatography, and high performance liquid chromatography for avenacin content. Avenacin was not detected in any creeping bentgrass cultivars, and pathogenicity assays confirmed that both C. graminis var. avenae and G. graminis var. tritici can infect creeping bentgrass and wheat (Triticum aestivum), but only G. graminis var. avenae incited disease on oats. These results are consistent with the root analyses and confirm that avenacinase activity is not required for creeping bentgrass infection by G. graminis. [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]

Isolates of an unidentified Rhizoctonia sp. (NP isolates), obtained from creeping bentgrass (Agrostis stolonifera var. palustris) in Japan that exhibited symptoms of a new disease, were compared with isolates of three varieties of Waitea circinata var. oryzae, var. zeae, and var. circinata. NP isolates also were compared with isolates of R. oryzae obtained from creeping bentgrass exhibiting white patch-like symptoms (RW isolates). The color and size of sclerotia, color of mycelia, and pigment deposition of NP isolates was similar to that of RW isolates and W. circinata var. circinata, but distinctly different from W. circinata var. oryzae and W. circinata var. zeae. The optimal temperature for hyphal growth of NP isolates, RW isolates, and W. circinata var. circinata was 28°C, and for W. circinata var. oryzae and W. circinata var. zeae was 30°C. Pathogenicity tests on creeping bentgrass showed that the severity of disease caused by NP isolates, RW isolates, and W. circinata var. circinata was greater than with W. circinata var. oryzae, but lower than with W. circinata var. zeae. No significant differences in symptom expression were apparent among NP isolates, RW isolates, and W. circinata var. circinata. A phylogenic tree, obtained using the results of random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR), showed that isolates of W. circinata var. oryzae and W. circinata var. zeae separated into individual clusters, while NP isolates, RW isolates, and W. circinata var. circinata clustered together. The lengths of the rDNA internal transcribed spacer (ITS) region of NP isolates, RW isolates, and W. circinata var. circinata were identical but smaller than those of W. circinata var. oryzae and W. circinata var. zeae. Restriction fragment length polymorphism (RFLP) analysis of the rDNA-ITS region, using three enzymes (HapII, HinfI, and MboI), also showed that NP isolates were the same as RW isolates and W. circinata var. circinata, but different from W. circinata var. oryzae and W. circinata var. zeae. Based on these results, the NP isolates causing a new disease on bentgrass are W. circinata var. circinata, and that RW isolates are also IV circinata var. circinata but not R. oryzae. We propose that the name of the disease on creeping bentgrass caused by W. circinata var. circinata is brown ring patch. [ABSTRACT FROM AUTHOR]

Pythium root rot (PRR) is a disease that can rapidly devastate large swaths of golf course putting greens, with little recourse once symptoms appear. Golf courses routinely apply preventive fungicides for root diseases, which may alter the rhizosphere microbiome, leading to unintended effects on plant health. A multiyear field trial was initiated on a 'T-1' creeping bentgrass ( Agrostis stolonifera L. cultivar T-1) putting green in College Park, Maryland to evaluate preventive PRR management for disease suppression and effects on rhizosphere bacterial communities. Fungicides commonly used to prevent PRR and a biological fungicide were repeatedly applied to experimental plots throughout the growing season. Rhizosphere samples were collected twice annually from each plot for evaluation of rhizosphere bacterial communities through amplicon sequencing and monitoring of biological control organism populations via quantitative PCR. Cyazofamid was the only treatment to suppress PRR in both years compared with the control. Fosetyl-Al on a 14-day interval and Bacillus subtilis QST713 also reduced PRR severity in 2019 compared with the nontreated control. Treatments did not significantly affect bacterial diversity or relative abundances of bacterial classes; however, seasonal environmental changes did. Repeated rhizosphere-targeted applications of B. subtilis QST713 appear to have established the bacterium into the rhizosphere, as populations increased between samples, even after applications stopped. These findings suggest that QST713 may reduce pathogen pressure when repeatedly applied and can reduce fungicide usage during periods of low PRR pressure.

The article focuses on a study related to the cause of dollar spot by Sclerotinia homoeocarpa on creeping bentgrass in Norway by T. Espevig and others, which was published online in the 2015 issue of the periodical.

An abstract of the article "First Report of Brown Ring Patch Caused by Waitea circinata var. circinata on Creeping Bentgrass in Arizona," by N. Hyder and C. M. Chen is presented.

Examines the presence of circular patches in Agrostis stolonifera and Poa annua turfgrasses caused by Typhula incarnata in a golf course in Italy. Blighted appearance of the turfgrasses; Fungal pathogenicity; Reisolation of the pathogen.