Dollar Spot Research Articles

Nonparametric exchange rate prediction?

Conditional heteroskedasticity is frequently found in the prediction errors of linear exchange rate models. It is not clear whether such conditional heteroskedasticity is a characteristic of the true data-generating process, or whether it indicates misspecification associated with linear conditional-mean representations. We address this issue by estimating nonparametrically the conditional-mean functions of ten major nominal dollar spot rates, 1973–1987, which are used to produce in-sample and out-of-sample nonparametric forecasts. Our findings bode poorly for recent conjectures that exchange rates contain nonlinearities exploitable for enhanced point prediction.

Measuring Exchange Rate Uncertainty: The Case of the Australian Dollar 1969 to 1987

AbstractIn this article indices of exchange rate uncertainty are measured from the perspective of potential impacts on trade flows. Empirical evidence based on movements in the Australian dollar spot rates and forward rates indicates that there has been an increase in currency risk between 1969 and 1987, which is not surprising given the progressive relaxation of the exchange rate regime during this period. More surprising is the finding that exchange rate uncertainty indices have risen relative to domestic financial price uncertainty indices. This would not have been expected to occur if increased currency risk had been solely due to growing instability of the underlying economic environment. However, since there is evidence that currency risk has been offset by domestic risk, the risk burden of diversified international traders may not have been adversely affected.

Anatomy and histochemistry of stromatal anamorphs in the Sclerotiniaceae

As part of comparative studies of stromata in the Sclerotiniaceae, mature sclerotial and substratal stromata produced in vitro by 19 species, and 1 form-species, representing 13 genera and 1 form-genus, were examined using light microscopy and histochemical staining. Sclerotial-stromatal taxa were Sclerotinia sclerotiorum, S. trifoliorum, S. minor. Sclerotium cepivorum, Botrytis cinerea, B. porri, Dumontinia tuberose, Ciborinia erythronii, Myriosclerotinia dennisii, M. borealis, Monilinia fructicola, and Stromatinia gladioli. Substratal-stromatal taxa were Lambertella subrenispora, Lanzia luteovirescens, Rutstroemia sydowiana, Stromatinia gladioli, Ovulinia azaleae, Sclerotinia homoeocarpa, Scleromitrula shiraiana, and Ciboria acerina. Histochemical staining, particularly 0.05% toluidine blue O in benzoate buffer at pH 4.4, was found to be useful in demarcating the zones within stromata: rind, cortex, and medulla. All sclerotia contained extensive reserves of carbohydrates in thick cell walls and copious extracellular matrix, while protein bodies were usually the major cytoplasmic storage reserve. A group of saprophytic, substratal isolates had thin medullary cell walls and less extracellular matrix, and did not store protein but stored large deposits of lipid in cytoplasm. A group of phytopathogenic, substratal-stromatal isolates appeared to be transitional, with anatomical features and extensive cytoplasmic protein body reserves suggesting that they produce indeterminate sclerotial stromata rather than true substratal stromata.

Occurrence of the dollar spot disease of bentgrass turf in Japan

Occurrence of the dollar spot disease of bentgrass turf in Japan

Efficient chemical control of dollar spot on bentgrass turf

Efficient chemical control of dollar spot on bentgrass turf

The dynamics of exchange rate volatility: A multivariate latent factor ARCH model

AbstractWe study temporal volatility patterns in seven nominal dollar spot exchange rates, all of which display strong evidence of autoregressive conditional heteroskedasticity (ARCH). We first formulate and estimate univariate models, the results of which are subsequently used to guide specification of a multivariate model. The key element of our multivariate approach is exploitation of factor structure, which facilitates tractable estimation via a substantial reduction in the number of parameters to be estimated. Such a latent‐variable model is shown to provide a good description of multivariate exchange rate movements: the ARCH effects capture volatility clustering, and the factor structure captures commonality in volatility movements across exchange rates.

Bermudagrass Turf Response to Mowing Practices and Fertilizer1

AbstractThe overall quality of ‘Tifway’ bermudagrass [Cynodon transvaalensis Burtt‐Davies × Cynodon dactylon (L.) Pers.] turf is often determined by the type of mower and fertilizer, and whether clippings are removed or returned. The purpose of this field research study was to determine bermudagrass turf response to N at 100 to 300 kg ha−1 and to K at 50 to 300 kg ha−1 as related to mowing treatments. Treatments were arranged in a split block with subunits in strips. The primary strips were mowing treatments, and subunit strips were fertilizer treatments. The soil type was a Cecil sandy loam (clayey, kaolinitic, thermic Typic Hapludult). A rotary mulching mower maintained the highest quality of bermudagrass, and flail mowing the lowest turf quality throughout the 3‐yr study. Turf quality was not consistent each year. Quality was higher when grass clippings were returned than when removed. In most instances, bermudagrass did not respond to N at rates above 200 kg ha−1. Turf quality and shoot density were as good when K was applied at 50 kg ha−1 as at higher rates. Neither fertilizer treatments nor returning grass clippings influenced thatch accumulation. However, turf cut with a rotary mulching mower had a greater thatch accumulation than did turf cut with a flail mower. Dollar spot (Moellerodiscus spp. and Lanzia spp.) disease occurred more frequently at the lowest N treatment.

Thatch and Quality of Tifway Bermudagrass Turf in Relation to Fertility and Cultivation1

AbstractSecondary cultural practices, such as core aeration, vertical mowing, and topdressing, are being used on homelawn turf to a greater extent, even though specific problems may not warrant their application. In a field study (clayey, kaolinitic, thermic Typic Hapludult soil), we applied secondary cultural practices on ‘Tifway’ bermudagrass [Cynodon dactylon (L.) Pers. ✕ C. transvaalensis (Burtt‐Davis)] in conjunction with annual N rates of 98, 196, and 296 kg ha−1 and K at 49, 98, and 196 kg ha−1. Neither N nor K influenced thatch accumulation, but a minimum of 196 kg N ha−1 was necessary for adequate shoot density and color. The 49 kg K ha−1 resulted in as good or better shoot density and color than did higher K rates. Three to four times more dollar spot (Moellerodiscus spp. and Lanzia spp.) occurred at the lowest N rate, while K had much less influence on disease incidence. Core aeration applied once or twice per year caused a loss of stand density and did not reduce thatch accumulation regardless of whether cores were removed or returned. Vertical mowing twice per year decreased thatch by 8% but shoot density was adversely affected. At the end of 4 yr, topdressing with sand reduced thatch by 44 to 62% for one or two applications, respectively, while maintaining adequate shoot density and color. Increasing N or K did not offset the adverse effects of core aeration or vertical mowing. Thus, under homelawn conditions, core aeration and vertical mowing should only be used if a specific problem exists and not as routine practices to prevent thatch accumulation.

The administered Bank rate and the Canada-U.S. spot exchange rate: 1975–1979

This paper analyzes, for the period 1975–1979, the announcement effect of the unanticipated Canadian administered Bank rate changes (the Bank rate is analogous to the discount rate in the U.S.) on the Canada-U.S. dollar spot exchange rate. Leading and/or lagged announcement effects are also investigated. By examining the behaviour of the residuals, on and surrounding the announced Bank rate changes, derived from an autoregressive equation of the daily changes (4:30 p.m. to noon the following day) in the logarithm of the spot $ Canadian/$ U.S. rate the evidence seems to indicate, on the average, a significant adjustment (appreciation of the Canadian dollar for Bank rate increases and depreciation for Bank rate decreases) of the exchange rate on the day of the effective unanticipated administered Bank rate changes regardless of the assumptions made with respect to the probability distribution of the residuals — whether it be normal, symmetric stable with a characteristic exponent of 1.8, or nonparametric.

RELATIONSHIP BETWEEN WEATHER FACTORS AND DOLLAR SPOT OF CREEPING BENTGRASS

In 1981 and 1982 epidemics of dollar spot of creeping bentgrass, caused by Sclerotinia homoeocarpa, proceeded in a series of steps. Each step began at a point where a decline in the epidemic rate was followed by an increase in the epidemic rate and continued until a new step began. A step in the epidemic occurred after two consecutive wet days if the average temperature for the period was at or above 22 °C or after three or more consecutive wet days if the average temperature for the period was 15 °C or greater. These weather conditions were referred to as "infection periods." In 1982, an application of Tersan 1991 (benomyl) 1 and 2 days after two infection periods provided an acceptable level of disease control as effective as that obtained from a regular preventive schedule of seven sprays.Key words: Agrostis palustris, disease control, Sclerotinia homoeocarpa, weather-timed spray

Sclerotinia homoeocarpa . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Sclerotinia homoeocarpa . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On turf grasses: Agrostis alba, A. canina, A. palustris, A. stolonifera, A. stolonifera subsp. compacta, A. tenuis, Avena, Cynodon dactylon, Digitaria didacryla, Festuca ovina, F. rubra, F. rubra subsp. comutata, F. rubra var. fallax, Holcus lanatus, Lolium, Paspalum notatum, Pennisetum clandestinum, Poa annua, P. pratensis, P. trivialis, Puccinellia maritima, Cyperus rotundus . By inoculation on radish, lettuce, beet, tomato, subterranean clover, pea, bean and wheat seedlings, barley, onion. DISEASE: Dollar spot of turf. The spots are about 5 cm diam. and approximately circular, though they sometimes coalesce to form irregular patches. They are brown at first, later becoming bleached to straw coloured. The fungus is present on leaves, stems and basal parts of the plants, which eventually die. GEOGRAPHICAL DISTIBUTION: Britain and Northern Ireland, Netherlands, Australia, New Zealand (57, 4372), USA. TRANSMISSION: No detailed studies made. The fungus is known to tee capable of overwintering in individual dollar spots (40, 689). Dissemination by infected leaf fragments has been reported (Smith, 1955).

Effect of Fertilization on Penncross Creeping Bentgrass1

AbstractAlthough turfgrass fertilization influences many factors that affect turfgrass quality, little information is presently available that encompasses the interrelationships between fertilization, soil fertility, and turfgrass response and quality. A field study was conducted on Hagerstown soil (fine, mixed, mesic Typic Hapludalf) to determine the effects of N sources (Agrinite, Milorganite, ureaform, and urea), P rates (0, 0.49, 0.98, and 1.95 kg/100 m2), and K rates (0, 0.76, and 1.52 kg/100 m2) on soil nutrient levels and the growth, quality, and chemical composition of ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) maintained as putting green turf. Wilting, disease, chlorosis, and annual bluegrass (Poa annua L.) infestation were used to assess quality.Fertilization with Milorganite increased available soil P and Mg. Available P and K in the soil ranged from 11 to 94 ppm and 0.06 to 0.28 meq/100 g, respectively. Elemental content of clippings was affected by all treatments, and treatment × date of sampling interactions that occurred could limit the usefulness of tissue analyses for diagnosing the nutritional status of turfgrasses.When K was applied at 0.76 kg/100 m2, both tissue and available soil K increased. When the K rate was increased to 1.52 kg/100 m2, the additional increment of K caused a greater increase in soil K and a smaller increase in tissue K than was obtained with the first increment of added K. The greatest change in tissue P occurred with the first incremental addition of P. Tissue P was not greatly affected by soil P above 24 ppm. Phosphorus fertilization had little effect on clipping yield; however, K fertilization tended to increase growth, as well as decrease chlorosis noted in early spring. Less severe summer wilting was observed with Agrinite, Milorganite, and K treatments. Less dollar spot (Sclerotinia homoecarpa F. T. Bennett) infection was noted with urea fertilization. Annual bluegrass invasion was favored by P and K fertilization and the effect of one was enhanced by the other. Milorganite, which increased soil P, also favored annual bluegrass. Results of this study indicated a need for more work in soil test calibration for turfgrasses.

Influence of Nitrogen Fertilizers on Washington Creeping Bentgrass, Agrostis palustris Huds. II. Incidence of Dollar Spot, Sclerotinia homoeocarpa, Infection1

AbstractA field experiment was established to evaluate influence of nitrogenous fertilizers on susceptibility of ‘Washington’ creeping bentgrass, Agrostis palustris Huds., to dollar spot disease, Sclerotinia homoeocarpa F. T. Bennett. The field study also supplied soil and plant tissue used in a series of laboratory experiments to investigate effects of activated sewage sludge and processed tankage on growth of S. homoeocarpa in pure culture. Influences of nitrogenous fertilizer on soil fungistasis and on plant tissue fungistasis were also investigated.High levels of available nitrogen reduced dollar spot injury in field tests. Activated sewage sludge, which was most effective in producting disease resistant turf, did not possess any measurable fungitoxic agents. Soil microbiological activity, fertility, fungistasis and pH were not altered significantly by fertilizer treatment.

Investigations into the Nature of Thatch and Methods for its Decomposition1

AbstractThe rate of thatch decay in turf was investigated following treatment with certain mono‐ and disaccharides in combination with calcium and fertilizer. In a field study on 15‐year‐old velvet bentgrass putting turf, sucrose treatments decreased turf quality and modified the stimulating effects of fertilizer. Lime had no influence on turf quality. Sucrose tended to increase the incidence of dollar spot disease, while fertilizer decreased it.In a greenhouse study on heavily thatched lawn sod, glucose, cellulase, and soil topdressings did not affect turf quality. No increase in thatch decomposition was obtained in these experiments. Chemical analysis of the thatch gave an average lignin content 10% higher than that reported for cereal straws and 12 to 13% greater than for live top growth.An investigation into the physical thatch structure showed that sclerified vascular strands of stems and leaf sheaths were more resistant to decay than clippings or sloughed leaves. Nodes and crown tissues were most resistant. Intact fibrous roots were numerous in the upper thatch layer; only few extended through the thatch into the soil.