No description available.

Pythium diseases are common in the greenhouse production of tobacco transplants and can cause up to 70% seedling loss in hydroponic (float-bed) greenhouses. However, the symptoms and consequences of Pythium diseases are often variable among these greenhouses. A tobacco transplant greenhouse survey was conducted in 2017 in order to investigate the sources of this variability, especially the composition and distribution of Pythium communities within greenhouses. The survey revealed twelve Pythium species. Approximately 80% of the surveyed greenhouses harbored Pythium in at least one of four sites within the greenhouse, including the center walkway, weeds, but especially bay water and tobacco seedlings. Pythium dissotocum, followed by P. myriotylum, were the most common species. Pythium myriotylum, P. coloratum, and P. dissotocum were aggressive pathogens that suppressed seed germination and caused root rot, stunting, foliar chlorosis, and death of tobacco seedlings. Pythium aristosporum, P. porphyrae, P. torulosum, P. inflatum, P. irregulare, P. catenulatum, and a different isolate of P. dissotocum, were weak pathogens, causing root symptoms without affecting the upper part of tobacco seedlings. Pythium adhaerens, P. attrantheridium, and P. pectinolyticum did not affect tobacco seeds or seedlings. The consequences of Pythium infection were more likely to be severe when they occurred during seed germination than at seedling emergence, or after plant stem elongation when seedling roots had started to grow into underlying nutrient solutions, depending on the species of Pythium. High and low variation was observed among isolates of P. dissotocum and P. myriotylum, respectively. Pythium myriotylum co-existed with multiple other Pythium or oomycete species in the same environments within tobacco greenhouses, and significant in vitro and/or in vivo interactions between P. myriotylum and some naturally co-existing species were revealed. Pythium porphyrae may have the potential to protect tobacco seeds and seedlings from P. myriotylum infection. Greenhouse Pythium control trials identified ethaboxam, mefenoxam, and copper ionization as potentially promising alternatives to etridiazole for Pythium disease management in tobacco transplant production. The outcomes of this project provide useful new information to better understand the composition, distribution, and diversity of Pythium communities in tobacco transplant greenhouses and to improve Pythium disease management for tobacco transplant production. / Doctor of Philosophy / Pythium diseases are common in tobacco transplant production and can cause up to 70% seedling losses in hydroponic (float-bed) tobacco transplant greenhouses. However, little is known about the composition and distribution of Pythium communities in tobacco transplant greenhouses. This project began with a tobacco transplant greenhouse survey, in which 12 Pythium species were recovered from center walkways, weeds, greenhouse bay water, and tobacco seedlings. Pythium dissotocum and P. myriotylum were the two types (species) of Pythium most commonly found in the survey. Pythium myriotylum, P. coloratum, and P. dissotocum were aggressive pathogens that suppressed seed germination and caused root rot, stunting, foliar chlorosis, and death of tobacco seedlings. Pythium aristosporum, P. porphyrae, P. torulosum, P. inflatum, P. irregulare, P. catenulatum, and an isolate of P. dissotocum, were weak pathogens causing root symptoms without affecting the upper part of tobacco seedlings. Pythium adhaerens, P. attrantheridium, and P. pectinolyticum did not affect tobacco seeds or seedlings. The symptoms caused by infection by Pythium species differed among host (tobacco) growth stages, except for the most aggressive species, P. myriotylum. High levels of variation were observed among isolates of P. dissotocum, in terms of vegetative growth rate (on V8 agar media) and aggressiveness on tobacco seed and seedlings. Pythium myriotylum was found to co-exist with multiple other Pythium or oomycete species (neighbor isolates) in the same environments within tobacco greenhouses. Significant interactions between P. myriotylum and some neighbor isolates were revealed, and these interactions significantly affect the consequences of P. myriotylum infection of tobacco seeds. Greenhouse Pythium control trials identified two chemical water treatments (ethaboxam and mefenoxam), and a non-chemical water treatment (copper ionization) as potentially promising alternatives to the current standard Pythium control (etridiazole) for Pythium disease management in tobacco transplant production. The outcomes of this project provide useful new information to both better understand the composition, distribution, and diversity of Pythium communities in tobacco transplant greenhouses and to improve Pythium disease management for tobacco transplant production.

Introduction: The studies reported in this thesis investigated a number of patient orientated aspects of its current diagnosis, management and treatment in Kuwait. A comprehensive literature survey is presented with a detailed critical analysis of the very limited number of published material relevant to type 2 diabetes in Kuwait is also provided. A concise list of aims and objectives is also provided. Methodology: The methodology used to derive knowledge of the present situation from the patient perspective, was a series of relevant questions, devised based on the internationally used diabetes Michigan questionnaire. Face to face interviews were used throughout for both patients and medical staff. Suitable data analysis was performed. Results: A pilot study consulted 10 Kuwaiti and 10 non-Kuwaiti patients, and after analysis of their data it was found to be reliable, appropriate and capable of being analysed and so was extended to a larger study of 109 diabetic patients. These 109 diabetic patients were studied in thirteen clinics distributed throughout Kuwait. Two groups of patients were studied – Kuwaiti nationals and non-Kuwaitis both of whom were treated at these clinics during their residency in Kuwait. 38 questions were asked including demographics, medical treatment, monitoring of their disease, physiological consequences and dietary aspects. The major findings were that patients considered two major areas could be improved to enhance the treatment of their disease. The first was to improve the degree of empathy shown to them by the medical/nursing staff and secondly to provide simple practical advice on exercise, dietary considerations and renal aspects of their disease. More comprehensive findings are presented in the thesis but many of these were minor compared with these two major aspects. Also presented are interviews with the medical staff in Kuwait who treat diabetic patients and the problems they face when treating their disease. The opinions and views of selected ophthalmologists and renal specialists are also presented. Medical views were also sought in the UK- Ascot Rehabilitation above their experiences treating diabetic patients from Kuwait. Another aspect of the study was to interview Kuwaiti nationals who had been sent to a clinic in Ascot, UK for the treatment of the serious consequences of their conditions. Many of these were had type 2 diabetes and their views and perspectives of their treatment in Kuwait were gathered as being representative of the long term treatment of this condition. Discussions and Conclusions: The thesis discusses in some detail all the results which were obtained and concludes with a series of recommendations which could be taken to improve the treatment of type 2 diabetes in Kuwait.

Spring dead spot (SDS) is the most destructive disease of bermudagrass and its hybrids, affecting intensively managed bermudagrass turf that is at least three years old. This bermudagrass disease is most prevalent in the United States where winter temperatures become cold enough to induce dormancy. The symptoms of SDS appear as sunken, necrotic patches of turf ranging from several centimeters to greater than 0.5 m in diameter. Field studies were conducted at Old Waverly Golf Club in West Point, MS on a Tifway bermudagrass fairway beginning January of 2005 and concluding December of 2006 to determine the frequency and the effects of soil temperature on occurrence of O. korrae in bermudagrass. Characterization of O. korrae isolates was conducted based on optimal in vitro growth temperatures and greenhouse pathogenicity studies. Cultural, nutritional, and chemical management practices were evaluated on the bermudagrass fairway for the reduction of SDS severity, promotion of improved turf color, quality, root health, and reduction of the thatch/mat layer. Treatments included core aerification with and without topdressing, vertical mowing, manganese, elemental sulfur, and myclobutanil fungicide applications. Each year was divided into seasons (winter, spring, summer, fall) based on the bermudagrass growth cycle in Mississippi. The frequency of O. korrae occurrence ranged from 14% in 2005 to 16% in 2006, and was similar for all treatments. Ophiosphaerella korrae occurrence was greatest in the winter and spring compared to the summer and fall. There was no direct association between mean soil temperature and frequency of O. korrae occurrence. Spring dead spot severity ratings were similar in 2005 and 2006. Vertical mowing had a significant effect on fall turf color in 2005 and fall turf color and quality in 2006. The aggressive cultural practices (i.e. vertical mowing, aerification) were the most consistent treatments for significantly reducing the thatch/mat layer and improving root health.

No description available.

No description available.

No description available.

Grapes (Vitis spp.), globally cultivated for wine and other grape-based products, are susceptible to various diseases, pests, and disorders. These challenges are particularly pervasive in Virginia and viticultural regions in similar climates. Thus, growers routinely use insecticides and fungicides to protect their fruits. However, frequent or excessive use of these chemicals can pose environmental and human health risks and increase the chances of fungicide resistance. Many crop production systems use physical barriers to shield plant surfaces from biotic and abiotic environmental factors, particularly in Asian countries. This study evaluated the efficacy of paper bags, umbrella-style covers, and fruit-zone shelters in mitigating fungal diseases, insect infestations, and other factors that damage grape clusters. A series of field experiments were conducted at four commercial vineyards in Virginia and one research experiment station at Virginia Tech in five years with eight grape cultivars. Our results highlighted the importance of bag and fruit-zone shelter applications. Especially when these protection measures were applied around bloom, we observed reductions in the level of multiple diseases and insect- and bird-related damages. Fruit bagging resulted in significantly lower (P ≤ 0.05) mean severity and incidence of black rot, sour rot, sooty mold, and grape berry moth damage. Similarly, we found a significantly lower mean incidence of black rot, ripe rot, sour rot, and bird damage with the application of fruit-zone shelters. Thus, fruit bagging and fruit-zone shelter can be an effective cultural method for safeguarding grape clusters from different diseases, potentially reducing pesticide use and offering economic advantages to growers. / Master of Science / Grapes are produced for making wine and other grape-based products worldwide. However, grape production often faces challenges from diseases, pests, and environmental factors, especially in humid regions like Virginia. Grape growers use pesticides (insecticides and fungicides) to protect their crops. However, these chemicals can harm the environment and human health; moreover, these disease organisms and pests can become resistant to pesticides. In many parts of the world, especially in Asia, farmers use physical barriers like bags or covers to protect their crops from various harmful factors. In this study, we tested the effectiveness of paper bags, umbrella-style covers, and special shelters around the fruit area of grape plants against fungal diseases, insect problems, and other damages. We conducted a series of experiments over five years in four commercial vineyards and a research station in Virginia, using eight grape cultivars. Our findings showed that using bags and shelters around the grapes, especially during the blooming period, was effective. Bagging the fruit led to significantly fewer cases of diseases (black rot, sour rot, and sooty mold) and grape berry moth damage. Likewise, using shelters around the fruit area resulted in significantly lower diseases (black rot, ripe rot, and sour rot) and bird damage. Therefore, these protective methods could offer more options for grape growers to protect yield from factors damaging their high-value crops.

Financial incentives offered by payers to health care providers and patients have been identified as a key mechanism to lower costs while improving quality of care. How to effectively design incentive programs that can align the varying objectives of health care stakeholders, as well as predict programs' performance and stakeholders' decision response is an unresolved research challenge. The objective of this study is to establish a novel approach based on multiscale decision theory (MSDT) that can effectively model and efficiently analyze such incentive programs, and the complex health care system in general. The MSDT model captures the interdependencies of stakeholders, their decision processes, uncertainties, and how incentives impact decisions and outcomes at the payer, hospital, physician, and patient level. In the first part of this thesis, we study the decision processes of agents pertaining to the investment and utilization of imaging technologies. We analyze the payer-hospital-physician relationships and later extend the model to include radiologist and patient as major stakeholders in the second part of this thesis. We focus on a specific incentive program, the Medicare Shared Savings Program (MSSP) for Accountable Care Organizations (ACOs). The multi-level interactions between agents are mathematically formulated as a sequential non-cooperative game. We derive the equilibrium solutions using the subgame perfect Nash equilibrium (SPNE) concept and the backward induction principle, and determine the conditions under which the MSSP incentive leads to the desired outcomes of cost reduction and quality of care improvements. In the third part of this thesis, we study the multi-level decision making in chronic disease management. We model and analyze patients' and physicians' decision processes as a general-sum stochastic game with perfect information and switching control structure. We incorporate the Health Belief Model (HBM) as the theoretical foundation to capture the behavioral aspect of agents. We analyze how incentives and interdependencies affect patients' engagement in health-promoting activities and physicians' delivery of primary care services. We show that a re-alignment of incentives can improve the effectiveness of chronic disease management. / Ph. D.

Labeling is a product differentiation mechanism which has increased in prevalence across many markets. This study investigated the potential for a labeling program applied in ornamental plant sales, given key ongoing issues affecting ornamental plant producers: irrigation water use and plant disease. Our research investigated how to better understand the market for plants certified as disease free and/or produced using water conservation techniques through segmenting the market by consumers' environmental preferences. Latent class analysis was conducted using choice modeling survey results and respondent scores on the New Environmental Paradigm scale. The results show that when accounting for environmental preferences, consumers can be grouped into two market segments. Relative to each other, these segments are considered: price sensitive and attribute sensitive. Our research also investigated market segments' preferences for multiple certifying authorities. The results strongly suggest that consumers of either segment do not have a preference for any particular certifying authority. / Master of Science