Cucumber (Cucumis sativus L.), pumpkin (Cucurbita maxima Duch. ex Lam.), and summer squash (Cucurbita pepo L.) are economically important crops in Virginia. Only a few herbicides are registered for weed control in these crops. Halosulfuron is a sulfonylurea herbicide which controls several broadleaf weeds and yellow nutsedge (Cyperus esculentus L.). Cucurbit crops have some tolerance to this herbicide. The efficacy of halosulfuron for control of several weed species and tolerance of four vine crops to halosulfuron were investigated in field and greenhouse studies in 1999, 2000, and 2001. In the field, halosulfuron was applied to cucumber, pumpkin, zucchini squash, and yellow summer squash at 4, 9, 18, and 27 g ai/ha preemergence (PRE) and postemergence (POST) in combination with clomazone at 174 g ai/ha plus ethalfluralin applied PRE at 630 g/ha. Crop injury, weed control, and crop yield was collected from the field studies. Weed control by halosulfuron was dependent upon application method. Halosulfuron applied preemergence controlled only common ragweed (Ambrosia artemisiifolia L.) and smooth pigweed (Amaranthus hybridus L.). Postemergence halosulfuron controlled common ragweed, smooth pigweed, morningglory species (Ipomoea spp.), yellow nutsedge, and rice flatsedge (Cyperus iria L.). All four crops treated with halosulfuron produced yields equal to or higher than the crops receiving clomazone and ethalfluralin alone or the hand-weeded check. In the greenhouse, tolerance of cultivars of each crop to halosulfuron was investigated with the same rates applied in the field. Cultivars responded similar to postemergence halosulfuron applications with respect to fresh and dry weights in all four crops. The response of several populations of acetolactate synthase inhibiting (ALS) resistant smooth pigweed to postemergence halosulfuron was also investigated. Halosulfuron activity against ALS-inhibitor resistant smooth pigweed was population dependent. In the greenhouse, postemergence halosulfuron at the same rates used in the field studies controlled yellow nutsedge. / Master of Science

Although High temperature drying (HTD) of southern yellow pine (SYP) is extensively used, quality problems still exist. Approximately 25 percent of all green lumber (2 x 4, 2 x 6 and 2 x 8's) are degraded during HTD. Warp degrade, specifically "crook", is the main cause for the loss of quality of SYP dried at temperatures above the boiling point of water. One of the major causes of warp degrade is excessive shrinkage that results from overdrying. In industrial practices, average final moisture contents for HTD of SYP lumber are usually well below the 15% MC maximum permitted by the grading rules. Overdrying the lumber causes not only lumber quality problems, but also constitutes a waste of energy. In order to improve the overall results of HTD of SYP, it is necessary to perform a better control of the process, so unnecessary extended drying can be prevented. In this study, a mathematical model based on the temperature drop across the load (TDAL) concept was proposed. The model relates TDAL to drying rates and according to the results, it appears to be an important alternative for controlling purposes during HTD of SYP. / Ph. D.

The yellow perch, (Perca flavescens), is an important commercial and sport fish in Indiana waters of Lake Michigan. The population is currently managed by temporary restrictions of commercial harvest. A computer simulation model was developed to examine the effects of various constant harvest quotas and alewife densities on yellow perch relative numbers.Model design is based on the SLAM II simulation language incorporating a FORTRAN biological subroutine. The age-structured population model includes measured or predicted biological characteristics of the dynamic pool model. Recruitment is based on a preestablished three-dimensional Ricker stock-recruitment function including alewife (Alosa pseudoharengus) species interaction as a constant or stochastic factor. Sex-specific natural mortality rates were established through life history parameter analysis and the von Bertalanffy growth factors. Density-dependent growth is incorporated into each year of a model run and fluctuates with the simultaneous density of fish. Constant levels of commercial harvest ranging from 0 to 700,000 kg were used in 20-year forecasts. Initial conditions for model runs were 1984 and 1994 trawl CPUE levels when yellow perch were at high and low levels, respectively according to standardized sampling. Response variables were examined as mean catches over each forecast length and included: age 2 fish, spawning stock (z 190 mm), and total catch > age 1.Alewife densities had a tremendous impact on mean catches of the response variables. Highest catches under any forecast period occurred when alewife was considered absent from the system. Catches declined as alewife density was increased as a 20-year constant under each harvest regimen.Catches of spawning size fish were maintained at highest levels for all forecast periods when harvest was set to zero. Catches of young fish were moderate with this harvest regimen if initial catch conditions were high such as in 1984. Catches of young fish were always higher in the absence of a commercial fishery if initial catch conditions were low such as in 1994. Low to moderate harvest quotas could maintain moderate levels of young fish for the forecast length if initial model conditions were high. However, these quota levels for the 1984-2004 forecast length resulted in lower mean catches of spawning size fish as compared to the no commercial fishery regimen. The best case scenario for all response variables when initial catch conditions were low was under a no commercial harvest regimen. / Department of Biology

Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3460. Adviser: Carl S. Hacker. Includes bibliographical references.

In 1996 and 1997, I studied the nest site selection of the yellow-billed cuckoo (Coccyzus americanus) in the George Washington National Forest, southwestern Virginia. Data were collected from nine 30 ha plots. I compared the habitat features of nest sites with two types of nonnest sites (nonuse and systematically random). Habitat features were measured at 3 spatial scales: nest tree, nest tree area (0.0049 ha centered on the nest), and nest stand (forest stand surrounding the nest). Yellow-billed cuckoo nests were oriented in a nonrandom direction (mean angle = 114°, r = 0.43, P = 0.05) with respect to the bole and were concealed more from above than from below (n = 14, M = 5, p = 0.01) or from the side (n = 14, M = 4, p = 0.04). Slope aspect was nonrandom at yellow-billed cuckoo nest sites (mean angle = 143°, r = 0.52, P < 0.05). Small stem density in the nest tree area was greater (P = 0.029) at nest sites than nonuse sites but species composition was similar. The density of grape (Vitus spp.) and dogwood (Cornus spp.) snags was greater at nest sites than random sites (P < 0.001). Total basal area at yellow-billed cuckoo nest stands was lower than nonuse or random sites with (P = 0.033, and 0.016, respectively) or without (P = 0.014, and 0.004, respectively) snags. Nest sites also occurred in areas with less (P = 0.008) canopy cover but more (P = 0.038) ground cover than random sites. Yellow-billed cuckoos appeared to select nest sites based on the structure and composition of the understory vegetation. Periodic disturbance that promotes the growth of shade intolerant species, but maintains the general structure of the stand may be beneficial for this species that appears to select disturbed areas in mature forests. / Department of Biology

I determined differences in yellow perch gill-net catch-per-unit-effort (CPUE) at two depths (10 and 15 m) in the Indiana waters of Lake Michigan during June, July, and August from 1989 to 2006. I evaluated the abiotic factors of water temperature, water clarity, wave height, and wind direction to determine whether they influence the differences in yellow perch CPUE. This study suggests that yellow perch in southern Lake Michigan may select habitat based on water temperature during the summer, moving in response to thermocline changes. We also evaluated mortality rates for two distinct periods (1984-1994 and 2000-2007) in order to identify the response of the population to changes in exploitation. Yellow perch during 1984-1994 (high exploitation) and 2000-2007 (low exploitation) displayed an increase in mortality for fish of harvestable size. In addition, during 2000-2007 (low exploitation) we identified that female yellow perch reached exploitable size earlier in life than males. / Department of Biology

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-06-20T18:12:54Z No. of bitstreams: 1 texto completo.pdf: 1756399 bytes, checksum: 4cd93ccd34ab97ff3909ee83598fa241 (MD5) / Made available in DSpace on 2017-06-20T18:12:54Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1756399 bytes, checksum: 4cd93ccd34ab97ff3909ee83598fa241 (MD5) Previous issue date: 2016-02-25 / A maioria dos begomovírus monossegmenados do Velho Mundo (família Geminiviridae) estão associados a DNAs satélites, classificados como alfa- e betassatélites. Os alfassatélites são capazes de replicar-se de forma autônoma, mas dependem do vírus auxiliar para o movimento, encapsidação e transmissão pelo inseto vetor (Bemisia tabaci). Recentemente, o Euphorbia yellow mosaic alphasatellite (EuYMA) foi encontrado em associação com o begomovírus Euphorbia yellow mosaic virus (EuYMV), infectando plantas de Euphorbia heterophylla no Brasil. Compreender a dinâmica da interação entre begomovírus e DNAs satélite em plantas não cultivadas, tais como E. heterophylla, é importante porque eles podem ser transferidos para plantas cultivadas, dado o hábito polífago de B. tabaci. Este estudo teve como objetivos: (i) analisar as diferenças fenotípicas da infecção pelo EuYMV na presença e na ausência do EuYMA; (ii) avaliar se a proteína alfa-Rep do EuYMA possui atividade supressora de silenciamento de RNA; (iii) comparar a transmissão do EuYMV por B. tabaci MEAM1, na ausência e na presença do EuYMA. Foram coletadas amostras (n=165) de E. heterophylla em diversos estados do Brasil. Clones infecciosos foram gerados para realizar-se a caracterização biológica e inoculação das plantas. EuYMV foi detectado em 126 amostras e EuYMA foi detectado em apenas seis amostras. Isoladamente, o EuYMV causa clorose internerval e mosaico amarelo. Em associação com o EuYMA, os sintomas são mais severos, caracterizados por mosaico amarelo muito mais intenso, encarquilhamento foliar e redução do crescimento. O DNA-A do EuYMV pode infectar E. heterophylla na ausência do DNA-B, provocando ou não um mosaico amarelo atenuado. A sequência codificadora completa do gene alfa-Rep do EuYMA foi clonada em vetor binário e transformada em células de Agrobacterium tumefaciens. Um ensaio de supressão de silenciamento de RNA foi realizado com esta construção em plantas de Nicotiana benthamiana. Os resultados indicam que a proteína alfa-Rep do EuYMA não atua como supressora de silenciamento de RNA. Foi realizado um ensaio de transmissão do EuYMV por B. tabaci, na presença e ausência de EuYMA, em duas repetições biológicas. Vinte plantas foram utilizadas para cada tratamento. Isoladamente, o EuYMV foi transmitido para 17 e 18 plantas na primeira e segunda repetição, respectivamente. Em associação com EuYMA, o vírus foi transmitido para 15 e 14 plantas na primeira e segunda repetição, respectivamente, uma diferença estatisticamente significativa. Assim, os resultados indicam que o EuYMA afeta negativamente a transmissão do EuYMV pelo vetor, consequentemente afetando a disseminação do vírus no campo. / The majority of Old World monopartite begomoviruses (family Geminiviridae) are associated with satellite DNAs, classified as alpha- and betasatellites. Alphasatellites are capable of autonomous replication, but depend on the helper virus for movement, encapsidation and transmission by the insect vector (Bemisia tabaci). Recently, Euphorbia yellow mosaic alphasattelite (EuYMA) was found in association with Euphorbia yellow mosaic virus (EuYMV), infecting Euphorbia heterophylla plants in Brazil. Understanding the dynamics of the interaction between begomoviruses and satellite DNAs in non-cultivated plants, such as E. heterophylla, is important as they can be transferred to cultivated plants, given the polyphagous habit of B. tabaci. The objectives of this study were: (i) to analyze phenotypic differences of EuYMV infection in the presence and absence of EuYMA; (ii) to evaluate whether the alpha-Rep protein of EuYMA possesses RNA silencing suppressor activity; (iii) to compare the transmission of EuYMV by B. tabaci MEAM1 in the absence and presence of EuYMA. Samples (n=165) of E. heterophylla were collected in several states of Brazil. Infectious clones were generated to perform the biological characterization and inoculation. EuYMV was detected in 126 samples and EuYMA was detected only in six samples,. Alone, EuYMV causes interveinal chlorosis and yellow mosaic. In combination with EuYMA, the symptoms are more severe, characterized by a more intense yellow mosaic, leaf shriveling and stunting. The DNA-A of EuYMV can infect E. heterophylla in the absence of the DNA-B, causing attenuated yellow mosaic or no symptoms at all. The complete coding sequence of the alpha-Rep gene of EuYMA was cloned in a binary vector and transformed in Agrobacterium tumefaciens. An RNA silencing supression assay was performed with this construct in Nicotiana benthamiana plants. The results indicate that the alpha-Rep protein of EuYMA does not act as an RNA silencing suppressor. A transmission assay of EuYMV by B. tabaci, in the presence and absence of EuYMA, was performed in two biological replications. Twenty plants were used for each treatment. Alone, EuYMV was transmitted to 17 and 18 plants, in the first and second replication respectively. In association with EuYMA, the virus was transmitted to 15 and 14 plants, in the first and second replication respectively, a difference which was statistically significant. Thus, our results indicate that EuYMA negatively affects the transmission of EuYMV by the vector, consequently affecting the spread of the virus in the field.

Trifolium L. (clover) are annual or perennial species established in pasturelands to improve forage productivity and quality. In the southeastern United States, Trifolium repens L. (white clover) and Trifolium pratense L. (red clover) are important species, susceptible to virus infection. Objectives of this research were to isolate bean yellow mosaic (BYMV), clover yellow vein (CYVV) and peanut stunt (PSV) viruses from naturally infected white and red clovers from different locations in Virginia; and, to compare Indirect Enzyme-Linked ImmunoSorbent Assay (i-ELISA) and tissue immunoblot assay (TIBA) as methods for virus detection. A total of five white clover samples from Augusta, Richmond and Washington Counties were positive against CYVV antiserum and four white clover samples from Augusta County were positive against PSV antiserum. Single red clover samples from Frederick and Montgomery Counties were positive against BYMV antiserum. There were notable differences in host range with samples that tested positive for CYVV and BYMV, indicating they may be different strains. PSV was evenly distributed in the plant, whereas CYVV was higher in older plant parts. Viruses were successfully detected by blotting leaf samples directly onto membranes, thereby simplifying the sample preparation step. A number of membranes, such as nitrocellulose, nylon, chromatography paper, filter paper and writing pad could be used to detect viruses. In terms of specificity, immunoblots were equal or superior to i-ELISA. The TIBA should be useful in support of breeding and plant pathology studies as it is simple and rapid, and is less laborious and less expensive than i-ELISA. / Master of Science

This paper analyzes the management problem of the conjunctive use of surface and ground water in an irrigation system on both sides of the Lower Yellow River. For this purpose, a stochastic dynamic programming model is developed. In the model, the statistical characteristics of seasonal rainfall within 2 years are considered; groundwater level control is also emphasized in order to prevent soil salinity and waterlogging. Through computer calculations, optimal operation policies are obtained for efficient conjunctive use of surface and groundwater. These policies take into account the interactions between pumping groundwater by farmers, canal diversions by irrigation system managers, and the physical response of the stream- aquifer system, and minimize the total operation costs. In this paper, we take an irrigation district, the People's Victory Canal System, as an example to illustrate the development and solution of the model. At the same time, the effects of system parameters, including surface irrigation efficiency and rainfall recharge coefficient, on the optimal policies or total operation costs, are discussed. The analytical results in this example indicate that the variation in optimal operation costs caused by the proportion of rainfall infiltrated is small, but the effect of surface irrigation efficiency on the costs is significant. Hence, the surface irrigation efficiency must be increased as much as possible. Then, efficient conjunctive use of surface and groundwater can be attained with the optimal policies.

"September 2002" Bibliography: leaves 77-85. Examines the persistence of the yellow-footed antechinus using live trapping in small, remnant patches and strips of forest, to document autecological sata and the investgate occurrence, breeding activity and inter-patch movements. Radio-tracking was conducted to compare home range properties of lactating females in restricted and unrestricted habitat.