VTechWorks Repository :: Browsing by Author "Fell, Richard D."

Browsing by Author "Fell, Richard D."

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Application of Chromosome Mapping to Understanding Evolutionary History of Anopheles Species
Kamali, Maryam (Virginia Tech, 2013-06-13)
Malaria is the main cause of approximately one million deaths every year that mostly affect children in south of Sub-Saharan Africa. The Anopheles gambiae complex consists of seven morphologically indistinguishable sibling species. However, their behavior, ecological adaptations, vectorial capacity, and geographical distribution differ. Studying the phylogenetic relationships among the members of the complex is crucial to understanding the genomic changes that underlie evolving traits. These evolutionary changes can be related to the gain or loss of human blood choice or to other epidemiologically important traits. In order to understand the phylogenetic relationships and evolutionary history of the members of the An. gambiae complex, breakpoints of the 2Ro and 2Rp inversions in An. merus and their homologous sequence in the outgroup species were analyzed using fluorescent in situ hybridization (FISH), library screening, whole-genome mate-paired sequencing and bioinformatics analysis. Molecular phylogenies of breakpoint genes were constructed afterwards. In addition, multigene phylogenetic analyses of African malaria vectors were performed. Our findings revised the chromosomal phylogeny, and demonstrated the ancestry of 2Ro, 2R+p and 2La arrangements. Our new chromosomal phylogeny strongly suggests that vectorial capacity evolved repeatedly in members of the An. gambiae complex, and the most important vector of malaria in the world, An. gambiae, is more closely related to ancestral species than was previously thought. Our molecular phylogeny data were in agreement with chromosomal phylogeny, indicating that the position of the genetic markers with respect to chromosomal inversion is important for interpretation of the phylogenetic trees. Multigene phylogenetic analysis revealed that a malaria mosquito from humid savannah and degraded rainforest areas, An. nili, belongs to the basal clade and is more distantly related to other major African malaria vectors than was assumed previously. Finally, for the first time a physical map of 12 microsatellite markers for the Asian malaria vector An. stephensi was developed. Knowledge about the chromosomal position of microsatellites was shown to be important for a proper estimation of population genetic parameters. In conclusion, our study improved understanding of genetics and evolution of some of the major malaria vectors in Africa and Asia.
Aspects of chemical control of the old house borer, Hylotrupes bajulus (L.) (Coleoptera: Cerambycidae)
Dodson, Bonny Lynn (Virginia Tech, 1987-03-20)
The formulation of Dursban®, manufactured by Dow Chemical Corp., and its diluting agent were found to influence the penetration abilities of the final spray when it is applied to pine sapwood. The diluent of choice for providing the best penetration of the active ingredient, chlorpyrifos, is an Oil-based carrier for the formulated product Dursban® WT. Dursban® TC, another product containing chlorpyrifos, will penetrate the wood surface better when diluted with water, not with an oil-based carrier such as kerosene. Residual amounts of Dursban® TC applied to pine sapwood will remain relatively constant six months after the initial treatment at depths of 400 - 600 microns below the surface. The wood moisture content (WMC) of treated pine sapwood did not significantly influence the penetration abilities of Dursban® TC at 7.5% - 8.0% and 14.5% - 16.0% WMC. A 1.0% water-diluted formulation of Dursban® TC applied to pine sapwood is predicted to be capable of penetrating the treated wood to a depth of 1320 microns.
Aspects of the biology, behavior, and economic importance of Camponotus pennyslvanicus (Degeer) and Camponotus ferrugineus (Fabricius) (Hymenoptera: formicidae)
Dukes, John (Virginia Tech, 1982-05-12)
Aspects of the behavior, biology, and economic importance of carpenter ants were examined. The overall objectives of this study were to determine the economic importance of carpenter ants, and to extend the data currently available on two of the most common and economically important species in the U.S. A survey for the economic importance of carpenter ants indicated that carpenter ants are considered a serious pest by homeowners. The results show that 90% of the homeowners who requested control for carpenter ants during 1980, paid more than $25 for carpenter ant control. The presence of detectable damage was not the definitive factor in the decision to request control. Camponotus ferrugineus and C. pennsylvanicus are similar in their colony foundation and biology. C. ferrugineus required 54 days to produce the first brood and there were 18 workers, including one intermediate worker, in the first brood. Queens of C. pennsylvanicus required an average of 46 days to rear the first brood. Ad libitum feeding did not have a significant effect on colony founding in C. pennsylvanicus. Two queens reared their first brood under artificial light. Food preference studies of C. pennsylvanicus and C. ferrugineus indicated that these two species have similar food preferences. Although honey was preferred to most foods tested, it may not supply sufficient nutrients to ensure proper colony nutrition. C. pennsylvanicus has become well adapted to man-made structures. Some foraging ants are present year round. C. pennsylvanicus optimizes its foraging by exploiting indoor and outdoor foraging sites. The division of labor during nest construction may be based on subcaste. Major workers appear to be responsible for most nest-building in mature colonies.
An Assessment of Non-Apis Bees as Fruit and Vegetable Crop Pollinators in Southwest Virginia
Adamson, Nancy Lee (Virginia Tech, 2011-02-03)
Declines in pollinators around the globe, notably the loss of honey bees (Apis mellifera L.) to Colony Collapse Disorder, coupled with a dearth of quantitative data on non-Apis bee pollinators, led to this dissertation research, which documents the role of non-Apis bees in crop pollination in southwest Virginia. Major findings of this first study of its kind in the region were that non-Apis bees provided the majority of pollination—measured by visitation—for several economically important entomophilous crops (apple, blueberry, caneberry, and cucurbits); diverse bee populations may be helping to stabilize pollination service (105 species on crop flowers); landscape factors were better predictors of non-Apis crop pollination service than farm management factors or overall bee diversity; and non-Apis bees in the genera Andrena, Bombus, and Osmia were as constant as honey bees when foraging on apple. Non-Apis, primarily native, bees made up between 68% (in caneberries) and 83% (in cucurbits) of bees observed visiting crop flowers. While 37–59 species visited crop flowers, there was low correspondence between bee communities across or within crop systems ("within crop" Jaccard similarity indices for richness ranged from 0.12–0.28). Bee community diversity on crop flowers may help stabilize pollination service if one or more species declines temporally or spatially. A few species were especially important in each crop: Andrena barbara in apple; Andrena carlini and A. vicina in blueberry; Lasioglossum leucozonium in caneberry; and Peponapis pruinosa and Bombus impatiens in cucurbits. Eight species collected were Virginia state records. In models testing effects of farm management and landscape on non-Apis crop pollination service, percent deciduous forest was positively correlated in apple, blueberry, and squash, but at different scales. For apple and blueberry, pollination service declined with an increase in utilized alternative forage but was positively related to habitat heterogeneity. For squash, percent native plants also related positively, possibly due to increased presence of bumble bees in late summer. Species collected from both bowl traps and flowers was as low as 22% and overall site bee diversity had no effect on crop pollination service, highlighting the value in pollination research of monitoring bees on flowers.
Bacteriophages in the honey bee gut and amphibian skin microbiomes: investigating the interactions between phages and their bacterial hosts
Bueren, Emma Kathryn Rose (Virginia Tech, 2024-06-14)
The bacteria in host-associated microbial communities influence host health through various mechanisms, such as immune stimulation or the release of metabolites. However, viruses that target bacteria, called bacteriophages (phages), may also shape the animal microbiome. Most phage lifecycles can be classified as either lytic or temperate. Lytic phages infect and directly kill bacterial hosts and can directly regulate bacterial population size. Temperate phages, in contrast, have the potential to undergo either a lytic cycle or integrate into the bacterial genome as a prophage. As a prophage, the phage may alter bacterial host phenotypes by carrying novel genes associated with auxiliary metabolic functions, virulence-enhancing toxins, or resistance to other phage infections. Lytic phages may also carry certain auxiliary metabolic genes, which are instead used to takeover bacterial host functions to better accommodate the lytic lifecycle. In either case, the ability to alter bacterial phenotypes may have important ramifications on host-associated communities. This dissertation focused on the genetic contributions that phages, and particularly prophages, provide to the bacterial members of two separate host-associated communities: the honey bee (Apis mellifera) gut microbiome and the amphibian skin microbiome. My second chapter surveyed publicly available whole genome sequences of common honey bee gut bacterial species for prophages. It revealed that prophage distribution varied by bacterial host, and that the most common auxiliary metabolic genes were associated with carbohydrate metabolism. In chapter three, this bioinformatic pipeline was applied to the amphibian skin microbiome. Prophages were identified in whole genome bacterial sequences of bacteria isolated from the skin of American bullfrogs (Lithobates catesbeianus), eastern newts (Notophthalmus viridescens), Spring peepers (Pseudacris crucifer) and American toads (Anaxyrus americanus). Prophages were additionally identified in publicly available genomes of non-amphibian isolates of Janthinobacterium lividum, a bacteria found both on amphibian skin and broadly in the environment. In addition to a diverse set of predicted prophages across amphibian bacterial isolates, several Janthinobacterium lividum prophages from both amphibian and environmental isolates appear to encode a chitinase-like gene undergoing strong purifying selection within the bacterial host. While identifying the specific function of this gene would require in vitro isolation and testing, its high homology to chitinase and endolysins suggest it may be involved in the breakdown of either fungal or bacterial cellular wall components. Finally, my fourth chapter revisits the honey bee gut system by investigating the role of geographic distance in bacteriophage community similarity. A total of 12 apiaries across a transect of the United States, from Virginia to Washington, were sampled and honey bee viromes were sequenced, focusing on the lytic and actively lysing temperate community of phages. Although each apiary possessed many unique bacteriophages, apiaries that were closer together did have more similar communities. Each bacteriophage community also carried auxiliary carbohydrate genes, especially those associated with sucrose degradation, and antimicrobial resistance genes. Combined, the results of these three studies suggest that bacteriophages, and particularly prophages, may be contributing to the genetic diversity of the bacterial community through nuanced relationships with their bacterial hosts.
Behavioral Investigation of the Light-Dependent Magnetoreception Mechanism of Drosophila melanogaster
Dommer, David H. (Virginia Tech, 2008-04-25)
Use of a magnetic compass has been demonstrated in all major classes of vertebrates as well as several classes of invertebrates, and is proposed to involve a photo-induced radical pair mechanism (RPM). My dissertation research consisted of characterizing a magnetic compass in a model species, Drosophila melanogaster. Preliminary experiments were carried out with adult flies, however, due to the behavioral complexity of adult responses a new behavioral assay of magnetic compass orientation was developed using larval Drosophila that elicits a robust magnetic compass response in a trained magnetic direction. This manuscript describes experiments that were conducted showing that larval magnetic compass orientation: 1) demonstrates a complex 3-dimensional pattern of response consistent with a RPM; 2) is consistent with a receptor mechanism that utilizes short- and long-wavelength antagonistic photopigments, proposed to explain wavelength dependent effects in vertebrates (e.g. amphibians and birds); and 3) produces axially symmetrical patterns of response with respect to the geomagnetic field. Additionally, tests of adult Drosophila under low and high intensities of monochromatic long wavelength light revealed a similar behavioral response to varying intensities of monochromatic light as previously reported in migratory birds (E. rubecula). These findings indicate that the magnetic compass of larval Drosophila shares a common functional architecture and similar biophysical mechanism with that of at least some vertebrates (e.g. amphibians and possibly birds), suggesting that the magnetic compass of modern vertebrates may have evolved once in a common ancestor of these three lineages over 450 million years ago. Furthermore, findings indicating a spontaneous preference for magnetic directions in D. melanogaster larvae suggest that a light-dependent magnetoreception mechanism is more widespread in insects than was previously suspected. The development of a behavioral assay to study the light-dependent magnetic compass in an organism with a simple nervous system, a limited behavioral repertoire, and with the possibility of using the full power of modern molecular and genetic techniques holds considerable promise to increase our understanding of the biophysical mechanism(s) and neurophysiological structures underlying magnetic orientation in terrestrial animals.
Biological and ecological studies of Hydrotaea aenescens (Wiedemann) (Diptera: Muscidae), and other arthropods of high-rise cage layer poultry houses
Dillon, Perian Lenore (Virginia Tech, 1994-05-15)
Laboratory and field studies of Hydrotaea aenescens were undertaken to provide information on this predator's biology and ecology under differing conditions, and to promote its use as a biocontrol agent for controlling house flies in poultry houses. Taxonomic diversity of arthropods in a new high-rise cage layer poultry house was determined from manure samples collected from different manure moisture categories. Stabilization of taxonomic diversity and taxonomic evenness of manure-inhabiting arthropods occurred after the house had been operating for eight months. In contrast, overall diversity in high-rise poultry houses at a well managed, longer established farm was significantly higher than that observed at the new farm, even after 1 1/2 years of operation. When the densities of selected manure-inhabiting predatory arthropods collected from the manure samples (including Carcinops pumilio, pseudoscorpions, a dermapteran species, an anthocorid species, and H. aenescens) were correlated with percent manure moisture, the results showed that, of these predators, only H. aenescens was positively correlated with both manure moisture and with densities of house fly larvae. This information emphasized that although predators such as C. pumilio may exhibit high predation rates on house fly eggs and first instars, their effectiveness 1s reduced by their spatial separation from their supposed prey. This contrasts greatly with H. aenescens performance. Decreases in survival of house fly larvae occurred when the larvae were exposed to H. aenescens of higher larval stadia. This was dramatically demonstrated when 100 first instar house flies were exposed to 100 second instar H. aenescens. No house fly larvae survived. Developmental times were determined at constant temperatures for egg, and larval H. aenescens. Developmental times decreased as temperature increased. Median time for egg and larval development ranged from 1.3 and 14.6 days at 22.2°C to 0.5 and 8.3 days at 35.0°C, for the respective stages. All of this information, together with developmental times and mortality of H. aenescens immatures gathered in a study of temperature dependent development has enhanced understanding of the biotic interactions in accumulated poultry manure. These data will be invaluable in designing integrated pest management programs especially in the area of computer-aided decision making.
Biology and Host-Range Testing of Laricobius kangdingensis sp. n. (Coleoptera: Derodontidae), a Newly Discovered Predator of Hemlock Woolly Adelgid, Adelges tsugae Annand (Homoptera: Adelgidae)
Gatton, Holly A. (Virginia Tech, 2005-04-25)
The biology and host-specificity of Laricobius kangdingensis sp. n. (Coleoptera: Derodontidae), a new predator of hemlock woolly adelgid (HWA), Adelges tsugae Annand (Homoptera: Adelgidae) were investigated and compared with that of a related predator of HWA, L. nigrinus Fender. Adults became active in June 2003; the males emerged first and in greater numbers than the females. The sex ratio of female to male was 1: 1.1. Laricobius kangdingensis sp. n. has four larval instars. The total number of eggs laid between 7 July 2003 and 7 August 2004 was 1327. Mean lifetime fecundity per female was 196.4 ± 53.4 eggs and 97.9 eggs for the P1 (parental gen.) and F1 generations, respectively. In comparison, lifetime fecundity for F1 L. nigrinus was 100.8 ± 89.6 eggs. Developmental rates were studied in fall 2003 and spring 2004. Combined with data gathered previously at 12 and 15ºC in early 2003, the 6, 9, and 18ºC data were used to determine lower temperature development thresholds for the egg (2.8ºC), larval (1.6ºC), and pre-pupal (5.8ºC) stages. The egg and larval thresholds are lower than those observed for L. nigrinus. Laricobius kangdingensis sp. n. individuals completed development only at 12 and 15ºC; however, these adults did not emerge from aestivation after pupation. Laricobius kangdingensis sp. n. appears to be host-specific. In paired-choice feeding tests, adults consumed significantly more HWA than two other adelgid species [eastern spruce gall adelgid, Adelges abietis (L.), and pine bark adelgid, Pineus strobi (Hartig)], the pine needle scale, Chionaspis pinifoliae (Fitch), and the woolly alder aphid, Paraprociphilus tessellatus (Fitch). In paired-choice oviposition tests, females laid more eggs on HWA-infested eastern hemlock than on any other test prey. In no-choice host suitability experiments larvae fed on HWA; eastern spruce gall adelgid; the larch adelgid, A. laricis Vallot; the balsam woolly adelgid, A. piceae (Ratzeburg); pine bark adelgid; and pine needle scale, but not on woolly alder aphid or elongate hemlock scale, Fiorinia externa Ferris. Although no larvae completed development in any of the bioassays, 6 out of 15 larvae (40%) in the HWA treatment reached the pre-pupal stage. One larva out of 6 reached the pre-pupal stage on pine bark adelgid.
Biology of Laricobius nigrinus Fender (Coleoptera: Derodontidae) and its potential as a biological control agent of the hemlock woolly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae) in the eastern United States
Zilahi-Balogh, Gabriella M. G. (Virginia Tech, 2001-11-09)
The biology of Laricobius nigrinus Fender (Coleoptera: Derodontidae) and its potential for control of hemlock woolly adelgid (HWA), Adelges tsugae Annand (Homoptera: Adelgidae) in the eastern United States were investigated. Laricobius nigrinus completed development on HWA in laboratory studies. There are four larval instars. Mean larval consumption was 225.9 and 252.3 HWA eggs at 12 and 18 °C, respectively. Post-aestivation activity period was 36.6 and 30.8 weeks for males and females at 13 °C, respectively. Mean lifetime fecundity was 100.8 eggs over a mean ovipositional period of 13.2 weeks. Laricobius nigrinus is host specific. In paired-choice and no-choice oviposition tests, L. nigrinus laid more eggs in HWA ovisacs than other test species. Laricobius nigrinus consumed more eggs of HWA than eggs of Adelges piceae (Ratzeburg) and Pineus strobi (Hartig) but not of Adelges abietis (L.). In larval development tests, L. nigrinus only completed development on HWA. A two-year field study conducted in British Columbia showed that: 1) the life cycle of HWA in British Columbia is similar to that previously reported in Virginia and Connecticut; 2) L. nigrinus adults undergo an aestival diapause that coincides with the diapause of the first instar HWA sistens. Adult activity beginning in autumn coincides with resumption of development of the sistens generation; 3) oviposition and subsequent larval development of L. nigrinus coincide with oviposition by HWA sistens adults. Temperature-dependent development was determined for egg, larval, pre-pupal and pupal stages of L. nigrinus at five constant temperatures (9, 12, 15, 18 and 21 °C). Development time was inversely proportional to temperature between 9 and 18 °C. Laricobius nigrinus did not complete development at 21 °C. Minimum developmental temperatures for eggs (6.5 °C), larvae (5.1 °C), pre-pupae (3.8 °C), and pupae (3.1 °C) were determined by extrapolation of linear regression equations to the x-intercept. Degree-days calculated for eggs, larvae, pre-pupae, pupae, and egg to adult were 54.6, 161.3, 196.1, 212.8, and 666.7, respectively. The laboratory derived degree-day model for predicting egg hatch was validated with field data collected in British Columbia. Observed median egg hatch at three of four sites over two years was within 15% of the predicted DD value (54.6).
Biomarkers of oxidative stress in atrazine-treated honey bees: A laboratory and in-hive study
Williams, Jennifer Rae (Virginia Tech, 2016-09-14)
The decline of honey bee (Apis mellifera) colony numbers in recent years presents an economic and ecological threat to agriculture. One outstanding threat to honey bees is the unintended exposure to agricultural pesticides. Previous studies report that acute exposures to the common-use herbicide atrazine elicit oxidative stress in non-target insects; however, little information is currently available on the exposure risk of atrazine to honey bees. This project examined biochemical and molecular oxidative stress response markers of honey bees following laboratory and field treatments of atrazine. Laboratory experiments were conducted with honey bees exposed to increasing concentrations of atrazine for 24 h whereas hive experiments were conducted with bees exposed to one sub-lethal concentration of atrazine for 28 d. The overall antioxidant enzyme activities of atrazine-treated honey bees were decreased compared to the untreated honey bees in both the laboratory and hive experiments. After exposure to atrazine in the laboratory and field, semi-quantitative RT-PCR analysis of antioxidant-encoding genes reveals the differential expression of genes in atrazine-treated bees that are important for oxidative stress tolerance in the laboratory and field experiments. Here, we provide evidence that the laboratory and hive exposure of honey bees to the common-use herbicide atrazine results in oxidative stress responses that can compromise the health of bee colonies. The data will be discussed with regard to the protection of these pollinators against the untended exposure of agricultural pesticides.
Bringing in the Garbage: Opening a Critical Space for Vehicle Disposal Practices
Surak, Sarah Marie (Virginia Tech, 2012-04-19)
This dissertation examines the relationship among practices and policies of waste/ing and economic structures to make visible the implications of vehicle disposal policies for environmental policy and theory. Consequently, I attempt to build upon the small body of literature that is now critically engaging with waste production and resulting actions/inaction in the form of policies of management. In doing this I use waste as a lens to examine the interrelationships among environmental degradation and economic and political structures. Further, I examine these phenomena in relation to a physical object, the automobile, to add materiality to abstract notions of waste as it relates to both the political and the economic. Through vehicle recycling policies, I analyze how underlying economic structures in contemporary capitalism result in specific responses to the "problems" of waste as well as how the related responses, or "solutions" perpetuate an un-ecological industrial system which severely restricts the possibilities of making substantial change in the production of environmental harms.
Characterizing the Role of Magnetic Cues Underlying Spatial Behavior
Painter, Michael Scott (Virginia Tech, 2017-01-09)
In the 50+ years since the discovery of magnetic compass orientation by migratory songbirds, evidence for the use of magnetic cues has been obtained for a range of taxonomic groups, including several classes of vertebrate and invertebrate taxa. Surprisingly, however, the biophysical mechanisms and biological substrate that underlie magnetic sensing are still not fully understood. Moreover, while use of magnetic cues for compass orientation is intuitive, the functional significance of other forms of behavioral responses mediated by magnetic cues, such as spontaneous magnetic alignment, is less clear. The following research was carried out to investigate the mechanisms underlying magnetic orientation in vertebrates and invertebrates. This involved the modification of existing experimental systems to characterize responses to magnetic cues in laboratory animals (flies, mice) and the development of novel techniques for studying the role of magnetic cues in the spatial behavior of free-living animals (red foxes). Chapter II examines magnetic orientation in wild-type Drosophila melanogaster larvae. We show that three strains of larvae reared under non-directional ultraviolet (UV) light exhibit quadramodal spontaneous orientation along the anti-cardinal compass directions (i.e. northeast, southeast, southwest, northwest) when tested in a radially symmetrical environment under UV light. Double-blind experiments cancelling the horizontal component of the magnetic field confirmed that the response is dependent on magnetic cues rather non-magnetic features of the test environment. Furthermore, we argue that the larval quadramodal pattern of response is consistent with properties of magnetic compass orientation observed in previous studies of adult Drosophila and laboratory mice, both of which have been proposed to be mediated by a light-dependent magnetic compass mechanism. Chapter III explores the use of novel biologging techniques to collect behavioral and spatial data from free-roaming mammals. Specifically, a previous observational study of free- roaming red foxes found a 4-fold increase in the success of predatory 'mousing' attacks when foxes were facing ~north-northeast, consistent with magnetic alignment responses reported for a range of terrestrial animals. The authors propose that the magnetic field may be used to increase accuracy of mousing attacks. Using tri-axial accelerometer and magnetometer bio-loggers fitted to semi-domesticated red foxes, we created ']magnetic ethograms' from behavioral and magnetic machine learning algorithms 'trained'] to identify three discrete behaviors (i.e. foraging, trotting, and mousing-like jumps) from raw accelerometer signatures and to classify the magnetic headings of mousing-like jumps into 45° sectors from raw magnetometer data. The classifier's ability to accurately identify behaviors from a separate fox not used to train the algorithm suggests that these techniques can be used in future experiments to obtain reliable magnetic ethograms for free-roaming foxes. We also developed the first radio-frequency emitting collar that broadcasts in the low MHz frequency range shown to disrupt magnetic compass responses in a host of animals. The radio-frequency collars coupled with biologgers will provide a powerful tool to characterize magnetic alignment responses in predatory red foxes and can be adapted for use in studies of magnetic alignment and magnetic compass orientation in other free-roaming mammals. Chapter 3 discusses findings from a magnetic nest building assay involving male labratory mice. Mice trained to position nests in one of four directions relative to the magnetic field exhibited both learned magnetic compass responses and fixed magnetic nest positioning orientation consistent with northeast-southwest spontaneous magnetic alignment behavior previously reported for wild mice and bank voles. This is the first mammalian assay in which both learned magnetic compass orientation and spontaneous magnetic alignment were exhibited in the same species, and suggests that the use of magnetic cues in rodents may be more flexible that previously realized.
Chlorothalonil Exposure Alters Virus Susceptibility and Markers of Immunity, Nutrition, and Development in Honey Bees
O'Neal, Scott T.; Reeves, Alison M.; Fell, Richard D.; Brewster, Carlyle C.; Anderson, Troy D. (Entomological Society of America, 2019-05-23)
Chlorothalonil is a broad spectrum chloronitrile fungicide that has been identified as one of the most common pesticide contaminants found in managed honey bees (Hymenoptera: Apidae: Apis mellifera L.), their food stores, and the hive environment. While not acutely toxic to honey bees, several studies have identified potential sublethal effects, especially in larvae, but comprehensive information regarding the impact of chlorothalonil on adults is lacking. The goal of this study was to investigate the effects of exposure to a field relevant level of chlorothalonil on honey bee antiviral immunity and biochemical markers of general and social immunity, as well as macronutrient markers of nutrition and morphological markers of growth and development. Chlorothalonil exposure was found to have an effect on 1) honey bee resistance and/ or tolerance to viral infection by decreasing the survival of bees following a viral challenge, 2) social immunity, by increasing the level of glucose oxidase activity, 3) nutrition, by decreasing levels of total carbohydrate and protein, and 4) development, by decreasing the total body weight, head width, and wing length of adult nurse and forager bees. Although more research is required to better understand how chlorothalonil interacts with bee physiology to increase mortality associated with viral infections, this study clearly illustrates the sublethal effects of chlorothalonil exposure on bee immunity, nutrition, and development.
Classic Hoarding Cages Increase Gut Bacterial Abundance and Reduce the Individual Immune Response of Honey Bee (Apis mellifera) Workers
Gregory, Casey L.; Fell, Richard D.; Belden, Lisa K.; Walke, Jenifer B. (Oxford University Press, 2022-03-01)
Laboratory experiments have advanced our understanding of honey bee (Apis mellifera) responses to environmental factors, but removal from the hive environment may also impact physiology. To examine whether the laboratory environment alters the honey bee gut bacterial community and immune responses, we compared bacterial community structure (based on amplicon sequence variant relative abundance), total bacterial abundance, and immune enzyme (phenoloxidase and glucose oxidase) activity of cohort honey bee workers kept under laboratory and hive conditions. Workers housed in the laboratory showed differences in the relative abundance of their core gut taxa, an increase in total gut bacterial abundance, and reduced phenoloxidase activity, compared to bees housed in hives.
Demography, cold hardiness, and nutrient reserves of overwintering nests of the carpenter ant Camponotus pennsylvanicus (De Geer) (Hymenoptera: Formicidae)
Cannon, Colleen A. (Virginia Tech, 1990-10-09)
Overwintering nests of C. pennsylvanicus were dissected and censused. All castes were assayed for glycerol and for changes in nutrient reserves. Spring queens were collected at swarming and allowed to initiate nests. Queens were analyzed for nutrient reserves during the early stages of nest founding. Overwintering nests contained large proportions of larvae and alates. Physical associations within the winter nest were evident between majors and alates, and between larvae and the queen; minors were associated with larvae to a lesser degree. Reproductives and larvae were negatively correlated, and worker caste ratios shifted according to whether an area was dominated by larvae or alates. Winter nest temperatures followed ambient temperatures, though fluctuations were less extreme. Glycerol was detectable in all castes and stages. Major and minor workers were similar in nutrient content. Lipid and protein contributed greater than 80% of dry weight, glycogen less than 20%, and free sugars less than 10%. Lipid was progressively depleted through winter. Majors lost most protein and dry weight between November and January, minors between February and April. Glycogen changes emulated mean ambient temperature patterns. Overwintering gynes possessed large reserves of lipid, up to approximately 62% in mid-winter. Glycogen levels rose and fell with mean ambient temperatures. Most nutrient reserves in founding queens were depleted from the head/thorax region between swarming and first larval emergence; between larval emergence and first worker eclosion, significant losses occurred only in the gaster. Protein alone increased significantly in the gaster prior to larval emergence, after which it was depleted.
Development of a Precision Mite Management Program for the Control of the Ectoparasite Varroa destructor in Hives of Apis mellifera L.
Means, Jackson C. (Virginia Tech, 2014-06-03)
The European honey bee, Apis mellifera, is an important pollinator of horticultural and agricultural field crops, providing ≈ 90% of all commercial pollination services (Genersch et al. 2010). The recent rise in colony loss due to Colony Collapse Disorder (CCD) has been a source of concern for both beekeepers and the apiculture industry. One of the factors implicated in CCD is infestation by the ectoparasitic mite, Varroa destructor. Initial efforts to control the mite relied heavily on regular application of miticides without regard to actual mite infestation levels. This approach has led to problems of resistance in the mite and contamination of the hive and hive-products. Because it is unlikely that miticides will be removed as an option for mite management, a precision mite management (PMM) approach using information on the spatiotemporal distribution of the mite to improve sampling and treatments is seen as a viable option, particularly with respect to treatment costs and impacts on the environment. The primary objective of this study was to develop an understanding of the spatiotemporal distribution of the Varroa mite and bee brood within hives for the purpose of developing a PMM approach for the mite. Varroa mite populations were sampled from May to June, 2012 and February to October, 2013. Sampling was conducted with three commonly used sampling methods: soapy water roll (SWR), brood uncapping, and a modified sticky board; brood uncapping, however, was discontinued during the study due to hive the labor cost and harmful effects of this method to the hives. Similar trends in mite population levels were observed using the soapy water roll and sticky board sampling methods. Spearman's nonparametric analysis showed that there was a significant correlation (ρ = 0.47, P<0.001) in mite population levels for the soapy water roll and sticky board methods for sampling conducted from February to September, 2013 (the SWR method was not used in October). This was despite the fact that there was no significant correlation (ρ= -0.03, P = 0.8548) between the two sampling methods during the spring sampling period from February to April, 2013. The observed lack of correlation between the two sampling methods in early spring was likely due to the low population of brood in the hive, which caused the majority of the mites to remain on adult bees. Mites per 100 adult bees, therefore, appear to reflect mite population levels within the hive more closely than mite fall on sticky borad during the February to April sampling period. This suggests that the soapy water roll method is a better method for estimating mite population levels within the hive in the early spring compared with the sticky board method. Geospatial analyses of the distributions of mite fall on the sticky boards were conducted using geostatistics and Spatial Analysis by Distance IndicEs (SADIE). Both analyses showed that mite fall on the sticky board was generally aggregated and the aggregation increased with mite population levels. The average range of the variogram from geostatistical analysis was estimated at 4 sticky board cells; this range value was increased to 5 cells and was used to develop a systematic outside-range sampling protocol for mites on a sticky board. The results showed that the accuracy of the systematic outside-range sampling compared well with that of the traditional sticky board counting method in estimating total mite fall, but required only 60% of the effort (i.e., counting 63 instead of 105 cells). SADIE analysis showed that there is an overall association between the distribution of mite fall on a sticky board and the distribution of brood within a hive. A greater degree of correspondence was also observed in the association of drone and mite distributions during May to June; greater correspondence in worker brood and mite associations was observed in August and September. These differences may be due to relative amounts of the two types of brood present within the hive. A test of the efficacy of precision application of Varroa mite treatment based on the association between drone brood and mite fall resulted in a significantly greater reduction in mite levels on the sticky board using a traditional miticide treatment method compared with the control and precision treatments (𝜒2 =362.571; df = 2; P <0.0001); mite population levels with the precision method, however, were significantly reduced compared with the control.
Distribution and Management of the Red Imported Fire Ant, Solenopsis invicta Buren, in Virginia
Allen, Hamilton Ross (Virginia Tech, 2010-09-06)
Red imported fire ant specimens were first collected in Virginia in 1989 from colonies located in Hampton, Va. Now colonies are established throughout the Hampton Roads area of Virginia. Because the fire ant is a new pest information regarding the distribution, biology, and management of the ant in Virgnia are absent. Therefore studies were conducted to compare the efficacies of four broadcast fire ant control products and an individual mound treatment to control fire ants and to determine the impact of Advion and Top Choice on non-target ant species. Additionally, twenty-six fire ant colonies in Virginia were sampled to determine colony social form and to detect biological control organisms. Lastly, the CLIMEX model was used to predict the potential spread of the fire ant in Virginia. Field trials showed that combination applications of Advion and Top Choice provided the fastest and greatest reduction in foraging three days after treatment and the longest residual control of fire ant colonies for one year. Field tests documenting the impacts of Advion and Top Choice on non-target ants indicate treatments do supress ant foraging but ant populations will rebound 10-12 months after treatment. Laboratory PCR assays revealed that colonies in Virginia are primarily polygyne. Also, Kneallhazia solenopsae, Pseudaction spp. parasitoid decapitating phorid flies, and Solenopsis invicta virues (SINV) genetic materials were detected in fire ant samples. CLIMEX model results indicate that fire ants will be able to spread as far east as the Greater Richmond area and as far north as Alexandria in Virginia.
Distribution of Carrion Beetles (Coleoptera: Silphidae) in Different Geographic Regions of Virginia
Beirne, Shana Margaret (Virginia Tech, 2013-01-24)
The distribution of beetles in the Family Silphidae has not been well studied in Virginia. The primary purpose of this study was to survey silphid beetles in a more systematic manner across different geographic regions of the state, with a special consideration for Nicrophorus species. The seasonal abundance and diversity of silphid beetles in Montgomery County, Virginia, was also examined. Baited pitfall traps were used to sample beetle distribution and abundance, and were placed in each of the five geographical regions of Virginia in the summers of 2007 and 2008. Traps were placed approximately one kilometer apart and were checked daily over a five day period for each of three sampling periods. A total of 4375 silphid beetles, consisting of 11 species in four genera, were collected in ten counties with beetles in the subfamily Silphinae being predominant. Within the Nicrophorinae, Nicrophorus tomentosus and N. orbicollis were dominant in 2007; whereas in the summer of 2008, N. tomentosus and N. pustulatus were the most commonly collected. Contingency analyses indicated that species abundance was associated with sampling period and geographic region. Nicrophorus americanus was not collected during either summer of surveying and only three N. carolinus were trapped in Suffolk County in the summer of 2008. For the Montgomery County survey, a total of 3276 beetles were found between the middle of April and the middle of October. The prevalent species within Nicrophorinae was Nicrophorus tomentosus and within the Silphinae it was Necrophila americana. Species abundance was associated with sampling period.
Ecological and behavioral factors associated with monitoring and managing pink hibiscus mealybug (Hemiptera: Pseudococcidae) in the southern US
Vitullo, Justin Matthew (Virginia Tech, 2009-06-25)
The pink hibiscus mealybug (PHM), Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae) was investigated with regard to damage caused to hibiscus by feeding, dispersal of nymphs, evaluation of management tactics, and the use of sex pheromone based monitoring in southern Florida from 2005 to 2008. Understanding the ability of PHM to locate and colonize new hosts, and the response of hosts is essential to optimized monitoring and management strategies. Investigation of the onset and severity of PHM feeding symptoms by Hibiscus rosa-sinensis L. showed that severity of symptoms differed among cultivars and that PHM were found on plants that did not exhibit feeding symptoms. Aerially dispersing PHM were predominantly first instars. Dispersal occurred with a diel periodicity that peaked between 14:00 and 18:00 h and was significantly influenced by mean wind speed. Initial infestation with 5, 10, or 20 PHM adult females had no significant affect on the number of dispersing individuals captured from hibiscus plants and PHM were captured at 50 m from infested source plants. The effects of mating disruption, the insecticide (dinotefuran), the parasitoid, Anagyrus kamali (Moursi), and the predator, Cryptolaemus montrouzieri (Mulsant) on PHM on hibiscus plants in screened field cages were evaluated. The total number of mealybugs captured in sticky band and pheromone traps during the study was reduced by dinotefuran and the predator. At the end of the study, the number of nymphs recovered from hibiscus terminals was reduced by the dinotefuran, predator and parasitoid treatments. Field experiments showed that the time of day during which male PHM were captured in pheromone traps in May and September was crepuscular, with most captures occurring from 18:00 to 21:00 h. Significantly more males were captured in traps placed in non-host trees at an elevation of 2 m above the ground than 6 m, and more males were captured in traps placed within host plants than in those 3 m upwind. Pheromone traps placed in hibiscus treated with soil applied dinotefuran or left untreated captured equal numbers of males during the 3 wk prior to treatment and during the 12 wk after treatment. Release of parasitoids at residential sites did not have a significant effect on the total number of males captured in sex pheromone traps over 18 mo. The number of mealybugs found at both parasitoid release and untreated sites were highly variable and corresponded with males captured in sex pheromone traps, as high and low levels of mealybugs corresponded with high and low levels of males captured. The number of males captured in pheromone traps during a two week survey at residential sites in May were a strong predictor of subsequent captures in 2006 (r2 = 0. 712), but not 2007 (r2 = 0.019). The relationship between PHM populations and males captured in sex pheromone traps was influenced by a multitude of factors that can impact the ability of traps to accurately reflect populations at a given location. Pheromone traps have the potential to provide meaningful information towards monitoring and mitigating risk from PHM. The contributions of this dissertation towards optimizing PHM sex pheromone monitoring, as well as facets of PHM monitoring that have yet to be resolved are discussed.
Ecological studies and pesticide response of Evergestis rimosalis (Guenee) (Lepidoptera: Pyralidae) and its parasitoid Cotesia orobenae Forbes (Hymenoptera: Braconidae)
Acosta-Martinez, Jaime A. (Virginia Tech, 1995-10-14)
The effects of temperature on emergence, development, oviposition, longevity and fecundity of Cotesia orobenae Forbes (Hymenoptera: Braconidae) were studied. Development time of parasitoid pupae decreased as temperature increased to 35°C. Temperatures between 20 and 25°C were most suitable for parasitoid development, oviposition and fecundity. Longevity was significantly affected by temperature, and was greatest between I5 and 20°C for both sexes. Sex ratios obtained from virgin females, females mated once and females exposed to multiple mating were compared. Virgin females produced only males, those with single or multiple mating produced more females than males. Cotesia orobenae exposed to five densities of third instar cross-striped cabbageworm, Evergestis rimosaiis (Guenee) (Lepidoptera: Pyralidae), for 24 h showed differences in percent parasitization among the treatments. The highest number of parasitoid cocoon masses was obtained from a density of 10 hosts.

Browsing by Author "Fell, Richard D."

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