Advisors/Committee Members: Borror, Donald J.

▼ This study investigated the impact of the variable flow rate system (VFRS) on some of the parameters of the dose transfer process. We utilized 2 standard flat fan nozzles (XR8008vs and XR8001vs) combined with the VFRS at 100 % duty cycle and 40 % duty cycle. The atomization results indicate that (1) the volume median diameters were increased at the 40% duty cycle and (2) the number median diameter significantly increased at 40% duty cycle in XR8008vs but decreased for XR8001vs. Distribution studies showed that the highest vertical deposits were found on the top, middle, and bottom plant sections respectively of all 3 canopies (tomato, soybean, and corn) On corn, the middle leaf sections retained spray deposits more than on the basal and terminal sections in all treatments and was more uniform than on soybean. The lowest CV values were obtained in the middle leaves in all treatments and increased with 40 % duty cycle for both flat fan nozzles. On soybean, the deposits in all treatments were higher on the top leaves than the middle and bottom leaves. The mortality of fall armyworm (FAW) Spodoptera frugiperda (J. E. Smith) and two insecticides indicated that larval mortality in the small droplet patterns was higher than in the large droplet patterns. Total larval feeding and feeding behavior under small droplet patterns was significantly different and less than under the large droplet patterns. These results indicated that small deposit structure was the most effective scenario controlling FAW populations and reducing foliage consumption. The development of resistance to an insecticide under various types of application methods and chemicals has yet to be reported in the literature. FAW larvae from several generations were fed for 72 hours on corn plant sprayed at a minimum recommended rate of cypermethrin and spinosad with small and large droplet nozzles. The results indicated that spinosad demonstrated an insecticidal activity less than cypermethrin. Larvae from all generations (F1-F7) under the XR8008vs treatments were less susceptible to cypermethrin and developed resistance faster than XR8001vs larvae. Advisors/Committee Members: Hall, Franklin R.

▼ Turfgrass lawns are an integral part of urban areas across the United States. Lawn management is, however, often viewed as an input intensive system, with growing concerns over potential health and environmental hazards from fertilizers and pesticides. Use of these inputs may be reduced by using environmentally-friendly alternatives and following integrated pest management (IPM) approaches. Unfortunately, alternatives have not been widely adopted because of limited information regarding their effectiveness and the perception that they are expensive. This study was conducted to: 1) examine the role of endophytes, mowing height and mowing frequency on competition between turfgrasses and weeds, 2) compare aesthetic (lawn quality), biological (weed and insect), and economic (lawn management cost) attributes of commercial, consumer, IPM, organic, and untreated lawn management programs, and 3) implement IPM in professional lawn care by comparing biological, aesthetic, and economic parameters of standard program and IPM programs managed by a professional lawn care operator. My results show that perennial ryegrass (PR) plots had significantly higher weed cover than tall fescue (TF) plots. Turfgrass plots with high levels of endophytes had significantly lower weed cover than plots with low levels of endophytes. However, plots high levels of endophytes had significantly higher dandelion cover than those with low levels of endophytes. Mowing height had a significant impact on weed cover. In general, plots mowed at 5 cm had significantly higher weed cover than plots mowed at 8.9 cm. I also found that weed cover was lowest in the commercial program followed by IPM, organic, and consumer programs. The commercial program had lower white grub density than all other programs, while the organic program had lower white grub density than the untreated program. The commercial program had the highest lawn quality while the untreated program had the lowest. The IPM and organic programs did not differ significantly in lawn quality, but both rated significantly higher than the consumer program. Annual costs were highest in the commercial ($382) followed by organic ($305), IPM ($252), and consumer program ($127), respectively. My results also show that the IPM program had significantly more lawns with weeds than the standard program in 2005 and 2006. However, 21% and 0% of IPM lawns required herbicide applications in 2005 and 2006, respectively. The IPM program also had significantly more lawns with insect damage than the standard program in June 2005 and August 2005, but not September 2005 and throughout 2006. Only 28% and 0% of IPM lawns required insecticide applications in 2005 and 2006, respectively. All standard program lawns received herbicide and insecticide application in both years. Lawn quality was significantly higher for standard program than for IPM program lawns in 2005, and June 2006 and September 2006, but not August 2006. Annual cost was lower for the IPM program ($282) than the standard program ($458). Thirty one percent of the IPM program customers cited satisfaction for continuing with the program in 2006. Among those who did not continue with the program in 2006, 33% cited weed or insect problems, while 33% expected better results. These results provide useful information for the development of lawn management programs in urban landscapes. Advisors/Committee Members: Grewal, Parwinder.

▼ Bacterium Moraxella osloensis is associated with slug-parasitic nematode Phasmarhabditis hermaphrodita, and bacteria from genus Photorhabdus and Xenorhabdus are with entomopathogenic nematode Heterorhabditis and Steinernema, respectively. We first determined gene expression of M. osloensis in the mollusk host Deroceras reticulatum by selective capture of transcribed sequences (SCOTS) technique. Two genes, ubiquinone synthetase (ubiS) and acyl-coA synthetase (acs) were up-regulated in both D. reticulatum and stationary phase in vitro cultures. Eleven genes were exclusively expressed in D. reticulatum and were thus infection specific. Mutational analysis on genes of protein-disulfide isomerase (dsbC) and ubiS confirmed that UbiS is important to M. osloensis growth and DsbC serves as a virulence factor. Bacteria Photorhabdus temperata and Xenorhabdus koppenhoeferi, the symbionts of nematodes Heterorhabditis bacteriophora and Steinernema scarabaei, respectively, were virulent to three white grub species Popillia japonica, Rhizotrogus majalis, and Cyclocephala borealis. The median lethal dose at 48h post injection and median lethal time at injection dose of 20 cells per grub showed that P. temperata was more virulent than X. koppenhoferi to C. borealis. However, although P. temperata grew faster than X. koppenhoeferi both in vitro and in vivo, there were no differences in virulence of two bacteria against R. majalis and P. japonica. Using SCOTS technique, 30 genes by P. temperata and 25 by X. koppenhoeferi were identified to be differentially expressed during infection to R. majalis. Most genes were unique to either P. temperata or X. koppenhoeferi, e.g. ttsL encoding a type III secretion system was only identified from P. temperata, and lpsE corresponding to lipopolysaccharide synthesis was unique to X. koppenhoeferi. Five nexus genes directly connecting to several other genes were identified as attractive candidates for future studies using the metabolic computational pathway analysis. Compared to the gene expression of M. osloensis, several common genes were found to be up-regulated during infection in all three bacteria, including dsb gene family and genes encoding outer membrane proteins, fatty acid synthesis proteins, and ubiquinone synthesis proteins. Advisors/Committee Members: Grewal, Parwinder S.

▼ I employed various approaches, including genome sequencing, comparative genomics, functional genomics, and conventional molecular techniques, to study the biology and pathogenicity mechanisms of S. kunkelii and AY-WB phytoplasma. The economically important insect-transmitted plant pathogenic mollicutes, Spiroplasma kunkelii and aster yellows witches' broom (AY-WB) phytoplasma, invade and replicate in various insect tissue cells, and inhabit and replicate in plant phloem tissues. The partial genome of S. kunkelii and the complete genome of AY-WB phytoplasma were sequenced. The genome sequence data provide genetic basis for the study of the biology and pathogenicity mechanisms of these organisms. Comparative genome analysis among mollicutes was conducted, and resulted in the identification of four genes that are present in the genomes of all plant-pathogenic mollicutes sequenced so far, but missing from the mycoplasmas. Another gene within both genomes might have been derived by horizontal gene transfer between spiroplasmas and phytoplasmas. Four traE gene homologs were identified as membrane-bound ATPases in S. kunkelii M2 strain and are possibly involved in spiroplasma conjugation and adhesion. The AY-WB phytoplasma genome sequences were mined for potentially secreted proteins that may directly interact with host cell components and hence are candidate effector proteins. High-throughput functional assays resulted in the identification of 17 candidate effector proteins. Plant localization studies with the YFP fusions of two NLS-containing proteins (A11 and A30) revealed their localization in the plant nuclei and confirmed the dependence of A11 on plant importin a proteins for nuclear import. Transcripts corresponding to the phytoplasma proteins were detected in AY-WB phytoplasma-infected insects and plants. Microarrays demonstrated that phytoplasma A11 protein could affect the expression of 53 tomato genes, supporting the hypothesis that A11 is an effector protein involved in plant pathogenicity. The importance of the research lies in the application of high throughput bioinformatics, genomics and molecular approaches in the study of agriculturally important organisms for which little information is available. The described research and approaches might be useful for other pathogenic mollicutes that are recalcitrant to in vitro manipulation, including the economically important mycoplasmas that impact human health and livestock industries. Advisors/Committee Members: Hogenhout, Saskia A.

▼ Methoprene tolerant (Met), a member of the bHLH-PAS family of transcriptional regulators, has been implicated in juvenile hormone (JH) signaling in Drosophila melanogaster. Met mutants are resistant to the toxic and morphogenetic defects of exogenous JH application. A paralogous gene in D. melanogaster, germ cell expressed (gce), forms JH-sensitive heterodimers with MET, but a function for gce has not been reported. DmMet orthologs from three mosquito species are characterized and, based on sequence analysis and intron position, are shown to have higher sequence identity to Dmgce than to DmMet. An evolutionary scheme for the origin of Met from a gce-like ancestor gene in lower Diptera is proposed. RNAi-driven underexpression of Met in the Yellow Fever mosquito, Aedes aegypti, results in the concomitant reduction of putative JH-inducible genes, suggesting involvement in JH signaling. The viability of D. melanogaster Met mutants is thought to result from functional redundancy conferred by gce. Therefore, genetic manipulation of gce expression was used to probe the function of this gene. Overexpression of gce was shown to alleviate preadult, but not adult Met phenotypes. RNAi-driven underexpression of gce resulted in preadult lethality in both Met+ and Met mutant backgrounds. Therefore, unlike Met, gce is a vital gene. Evolutionary analysis of 12 Met and gce orthologs showed that these genes are conserved across the genus Drosophila. Additionally, distinct signatures of selective pressure were identified in Met and gce via dN/dS analysis. The paucity of introns in Met relative to gce supports the notion of a retrotransposition mechanism of duplication, through which Met arose from a gce-like ancestor following the divergence of higher and lower Diptera. Furthermore, RT-PCR analysis revealed discrete embryonic expression profiles for Met and gce. Together, these results show a degree of post-duplication subfunctionalization. Advisors/Committee Members: Wilson, Thomas G.

▼ Pardosa milvina is a small wolf spider commonly associated with agricultural ecosystems. P. milvina produces dragline silk that is attached to the substrate over which it moves, but is not used in capturing prey. The effect relative humidity on P. milvina behavior and biology was examined through a series of experiments. The water balance constraints of P. milvina were studied to determine its body water content and its water loss rate at 0% RH. The calculated water loss rate is comparable to that of other terrestrial arthropods, and body water content was similar to other Pardosa spp. To examine the degree to which prey items are utilized as a water source, a study was conducted to determine if dehydrated spiders were more likely to take prey than hydrated spiders of comparable satiation levels. The individuals tested did not show an increase in prey taking when under water stress, as no spiders in either treatment took prey. Although they did not take prey, the dehydrated spiders regained a significantly greater mass when presented with water, indicating that free-standing water sources are preferred over prey if the spider is not hungry. The effect of relative humidity on silk deposition was examined, which necessitated the development of a technique for visualizing the silk. A difference in silk production between spiders maintained at different relative humidity levels was not found. Although there was no difference between relative humidity treatments, an analysis of a subset of individuals by mating status did reveal a difference in silk deposition between mated and virgin females. Virgin females deposited significantly more silk than mated spiders. Advisors/Committee Members: Needham, Glen.

▼ Dehydration tolerance in terrestrial arthropods is defined by two factors: an individual’s ability to maintain water balance and capability to respond to the stress generated during fluctuations in the water content. To maintain water balance, an arthropod has to balance water loss and water gain. This is accomplished by reducing water lost through cuticular and respiratory route, improving water re-absorption by the alimentary canal or by increasing water uptake by drinking or absorbing water vapor. Water stress is alleviated by increasing the internal concentrations of protective sugars and polyols and up-regulating stress-related proteins that repair damaged proteins, reduce oxidative stress and maintain cellular integrity. In this thesis, select underlying molecular and physiological changes during dehydration in blood feeding arthropods were examined. Fully hydrated Aedes aegypti, Anopheles gambiae and Culex pipiens females contained nearly the same amount of water (66-68%), but water loss rates differed among the species, with A. aegypti having the lowest water loss rate (2.6%/h), followed by C. pipiens (3.3%/h), and A. gambiae (5.1%/h). In all three species water could be replaced only by drinking water (or blood). Diapause in C. pipiens improved the ability of females to resist dehydration. Multiple dehydration bouts reduce the nutritional reserves of mosquitoes, likely due to the cost of responding to dehydration stress, leading to reduced survival and reduced egg production. Dehydration elicited expression of hsp70, and hsp90 was constitutively expressed in A. gambiae, A. aegypti, and C. pipiens. Injection of dsRNA to knock down expression of hsp70 and hsp90 in A. aegypti did not alter water content or water loss rates, but the dehydration tolerance was lower. Instead of surviving a 36% water loss, females were able to survive only a 28% water loss in response to RNAi directed against hsp70 and a 26% water loss when RNAi was directed against hsp90. The bed bug, Cimex lectularius, and the seabird tick, Ixodes uriae, are much more resistant to dehydration than mosquitoes. Both arthropods have low water loss rates and they further reduce water loss by forming aggregations. Bed bugs are incapable of absorbing water vapor from the air and rely solely on blood for liquid water. In contrast, the seabird tick absorbs water from the atmosphere but cannot drink free water. Bed bug water loss rates increase in response to alarm pheromone components, (E)-2-hexenal and (E)-2-octenal, presumably due to the increase in bed bug activity elicited by the alarm pheromones. When these chemical were applied in combination with insecticidal desiccant dust, the effectiveness of this control method increased by nearly 50%. Overall, these experiments define the water balance characteristics of mosquitoes, the common bed bug, and seabird ticks. Establishing the water balance profiles of these arthropod vectors is a critical aspect for determining their possible distribution and impact on public health. Advisors/Committee Members: Denlinger, David.

Advisors/Committee Members: Phelan, P.L.

Advisors/Committee Members: Kennedy, Clarence.

▼ Ecological risk assessment is an important tool for evaluating potentially hazardous contaminants on a site-specific basis. Few methods exist for evaluating population and community level effects of contaminants on terrestrial invertebrates, though such assessments may aid in site evaluation and subsequent decision-making with regard to site remediation. A particularly promising group of invertebrates for terrestrial site-based risk assessment is ground beetles (Carabidae) due to their high diversity in most terrestrial ecosystems. Ground beetles have also been shown to be important indicators of physical disturbances in their habitats. In the current study, we investigated the utility of ground beetles as indicators of elevated metal concentrations originating from lead-based shot in a trap and skeet shooting range. Concentration of the metals lead (Pb), arsenic (As), and antimony (Sb) were 3668, 46, and 0.28mg/kg in the shotfall and 537, 22, and 0.15mg/kg in the reference site, respectively. Ground beetles were collected in 2008 and 2009 using pitfall traps placed in the shotfall region of the shooting range and an adjacent reference site. Overall, ground beetle species richness did not differ between sites. Abundance of the most common species was either not significantly different between sites or they were more abundant in the reference site. A total of 45 species was collected in the two sites over both years. In addition to the ground beetle data, bioassays using the earthworm Eisenia andrei were used to determine bioavailability and sub-lethal effects of the metals in the shooting range. Bioavailability of Sb, As, and Pb was greater in the shotfall soil compared to the reference soil. There was no mortality in any of the test soils during the 28-day toxicity test. Earthworm cocoon production was reduced in shotfall soil relative to the soil from the reference area and Webster, a lab standard soil. Although earthworm data suggests that there are sub-lethal reproductive effects from exposure to shotfall associated metals, ground beetle diversity appeared to be robust to these environmental changes. Additional years of sampling may reveal additional trends in ground beetle distribution and abundance. Advisors/Committee Members: Lanno, Roman.

▼ The phylogenetics, systematics, taxonomy, and biology of Gelechioidea (Insecta: Lepidoptera) are investigated. This superfamily is probably the second largest in all of Lepidoptera, and it remains one of the least well known. Taxonomy of Gelechioidea has been unstable historically. In Chapters Two and Three, I review the taxonomy of Gelechioidea and characters that have been important. Chapter Four provides the first phylogenetic analysis of Gelechioidea to include molecular data. I combine novel DNA sequence data from Cytochrome oxidase I and II with morphological matrices for exemplar species. The results challenge current concepts of Gelechioidea, suggesting that traditional morphological characters may not be homologous structures and are in need of further investigation. I conduct in Chapter Five an in-depth study of morphological evolution, host-plant selection, and geographical distribution of a medium-sized genus Depressaria Haworth (Depressariinae), larvae of which generally feed on plants in the families Asteraceae and Apiaceae. Host-plant use is commonly studied in this group because of physiological and behavioral responses exhibited by Depressaria pastinacella to furanocoumarins produced by their host plants, yet no species level phylogeny is available. This study is the only modern phylogeny of the genus, and includes all North American species but one, and about half the Old World species. In Chapter Six I describe nine new species of Scythris Hübner (Scythridinae) from the Galápagos Islands, Ecuador, and provide a key and illustration of genitalia and abdominal modifications. Finally, Chapter Seven represents an application of moth taxonomy to address questions of sampling protocols used for studies of biodiversity and conservation. I use Gelechioidea in eastern North America as indicators of diversity, with attention to the effectiveness of different sampling protocols with respect to active versus passive sampling, and plot-based versus plotless sampling. A list of Gelechioidea was produced from trap sites from an Appalachian forest in southern Ohio. The composition and diversity of Ohio Gelechioidea captured in a passive, plot-based protocol compares favorably to more exhaustive sampling, and reinforces recent (and counterintuitive) recommendations that it is more efficient and repeatable to focus surveys on target groups in focal localities rather than to conduct extensive sampling programs. Advisors/Committee Members: Wenzel, John W.

▼ Imidacloprid, the first neonicotinoid registered for use as an insecticide, is used worldwide against sucking and chewing insect pests in a variety of crops and environments. Some recent studies have suggested that imidacloprid can induce systemic resistance pathways, stimulate faster growth, enhance recovery from abiotic stresses, and increase yield when applied to plants growing under sub-optimal environmental conditions. The limited research has been conducted with agronomic and vegetable crops; few studies have addressed these effects in woody plants.The central objective of this research was to investigate the physiological responses of woody plants to imidacloprid. Three studies were conducted under controlled-environment conditions in the summers of 2006 and 2007. The first provided evidence that imidacloprid (Merit® 2F) increased the growth of hybrid poplar (Populus nigra clone NC5271) through morphological and physiological effects that are independent of its insecticidal properties. Specifically, the growth enhancing effect of imidacloprid was attributed to increased total leaf area and total number of leaves and was expressed in stressful and optimal nutrient and watering regimes. Both above and below ground growth was increased, suggesting that increased leaf production did not come at the cost of decreased root production. The second study showed that effects of imidacloprid formulations (Merit® 2F drench and Merit® FXT tablets) differed positively depending on species of plants and nutrient regime. Physiological parameters of hybrid poplar and burning bush (Euonymus alatus) treated with imicaloprid were not significantly different than those of untreated controls. However, the trend towards greater growth and biomass was consistent with that observed in previous experiments. Furthermore, the experiment was conducted over a shorter period of time, which may have precluded significant effects. Finally, the third study tested the generality of patterns observed with hybrid poplar in the first experiment by extending the evaluation of the effects of Merit® 2F on physiology of burning bush, river birch (Betula nigra), and shrub willow (Salix sericea). Once again Merit® 2F had positive effects on the growth of hybrid poplar grown under optimal environmental conditions as well as the variation of these effects depending on the fertilization rate. The other three woody species also had greater growth when treated with imidacloprid, but the effects were not significant. Laboratory bioassays performed in this study to test the effects of imidacloprid on the performance of twospotted spider mite (Tetranychus urticae), imported willow leaf beetle (Plagiodera versicolora), and fall webworm (Hyphantria cunea) showed that imidacloprid increased the fecundity of twospotted spider mite on burning bush, but only in the low fertility treatment, raising egg production to the same level observed in the high fertility treatment. Imidacloprid decreased larval growth and survival of fall webworm on B. nigra, and P. nigra, and S. sericea and imported willow leaf beetle on P. nigra and S. sericea. Advisors/Committee Members: Herms, Daniel.

▼ Phenotypic variation in host quality can affect ecological and evolutionary interactions between plants and herbivores. Effects of phenotypic variation in host quality of woody-plants on performance of leaf feeding insects were investigated in three studies: (1) phenological variation of Scots pine (Pinus sylvestris) needle quality for the European pine sawfly (Neodiprion sertifer) as a test of the "phenological window of host susceptibility hypothesis", (2) effects of fertilization on the expression of defoliation-induced resistance of Austrian pine (P. nigra) to European pine sawfly, and (3) manipulation of growth/defense trade-offs in paper birch (Betula papyrifera) and Austrian pine through application of the plant growth regulator paclobutrazol. Consistent with the predictions of the phenological window hypothesis, larval growth and survival decreased as host-insect synchronicity was modified. Foliar quality declined as current-year shoots and needles elongated, which suggests that larvae tolerate plant defenses only if nutrient concentrations are high relative to chemical defenses. A slow increase in host quality occurred late in the growing season as mature foliage once again became suitable. The survival of an experimentally-generated second generation of larvae manipulated to emerge in September was only 20% on current- or previous-year foliage; however survival was 80% the following spring. This phenological window of host susceptibility appears to constrain the evolution of a second generation. The expression of defoliation-induced responses of Austrian pine to European pine sawfly larvae varied with level of fertilization. In the nutrient-rich environment, previous defoliation improved host quality for European pine sawfly larvae, which may promote insect outbreaks through positive density dependent (Allee) effects on population growth. However in the low nutrient treatment, host quality rapidly decreased following defoliation, which is thought to generate negative density dependent effects on population growth, thus stabilizing population density. Austrian pines tolerated defoliation through compensatory growth responses, an effect that was independent of the fertilization level and that was evident two growing seasons after the defoliation event. Concentration of foliar monoterpenes strongly increased one year after the defoliation treatment across all fertility levels. These results are inconsistent with predictions of the carbon nutrient balance hypothesis, which proposes that physiological constraints prevent defoliation-induced accumulation of carbon-based secondary metabolites in evergreens. These results suggest that in nutrient-poor soils Austrian pines would express rapid induced resistance that would help limit outbreaks and thus defoliation, while compensatory growth responses would enhance competitive ability. Application of the plant growth regulator paclobutrazol slowed the growth of paper birch and Austrian pine with no effect on photosynthesis. Consistent with the predictions of the growth-differentiation balance hypothesis, application of paclobutrazol increased the concentration of tannins and resistance of paper birch to gypsy moth (Lymantria dispar) and whitemarked tussock moth (Orgyia leucostigma), but only in the second growing season following treatment. Conversely, paclobutrazol had no effect on defensive chemistry of Austrian pine or its resistance to European pine sawfly. Although it has been suggested that paclobutrazol generally enhances tree resistance to insects, it was found here that its effect on tree resistance to leaf-feeding insects was species-specific and time-sensitive. Advisors/Committee Members: Herms, Daniel A.

Advisors/Committee Members: Colinvaux, Paul A.

Advisors/Committee Members: Kennedy, Clarence H.

Advisors/Committee Members: Snyder, Laurence H.

▼ The potential of Beauveria bassiana to suppress Amblyomma americanum and Dermacentor variabilis populations was evaluated. In the laboratory the fungus was pathogenic to both species. Two (A. americanum) or five (D. variabilis) weeks was required for significant mortality. In the field there was significant mortality of A. americanum exposed to B. bassiana (F 124.45; p <0.001; df 1,6). This was not observed for D. variabilis (F 0.60; p 0.47; df 1,6). The experimental design of the field trial is recommended for evaluations of fungus-arthropod interactions as the majority of the test organisms could be recovered. The enclosures did not have biologically significant effects on relative humidity and temperature conditions. Suitability of the central Ohio mesoclimate for B. bassiana was determined. Optimal conditions for fungal infection (20-30°C; RH >90%) usually occurred concurrently after 18h00 from June-August. To avoid inactivation by ultraviolet radiation and maximize the chances of infection applications should occur after this hour during months when ticks are active. Beauveria bassiana increased the respiration rate of A. americanum (F 7.76, df 5,36; R-square 0.52), although this was only significant two weeks post-exposure (p 0.02). The fungus negatively impacted the water balance of A. americanum as determined by weight (water) loss. When all fungus-exposed ticks had died, they had lost 25.2% ± 0.84 of their starting weight. Control ticks by comparison had lost 14.08% ± 0.85 of their starting weight. This difference was significant (p 0.01; df 96). The difference in percentage weight change at the time of death was significant (p 0.011; df 83). Exposed ticks lost less weight (µ 25.2% ± 0.84) compared to the controls (µ 27.8% ± 0.55). Most weight loss occurred in the two days following inoculation. The physical state of ticks was affected by exposure. Ticks became morbid quicker and died more rapidly than individuals in the control. These physiological costs may reduce survival and/or contribution to the next generation. This may make entomopathogenic fungi useful, even with low direct mortality, with population suppression over time following repeated applications. Beauveria bassiana is recommended for management of A. americanum, but not D. variabilis. Advisors/Committee Members: Needham, Glen R.

Advisors/Committee Members: Triplehorn, Charles A.

Advisors/Committee Members: Edwards, Clive A.

Advisors/Committee Members: Delong, Dwight M.

Advisors/Committee Members: Peterson, Alvah.

Advisors/Committee Members: Rothenbuhler, Walter C.

Advisors/Committee Members: Venard, Carl.

Advisors/Committee Members: Rothenbuhler, Walter C.

▼ The eastern subterranean termite, Reticulitermes flavipes, is highly susceptible to desiccation and moisture is a critical factor for its survival. Termites possess a pair of salivary reservoirs (water sacs) that store water, which presumably are used to increase the humidity in unfavorable microclimates. The function and structure of salivary reservoirs in R. flavipes was investigated. This dissertation investigates the physiological mechanisms of water transport, specifically how water is maintained within the termite salivary reservoirs and how it is moved to new food sources. The main objective of the first study was to measure the moisture change of a dry food source (cellulose pad) in the presence of R. flavipes workers during a 21-day period. Termites rapidly transported water to a dry food source, with the mean moisture content of the cellulose pad reaching ~7% just 3 hours after termites entered the test arena; the cellulose pad subsequently attained a maximum moisture content of ~46% at the 21-day observation. Salivary reservoir volume was smallest for termites removed from the food source in comparison to termites removed from the moist sand throughout the entire study (except on day 7). These data indicate that termites indeed use their salivary reservoirs as “water sacs” to relocate water from moist areas to dry resources. The objective of the second study was to evaluate the variability of salivary reservoir dimensions among the various castes, when collected from different locations in laboratory colonies and at field sites. Salivary reservoirs dimensions differed among castes and stages when collected from food sources, shelter tubes and nurseries. Salivary reservoir volume was always larger for termites collected from food sources and nurseries. Salivary reservoirs were usually depleted in termites collected from shelter tubes. Soldiers always had the largest salivary reservoirs, followed by workers (which were categorized into three sizes based on head width). Alates and nymphs consistently had empty salivary reservoirs. These data demonstrate that salivary reservoir dimensions differ among stages and worker sizes; however this apparently is not related to any task specialization. Current data are conflicting on how water enters the salivary reservoirs. This study investigated the route of water into the salivary reservoirs over a 6-hr period. When dehydrated workers were placed on moist sand, their crops were the first to fill (~80-85% full) after 15 minutes. Crops remained near full capacity (>75%) for 30–60 minutes before decreasing in size. An increase in salivary reservoir volume appeared to coincide with the decrease in crop volume. Salivary reservoir volumes were more than 50% full by 30-60 minutes and typically increased in size thereafter, though some colony variation was observed. Furthermore, water used in this study contained blue food coloring that was observed in the crop, but never in the salivary reservoirs. These data indicate that water reaches the salivary reservoirs via the hemolymph. Furthermore, preliminary gas chromatography and mass spectrometry results suggest the salivary reservoir contents may have a similar chemical profile to hemolymph. However, further analyses are required to determine if amino acids or sugars are present in the reservoirs. An ultrastructural investigation was performed at the same time as the previous study to gather additional information on any mechanisms involved with water release and/or retention in the salivary reservoirs. Salivary reservoirs were composed of one layer of epithelial cells and were surrounded by an inner cuticle layer. Secretory-like cells were found in the reservoir walls and a lipid-like secretion was found in the reservoir lumen. No evidence of structures associated with an ionic gradient or valve-like structures where observed in the reservoirs. Two types of secretory cells were found in the salivary glands of workers. Type I secretory cells contained electron lucent secretion material, while Type II secretory cells contained electron dense secretion material. Furthermore, Type II could be separated into Type IIa and Type IIb, as Type IIa contained material of variable electron density and Type IIb was more uniform in density. The salivary reservoirs are an important structure within the termite and the more information we gather on termite biology and colony dynamics, the better equipped we are to control them. Termite inspectors should not focus strictly on moisture-prone areas, as termites can relocate water to dry areas. This research also emphasizes the importance of educating homeowners on moisture reduction around homes. Furthermore, salivary reservoirs may be a candidate to target using RNA interference (RNAi)-based termiticides. Advisors/Committee Members: Jones, Susan.

▼ Feeding on sugar from floral and extra-floral nectaries is an important, if less well known, part of mosquito biology. Male mosquitoes, as well as females of a few species, feed only on nectar. Females of blood feeding species feed on sugar to provide energy for flight and survival as well as to improve fecundity. This is the case for every species so far examined. One possible exception to this rule is Anopheles gambiae, the world’s most important malaria vector. This endophilic, anthropophilic species is thought to forego sugar-feeding, instead taking multiple blood meals when necessary. However, this belief is based largely on observations that nectar sources and fructose-positive females are too infrequent to suggest that nectar feeding is obligatory. My laboratory experiments show that extra-floral nectar-producing plants found commonly near homes in Africa, as well as homopteran honeydew, contributed significantly to the survival of male and female An. gambiae when kept in their presence and that males require early access to sugar sources in order to survive and have any reproductive success. Results of a sugar digestion study show that An. gambiae digest even large sugar meals at a more rapid rate than other species, and the rate is even higher if metabolic reserves are low or if sugarmeal concentration is low, indicating the need for exercising restraint when interpreting field fructose results. Experiments focusing on the first gonotrophic cycle suggest that sugar feeding increases fecundity more than blood feeding alone. In addition, multiple blood meals, which occurred mostly after females were gravid, increased fecundity but delayed oviposition. There was no evidence of overlapping gonotrophic cycles due to multiple blood meals. The final set of experiments showed that, while males feed daily on sugar, females do not feed on sugar while developing their eggs. Instead, they sugar-feed after ovipositing and before taking their next blood meal. If blood or oviposition is delayed, they continue to sugar-feed daily for survival. Females can survive equally well on either blood or sugar, but feed less frequently on blood when sugar is available, suggesting that plants might be used to impede malaria transmission. Advisors/Committee Members: Foster, Woodbridge A.

Advisors/Committee Members: Valentine, Barry D.

Advisors/Committee Members: Borror, Donald J.

Advisors/Committee Members: Ekis, Ginter.