Master of Science / Department of Entomology / Frank Arthur / The control of Indianmeal moth [Plodia interpunctella (Hübner)], a commonly found serious stored product pest around the world, relies mainly upon chemical control methods. Because of recent changes in the laws and regulations governing pesticide usage in the United States, there is an increasing need for finding safer chemicals to control insect pests. Hydroprene, an insect growth regulator, is considered to be a safe alternative. In this study, I quantified the effects of hydroprene on two critical life stages of Indianmeal moth, the eggs and 5th instar wandering phase larvae. Maximum development time in the untreated controls was 13.6 ± 0.6 d at 16°C and minimum development time was 2.3 ± 0.4 d at 32°C. At 20°C and 24°C, the effect of hydroprene on egg development became more evident; development time generally increased with exposure interval, with some variability in the data. The mean egg mortality among all temperatures was 7.3 ± 4.6%. Among the treatments, mortality of eggs increased as the exposure periods increased within any given temperature, with a dramatic increase in mortality with increase in temperature. Egg mortality was lowest at 16°C when exposed for 1 h (0 ± 3%), but mortality gradually increased up to 32 ± 3% when exposed for 18 h. Within each exposure interval, there was a direct increase in mortality as the temperatures increased. For the 5th instar wandering phase larvae, the longest development time among the treatments of 47.2 ± 1.3 d occurred at 16ºC when the larvae were exposed for 30 h, whereas the shortest development time of 7.0 ± 0.5 d occurred when the larvae were exposed for 1 h at 32ºC. Among treatments, the greatest larval mortality (82.0 ± 0.1%) occurred when larvae were exposed for 30 h at 28ºC, while the minimum mortality of 0.0 ± 0.5% occurred at 16ºC when larvae were exposed for 1 h. Response-surface models derived from this study can be used in simulation models to estimate the potential consequences of hydroprene on Indianmeal moth population dynamics.

Doctor of Philosophy / Department of Entomology / Gerald R. Reeck / John C. Reese / Salivary secretions are a key component of aphid-plant interactions. Aphids’ salivary proteins interact with plant tissues, gaining access to phloem sap and eliciting responses which may benefit the insect. In an effort to isolate and identify key components in salivary secretions, we created a salivary gland cDNA library. Several thousand randomly selected cDNA clones were sequenced. We grouped these sequences into 1769 sets of essentially identical sequences, or clusters. About 22% of the clusters matched clearly to (non-aphid) proteins of known function. Among our cDNAs, we have identified putative oxido-reductases and hydrolases that may be involved in the insect's attack on plant tissue. C002 represents an abundant transcript among the genes expressed in the salivary glands. This cDNA encodes a novel protein that fails to match to proteins outside of aphids and is of unknown function. In situ hybridization and immunohistochemistry localized C002 in the same sub-set of cells within the principal salivary gland. C002 protein was detected in fava beans that were exposed to aphids, verifying that C002 protein is a secreted protein. Injection of siC002-RNA caused depletion of C002 transcript levels dramatically over a 3 day period after injection. With a lag of 1 – 2 days, the siC002-RNA injected insects died, on average 8 days before the death of control insects injected with siRNA for green fluorescent protein. It appears, therefore, that siRNA injections of adults will be a useful tool in studying the roles of individual transcripts in aphid salivary glands.

Doctor of Philosophy / Department of Entomology / C. M. Smith / Brenda Oppert / Coleopteran insects compensate for dietary protease inhibitors by a number of mechanisms. To study this compensation response at the molecular level, the digestive proteases of Tenebrio molitor were studied. Biochemical studies of the pH optima and inhibitor sensitivity of proteases indicated the cysteine proteases were mostly in the anterior and serine proteases were in the posterior midgut of T. molitor larvae. Expressed Sequence Tags (ESTs) from T. molitor larval midgut cDNA libraries contained sequences encoding putative digestive proteases. Of a total of 1,528 cDNA sequences, 92 cDNAs encoded proteases, and 50 full-length cDNAs were grouped into serine, cysteine and metallo protease classes. Sequences tmt1a, tmt1b and tmt1c were identified as genes encoding isoforms of T. molitor trypsin, and tmc1a encoded T. molitor chymotrypsin. The general distribution cysteine protease transcripts in the anterior and serine protease transcripts in the posterior midgut, of T. molitor larvae, was in agreement with the biochemically-characterized compartmentalization of proteases. Expression analyses of selected transcripts demonstrated varied expression patterns across five developmental stages of T. molitor, with maximal expression of most protease transcripts in first instar larvae. Dietary serine and cysteine protease inhibitors fed in combination to early-instar T. molitor larvae caused a significant delay in larval growth in 21-day-old larvae. Real-time quantitative PCR analysis of RNA isolated from larvae fed different protease inhibitor treatments indicated that dietary inhibitors affected the expression of serine and cysteine proteases. Larvae fed soybean trypsin inhibitor, a serine protease inhibitor, compensated by the hyperproduction of proteases from the same class, as well as the upregulation of cysteine proteases. A cysteine protease inhibitor, E-64, caused a reduction in the hyperproduction of all proteases, and, in combination with the soybean trypsin inhibitor, lowered the compensation response of T. molitor larvae to negligible levels. These data suggest that T. molitor larvae are more sensitive to the effects of cysteine protease inhibitors, perhaps because these proteases are the first line of defense for larvae against plant protease inhibitor. The bioassay and molecular studies suggested that combinations of inhibitors that target both serine and cysteine proteases are needed to effectively control larval infestations of T. molitor.

Doctor of Philosophy / Department of Entomology / James R. Nechols / Tetranychus kanzawai Kishida and Panonychus citri (McGregor) are the two major arachnid pests of screenhouse-cultivated papayas in Taiwan. Control of these mites has become more difficult because both pests have become resistant to most registered miticides. This laboratory study investigated the feeding behaviors, predatory potential, and prey preference of a domesticated line of Mallada basalis Walker, a commonly-occurring chrysopid in Taiwan, to both of these pest mites. A laboratory assessment on control efficacies of different predator:prey release ratios to single and mixed-pest species was also conducted. Behavioral study showed that all larval stages of M. basalis exhibited a high rate of acceptance of all life stages of both T. kanzawai and P. citri. Second and third instar predators foraged actively during most of the 2-h tests. Numbers and rates of prey consumption were measured for each instar of predator and prey. Results showed that consumption increased and prey handling time decreased as predator life stage advanced, and prey stage decreased. Mallada basalis exhibited both a shorter handling time and corresponding higher consumption rate on P. citri compared with T. kanzawai. Handling time and consumption rate also were positively affected by increasing prey density. Mallada basalis did not exhibit notable species or life stage preferences, and prior feeding experience on one mite species did not affect subsequent prey choice between the two mites. Lacewings significantly reduced T. kanzawai and P. citri populations at a predator:prey ratio of 1:30 and this improved at ratios of 1:15 and 1:10. Control of T. kanzawai was slightly better than P. citri when the mites occurred singly and together. Consumption by M. basalis increased with temperature up to 30C. I conclude that M. basalis has high potential for augmentative biological control of papaya mites. Further field investigations are needed for making final recommendations.

Doctor of Philosophy / Department of Entomology / James F. Campbell / James R. Nechols / Theoretical and empirical ecological research has emphasized the need for understanding how animals perceive and respond to landscape structure and the importance of integrating both behavioral and landscape approaches when studying movement behavior. Knowledge of insect movement behavior is essential for understanding and modeling dispersal and population structure and developing biologically-based integrated pest management programs. My dissertation research addresses questions concerning how insects respond to landscape structure by examining movement behavior of an important stored-product pest, red flour beetle (Tribolium castaneum), in experimental landscapes. Results show that beetles modify movement behavior depending on landscape structure. Edge effects and interpatch distances may influence landscape viscosity, or the degree to which landscape structure facilitates or impedes movement, resulting in significant differences in velocity and tortuosity (amount of turning) of movement pathways, as well as retention time in landscapes with different levels of habitat abundance and aggregation. Perceptual range, or the distance from which habitat is detected, appears to be limited while beetles are moving in a landscape as they did not respond to a flour resource before physical encounter. Beetles showed differential responses to patches with various characteristics, entering covered patches more quickly than uncovered patches with more resource or the same amount of resource. Permeability of patches changed with subsequent encounters suggesting that full evaluation of patch quality may only occur after entering a patch. Beetles responded to landscape structure differently depending on the activity in which they were engaged. Distribution of movement pathways was similar to that of the habitat, but distribution of oviposition sites were significantly more aggregated than pathways and habitat. Oviposition site choice may be influenced by a complex set of factors which include previous visitation, amount of resource, travel costs, and edge effects. Insights were gained concerning how red flour beetle perceives resources, modifies search strategies, responds to boundaries, and chooses reproductive sites in patchy landscapes. This research provides new information regarding how red flour beetle interacts with landscape structure that has implications in the areas of behavioral and landscape ecology and applications in stored-product insect ecology.

Doctor of Philosophy / Department of Entomology / C. Michael Smith / The Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae) (RWA), is an important pest in the U.S. Western Plains, causing hundreds of millions of dollars of losses to wheat and barley production through reduced yields and insecticide application costs. The objectives of this research were to evaluate the performance of two RWA-resistant barley varieties planted approximately one month earlier than normal in experimental fields at Fort Collins, Colorado; Tribune, Kansas; and Sidney, Nebraska during 2007, 2008, and 2009. The experimental design was a split-plot design with two main plot treatments (early and normal planting dates), and four split plot treatments (barley varieties) that were randomized within each main treatment plot. The varieties included two RWA-barley resistant varieties, Sidney and Stoneham, and the susceptible variety, Otis, under thiamethoxam-protected and unprotected regimes. Sampling of RWA, other cereal aphids, and natural enemy populations was conducted on four dates from mid May through early July. RWA populations collected from early-planted plots (first week of March) were significantly lower than normal-planted plots in 2007-2009 at the Fort Collins, Colorado and Tribune, Kansas sites. In samples collected from early planting date plots, RWA-resistant varieties yielded RWA populations similar to those found on the insecticide-treated susceptible variety at both Fort Collins and Tribune. At the Sidney, Nebraska site, very low RWA populations were present and there were no differences between either planting date or varietal treatments. The combined effect of early planting and RWA-resistant varieties reduced RWA populations at the Fort Collins, Colorado site in all three years. Results were similar at the Tribune, Kansas site in 2007, but differences due to planting date or variety were not observed in 2008 or 2009. The lowest RWA populations occurred at the Sidney, Nebraska site, were independent of planting date and varietal treatments. The RWA-resistant barley varieties had no negative impact on populations of other cereal aphids compared to those found on the susceptible variety, Otis at any of the three research sites. The only treatment effective in reducing other cereal aphids was the insecticide, thiamethoxam. There was also no clear response of populations of other cereal aphids to different planting date. Neither the RWA-resistant barley varieties nor the systemic, short residual action insecticide treatment had adverse affects on the abundance of natural enemies.

Master of Science / Department of Biology / Tonia L. Von Ohlen / The Drosophila embryonic nervous system develops from an array of neural precursor cells called, neuroblasts. These neuroblasts give rise to all the cell types that populate the mature central nervous system (CNS). The CNS originates from a bilateraly symmetric neurectoderm that is subdivided into three domains along the dorso-ventral (DV) axis. One of these domains is defined by the expression of the Homeodomain protein ventral nervous system defective (vnd). Regulation of neuroblast designation is very precise and controlled. Extensive research has been done on neuroblast formation along the anteroposterior axis, most of which indicates that neuroblast selection within a cluster of neurectodermal cells is controlled by segmentation genes. However, much more research is required to elucidate the function of genes along the DV axis. Early studies indicate that vnd is required for neuroblast formation in the ventral column. Here, we show that vnd function, but not expression, is dependent on MAPK activity downstream of Drosophila EGF-R (DER). Specifically, we show that vnd activity is eliminated in EGF-R mutant embryos in a stage specific manner by evaluating vnd’s ability to inhibit intermediate neuroblast defective (ind), muscle segment homeobox (msh), and the newly identified neural tube development player, neu3. Finally, we show that DER functionality in the ventral column is entirely dependent on the processing protein rhomboid (rho) in later stage embryos.

Master of Science / Department of Entomology / Brian P. McCornack / Robert J. Whitworth / No-till management of soybean benefits producers by lowering input costs and retaining soil moisture, but may also provide optimal conditions for increasing populations of soil-inhabiting pests. For Kansas soybean, damaging populations of soil-inhabiting isopods (Malacostraca: Isopoda) have been observed in fields under no-tillage management. To control damage to soybean stands from feeding isopods, current management strategies need to be evaluated. The objectives of my research were to evaluate the effects of chemical and cultural control combinations (seed treatment and planting date, planting date and seed size, seed treatment and natural crop residue removal, and seeding rate and seed treatment) on soybean stand densities exposed to natural isopod populations, and to evaluate the effects of burning crop residue on isopod populations and emergence rates in soybean under no-tillage management. Field studies were conducted in consecutive years (2009 and 2010) in two separate soybean fields within each year. All fields were under no-till management and had a history of damaging isopod populations. In the second chapter, we demonstrated that seed treatment with an insecticide is not a reliable strategy. Doubling normal seeding rates can potentially reduce the number of trips a grower makes across a field (single, high-density versus multiple, low-density plantings). In doing so, growers may save time and money (e.g., fuel). A high seeding rate (563,380/ha), along with a low rate (50 g a.i. / 100 kg seed) of neonicotinoid seed treatment, appears to improve soybean stands (P < 0.05). No other combinations of control methods appeared to affect stand density. In the third chapter, we show burning to be an effective strategy to directly influence isopod populations but its overall effect on soybean stands needs further investigation.

Doctor of Philosophy / Department of Entomology / Ludek Zurek / Enterococci are a group of commensal bacteria that are important nosocomial pathogens. They are abundant in human sewage and wastewater treatment facilities (WWTF). This study focused on the role of house flies, Musca domestica, in the ecology of enterococci at WWTF in both field and laboratory experiments. The first study objective focused on sampling and characterizing enterococci from house flies and wastewater sludge from four WWTF in northeastern Kansas. Enterococci were quantified, identified, and screened for antibiotic resistance and virulence traits, and genotyped. The profiles of enterococci (spp. diversity, antibiotic resistance and virulence) from WWTF sludge and the house flies were similar, indicating that the flies successfully acquired the bacteria from the WWTF substrate. Enterococci with the greatest amount of antibiotic resistant and virulence traits originated from the WWTF that processed meat waste from a commercial sausage plant. Genotyping of E. faecalis revealed clonal matches from sludge and house flies. The second study objective involved tracking the fate of E. faecalis in the digestive tract of house flies in laboratory assays. Colony forming unit (CFU) counts were highest in the midgut at 1 h and declined during the first 24 h. In the labellum, foregut and hindgut, E. faecalis concentrations were more variable but were overall higher after 24 h. Observations from CFU counts and visualizations under a dissecting microscope revealed that E. faecalis peaked in the crop after 48 h suggesting active proliferation in this region. The third objective of the study involved tracking the emergence of calyptrate muscoid flies from stockpiled biosolid cake at one of the four WWTF. Traps were employed at the site for a total of 47 weeks, totaling 386 trap-weeks. A total of 11,349 calyptrate muscoid flies were identified with the two most common species being stable flies (Stomoxys calcitrans) (9,016, 80.2%) and house flies (2022, 18.0%). Numbers of stable flies and house flies peaked around mid-July each year and a second, smaller peak was observed for stable flies 5-8 weeks later. Estimated annual emergence of stable flies was 551,404 and for house flies 109,188.

Master of Science / Department of Entomology / Frank H. Arthur / Kun Yan Zhu / Experiments were conducted to assess the effects of direct and indirect exposure scenarios, different degrees of residual flour, open and obstructed positions, and seasonal temperature variations on the efficacy of synergized pyrethrin against the red flour beetle, Tribolium castaneum (Herbst) and the confused flour beetle, Tribolium confusum Jacquelin du Val. To evaluate effects of direct and indirect exposures of T. castaneum and T. confusum eggs, larvae, pupae, or eggs to the insecticide aerosol within a flour mill, the following treatments were made to each life stage: insects treated with aerosol and transferred to treated or untreated flour, untreated insects transferred to treated flour, and insects and flour combined and treated together. Different degrees of harborage or sanitation levels were created by exposing T. confusum larvae, pupae, and adults to pyrethrin aerosol in Petri dishes containing 0, 0.1, 1, 5, and 10 g of wheat flour. Effects of pyrethrin dispersal in open and obstructed positions and seasonal temperature variations were assessed by exposing T. confusum pupae and adults in open positions and inside wooden boxes (1 m long, 20 cm wide, and 5, 10, or 20 cm high) inside experimental sheds maintained at target temperatures of 22, 27, and 32 °C. Results showed that when T. castaneum and T. confusum were directly exposed to aerosol without the flour source, or with a low amount of flour at open exposed areas, the aerosol provided good control against all life stages of T. castaneum and T. confusum. However, when insects were indirectly exposed (treated together with flour or untreated insects were transferred to treated flour), or treated together with deeper flour amounts, and exposed inside the boxes, the efficacy was greatly reduced. Eggs and pupae of both the species were more susceptible compared to larvae and adults. Additionally, the moribund adults initially observed in indirect exposure treatments, or at the deeper flour depth and exposure positions insides the boxes, were better able to recover. Generally, temperatures in the range of 22-32 °C had no significant effects on overall efficacy of pyrethrin aerosol.