We used the nuclear polyhedrosis virus (LdNPV) of the gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae), to test a basic assumption of most models of disease dynamics; that the rate of horizontal transmission is directly proportional to the product of the densities of healthy larvae and virus. We made measurements of virus transmission, using small-scale experiments in bags on red oak (Quercus rubra) and black oak (Q. velutina) and observed a decline in the transmission constant as the densities of both healthy larvae and pathogen increased. We hypothesized two possibilities for the non-linearity observed in this system: (1) pathogen inhibition via the effects of induced foliage chemistry and (2) the effect of spatial heterogeneity of LdNPV (pathogen clumping effects). Previous work has linked larval damage on oak foliage to subsequently higher levels of tannins in damaged leaves; and laboratory bioassays have linked higher levels of tannins to a decrease in mortality caused by LdNPV. We damaged LdNPV-contaminated oak foliage using larvae, then bioassayed foliage with test larvae and measured tannins in damaged leaves. None of the experiments showed significant effects of foliage damage on mortality of test larvae or tannin content of damaged leaves, and we concluded that induced foliage responses cannot explain non-linearity of transmission in our previous work, or transmission dynamics in the field. To evaluate the role of pathogen clumping in transmission dynamics, we redefined parameters of the host-parasitoid model of Nicholson and Bailey (1935) for use in the gypsy moth-LdNPV system: a relationship between the assumptions of this model and the continuous time Anderson-May model was described. Using a version of this discrete-time model incorporating spatial heterogeneity, we observed transmission dynamics similar to those in field experiments. To evaluate safety issues in use of genetically altered baculoviruses as insecticides, we field-tested LdNPV that had been genetically-engineered for non- persistence. The EV was released in a forest setting, and did not persist or spread past the first year of release. Concerns regarding movement of baculoviruses were also addressed in experiments exploring the action of rainfall on the translocation of LdNPV.

Brachymeria intermedia is a primary parasitoid of pupae of the gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae). Previous studies established how females determine the acceptability of potential hosts through contact with their cuticular kairomones. This work investigates how olfactory cues initially may lead females to their hosts. Inexperienced females were less likely to walk toward the host than females with oviposition experience; however, a single antennal contact with the host was sufficient to increase the probability of walking to the host suggesting that females learned the odor of their host on the first encounter (Chapter 1). Olfactory conditioning was then demonstrated using a novel odor (Chapter 2). Through a single oviposition experience on their natural host in presence of vanilla odor, wasps were induced to drum and drill in a vanilla-scented paper roll. Although some wasps were conditioned when exposure to odor coincided with pre-oviposition drumming on the host, conditioning was most successful when odor exposure coincided with oviposition. Evidently, conditioning occurred through the formation of an association between the odor and the 'aroused' state underlying host acceptance. Results support the hypothesis that conditioning occurs through a stimulus-arousal association rather than, as is generally assumed, through a stimulus-stimulus association. Wasps were also conditioned to fly toward a source of vanilla odor in a wind tunnel (Chapter 3). Then, upon approaching vanilla-scented paper rolls hung on a vertical cylinder, conditioned wasps landed on them readily, whereas few wasps landed on real pupae. However, more wasps reached pupae or pupal cases than white scented paper rolls. Thus, visual and olfactory cues appeared to mediate the foraging behavior of wasps in conflicting ways. Conditioned wasps flying upwind, along a plume of vanilla odor flew shallow zigzag tracks (Chapter 4). Contrary to male moths flying to sex pheromone, wasps flew similar zigzag tracks along ribbon and turbulent plumes of vanilla odor. When the plume was removed while wasps were flying upwind, wasps either maintained an upwind course, or drifted sideways, flying alternately upwind and downwind before turning around and flying downwind. No wasp casted upon plume loss, as is typical of male moths.

Using controlled-release technology, a prototype novel biodegradable sphere, which is used for controlling apple maggot fly, Rhagoletis pomonella (Walsh), designed for long-lasting residual effectiveness of feeding stimulant and insecticide has been created. The sphere body consists of 42–50% sugar entrapped in a mixture of gelatinized corn flour and wheat flour in the presence of glycerin, and coated with a layer of latex paint containing insecticide. The sphere body serves as a slow-release sugar reservoir. First, the lethal and sublethal toxicity and the effects of tree sprays of the new insecticide imidacloprid on apple maggot flies were investigated. Females tested in the laboratory showed great mortality and reduced fecundity regardless of whether exposure was by oral or by surface contact. However, foliar sprays resulted neither in significant mortality nor reduced fecundity over a 7-day period. Secondly, technical-grade or formulated insecticides were incorporated in sphere coating mixtures and evaluated for acute toxicity and residual effectiveness in laboratory, semi-field and field experiments. Results indicated that imidacloprid is a promising substitute for dimethoate as a fly killing agent on spheres. A wettable powder formulation of imidacloprid (Merit) proved better than a flowable formulation (Provado) in terms of residual efficacy. Females feeding on imidacloprid-treated spheres exhibited very little tendency to forage within host plants or to lay eggs before dying, compared with females tested on dimethoate-treated spheres and control spheres. The sucrose pH shown to stimulate maximal feeding response was 6.4, with little feeding occurring at pH values of 5.0 or less and 8.0 or greater. Males were more responsive to varying pH than females. Such information is relevant to formulation improvements of coating mixtures of sucrose and insecticide applied to lethal spheres as part of tephritid fly control programs. (Abstract shortened by UMI.)

No description available.

No description available.

Willamette mite (WM), Eotetranychus willamettei, is a major pest throughout most winegrape regions in coastal California and Oregon. These mites puncture leaf tissue with their chelicerae and cause loss of photosynthetically active area. Chemical control treatments on grape include nearly ten registered synthetic miticides, plus soaps and oils. Oils can be petroleum based (mineral oil) or botanical (from seeds of various plants). There has been a lot of interest of late in the use of botanical oils other than soybean, including those derived from the seeds of plants including spearmint, rosemary and clove. This project tested for differences in the efficacy of a mineral vs. a botanical oil. The botanical oil was a blend of rosemary and peppermint oil (Ecotrol®) and was tested against a petroleum based oil (Omni Oil®), then compared to a commonly used synthetic miticide (Nexter®, common chemical name pyridaben). The field experiment (San Juan Vineyards in Shandon, CA) tested effects on adult mite and egg populations, with five treatments: Omni Oil®, Ecotrol®, Nexter®, Ecotrol® + Nexter®, and water as a control. Laboratory experiments tested effects on adult females and eggs. Treatments were Omni Oil®, Ecotrol® (1.0%), Ecotrol® (0.5%) and water as a control. Field data showed that Omni Oil® (at 1.5%) was the only effective treatment, Ecotrol® (at 0.5% or 1.0%) did not differ from the control. Omni Oil® was the most effective treatment against adult mites in the laboratory studies, followed by Ecotrol® at 1.0%, with Ecotrol® at 0.5 % not very effective. Egg mortality was high with Omni Oil® 1.5% or Ecotrol® 1.0% but low with Ecotrol® 0.5%.

As most multicellular organisms age, they undergo senescence: a progressive physiological deterioration that leads to declines in survival, reproduction, and performance in late life. Although senescence was once thought to be a phenomenon peculiar to captive animals and humans, field data have demonstrated age-related performance declines in a variety of taxa. Nevertheless, the ecology and evolution of senescence is not fully understood. The bulk of our knowledge about senescence in wild populations comes from studies of long-lived vertebrates, while short-lived invertebrates are often studied in the lab. Male antler flies (Protopiophila litigata; Diptera: Piophilidae) are an emerging insect model for studying senescence in nature, as they have short lifespans and high site-fidelity, facilitating collection of longitudinal data, and they can be easily reared and manipulated in the lab. This species is an ideal model to connect our lab-invertebrate- and field-vertebrate-based insights into aging biology. The developmental environment can have an especially large impact on life-history plasticity, including plasticity in senescence. This is because a developing organism makes “decisions” affecting phenotypes such as body size, sexual investment, metabolic rate, etc., which in turn can influence longevity and senescence. In my dissertation, I investigate how the early life environment, including larval diet and parental effects, plastically alters longevity and senescence in antler flies, primarily in the field in Algonquin Provincial Park. First, I quantified the effect of experimentally manipulated larval nutrient concentration on both early-life (growth and development) and late-life traits (reproduction, survival, senescence). Rich larval diet decreased development time, and although fast developers grew large and had low initial mortality in the field (and high average lifespan), they aged rapidly and had low mating rate. Due to these contrasting effects, diet and development time did not predict lifetime mating success, suggesting trade-offs among fitness components and alternative strategies in low condition males. Only male antler flies can be tracked in the field, so nothing is known about aging in females. In my second study, I compared longevity and aging of female and male antler flies in the lab. Theory suggests that males may age faster and die sooner than females, but empirical data are highly variable. Furthermore, the sexes may respond differently to variation in nutrition, so I reared flies on different larval diets based on the design of my first chapter. The sexes did not differ in senescence or longevity in the lab, and diet had a negligible effect. Large-bodied flies of both sexes senesced slower, in contrast to previous field data, highlighting plastic differences in senescence between wild and captive populations. In my third study, I quantified parental age effects on male antler flies. Offspring quality often changes with parental age, due to accumulation of germline mutations and/or changes in nongenetic maternal or paternal effects. To investigate whether and how parental age influences performance in wild insects, I mated lab-reared young and old females and males to one another in all combinations, and tracked their male offspring’s performance in the wild. Old fathers had long-lived sons, while maternal age had no effect on offspring survival in the field. Parental age did not affect mating success. Thus, the one parental age effect I observed was in fact positive, not negative. In my final study, I looked at how natural differences in larval diet, rather than artificial lab diets, influenced survival, mating, and senescence in wild male antler flies. Antlers become depleted of resources from year to year, as multiple generations of larvae feed within them. I collected larvae that grew inside nine different shed moose antlers, and tracked them in the field as adults. Males from high quality antlers (those that were more attractive to adult flies) completed metamorphosis more quickly, but did not differ in body size, longevity or lifetime mating success. However, large flies tended to live longer and have higher mating success. In conclusion, my dissertation research expands our understanding of plasticity in life history and senescence, particularly in insects, which are enormously abundant but understudied in this area. I quantified, for the first time to my knowledge, the effects of juvenile diet and parental age on longevity, mating success, and senescence in a wild insect.

archives@tulane.edu / In a laboratory setting, mosquito blood feeding is an essential step in investigating many aspects of mosquito biology. Standard laboratory procedures often place the blood membrane feeder on top or inside the cage. Previous research has suggested that blood feeding position improves mosquito feeding but was limited to vertical and horizontal placements. To enhance the current understanding of mosquito feeding behavior, this study sought to further optimize feeding at multiple angles between 0° and 180°. Aedes aegypti Rockefeller, field-derived New Orleans Aedes aegypti, field-derived New Orleans Aedes albopictus and Culex quinquefasciatus Orlando were tested to evaluate blood feeding success. A Hemotek feeding membrane system was attached to a custom-designed apparatus and four distinct mosquito colonies were fed separately during 30 minute feeding trials. Once fed, all mosquitoes were placed into emergence chambers and their eggs were collected. Ae. aegypti Rockefeller, field New Orleans Ae. aegypti and Cx. quinquefasciatus Orlando fed better at all angles measured compared to the control, suggesting that this trait has a potential role in mosquito feeding behavior. Lab-adapted mosquitoes laid on average more eggs at vertical and horizontal angles, suggesting physiological constraints. Feeding angle is proven to have an impact on mosquito feeding which may help improve future mosquito feeding assays. / 1 / Chance Erik Liedig

Neonicotinoids are broad spectrum insecticides that are widely used to control many insect pests. In Ontario they are applied directly to the seeds of most corn and soy crops, after which they are incorporated into the tissues of the developing plant. While researchers have investigated how these insecticides impact honeybee health, much less attention has been given to the effects of neonicotinoids on wild pollinators. Ground nesting bees face exposure to neonicotinoids both in the soil, where they nest, as well as through other exposure routes (e.g, nectar and pollen of treated plants). I studied whether a higher concentration of neonicotinoid pesticides in soils within and near corn and soy crops is negatively associated with the abundance and diversity of ground nesting bees. To determine whether an association exists between soil neonicotinoid concentration and the abundance of associated ground nesting bee communities, I surveyed 16 eastern Ontario (mainly corn and soy) farms once per month from May to August, 2019, sampling the bee communities, soil pesticide levels, and floral resources. I found a significant interaction between the sampling period and neonicotinoid soil concentrations on ground nesting bee abundance. However, no similar relationship existed for an analysis with non ground nesting bees only. Specifically, I found that high concentrations of soil neonicotinoids were associated with lower expected bee abundances and low seasonal variation, a low concentration of soil neonicotinoids was associated with a high degree of seasonal variation, including spikes of relatively high expected abundances, and that sites with no neonicotinoids were associated with low seasonal variation and moderately high expected bee abundances. The number of floral units at a site was also positively associated with bee abundance, which is consistent with what has been reported in other studies. Diversity data are currently being processed off-site and unavailable at the time of publication. My results provide evidence that there exists the potential for higher risks of neonicotinoid seed treatments to ground nesting bees compared to the non-ground nesting community.

Mosquito-borne arboviruses are of considerable public health importance as they cause some of the most important emerging and re-emerging infectious diseases affecting humans and animals in many parts of the world including southern Africa. The threat of large epidemics of mosquito-borne arboviruses are often associated with climatic conditions, global warming, animal migrations, surface water, wind, topography, harbourage, vegetation, food supply and abundance of competent mosquito vectors. The goal of this project is to provide an in depth understanding of mosquito community dynamics and the importance of mosquito vector populations in the maintenance and transmission of mosquito-borne diseases in southern Africa. Firstly, a review of past and current literature was conducted to highlight: (a) the current state of knowledge regarding the most important mosquito-borne viruses of medical significance in southern Africa (b) lesser known mosquito-borne arboviruses with the potential of causing zoonotic health threats for humans in southern Africa. (c) key aspects of the ecology of mosquito vectors of medically significant mosquito-borne viruses in southern Africa. d) gaps in knowledge regarding southern African arbovirus mosquito vectors. Most of the studies on mosquito-borne viruses in southern Africa can be clustered into specific programmes led by Kokernot and Smithburn in the 1950s, McIntosh in the 1970s and 1980s, Swanepoel in the 1970s, Venter and others in more recent years, and have largely been restricted to South Africa, Mozambique and Zimbabwe. Twenty-six (26) arboviruses have been isolated from mosquitoes in southern Africa. Of these, Chikungunya (CHIK), Sindbis (SIN), West Nile (WN), Wesselsbron (WES), Spondweni (SPO), Banzi (BAN), Dengue (DEN), Bunyamwera (BUN), Germiston (GER) and Rift Valley fever (RVF) viruses are known to cause human illness. Middelburg (MID) and Shuni (SHUN) viruses are also important, causing neurological symptoms in animals with zoonotic potential for humans in South Africa. There are eight mosquito-borne arboviral infections most likely to impact humans in southern Africa (CHIK, MID, SIN, DEN, WES, WN, SHUN and RVF viruses). Mosquitoes in the subfamily Culicinae (mostly Aedes and Culex mosquitoes) are the most frequently associated with arbovirus transmission (115 and 105 types of arbovirus, respectively). Understanding the role of mosquito vector species in arbovirus transmission is vital for the development of new strategies to control the spread of arboviral diseases. In southern Africa, a few species in the genera Anopheles, Coquillettidia and Mansonia have also been implicated as vectors of arboviruses. Surveys over multiple decades across southern Africa have provided an insight regarding which species of mosquitoes are involved in the transmission of at least the most common of the mosquito-borne zoonotic arboviruses. These cluster within the genera Aedes and Culex, each representing a different transmission strategy. Aedes-borne viruses such as CHIK, DEN and WES tend to have primate or human reservoir hosts (McIntosh, 1986), while Culex-borne viruses often use birds as reservoir hosts, and these factors influence the distribution and epidemiology of the diseases they cause in humans and animals. Aedes and Culex have different breeding strategies and preferences which also represent fundamental differences. These mosquitoes are Aedes aegypti, Aedes furcifer/cordellieri, Aedes circumluteolus, Aedes unidentatus, Aedes mcintoshi, Aedes caballus, Aedes juppi, Culex theileri, Culex zombaensis, Culex univittatus, Culex neavei and Culex rubinotus. To determine mosquito community dynamics and mosquito vector distributions, sampling mosquito vectors at six sentinel sites in three provinces in the northern part of South Africa where recent cases had been detected in animals. Adult mosquitoes were collected from two horse properties in Gauteng Province; two wildlife reserves in Limpopo Province and at Orpen Gate in Kruger National Park and Mnisi Area in Mpumalanga Province between 2014–2017, using carbon dioxide-baited light and tent traps. Culex poicilipes, was the most abundant species caught during the study period. Highest diversity and species richness were found at Lapalala Wilderness Reserve, while the lowest diversity and abundances were at Orpen in Kruger National Park. Aedes aegypti, Ae. mcintoshi, Ae. metallicus, Ae. vittatus, Cx. pipiens sensu lato, Cx. theileri and Cx. univittatus, which are potential arbovirus vectors, had the widest geographical distribution in northern South Africa. Also collected were Anopheles arabiensis and An. vaneedeni, both known malaria vectors in South Africa. Therefore, arbovirus surveillance and vector control programs should be augmented in peri-urban and mixed rural settings where there is greater risk for arbovirus transmission to humans and domestic stock. Since climate has reportedly been associated with disease transmission, it’s important to understand the extent of its influence on mosquito abundance and distribution in northern South Africa. Thus, population composition, abundance and diversity of mosquitoes collected over a three-year period were determined and correlated to diverse climatic conditions during those years in order to determine seasonal trends in occurrence, abundance and distribution. Marked differences in the temporal distribution and seasonal abundances of the seven medically important mosquito vectors encountered from the two distinct geographic regions and climates. Statistical models have shown that climatic factors play a crucial role in shaping the population dynamics of Ae. mcintoshi, Ae. vittatus, An. arabiensis, Cx. pipiens s.l., Cx. poicilipes, Cx. theileri and Cx. univittatus both in Highveld Grassland and Middleveld Bushveld regions of northern South Africa. High summer temperatures and rainfall lead to increased vector density which might trigger outbreaks of RVF, SIN and WN viruses on the inland plateau of South Africa. This study also showed that abundances of RVF and WN virus vectors are related to elevation. These findings will be important in predicting the timing of onset and spread of future epidemics such as WN and RVF viruses, in southern Africa and other geographical settings with similar climates. / Thesis (PhD)--University of Pretoria, 2020. / University of Pretoria US Centers for Disease Control and Prevention / Medical Virology / PhD / Unrestricted