To determine the optimal seeding rate and utilization of seed treatment combinations for maximizing soybean yield within optimal and late planting dates. Also, experiments were conducted to quantify effects of soybean stand loss and to determine optimal seeding rates at various planting dates comparing three seed treatments. Experiments were conducted to test influence of planter type and seeding rate on soybean. Soybean seed treated with at planting insecticides showed no difference in yield compared to fungicide only treated seed. Also, yields were maximized at low seeding rates where no stand loss occurred. Soybean yields benefited from where seeding rates were increased at 20% and 40% stand loss. Higher seeding rates can provide significant risk of yield and economic losses if no stand loss occurs. Optimal plantings can significantly increase soybean yields compared to later plantings. There was a significant difference in yield where fungicide only treated seed was planted compared to seed treated with a neonicotinoid. Low seeding rates maximized yield at optimal planting dates but were penalized at late planting dates. Soybean yields benefited from increased seeding rates at the later planting dates but there was no difference in any of the seed treatments compared to untreated soybean. Also, there was less variation in inter-spacing of plants at the lower seeding rate compared to higher seeding rate when using the cone planter compared to the other planter types. There was no difference in yield for soybean planted with any of the evaluated planter types. Yield differences were observed from higher seeding rate compared to low seeding rate.

Bumble bees provide valuable pollination services to many agricultural crops and wild flower species. Consequently, evidence that wild populations are in decline has caused widespread concern. Among multiple causal factors, some have singled out neonicotinoid pesticides as potentially a major contributor to these declines. Bumble bees are exposed to neonicotinoids, such as imidacloprid and thiamethoxam, whilst foraging for nectar and pollen from treated crops. For neonicotinoids to cause population decline, the typical residues that bumble bees encounter in the field (defined here as between 1–12 μg kg-1) should be capable of reducing colony success by detrimentally impacting demographically relevant endpoints such as reproduction and worker performance. Whether field-realistic neonicotinoids are capable of causing such effects is yet to be fully established. The overall aim of this thesis was to investigate the effects of field-realistic neonicotinoids on endpoints of demographic importance and improve understanding of the effect mechanisms of neonicotinoids in bumble bees. Laboratory experiments were conducted with Bombus terrestris L. exposed to dietary neonicotinoids up to 98 μg kg-1. Results showed that food consumption and production of brood (eggs and larvae) in queenless B. terrestris microcolonies were significantly reduced by the two highest concentrations of imidacloprid and thiamethoxam tested (39, 98 μg kg-1), but only imidacloprid produced a negative effect when concentrations were in the typical field-realistic range. Imidacloprid’s affect on microcolonies was mirrored in queenright colonies where field-realistic concentrations substantively reduced both feeding and brood production. It was postulated that the detrimental effects of imidacloprid on brood production emerge principally from nutrient limitation imposed by the failure of individuals to feed. Removing imidacloprid from the bees’ diet resulted in the recovery of feeding and brood production in queenright colonies, even when previously exposed to high doses (98 μg kg-1). Investigation into the effect mechanisms of imidacloprid in B. terrestris revealed that cytochrome P450 enzymes are not important for metabolism of the neonicotinoid in adult workers. A transcriptomic analysis indicated B. terrestris exhibit a general stress response to imidacloprid, characterised by the alteration in expression of genes involved in, for example, metabolism and storage of energy. The thesis findings raise further concern about the threat of imidacloprid to wild bumble bees. However, they also suggest that some demographically important endpoints are resilient to imidacloprid as a realistic pulsed exposure, and that bumble bees may be less sensitive to field-realistic concentrations of thiamethoxam. Further research, which is required to fully establish the demographic consequences for bumble bees of exposure to neonicotinoids, can be developed based on the foundation of work presented here.

4 pp. / Arizona enjoys a sustained recovery from the devastating whitefly outbreaks of the early 1990's. This success is built on an IPM strategy that includes the use of selective and effective chemistry. Admire has been a key soil insecticide protecting vegetables and produce throughout Arizona and is the first member of a burgeoning class of chemistry known as the neonicotinoids. New members of this valuable, reduced-risk, class of chemistry are now available to agricultural producers, placing a burden on users of these compounds to adopt rational plans for sustaining their efficacy. This consensus document represents our best guess efforts to limit and share this chemistry among different agricultural interests. Our goal is to preserve the long-term efficacy of the neonicotinoids and protect growers' interests in sustainable and economical whitefly management. Through identification of crop communities (i.e., "multi-crop", "cotton-intensive", and "cotton/melon") common to Arizona agriculture, we have sculpted sensible plans of use that should allow access to this valuable chemistry for everyone, while protecting it from resistance.

Populations of Cimex lectularius, the bed bug, have resurged around the world posing significant challenges for pest management professionals and causing physical, economic, and emotional strife. Pyrethroid resistance has been found in the vast majority of populations making pest management more difficult. The objectives of my dissertation research were to document the evolution of resistance to pyrethroid and neonicotinoid combination products (called combination products here) and to a neonicotinoid in the laboratory, to record potential fitness costs to resistance to the combination products, and to compare the efficacy of nine insecticides on six populations. In the laboratory, populations of bed bugs evolve resistance rapidly to a combination product and that resistance translates into cross resistance to another combination product. In a follow up experiment, resistance to a neonicotinoid occurred after three generations of selection. Cross resistance between neonicotinoid and pyrethroid resistance was also found, likely due to a common detoxification mechanism (cytochrome P450 mediated metabolism). Resistance was associated with life history costs in three populations that had been selected with a combination product. Therefore, in the absence of selection pressure, populations of bed bugs should revert towards increasing susceptibility. Two pyrethroid products and three combination products were effective at killing three populations of bed bugs but were relatively ineffective against three other populations. However, the combination product, Transport GHP®, the single action pyrrole product, Phantom SC®, and the single action desiccant, CimeXa®, killed 95 to 100% of all populations investigated over a 14-day exposure. Taken together, results reported in this dissertation suggest that insecticide resistance management may be a useful tool for extending the efficacy of insecticides for control of C. lectularius.

Neonicotinoid exposure has been recognised as potentially impacting upon bee health, but whether realistic exposure scenarios are driving declines in bee health is not known. This thesis contributes new insights and perspectives to this research field investigating the use of molecular, physiological and behavioural endpoints as potential ecotoxicological markers for pesticide risk assessment. The thesis presents experimental data for dietary exposures of the European honey bee, Apis mellifera, and the buff-tailed bumble bee, Bombus terrestris, to one of two neonicotinoid pesticides, imidacloprid and thiamethoxam. The first part of this thesis explores impacts of chronic dietary exposures to neonicotinoid pesticides on bee immunocompetence- the ability to mount an immune response- using an artificial challenge to invoke an immune response in adult workers. Levels of phenoloxidase, an enzyme involved in melanisation and part of the bee’s defence system, were largely constitutive and resilient to exposure in honey bees and bumble bees. In honey bees, transient transcriptional changes in antimicrobial effector genes were observed following neonicotinoid exposure, but the physiological antimicrobial response was unaffected. In bumble bees, the induced antimicrobial response was impaired following neonicotinoid exposure, but only when exposed to concentrations likely higher than realistic environmental exposure scenarios. The next phase of this thesis investigates whether transcriptional, physiological and behavioural endpoints associated with the functioning of the honey bee hypopharyngeal gland were altered by imidacloprid exposure. Imidacloprid exposure led to transcriptional changes in foraging genes (associated with the control of temporal polyethism) and major royal jelly proteins (fed to developing larvae by nurse workers) and enzymatic changes in glucose oxidase (an enzyme involved in social immunity), which I hypothesise are linked with hypopharyngeal gland development. Despite these laboratory observations, no behavioural effects were observed in a field setting, monitored using Radio Frequency Identification transponders. Lastly, using RNA-Sequencing to investigate changes across the honey bee transcriptome, this thesis identified a suite of genes that were differentially expressed in adult workers in response to immune challenge and/or dietary neonicotinoid exposure. Wounding and bacterial-like infection led to upregulation of known immune genes, including a peptidoglycan recognition protein and antimicrobial effectors. Chronic exposure to thiamethoxam and imidacloprid led to downregulation of genes associated with several metabolic pathways, such as oxidative phosphorylation, pyruvate- and purine- metabolic pathways, as well as ribosomal activity. Some of these genes identified provide candidates for further study to elucidate functional effects mechanisms and better understand health outcomes, as well as potential new biomarkers for use in pesticide risk assessment. This thesis presents novel findings and offers opportunities for future research that will be of interest to a wide audience, including risk assessors and policy makers, as well as the broader biological community, including ecotoxicologists, insect physiologists and molecular biologists.

<p>The primary goal of this research study was to provide updated pest management recommendations to growers, including the reduction of insecticide applications on a calendar basis by the use of pest economic thresholds, with the purpose of maximizing insecticide efficacy while minimizing the associated negative impacts on natural enemies and their ecosystem services. </p> <p>Commercial watermelon (<i>Citrullus lanatus</i>) production in the Midwest typically relies on neonicotinoid and pyrethroid insecticides to manage insect pests, particularly striped and spotted cucumber beetles (<i>Acalymma vittatum </i>Fabricius and <i>Diabrotica undecimpunctata</i> <i>howardi</i> Barber, respectively). The role of arthropod predators in managing cucumber beetles is not well documented, and data on the effects of insecticides on predators in watermelon production are deficient. Common cucumber beetle predators include coccinellid beetles found on plants, ground-dwelling carabid beetles (Coleoptera: Carabidae) and spiders in several families that inhabit the soil surface in watermelon fields. I hypothesize that these generalist predators and the ecosystem services (e.g., pest predation) they provide are at risk from insecticides used for pest management without regard to economic thresholds. My study compared the effect of insecticide use on cucumber beetle pests, spider predators, collembola populations and field pest predation under two treatments: 1) watermelons treated with neonicotinoid soil drench and subsequent pyrethroid sprays, surrounded by corn with neonicotinoid-treated seeds (Conventional), and 2) watermelons treated only with pyrethroid spray when economic thresholds were reached, surrounded by corn with untreated seeds (IPM).</p> <p>The frequent application of insecticides decreased cucumber beetles in the watermelon plots managed with Conventional pest management; however, they also reduced spider predators, collembola densities, and field pests predation measurements, possibly due to the subsequent pyrethroids applications during the growing season. In addition, our study showed that neonicotinoid seed treatment in corn had no negative impact on any of the above-mentioned response variables measured. </p> <p>Ultimately, following an IPM strategy and the use of pest monitoring helped to reduce unnecessary insecticides applications, conservation of pest regulatory services provided by natural enemies, and possibly less ecological impact to manage significant insect pests in watermelon plots. <b><br> </b></p>

Solenopsis invicta is an invasive ant that has caused detrimental impacts to ecosystems and economies in the Southeastern United States, recently including Virginia. In this study, we explored the invasion ecology of S. invicta through two main objectives. First, we established a comprehensive distribution map of S. invicta in Virginia through multiple survey techniques. We then compared our findings with published models quantifying the potential spread of S. invicta and created our own species distribution model. In 2020-2021, S. invicta occurrences were found in 7 counties beyond the current Quarantine and our data show that S. invicta has spread further than predicted. Our own species distribution model suggests that the distribution area for S. invicta is likely to increase under the projected climate change. This study provides insights into the range expansion of S. invicta at the border of its suitable habitat and allow for improvements to models of its spread under these conditions. Additionally, it provides useful information to inform county extension agents to know where they are to expect new infestations of S. invicta. Second, we investigated the impacts of pesticide residue on the behavior of S. invicta through neonicotinoid exposure. We found detectable levels of neonicotinoids in the soil of the ant mounds as well as in the ants themselves. In addition, we investigated the effects of dietary exposure to imidacloprid on foraging behavior in a laboratory setting. We found that unexposed colonies were able to locate the food source more quickly during the second trial while exposed ants were unable to improve their performance. We also found that more exposed ant workers were unable to successfully navigate the maze as compared to unexposed workers. Our results suggest impaired learning of maze tasks and impaired navigational skills in neonicotinoid-exposed ants. / Master of Science in Life Sciences / The red imported fire ant (RIFA) is an invasive ant species found throughout the Southeastern United States that has negatively impacted ecosystems and economies. In the past few decades, RIFA has invaded the Coastal Plain of Virginia, resulting in legislation that restricts the movements of soil, plant products, and some equipment in and out of several southeastern counties and independent cities. To develop better management practices, there is a critical need to understand the spread, establishment, and impacts of RIFA in greater detail. We aimed to do this by surveying the current distribution of RIFA in Virginia and investigate the impact of insecticide use on their spread and behavior. In 2020-2021, we found RIFA occurrences in 7 counties beyond the current Quarantine, which is further than previously predicted. We then built a model using climatic variables that predicts the distribution of RIFA and found their habitable range is likely to increase under the projected climate change. Additionally, we investigated the impacts of common agricultural pesticides on the behavior of RIFA. We found these chemicals present in both the soil of the ant mounds and in the ants themselves. We also found that dietary exposure to imidacloprid, a neonicotinoid pesticide, altered the foraging behavior of RIFA. This study provides useful information to advise county extension agents to know where they are to expect new infestations of RIFA. Our results also suggest that human activity alters the invasion ecology of recent arrivals such as the red imported fire ant.

The current project examined the ability of a novel series of guandine and amidine-containing nicotine analogs to interact with several native and recombinantlyexpressed mammalian neuronal nicotinic-acetylcholine receptor (nAChR) subtypes. Rational drug design methods and parallel organic synthesis was used to generate a library of guanidine-containing nicotine (NIC) analogs (AH compounds). A smaller series of amidine-containing nicotine analogs (JC compounds) were also synthesized. In total, >150 compounds were examined. Compounds were first assayed for affinity in a high-throughput [3H]epibatidine radioligand-binding screen. Lead compounds were evaluated in subtype-selective binding experiments to probe for affinity at the α4β2* and α7* neuronal nAChRs. Several compounds were identified which possess affinity and selectivity for the α4β2* subtype [AH-132 (Ki=27nm) and JC-3-9 (Ki=11nM)]. Schild analysis of binding suggests a complex one-site binding interaction at the desensitized high-affinity nAChR. Whole-cell functional fluorescence (FLIPR) assays revealed mixed subtype pharmacology. AH-compounds were identified which act as activators and inhibitors at nAChR subtypes, while lead JC-compounds were found which possess full agonist activity at α4β2* and α3β4* subtypes. Compounds were identified as partial agonists, full agonists and inhibitors of multiple nAChR subtypes. Several SAR-based, ligand-receptor pharmacophore models were developed to guide future ligand design. Second-generation lead compounds were identified.

Os inseticidas neonicotinóides são atualmente o principal grupo químico utilizado para o controle de insetos sugadores, constituindo-se uma boa opção para o controle de Diaphorina citri Kuwayama. Outra opção de controle do psilídeo tem sido a exploração do parasitóide Tamarixia radiata (Waterson). A compatibilidade dessas duas estratégias de controle poderia auxiliar na implementação de programas de manejo integrado de pragas na cultura do citros. No entanto, faltam estudos sobre a caracterização da suscetibilidade de D. citri para os inseticidas neonicotinóides e o impacto desses inseticidas sobre T. radiata. Sendo assim, os objetivos do trabalho foram o de caracterizar a suscetibilidade de D. citri a inseticidas neonicotinóides, realizar o monitoramento da suscetibilidade a esses inseticidas em populações de D. citri coletadas em pomares de diferentes regiões do Estado de São Paulo e avaliar os efeitos letais e subletais desses inseticidas sobre o parasitóide T. radiata. Os inseticidas avaliados foram: thiamethoxam, thiacloprid e imidacloprid. O método de bioensaio adotado foi o de contato residual para a caracterização da suscetibilidade de D.citri a esses inseticidas. O monitoramento da suscetibilidade a esses inseticidas em diferentes populações de D. citri foi realizado com concentrações diagnósticas baseadas na concentração letal 95 (CL95) de cada inseticida. Para avaliar os efeitos letais e subletais desses inseticidas sobre T. radiata foram realizados bioensaios de contato direto em adultos e pupas, toxicidade residual em adultos, e persistência da atividade biológica desses inseticidas sobre a superfície de folhas de citros. Entre os neonicotinóides testados, a maior toxicidade a D. citri foi observado com thiametoxam, seguidos por imidacloprid e thiaclopid. Os resultados do monitoramento apresentaram diferenças significativas na suscetibilidade das populações de D. citri aos inseticidas neonicotinóides. Para thiamethoxam, a sobrevivência estimada para as populações de D. citri testadas na concentração diagnóstica variou entre 5,5 e 16%, para thiacloprid variou entre 4,5 e 22,5 % e para imidacloprid entre 4 e 14%. Uma alta toxicidade desses inseticidas foi observada para adultos e pupas de T. radiata. No entanto, os efeitos subletais desses inseticidas a 10% da concentração recomendada sobre o estágio de pupa causou redução significativa no parasitismo somente com thiamethoxam. A emergência, longevidade e razão sexual de T. radiata não foram afetadas pelos inseticidas avaliados. A toxicidade residual de thiametoxam, thiacloprid e imidaclopid em folhas de mudas de citros foi relativamente elevada para adultos de T. radiata e com persistência de pelo menos 14 dias. / The neonicotinoids insecticides are currently the main chemical group used for controlling sucking pests and represent a good option for the control of Diaphorina citri Kuwayama. Another control alternative of this pest is the exploitation of parasitoid Tamarixia radiata (Waterson). The compatibility of these control strategies could be very helpful for the implementation of integrated pest management program in citrus. However, there are few studies on the characterization of the susceptibility of D. citri to neonicotinoid insecticides and the evaluation of the impact of these insecticides on T. radiata. Therefore, the objectives of this research were to evaluate the susceptibility of D. citri to neonicotinoid insecticides, to monitor the susceptibility to these insecticides in D. citri populations collected from different citrus groves in the State of São Paulo, and to evaluate the lethal and sublethal effects of these insecticides on T. radiata. The insecticides evaluated in this study were: thiamethoxam, thiacloprid e imidacloprid. A residual contact bioassay was used to characterize the susceptibility of D. citri to these insecticides. A diagnostic concentration bioassays based on lethal concentration 95 (LC95) of each insecticide were used for monitoring the susceptibility of D. citri populations. The lethal and sublethal effects of these insecticides on T. radiata were conducted by using direct contact bioassays on adult and pupal stages of T. radiata, residual contact bioassays and persistence of biological activity of these insecticides on citrus leaf surface. Among the neonicotinoid insecticides tested, the highest toxicity was observed with thiametoxam, followed by imidacloprid and thiaclopid. A significant difference in the susceptitibity to neonicotinoid insecticides was detected in D. citri populations. For thiamethoxam, the survivorship at diagnostic concentration varied from 5.5 to 16%, for thiacloprid varied from 4.5 to 22.5 %, and for imidacloprid from 4 to 14%. The toxicity of these insecticides was high to adult and pupal stages of T. radiata. However, the sublethal effects of these insecticides at 10% of the recommended rate on pupae stage caused the reduction of the parasitism capacity only with thiamethoxam. The emergence, longevity and sexual ratio of T. radiata were not affected by any insecticide tested. The residual toxicity of thiametoxam, thiacloprid and imidaclopid sprayed on citrus seedling leaves was relatively high to D. citri adults and lasted at least 14 days.

The non-alcoholic fatty liver disease (NAFLD) is the most common liver pathology in developed countries with an estimated prevalence of 20 to 30% in the American population. A typically benign and asymptomatic pathology, NAFLD is characterized by hepatic steatosis and abnormal levels of hepatic enzymes stemming from an increase in circulating free fatty acids originating from white adipose tissue lipolysis, an increased de novo lipogenesis, reduced fatty acid oxidation and decreased hepatic triglycerides secretion, all within an insulin resistance context. NAFLD has the potential to progress to the non-alcoholic steatohepatitis (NASH), a condition marked by inflammation, advanced oxidative stress and fibrosis. NASH is expected to be the leading cause of liver transplant by 2020 due to its complications (i.e.: cirrhosis, hepatocellular carcinoma and liver failure). Various xenobiotics such as pesticides have been shown to promote the apparition and development of NAFLD. Of interest to this study is the neonicotinoid imidacloprid, more contemporarily known for its suspected role in the colony collapse disorder of various anthophilae species. Imidacloprid has been shown to induce hepatic oxidative stress in rats, a significant factor in the development of NAFLD and its progression to NASH. Lifestyle modifications, namely physical exercise, is a current treatment which has been proven beneficial to prevent and treat NAFLD by reducing hepatic steatosis, oxidative stress and improving insulin sensitivity. The role of any neonicotinoid on the development of NAFLD has yet to be examine and few have looked at the role of exercise in the treatment of NAFLD brought about by pesticide contamination.