Browsing by Author "Taylor, Sally Vann"

Now showing 1 - 4 of 4
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    Alternatives to chlorpyrifos in Virginia type peanut production for control of southern corn rootworm
    Hoar, Elijah Kael (Virginia Tech, 2024-06-05)
    Historically, the organophosphate insecticide chlorpyrifos was used to protect peanuts (Arachis hypogaea L.) from soil-dwelling insect pests. In 2022, its registration was canceled by the Environmental Protection Agency (EPA) for all food crops. The southern corn rootworm, Diabrotica undecimpunctata howardi Barber (Coleoptera: Chrysomelidae) (SCR), was the major pest of developing peanut previously managed by chlorpyrifos and there are no known alternative insecticides for its control. The SCR larvae can cause economic damage by feeding on developing pods and pegs. Field condition is an important factor in SCR survival as the larvae rely on soil moisture to survive, and larvae cannot feed on fully developed pods. The dependency of SCR on soil moisture and host availability allows for cultural modifications (e.g., planting date, judicious irrigation practices, selecting fields based on soil characteristics) to reduce losses to this pest. Alternatively, or in addition to these strategies, identifying varieties with resistance to SCR can provide growers with non-chemical methods to mitigate losses. Therefore, this project was developed to identify sources of resistance in commercial cultivars and advanced breeding lines of Virginia type peanuts to SCR and examine whether early digging can reduce SCR injury. Implementing an effective integrated pest management (IPM) plan relies on a clear understanding of the pest life cycle in relation to the susceptible stage of the crop. We also evaluated SCR phenology in relation to peanut development. Replicated field trials were used to screen cultivars and investigate the effect, if any, of early digging in reducing pod injury. We monitored SCR adult populations over time using sticky traps. Our research will help manage a problematic pest in this region with limited, or no, reliance on insecticides.
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    Diapause biology, dispersal capabilities and insecticide use for Lygus lineolaris in Mid-Atlantic cotton systems
    Schepis, John Philip (Virginia Tech, 2024-06-03)
    Cotton (Gossypium hirsutum L.), is cultivated in the United States, primarily in regions characterized by long, hot summers to optimize plant growth. Virginia is the northernmost state where cotton is grown, with approximately 84,000 acres annually. The unique challenges of cultivating cotton in Virginia stems from its relatively short season due to its geographical location, lack of large contiguous acreage, and distinctive issues with pests. A significant pest of this region is the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), which emerged as a major threat to mid-Atlantic cotton during the late 2010s. L. lineolaris utilize a variety of wild and cultivated hosts to survive the winter months. The overwintering success and distribution of diapause survival L. lineolaris was measured on cover crops and weeds common in the Mid-Atlantic. Densities varied between weed and cultivated hosts, with L. lineolaris exhibiting increased survival in legumes compared to grains. Carbohydrate, lipid and protein levels were measured within diapausing and non-diapausing L. lineolaris specimens. Overwintering specimens usually had elevated level of carbohydrates and lipids, while containing decreased concentrations of protein. Nutrient quantification provided an effective tool in selecting for diapause status in L. lineolaris. Through the results from this study, an alternative method to dissection for determining diapause status in L. lineolaris has been identified. In the spring, movement of L. lineolaris throughout the landscape is highly dependent on host senesce. Flight analysis, behavioral assays and nutritional quantification assays on L. lineolaris populations from different weed hosts were performed to assess the flight capacity of specimens fed from different hosts. While weed hosts type provided populations with differing internal nutrient levels, sustained flight was not different between populations. When dispersal of L. lineolaris into cotton occurs, insecticide treatments following scouting are often necessary to prevent economic damage to the plant. Insecticide experiments were conducted aiming to assess the impact of different active ingredients on L. lineolaris, secondary pests, and natural enemy populations. Findings indicated that insecticides used to control L. lineolaris were successful at lowering pest populations and acephate was found to impact natural enemy populations. Plots applied with acephate experienced secondary pest outbreaks, highlighting the crucial role of natural enemies.
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    Drinking from the Magic Well: Studies on Honey Bee Foraging, Recruitment, and Sublethal Stress Responses using Waggle Dance Analysis
    Ohlinger, Bradley David (Virginia Tech, 2023-06-05)
    Anthropogenic landscape changes threaten our ecologically and economically critical honey bees by decreasing the availability of quality foraging resources. Importantly, waggle dance analysis provides a versatile and relatively cost-effective tool for investigating the obstacles that honey bees face, such as habitat loss, in our changing landscapes. While this emerging tool has improved our understanding of honey bee foraging in specific landscape contexts, additional research is needed to identify broad trends that span across landscapes. For this dissertation, I used waggle dance decoding and analysis to investigate honey bee foraging, and sublethal stress responses, across three ecologically distinct landscapes in Virginia. In Chapter 1, I introduce waggle dances as a model study system for investigating honey bee foraging and sublethal stress responses by summarizing modern methodological advances in its analysis and emerging research gaps. In Chapter 2, I tested the effects of sublethal imidacloprid exposure on honey bee foraging and recruitment using a semi-field feeder experiment. In doing so, I report that honey bees decreased their foraging, but not recruitment, to an imidacloprid-laced sucrose solution, compared to a control solution. Together, these effects could potentially harm honey bee health by increasing their exposure to pesticides and decreasing their food intake. In Chapter 3, I compared the foraging distances communicated by waggle dancing nectar and pollen foragers across landscapes to explore the economic forces driving foraging to these resources. I observed higher overall and monthly nectar foraging distances compared to pollen foraging distances. Such results suggest that nectar foraging cost dynamics are driven by supply, while pollen foraging cost dynamics are driven by demand. In Chapter 4, I used waggle dance decoding to map and quantify foraging to agricultural grasslands in a mixed-use landscape. In doing so, I demonstrate that honey bees recruit to agricultural grasslands throughout the season, but that this land type was not more attractive than the broader landscape after correcting for foraging distance, which is a relevant cost that flying bees must consider. Additionally, I qualitatively observe a foraging hot spot, representing high honey bee interest, over a highly heterogenous section of the landscape. The collective results of this chapter identify agricultural grasslands as a potential management target and support the importance of landscape heterogeneity to honey bees/pollinators. In Chapter 5, I used waggle dance decoding to investigate honey bee foraging spatial patterns in the context of optimal foraging theory. In particular, I explore whether co-localized honey bee colonies forage optimally by converging on the same resource patches, or by partitioning the landscape in to distinct foraging territories. Spatial analysis revealed that the colonies widely distributed their foraging at the landscape-scale, with dances from the same and different colonies being similarly distributed, while also establishing distinct, patch-scale, colony-specific, foraging aggregations. Together, these results suggest that the honey bee foraging system produces an emergent foraging pattern that may decrease both within- and among-colony foraging competition. Finally, in Chapter 6, I place my research findings in the context of historical and current trends in honey bee behavioral ecology. Overall, my dissertation improves our understanding of honey bee foraging ecology across landscape contexts using waggle dance analysis, while demonstrating its versatility and effectiveness as a tool for ecologists.
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    Waggle Dance Your Own Way: Individuality, Network Structure, and an Herbicide Stressor in Recruitment, Foraging, and Neurobiology in the Honey Bee (Apis mellifera L.)
    McHenry, Laura Covington (Virginia Tech, 2024-10-22)
    The waggle dance of the honey bee (Apis mellifera L.) is perhaps the most celebrated animal communication behavior. With a waggle dance, a forager bee who has discovered a profitable resource on the landscape, usually floral nectar or pollen, can inform her nestmates of its location and recruit them to exploit it by communicating both a distance and a direction. Since Karl von Frisch described the waggle dance in 1942, scientific exploration of the dance has exploded into the realms of its structure, function, role in the regulation of collective foraging in the context of the hive as a super-organism, and even its utility as a study system for understanding sublethal behavioral effects of pesticide exposure. This dissertation presents three novel studies of the waggle dance. In the first, we asked whether consistent inter-bee differences (i.e., individuality) in a waggle dance distance - duration calibrations could affect communication success. In the second, we characterized the networks of recruitment arising from waggle dance communications and explored the role of the aforementioned individuality in network formation. In the third, we tested whether sublethal exposure to glyphosate (GLY), the most-applied herbicide in the world, could affect foraging, recruitment, or the levels and balance of biogenic amines in the bee brain. In each of these experiments, we housed bees in clear-walled observation colonies and trained cohorts of bees to visit artificial feeders to record both foraging and recruitment data. In our first experiment, we found that individuality in waggle dance behavior does shape communication outcomes, indicating that individual-level behavioral differences should not be discounted as factors at work in eusocial insect societies. In the second, we present the first network density and dance burstiness data from in vivo bee networks, revealing that recruitment networks are sparse, and waggle dancers are partitioned into bursty and non-bursty behavioral types. In the third, we show that not only can sublethal GLY exposure reduce foraging, but it can also produce significant correlations between levels of the important insect neurotransmitter octopamine and its two biosynthetic precursors, tyramine and tyrosine, where levels in control bees were unrelated. The results of this dissertation research, while distinct by experiment, together emphasize the continuing usefulness and tractability of the honey bee colony as a system in which to study the role of individuality in animal communication and to better understand the threat posed by non-insecticidal pesticide chemistries to the planet's most economically impactful pollinator.