Entomology
Permanent URI for this communityhttp://hdl.handle.net/1903/11813
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Item Home sick: impacts of migratory beekeeping on honey bee (Apis mellifera) pests, pathogens, and colony size(PeerJ, 2018-11-02) Alger, Samantha A.; Burnham, P. Alexander; Lamas, Zachary S.; Brody, Alison K.; Richardson, Leif L.Honey bees are important pollinators of agricultural crops and the dramatic losses of honey bee colonies have risen to a level of international concern. Potential contributors to such losses include pesticide exposure, lack of floral resources and parasites and pathogens. The damaging effects of all of these may be exacerbated by apicultural practices. To meet the pollination demand of US crops, bees are transported to areas of high pollination demand throughout the year. Compared to stationary colonies, risk of parasitism and infectious disease may be greater for migratory bees than those that remain in a single location, although this has not been experimentally established. Here, we conducted a manipulative experiment to test whether viral pathogen and parasite loads increase as a result of colonies being transported for pollination of a major US crop, California almonds. We also tested if they subsequently transmit those diseases to stationary colonies upon return to their home apiaries. Colonies started with equivalent numbers of bees, however migratory colonies returned with fewer bees compared to stationary colonies and this difference remained one month later. Migratory colonies returned with higher black queen cell virus loads than stationary colonies, but loads were similar between groups one month later. Colonies exposed to migratory bees experienced a greater increase of deformed wing virus prevalence and load compared to the isolated group. The three groups had similar infestations of Varroa mites upon return of the migratory colonies. However, one month later, mite loads in migratory colonies were significantly lower compared to the other groups, possibly because of lower number of host bees. Our study demonstrates that migratory pollination practices has varying health effects for honey bee colonies. Further research is necessary to clarify how migratory pollination practices influence the disease dynamics of honey bee diseases we describe here.Item Diversity and structure of Metrosideros polymorpha canopy arthropod communities across space and time(2019) Tielens, Elske Karolien; Gruner, Daniel S; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Global biodiversity is under pressure from climate change, habitat fragmentation and other anthropogenic change, and our ability to predict biodiversity responses to change requires a better understanding of the processes that drive diversity and structure local communities. However, quantifying these processes has proven to be challenging for multiple reasons; diversity is multidimensional, and both diversity and the processes that generate it vary across scale. In this dissertation, I examine temporal and spatial patterns in community structure to test hypotheses about the drivers of local diversity and composition in communities of varying age, focusing on arthropod communities associated with the native tree Metrosideros polymorpha on the Hawaiian Islands. Analysis of Hemiptera (true bug) communities reveals a temporal pattern in community structure, where young substrate communities were variable in species composition and beta dispersion decreased with substrate age, indicating convergence. However, substrate age did not correlate with community dissimilarity in a directional way. Similarly, geographic distance did not correlate with compositional dissimilarity, suggesting a lack of dispersal limitation. I confirmed this result by examining connections between arthropod communities in a historically fragmented ‘kīpuka’ landscape, using species-area relationships and graph theory analyses. Finally, if canopy arthropods are dispersive and differences in species composition across sites are not driven by substrate age, local habitat characteristics may influence species composition. I determined the role of local beta diversity and identified habitat characteristics regarding forest structure and host leaf traits that are strong drivers of beta diversity and species composition. Then, to further explore local habitat drivers I examined forests with high intraspecific variation in co-occurring Metrosideros. In this hybrid zone, insect life history traits shape species’ response to intraspecific variation in host plant characteristics, highlighting the importance of including dimensions of biodiversity beyond taxonomic diversity. Together, these results demonstrate the importance of local habitat conditions for canopy arthropods, suggest that canopy arthropod communities are highly connected and that substrate age plays a limited role in determining local arthropod communities. Such insights into biodiversity and plant-insect interactions across temporal and spatial scale are integral to understanding and conserving our natural world.Item EVALUATING THE EFFECT OF POTATO LEAFHOPPER (EMPOASCA FABAE) FEEDING ON BIOLOGICAL NITROGEN FIXATION IN ALFALFA (MEDICAGO SATIVA)(2019) Thompson, Morgan; Lamp, William O; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Aboveground feeding by potato leafhopper (PLH), Empoasca fabae, (Hemiptera: Cicadellidae) causes significant injury to alfalfa (Medicago sativa), including disrupting translocation of fixed carbon from leaves to roots. Basal transport of fixed carbon in alfalfa fuels a critical mutualism between roots and nitrogen-fixing bacteria (Sinorhizobium meliloti). Above- and belowground nutrient allocation in alfalfa determines perennial persistence across growing seasons, as well as forage quality. Whether leafhopper feeding alters nutrient allocation and subsequently affects nitrogen fixation, however, is not clear. To test this, my objectives were 1) to examine the effect of different management strategies on PLH injury and nitrogen fixation, and 2) to quantify the amount and location of fixed nitrogen in whole alfalfa plants when fed on by leafhoppers. Overall, my work contributes to an understanding of how aboveground pest pressure can disrupt belowground processes in plants and ultimately affect the economic viability of crops for growers.Item SPATIAL DISTRIBUTION, HABITAT PREFERENCE, AND SOCIETAL IMPACT OF THE NUISANCE BLACK FLY, SIMULIUM JENNINGSI(2018) Wilson, Rebecca Cathleen; Lamp, William; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Black flies (Diptera: Simuliidae) can cause pest problems through the females’ blood-seeking behavior. Nuisance black flies are managed through area-wide pest management at the larval stage, which necessitates tracking the distribution of both life stages. The species Simulium jenningsi is a nuisance pest in the mid-Atlantic United States. In Washington County, Maryland, residents began campaigning for state management of S. jenningsi in 2013. In my dissertation I used the localized nature of the S. jenningsi nuisance in western Maryland to investigate the environmental correlates to S. jenningsi abundance patterns and how this pest impacts the lives of residents. Survey responses regarding the annoyance and impact of black flies on resident quality of life were used to assess the societal component of S. jenningsi nuisance. Online respondents, those with children, and those who had lived in the region for a shorter amount of time were more likely to report black flies as “extremely annoying.” Quality of life concerns stemmed from avoidance of exercise and dissatisfaction with preventative strategies. The results contextualized the needs of residents in future management and topics for outreach efforts. Distribution patterns of the host-seeking females were studied within a 2000 km2 area centered on Washington County. High counts of flies were clustered in southern Washington County, although S. jenningsi could be found throughout the sampling area. Regression analysis showed relationships between higher adult fly abundance and environmental factors, including higher elevation, less surrounding impervious surface, and closer proximity to productive larval habitat. The factors associated with immature S. jenningsi abundance were studied at eight sites spanning the Potomac and Shenandoah Rivers. Simulium luggeri, a related species not identified as a pest in Maryland, was also found at each location. S. jenningsi was associated with higher flow velocity and temperature, while S. luggeri was associated with higher seston chlorophyll a content. Both species were associated with higher surrounding tree canopy, implying a possible connection to oviposition cues. Results from this dissertation suggest factors associated with optimal monitoring locations for adult S. jenningsi and indicate management should focus on areas of high flow velocity for larval populations.Item NOVEL ADAPTATIONS IN MORPHOLOGY, DEVELOPMENT, AND NUTRIENT AQUISITION FOR HOST EXPLOITATION IN THE MESOSTIGMATID HONEY BEE PARASITE VARROA DESTRUCTOR(2018) Ramsey, Samuel David; vanEngelsdorp, Dennis; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The parasitic mite Varroa destructor is the most significant single driver of the global honey bee health decline. Better understanding of the association of this parasite and its host is critical to developing sustainable management practices. This work shows that Varroa is not consuming hemolymph as has been the accepted view, but damages host bees by consuming fat body. Feeding wounds in adult bees were imaged for the first time showing that Varroa feed on the underside of the abdomen where fat body is the immediate underlying tissue. Fat body at the wound site showed evidence of external digestion. Hemolymph and fat body in honey bees were then marked with fluorescent biostains. Fluorescence associated with the fat body was consistently detected in the gut of mites fed on these bees while comparatively little fluorescence was detected from the hemolymph biostain. Mites were then fed a diet composed of one or both tissues. Mites fed fat body tissue survived longer and produced more eggs than those fed hemolymph. Mites fed hemolymph showed fitness metrics no different from the starved control group. Collectively, these findings show that Varroa are exploiting the fat body as their primary source of sustenance; a tissue integral to proper immune function, pesticide detoxification, overwinter survival and several other essential processes in healthy adult and immature bees. Additional study was undertaken to better understand how the Varroa accelerates its reproductive rate. Via gel electrophoresis and immunodetection, undigested honey bee vitellogenin was found in Varroa eggs. The presence and identity of these host proteins was confirmed via HPLC MS/MS. This particular cleavage of vitellogenin is found only in the fat body. These findings fundamentally alter our understanding of the etiology of varroosis and underscore a need to revisit our understanding of this parasite and its impacts, both direct and indirect, on honey bee health. Further study of Varroa adaptations focused on expanding knowledge of Varroa morphology with the aim of determining features that can distinguish between Varroa species. Using low temperature scanning electron microscopy, we were able to provide better resolution of key morphological features, detail variability within traits, and provide novel descriptions of certain characters.Item USING A LIVING MULCH AND WOLF SPIDERS TO MANAGE PEST ARTHROPODS IN CUCUMBER(2017) Kahl, Hanna Maria; Hooks, Cerruti; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Pest management practices that conserve beneficial organisms and improve yield are needed. This research aims to determine how: 1) red clover living mulch impacts insect herbivores, arthropod natural enemies, and cucumber quality and yield, and 2) wolf spiders influence cucumber beetles and cucumber plant attributes. Herbivore and natural enemy abundances on cucumber plants in plots with and without interplanted red clover (RC) were compared using foliage searches and sticky cards. Effects of spiders on cucumber beetle behavior, densities, and mortality was assessed in cages with and without a wolf spider and/or their cues. RC plots had fewer striped cucumber beetles and aphids, and more big-eyed bugs and minute pirate bugs. Spotted cucumber beetle densities were reduced and striped cucumber beetle mortality was higher in cages with than without spiders. These studies demonstrated that red clover living mulch and wolf spiders can be used to decrease pest arthropods in cucumber.Item INFLUENCE OF A NATIVE INSECTARY PLANT, CHAMAECRISTA FASCICULATA (MICHX.) ON ORGANIC FIELD CORN AND ARTHROPOD COMMUNITIES(2016) Hunt, Lauren; Hooks, Cerruti R.R.; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Increasing plant diversity in conventionally monoculture agrosystems has been promoted as a method to enhance beneficial arthropod density and efficacy, suppress herbivory and provide a range of ecosystem services. I investigated the pest suppressive potential and economic impact of plant diversification in organic field corn. The experiment consisted of two treatments, corn grown in monoculture (C) and bordered by strips of partridge pea (PP). Pest and natural enemy populations, corn damage, yield, and profits were compared among treatments. Natural enemy and herbivore arthropod populations were affected by treatment and distance from plot border. Corn damage due to pests was also affected by treatment and location, but did not significantly affect yield. Yield in monoculture plots was generally greater than in PP but did not result in greater profit. Pest and natural enemy arthropod abundances were elevated in partridge pea treatment borders, but these populations did not consistently diffuse into plot interiors. The potential causes and implications of findings are discussed.Item Alterations to headwater stream microbial communities and carbon cycling in response to environmental change.(2015) Hosen, Jacob Daniel; Palmer, Margaret A; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Organic carbon, principally as dissolved organic matter (DOM), is a fundamental energy source that powers microbial metabolism and shapes food webs in stream ecosystems. The community structure and metabolic activity of stream microbes are significantly impacted by the quantity and quality (i.e. molecular structure) of organic matter resources. Much of the organic matter in headwater streams originates on landscapes. Thus, external inputs of terrestrial organic carbon shape microbial community structure and, subsequently, food webs of headwater streams. Despite the recognized importance of DOM, there is limited understanding of how stream organic matter resources and bacterial community structure respond to watershed urbanization. I studied DOM quantity and quality, microbial heterotrophic function, and bacterial community composition along a gradient of watershed urbanization in headwater streams of the Parkers Creek watershed (Coastal Plain, Maryland, USA). In Chapter 1, I found that watershed impervious cover was significantly related to stream water DOM composition: increasing impervious cover was associated with decreased amounts of natural humic-like DOM and enriched amounts of anthropogenic fulvic acid-like and protein-like DOM. The DOM found in urbanized streams was more bioavailable, but only during spring and summer experiments. I report in Chapter 2 that microbial heterotrophic enzyme production was not strongly related to urbanization. Instead, enzyme levels were most strongly related to temperature and natural groundwater chemical gradients. I show in Chapter 3 that bacterial community composition and co-occurrence patterns also changed significantly in response to increasing urbanization, becoming more dominated by primary producers common to eutrophic waters. I conclude from my research that watershed urbanization fundamentally alters microbial communities and carbon cycling in headwater streams. This urbanized material is more readily metabolized by microbial communities, but only during warmer months. Increased biodegradation of DOM in warm seasons was related to greater microbial enzyme activity, which generally responds positively to increasing temperature. Thus, rising temperatures with climate change and urbanization combined with altered organic matter content are predicted to result in greater CO2 evasion from urbanized streams.Item Spatial heterogeneity of stink bug (Hemiptera: Pentatomidae) populations in agricultural systems(2014) Venugopal, Dilip; Lamp, William O; Dively, Galen P; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Knowledge on spatial patterns of insect pest populations and the ecological processes influencing these patterns can be directly applied to the management of pests in agricultural systems. Recent increases in stink bug populations, importantly the invasive Halyomorpha halys (Stål 1855), has caused unprecedented economic losses in the mid-Atlantic United States. To inform integrated pest management programs, I quantified the spatial heterogeneity of stink bug population density in field crops at multiple spatial scales (field edge, entire fields and regional), and identified the associated environmental factors and the underlying ecological mechanisms (i.e. climatic tolerances, resource quality and availability). At corn and soybean field edges, highest density of stink bugs was limited to the first few crop rows. At some study sites, fields adjacent to woods and buildings harbored higher density of stink bugs than those adjacent to open areas. Injury to corn kernel damage, and soybean pod and seed increased with stink bug density, and was highest at the field edges. Stink bug density was also positively associated with yield loss in soybean. In entire fields of corn-soybean, H. halys was found in very low density or absent beyond 25m from the field edge. At study sites with high stink bug populations, interpolated density values showed potential dispersal of H. halys, particularly adults and large nymphs, from corn into soybean, coinciding with the end of dough stage in corn and beginning of soybean seed development stage. Temperature and developed areas, and proportion of forest and crop areas were important predictors of regional patterns in H. halys and Chinavis hilaris abundance, respectively. For Euschistus servus, temperature and forest cover influenced patterns at broad spatial scale. Adjacent habitat influence, with highest abundance along woods, on stink bug density was limited to within field scale, and difference in abundance between sites was driven primarily by temperature gradient. These results directly inform field level stink bug management strategies through planting date and orientation of fields in the landscape, and for timing and intensity of treatments, as well as area-wide management. This research also identified roles of temperature and landscape in facilitating or impeding invasive pest populations.Item Community Ecology and Sirex noctilio: Interactions with Microbial Symbionts and Native Insects(2013) Thompson, Brian Matthew; Gruner, Daniel S; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Sirex noctilio is an invasive woodwasp with a global distribution that feeds on the sapwood of pine trees. Wood-feeding in the basal Hymenoptera (sawflies) arose out of sequential adaptations to feeding on nutrient poor and digestively refractive internal plant organs (xylem). Symbiotic association with White-rot fungi are thought to aid overcoming nutritional and digestive barriers, including exceedingly low nitrogen (N) and refractory lignocellulosic polymers. In this dissertation I evaluate wood-feeding relative to nutrition, symbiosis and biotic resistance to invasion of exotic North American habitats in Sirex noctilio [Hymenoptera: Siricidae]. I evaluated nutrient relations within fungal mutualism using: 1) functional morphological analysis of insect feeding, 2) sterol molecules to determine diet sources and 3) metagenomic and isotopic analyses for discovery of novel microbial associates and their associated nutrient pathways. Nutritional constraints of wood feeding are potentially compounded by the presence of diverse fungal and insect communities as they divide the tree resource. I examined the role biotic resistance to Sirex and its fungal mutualist, Amylostereum, in North America using field and laboratory experiments. Morphological evidence supported a role for Amylostereum in external digestion of wood. Observational evidence confirmed Sirex larvae did not ingest wood biomass but preferentially extracted liquid substances via specialized structures of mandibles. Sterol analysis indicated plant compounds as the primary constituent of the diet, while metagenomic analysis of bacteria and their metabolic pathways showed a bacterial microbiome adapted to short chain plant polymers, starch and sugar metabolism. Stable isotopes suggested an additional symbiotic association with nitrogen fixing bacteria enriched the nitrogen deficient food substrate. These studies point toward herbivory with microbial supplementation of nutrients as a tri-partite relationship, pending conclusive identification of the bacterial symbiont for Sirex. Specific constraints of wood feeding by the Sirex-Amylostereum symbiotic complex were antagonized by intraguild predation and fungal competition in North America. Competition interfered with Amylostereum, while intraguild predation accounted for an additional 15% mortality of larval populations. This research describes the evolutionary role of microbial symbionts in wood-feeding in the Hymenoptera and the internal and external constraints to foraging this ubiquitous, yet nutrient poor food resource.