Entomology

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    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.
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    Effects of post-harvest management practices on the degradation of Bacillus thuringiensis proteins in genetically modified corn residue
    (2018) Johnson, Veronica; Hooks, Cerruti RR; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Most studies addressing the ecological effects of Bt crops have focused on non-target effects during the crop growing cycle. Less information is available on the fate of expressed toxins in crop residue after harvest in a no-till production system. This research investigated the effects of four post-harvest management practices on the degradation rates of Cry proteins expressed in SmartStax field corn. Cry protein degradation expressed as growth inhibition of Ostrinia nubilalis larvae after harvest was measured by a feeding bioassay, and enzyme-linked immunosorbent assays were used to detect the presence of Cry proteins. Cry proteins retained significant levels of biological activity at crop senescence and were still present in corn residue for more than 20 weeks after harvest. Despite inconsistencies in treatment effects, the study demonstrated that post-harvest practices that increase soil-residue contact increase protein degradation, thereby reducing the period of exposure for non-target organisms.
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    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.
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    POLLEN NUTRITION, PESTICIDES, AND PATHOGENS: INTERACTIVE EFFECTS ON HONEY BEE HEALTH
    (2017) Garavito, Andrew; vanEngelsdorp, Dennis; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    While a variety of stressors influence honey bee (Apis mellifera) health, it is the additive and interactive effects of these factors on bee health that have been driving modern research. We devised a set of two experiments to test the effects of multiple stressors on honey bee health. First, we grew sunflowers to test the effects of drought stress and seed treatment on sunflower pollen. We fed the pollen collected from these sunflowers to cohorts of bees that were either infected or uninfected with the microsporidian pathogen Nosema ceranae to find that drought stressed pollen leads to increased mortality in infected bees. Next, we fed 37 experimental pollen diets of different floral varieties and pesticide loads to honey bees infected with N. ceranae, but we were unable to find a connection between diet variety and pesticide exposure on bee health.
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    The Effect of Barley Cover Crop Residue and Herbicide Management on the Arthropod Community in No-Till Soybeans
    (2016) Rosario-Lebron, Armando; Hooks, Cerruti RR; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Cover cropping has long been used as a method of reducing soil erosion, increasing soil quality and suppressing weeds. However, effects of cover crops in local farming systems are varied and can be affected by timing and method of cover crop termination. We conducted two field studies each in Upper Marlboro and Beltsville, Maryland between 2013 and 2014. The study consisted of three cover crop and one Fallow(F) treatments. Cover crop treatments were Early-Kill (EK) and Late-Kill in which the cover crop was killed with a post-emergent herbicide in late April and May, respectively; and flail mow (FM), in which a flail mower was used to terminate the cover crop in late May. In 2013 and 2014, plant sucking insects were consistently more numerous in EK than LK treatment. Our findings suggest chemical and mechanical termination on cover crops produce similar results on arthropod populations.
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    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.
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    UNDERSTANDING THE RELATIONSHIP BETWEEN THE BROWN MARMORATED STINK BUG, HALYOMORPHA HALYS (STÅL), AND ITS SYMBIONT, PANTOEA CARBEKII, WITH IMPLICATIONS FOR STINK BUG MANAGEMENT
    (2016) Taylor, Christopher Michael; Mitter, Charles; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Symbiotic relationships between insects and beneficial microbes are very common in nature, especially within the Hemiptera. The brown marmorated stink bug, Halyomorpha halys Stål, harbors a symbiont, Pantoea carbekii, within the fourth region of the midgut in specialized crypts. In this dissertation, I explored this insect- microbe relationship. I determined that the brown marmorated stink bug is heavily reliant on its symbiont, and that experimental removal of the symbiont from the egg mass surface prior to nymphal acquisition led to lower survival, longer development, lower fecundity, and aberrant nymphal behavior. Additionally, I determined that even when the symbiont is acquired and housed in the midgut crypts, it is susceptible to stressors. Stink bugs reared at a higher temperature showed lower survival, longer development, and a cease in egg mass production, and when bugs were screened for their symbiont, fewer had successfully retained it while under heat stress. Finally, with the knowledge that the stink bug suffers decreases in fitness when its symbiont is missing or stressed, I wanted to determine if targeting the symbiont was a possible management technique for the stink bug. I tested the efficacy of a number of different insecticidal and antimicrobial products to determine whether prevention of symbiont acquisition from the egg mass was possible, and results indicated that transmission of the symbiont from the egg mass to the newly hatched nymph was negatively impacted when certain products were applied (namely surfactants or products containing surfactants). Additionally, direct effects on hatch rate and survival were reported for certain products, namely the insect growth regulator azadirachtin, which suggests that nymphs can pick up residues from the egg mass surface while probing for the symbiont. I conclude that P. carbekii plays a critically important role in the survival of its host, the brown marmorated stink bug, and its presence on the egg mass surface before nymphal hatch makes it targetable as a potential management technique.
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    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.