Browsing by Author "Angelella, Gina M."

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    Conservation Wildflower Plantings Do Not Enhance On-Farm Abundance of Amblyomma americanum (Ixodida: Ixodidae)
    McCullough, Christopher T.; Angelella, Gina M.; O'Rourke, Megan E. (MDPI, 2020-09-09)
    Planting wildflowers is a commonly suggested measure to conserve pollinators. While beneficial for pollinators, plots of wildflowers may be inadvertently performing an ecosystem disservice by providing a suitable habitat for arthropod disease vectors like ticks. The lone star tick, Amblyomma americanum (L.), is a medically important tick species that might be able to utilize wildflower plantings as a suitable habitat. In this two-year study, ticks were sampled using dry ice baited traps from wildflower plots, weedy field margins, and forested areas to determine if wildflower plantings were increasing the on-farm abundance of A. americanum. Abiotic and biotic environmental variables were also measured to better understand which factors affect A. americanum abundance. We found no more A. americanum in wildflower plots than in weedy field margins. Forested areas harbored the greatest number of A. americanum sampled. The height of the vegetation in the sampled habitats was a significant factor in determining A. americanum abundance. Depending on the sampled habitat and life stage, this relationship can be positive or negative. The relationship with vegetation height may be related to the behavior of the white-tailed deer and the questing success of A. americanum. Overall, wildflower plots do not pose an increased risk of exposure to A. americanum on farms.
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    Honey bee hives decrease wild bee abundance, species richness, and fruit count on farms regardless of wildflower strips
    Angelella, Gina M.; McCullough, Christopher T.; O'Rourke, Megan E. (2021-02-05)
    Pollinator refuges such as wildflower strips are planted on farms with the goals of mitigating wild pollinator declines and promoting crop pollination services. It is unclear, however, whether or how these goals are impacted by managed honey bee (Apis mellifera L.) hives on farms. We examined how wildflower strips and honey bee hives and/or their interaction influence wild bee communities and the fruit count of two pollinator-dependent crops across 21 farms in the Mid-Atlantic U.S. Although wild bee species richness increased with bloom density within wildflower strips, populations did not differ significantly between farms with and without them whereas fruit counts in both crops increased on farms with wildflower strips during one of 2 years. By contrast, wild bee abundance decreased by 48%, species richness by 20%, and strawberry fruit count by 18% across all farm with honey bee hives regardless of wildflower strip presence, and winter squash fruit count was consistently lower on farms with wildflower strips with hives as well. This work demonstrates that honey bee hives could detrimentally affect fruit count and wild bee populations on farms, and that benefits conferred by wildflower strips might not offset these negative impacts. Keeping honey bee hives on farms with wildflower strips could reduce conservation and pollination services.
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    Using host‐associated differentiation to track source population and dispersal distance among insect vectors of plant pathogens
    Angelella, Gina M.; Michel, Andy P.; Kaplan, Ian (Wiley, 2018)
    Small, mobile insects are notoriously challenging to track across landscapes and manage in agricultural fields. However, genetic differentiation among insect populations and host plants acquired through host‐associated differentiation could be exploited to infer movement within crop systems and damage potential. Although many insects exhibit host‐associated differentiation, management strategies for insect vectors of plant pathogens assume a homogenous population. Nevertheless, phenotypic changes derived from host‐associated differentiation could manifest in altered behavior or physiology affecting the likelihood of vector–pathogen–plant interactions, or the subsequent efficiency of pathogen transmission. We used SNPs to assess genotypic structure and host‐associated differentiation in the cowpea aphid, Aphis craccivora Koch (Hemiptera: Aphididae). To do so, we sampled A. craccivora across the Midwestern United States. from two host plants, alfalfa (Medicago sativa) and black locust (Robinia pseudoacacia)—putative source populations for winged migrants. Simultaneously, we sampled winged A. craccivora landing in pumpkin fields where they transmit viruses. Structure analyses supported host‐associated differentiation by identifying two major genotypic groups: an alfalfa group containing a single multilocus genotype and a locust group containing all others. Winged locust‐group aphids landed at a much greater magnitude within focal fields during year 2 than year 1, while those in the alfalfa group remained fairly consistent. Spatial autocorrelation analyses indicated locust‐group aphid movement was characterized by small‐scale dispersal during year 2, likely originating from populations within 10 km. We also detected strong temporal differences in colonization from the two host plants. Early in the summer, most winged aphids (79.4%) derived from the locust group, whereas late in the summer more (58.3%) were from the alfalfa group. Because early crop growth stages are more susceptible to damage from aphid‐vectored viruses, these data implicate locust as the more important source and illustrate how host‐associated differentiation can be used to track dispersal and inform management of heterogeneous pest populations.