Browsing by Author "McCullough, Christopher T."

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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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    The effects of wildflower plots and diverse landscapes on ecosystem services, bee communities, and on-farm tick abundance
    McCullough, Christopher T. (Virginia Tech, 2020-06-03)
    Conservation of natural habitats and planting wildflower plots are two commonly promoted tactics to enhance pollination services and biological control of crop pests, which are ecosystem services that can improve agricultural outputs. There are several programs at various levels of government in the United States that landowners can use to defray the costs of implementing these conservation strategies. Studies of European Agricultural Environmental Schemes have shown these tactics to have positive outcomes for crop production. However, real-world applications of cost-sharing programs have not been evaluated in the United States on pollination services and biological control. Furthermore, these tactics may inadvertently perform ecosystem disservices, like increasing crop pests or creating habitat for disease vectors. In this study, we evaluated the effects of natural habit and wildflower plots on biological control, pollination services, bee communities, and tick populations in Eastern Virginia and Maryland. This research was conducted on 22 farms. 10 of these farms had wildflower plots that were designed by Natural Resource Conservation Service personnel, and implemented by cooperating farmers. Collards, strawberries, tomatoes, and squash were used as model systems. We measured pest density, sentinel egg predation, crop damage, seed pollination, biomass production, marketable crop yield, sampled the bee community, and recorded tick abundance in wildflower plots. Many of the measures of biological control and pollination services had idiosyncratic results in regards to the wildflower plots and natural habit in the landscape. However, the proportion of high quality yield for all four crops increased with increasing natural habitat in the landscape. Bee communities between sites with and without wildflower plots were not different. Bee abundance did increase at wildflower sites when natural habitat comprised a certain proportion of the habitat around the site. Ticks were sampled from wildflower plantings, but not in greater abundance compared to field margins. In this study, the effects of wildflower plots were overshadowed by the landscape effects of natural habitat. Government personnel that oversee these programs may need to consider the surrounding landscape when helping implement on-farm conservation measure like wildflower plots. Such measures, do not perform an ecosystem disservice in regards to ticks.
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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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    Pest Management Needs and Limitations for Corn Earworm (Lepidoptera: Noctuidae), an Emergent Key Pest of Hemp in the United States
    Britt, Kadie E.; Kuhar, Thomas P.; Cranshaw, Whitney; McCullough, Christopher T.; Taylor, Sally V.; Arends, Benjamin R.; Burrack, Hannah; Pulkoski, Melissa; Owens, David; Tolosa, Tigist A.; Zebelo, Simon; Kesheimer, Katelyn A.; Ajayi, Olufemi S.; Samuel-Foo, Michelle; Davis, Jeffrey A.; Arey, Nathan; Doughty, Hélène; Jones, Joanne; Bolt, Marguerite; Fritz, Bradley J.; Grant, Jerome F.; Cosner, Julian; Schreiner, Melissa (Oxford University Press, 2021-09-11)
    Corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), has emerged as an injurious insect pest to hemp, Cannabis sativa L., a crop newly reintroduced to the United States. Growing hemp presents a potential alternative economic opportunity for farmers but can be challenging with a market that is unstable and just developing. One of the most notable production challenges is managing corn earworm, an insect pest that is particularly damaging when it feeds on flower buds produced in cannabinoid varieties, creating extensive bud tunneling and wounds that allow entry of pathogens that can aid development and presence of bud rot. Damage to seeds is of lesser concern in hemp cultivars grown for grain and minimal risk is associated with hemp grown for fiber. Our ability to research hemp has only recently been allowed as production was largely suspended following World War II and, as such, there has been limited opportunity to develop information for empirically-based pest management recommendations. Further complicating development of integrated pest management (IPM) strategies are regulatory challenges associated with providing registration support to add hemp to pesticide labels, as it was not formally recognized as a crop by U.S. regulatory agencies until late 2019. Research needs and challenges to develop effective IPM programs for corn earworm on hemp are discussed here.
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    Phenology and Dispersal of the Wheat Stem Sawfly (Hymenoptera: Cephidae) Into Winter Wheat Fields in Nebraska
    McCullough, Christopher T.; Hein, Gary L.; Bradshaw, Jeffrey D. (2020-08)
    Historically, the wheat stem sawfly, Cephus cinctus Norton was a pest in spring wheat-growing regions of the northern Great Plains. However, in the 1980s, it was found infesting winter wheat fields in Montana. Infestations were first detected in western Nebraska in the 1990s, and have since spread throughout the Nebraska Panhandle. Larval damage occurs from stem-mining, but stem girdling that results in lodged stems that are not harvested results in the greatest yield losses.The biology and phenology of the wheat stem sawfly are well described in the northern portion of its range, but they are lacking in Colorado, southeast Wyoming, and Nebraska. In this study, the phenology and dispersal of the wheat stem sawfly in Nebraska winter wheat fields is described using sweep net and larval sampling. During this 2-yr study, adult activity began on May 23 and ended on June 21. Adult sex ratios were 2.32 males per female in 2014 and 0.46 males per female in 2015. Both sexes demonstrated an edge effect within the wheat fields, with greater densities near the field edge.The edge effect was stronger for male wheat stem sawfly than females. Wheat stem sawfly larval density also had an edge effect, regardless of the density of female wheat stem sawfly present. This information will be useful for developing management plans for the wheat stem sawfly in Nebraska and neighboring regions.