Browsing by Author "Nikoukar, Atoosa"

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    Ecology and management of wireworms (Coleoptera: Elateridae) in conventional and organic production systems
    Nikoukar, Atoosa (Virginia Tech, 2024-06-12)
    Wireworms are the subterranean larval stage of click beetles (Coleoptera: Elateridae), generalist herbivores that feed on a wide range of crops and cause serious damage. Wireworm management is challenging due to their long life cycle, subterranean habitat, wide range of host plants, and lack of effective chemical approach in most crops. Thus, developing an effective alternative control approach is an urgent need. The overall aim of this research study was to evaluate alternative [to insecticides] tactics that could be used as components of effective IPM strategies against wireworms. In Chapter 1 we provide an overview of wireworm's biology and management practices. In Chapter 2 we focused on biological control to evaluate the efficacy of entomopathogenic nematodes and fungi as single and mixed application against Limonius californicus and L. infuscatus in organic vegetable farms. The results showed the higher efficacy of commercial EPN, Steinernema feltiae, against Limonius species than entomopathogenic fungi. In Chapter 3, we focused on cultural control as a component of integrated pest management for wireworm control. We evaluated the efficacy of brown and yellow mustard and their byproducts, including defatted seed meal and seed meal concentrated extract against Limonius spp. Our finding indicated the effectiveness of brown mustard concentrated extract on reducing the wireworm population. However, it has a negative impact on the field-residing entomopathogenic nematodes. In Chapter 4, in the component of cultural control, we evaluated the wireworm, L. californicus, preference to three different crops, pea, bean, and wheat, for identifying an effective trap crop. We also quantified CO2 and organic volatile compounds released from each plant's root and evaluated the wireworm response toward the synthetic volatiles. Detailed results are provided in chapter 4. Finally, we looked at the novel new technology of RNA interference to find the effective target genes in wireworms for application as bioinsecticides and/or transgenic plants to control wireworms. In the concluding chapter, Chapter 6, we summarized our findings on the efficacy of different management tactics, biological, cultural, and molecular, to control Limonius species in cereals and organic production systems.
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    Integrated Pest Management of Wireworms (Coleoptera: Elateridae) and the Rhizosphere in Agroecosystems
    Nikoukar, Atoosa; Rashed, Arash (MDPI, 2022-09)
    The name 'wireworm' refers to the subterranean larvae of click beetle (Coleoptera: Elateridae) species, of which several are serious pests of a wide range of crops. The limited effectiveness of the available insecticides, their wide host range, their long life cycle, and their cryptic subterranean habitat make wireworms a challenging pest to control. Integrated pest management (IPM) strategies have been recommended to reduce wireworm damage. Although IPM is generally considered to be an approach that is relatively more compatible with the environment and non-target organisms, the implementation of some of the tactics of managing subterranean wireworms is expected to induce stress in the rhizosphere and the established ecological interactions within, some of which could negatively impact various soil health parameters and, subsequently, plant growth. In this paper, we highlight some of the IPM tactics against wireworms and their effects on the rhizosphere and soil microbiome. Awareness of the potential impacts of IPM approaches to the management of subterranean pests will help professionals to develop and implement IPM strategies that minimize disturbance in the rhizosphere and support agroecosystem sustainability. The rhizosphere is where plant roots, physical soil, and subterranean organisms interact to contribute to soil fertility and plant growth. In agroecosystems, the nature of the ecological interactions within the rhizosphere is highly dynamic due to constant disruptions from agricultural practices. The concept of integrated pest management (IPM) was developed in order to promote an approach which is complementary to the environment and non-target organisms, including natural enemies, by reducing the sole reliance on synthetic pesticides to control pests. However, some of the implemented integrated cultural and biological control practices may impact the rhizosphere, especially when targeting subterranean pests. Wireworms, the larval stage of click beetles (Coleoptera: Elateridae), are generalist herbivores and a voracious group of pests that are difficult to control. This paper introduces some existing challenges in wireworm IPM, and discusses the potential impacts of various control methods on the rhizosphere. The awareness of the potential implications of different pest management approaches on the rhizosphere will assist in decision-making and the selection of the control tactics with the least long-term adverse effects on the rhizosphere.