Field Crop 2024, Vol.7, No.3, 182-190 http://cropscipublisher.com/index.php/fc 187 Additionally, the persistence of these chemicals in the soil can lead to long-term changes in microbial diversity and activity, which are crucial for maintaining soil health and plant growth (Modic et al., 2020). 6.2 Impact on beneficial insects Soil insecticides not only target WCR but can also affect non-target beneficial insects, including pollinators and natural predators of pests. For instance, the use of neonicotinoids has been linked to declines in bee populations, which are essential for pollination1. Moreover, beneficial soil organisms such as entomopathogenic nematodes and Pseudomonas bacteria, which can naturally control WCR populations, may also be adversely affected by chemical insecticides (Jaffuel et al., 2019). The reduction in these beneficial organisms can lead to an imbalance in the ecosystem, making crops more vulnerable to other pests and diseases (Jaffuel et al., 2019; Modic et al., 2020). 6.3 Risk of water contamination The application of soil insecticides poses a risk of water contamination through leaching and runoff, which can carry these chemicals into nearby water bodies. This contamination can have detrimental effects on aquatic ecosystems, affecting both flora and fauna. Studies have shown that insecticides like tefluthrin and bifenthrin can persist in the environment and contaminate groundwater and surface water, posing risks to aquatic life and potentially entering the human water supply (Jaffuel et al., 2019; Meinke et al., 2021). The environmental persistence and mobility of these chemicals necessitate careful management and monitoring to mitigate their impact on water quality (Meinke et al., 2018). 7 Resistance Management Strategies 7.1 Insecticide rotation and combination Insecticide rotation and combination are critical strategies to manage resistance in western corn rootworm (WCR). The continuous use of the same class of insecticides has led to the evolution of resistance in WCR populations. For instance, field-evolved resistance to pyrethroids, organophosphates, and carbamates has been documented, significantly reducing the efficacy of these insecticides (Souza et al., 2019; Meinke et al., 2021). Rotating insecticides with different modes of action can help mitigate resistance development. Additionally, combining insecticides with other control methods, such as Bt maize, can enhance overall pest management efficacy. However, it is essential to monitor resistance levels continuously and adjust management strategies accordingly (Souza et al., 2019; Meinke et al., 2021). 7.2 Integrated pest management (IPM) Integrated Pest Management (IPM) is a holistic approach that combines multiple tactics to manage pest populations sustainably. For WCR, IPM strategies include crop rotation, use of resistant hybrids, biological control, and judicious use of insecticides. Crop rotation, in particular, has been shown to be highly effective in reducing WCR populations and minimizing damage without relying solely on insecticides (Furlan et al., 2019). Implementing IPM can delay resistance development and reduce the environmental impact of chemical controls. Studies have demonstrated that IPM practices, such as rotating crops and integrating biological controls, can maintain WCR populations below economic thresholds, thereby reducing the need for insecticides (Furlan et al., 2019; Meinke et al., 2021). 7.3 Genetic approaches and biotechnology Genetic approaches and biotechnology offer promising solutions for managing WCR resistance. Transgenic maize expressing Bt toxins, such as Cry3Bb1 and Cry34/35Ab1, has been widely adopted to control WCR. However, resistance to these Bt traits has emerged, necessitating the development of new strategies (Shrestha et al., 2018; Furlan et al., 2019; Reinders et al., 2021). Pyramiding multiple Bt genes in a single hybrid can provide more robust protection against WCR by targeting different mechanisms of action. Additionally, ongoing research into novel Bt toxins and other genetic modifications aims to enhance resistance management. The use of genetically engineered crops should be integrated with other IPM practices to ensure long-term sustainability and effectiveness (Shrestha et al., 2018; Furlan et al., 2019; Reinders et al., 2021).
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