Molecular Soil Biology 2024, Vol.15, No.3, 140-150 http://bioscipublisher.com/index.php/msb 145 underlying this resistance are multifaceted. For instance, resistance to Bt maize has been linked to non-recessive inheritance, minimal fitness costs, and limited adult dispersal. Additionally, oxidative and hydrolytic metabolism have been implicated in resistance to organophosphate, carbamate, and pyrethroid insecticides, facilitating cross-resistance between these classes. Laboratory studies have shown that WCR populations can evolve resistance to Bt toxins such as Cry3Bb1 and Cry34/35Ab1, with some populations displaying resistance to all commercially available Bt traits (Gassmann et al., 2011). Esterase activity has also been identified as a potential resistance mechanism, with significant elevation observed in resistant populations. 6.2 Case studies of resistance evolution in different regions Field-evolved resistance to Bt maize by WCR has been documented in various regions, particularly in the U.S. Corn Belt. The first cases of resistance were reported in Iowa in 2009, where WCR populations had been exposed to Cry3Bb1 maize for multiple consecutive years. Subsequent studies confirmed that these populations exhibited significantly higher survival rates on Cry3Bb1 maize compared to non-resistant populations (Souza et al., 2019). In Nebraska, field trials revealed that pyrethroid-resistant WCR populations significantly reduced the efficacy of soil-applied insecticides such as bifenthrin and tefluthrin. Another study in Phelps County, Nebraska, demonstrated that resistance to methyl parathion in adult WCR also conferred resistance in larvae, although not to all organophosphate insecticides. These case studies highlight the rapid and widespread evolution of resistance in WCR populations across different regions. 6.3 Management strategies to delay or prevent resistance To delay or prevent the development of resistance in WCR populations, integrated pest management (IPM) strategies are essential. These strategies include rotating fields out of maize production, using soil-applied insecticides with non-Bt maize, and planting refuges of non-Bt maize (Gassmann, 2021). The combination of Bt maize with conventional insecticides has been shown to be ineffective in increasing yield or reducing root injury, suggesting that a more integrated approach is necessary (Petzold-Maxwell et al., 2013). Additionally, early detection and mitigation of resistance through adaptive IRM approaches and proactive, integrated IRM-pest management strategies are crucial. Reducing reliance on single Bt traits and employing a multitactical approach can help mitigate resistance evolution and prolong the effectiveness of current and future transgenic technologies (Gassmann et al., 2019). 7 Environmental and Non-target Effects 7.1 Impact of soil insecticides on soil health and microbial communities The application of soil insecticides to control the western corn rootworm (WCR) has significant implications for soil health and microbial communities. Studies have shown that while soil insecticides can effectively reduce WCR larval density and subsequent root damage, they may also impact the soil's microbial ecosystem. For instance, the use of synthetic insecticides such as tefluthrin and bifenthrin has been associated with alterations in soil microbial populations, potentially disrupting beneficial microbial interactions that are crucial for soil health (Blandino et al., 2017). Additionally, the persistence of these chemicals in the soil can lead to long-term changes in microbial community structure, which may affect nutrient cycling and soil fertility7. On the other hand, biological control methods, such as the application of entomopathogenic nematodes and beneficial bacteria like Pseudomonas, have shown promise in managing WCR populations while promoting soil health. These biological agents not only target WCR larvae but also enhance plant growth and resilience by fostering beneficial microbial communities (Modic et al., 2020). 7.2 Non-target effects on beneficial insects and other soil organisms The use of soil insecticides can have unintended consequences on non-target organisms, including beneficial insects and other soil-dwelling organisms. Beneficial insects such as pollinators and natural predators of pests can be adversely affected by exposure to soil-applied insecticides. For example, the application of tefluthrin and bifenthrin has been shown to reduce the populations of non-target soil organisms, which play essential roles in maintaining soil health and ecosystem balance (Souza et al., 2019). Moreover, the disruption of these beneficial organisms can lead to secondary pest outbreaks, further complicating pest management efforts. In contrast,
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