Molecular Soil Biology 2024, Vol.15, No.3, 140-150 http://bioscipublisher.com/index.php/msb 144 highlighting the importance of considering resistance levels when selecting insecticides. Additionally, a study in Slovenia indicated that soil conditioners mixed with entomopathogenic nematodes could enhance the persistence and effectiveness of biological control agents in different soil types. Environmental conditions, such as temperature and moisture levels, can also affect the performance of soil insecticides, as demonstrated by varying results in field trials conducted over multiple years and locations (Meinke et al., 2021). In conclusion, soil insecticides have proven to be effective in controlling WCR populations and reducing root damage in maize crops. However, their efficacy can be influenced by factors such as resistance levels, soil type, and environmental conditions. Integrating soil insecticides with other management strategies, such as crop rotation and biological control agents, may enhance their effectiveness and contribute to sustainable WCR management. 5 Impact on Maize Yield 5.1 Relationship between WCR infestation levels and maize yield loss The impact of soil insecticides on maize yield is multifaceted, involving the relationship between Western Corn Rootworm (WCR) infestation levels and maize yield loss, a comparative analysis of maize yield with and without soil insecticide application, and the long-term effects of soil insecticide use on maize productivity. WCR infestation levels have a direct and significant impact on maize yield loss. The larvae of WCR feed on maize roots, which impairs the plant's ability to uptake water and nutrients, leading to reduced plant vigor and yield. Studies have shown that higher densities of WCR eggs correlate with increased root damage and subsequent yield loss. For instance, untreated plots with higher egg densities experienced significant yield reductions, while insecticide-treated plots showed less yield loss, indicating the critical role of managing WCR populations to protect maize yield (Ferracini et al., 2021). Additionally, root pruning by WCR larvae has been linked to decreased shoot dry weight and grain yields, further emphasizing the detrimental effects of WCR on maize productivity (Kahler et al., 1987). 5.2 Comparative analysis of maize yield with and without soil insecticide application The application of soil insecticides has been shown to significantly improve maize yield compared to untreated controls. In various studies, soil-applied insecticides led to a reduction in WCR larval density and root damage, resulting in higher grain yields. For example, insecticide-treated plots exhibited an 8% increase in grain yield at physiological maturity compared to untreated plots (Modic et al., 2020). Similarly, the use of different chemical control strategies, including pyrethroid, neonicotinoid, and organophosphate insecticides, resulted in a maximum grain yield increase of up to 19% compared to untreated controls. These findings highlight the effectiveness of soil insecticides in mitigating WCR damage and enhancing maize yield. 5.3 Long-term effects of soil insecticide use on maize productivity The long-term use of soil insecticides has shown consistent benefits in terms of maize productivity. Over multiple years and varying environmental conditions, soil insecticides have consistently reduced WCR larval density and root damage, leading to sustained yield improvements. For instance, a four-year study in Northern Italy demonstrated that soil-applied insecticides provided a steady yield advantage, with a positive yield increase observed in 95% of the production situations evaluated. Additionally, the persistence of entomopathogenic nematodes in soil for extended periods has been shown to provide long-term control of WCR larvae, further supporting the sustainable use of biological control agents alongside chemical insecticides (Blandino et al., 2017). However, it is important to consider the potential for resistance development in WCR populations, as evidenced by reduced efficacy of certain soil insecticides in areas with pyrethroid-resistant WCR populations (Souza et al., 2019). Therefore, integrated pest management strategies, including crop rotation and the use of multiple control tactics, are recommended to maintain the long-term effectiveness of soil insecticides and ensure sustainable maize productivity (Furlan et al., 2022). 6 Resistance Development in WCR 6.1 Mechanisms of resistance development in WCR populations The western corn rootworm (WCR), Diabrotica virgifera virgifera, has demonstrated a remarkable ability to develop resistance to various control measures, including Bt maize and soil insecticides. The mechanisms
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