Molecular Entomology 2024, Vol.15, No.5, 179-191 http://emtoscipublisher.com/index.php/me 181 the corn rootworm, significantly reducing their impact on crop yields. These biochemicals are environmentally safe and effective at low doses, making them attractive alternatives to conventional pesticides (Kumar et al., 2021). Another category of biochemical biopesticides is plant-derived Volatile Organic Compounds (VOCs), which can repel or inhibit pests. For example, VOCs from certain fungi or plants are used to protect stored maize from pests such as the maize weevil (Sitophilus zeamais). These compounds have shown significant potential in controlling pest populations while being non-toxic to humans and beneficial insects. Although biochemical biopesticides are highly specific and environmentally friendly, their use is often limited by high production costs and the need for advanced delivery systems (Herrera et al., 2015). 1.4 Insect-resistant transgenic maize as a biopesticide Insect-resistant transgenic maize, such as Bt maize, is a form of biopesticide that involves the insertion of genes fromBacillus thuringiensis into the maize genome. This enables the plant to produce insecticidal proteins that target specific pests like the European corn borer and the corn rootworm. The introduction of Bt maize in the 1990s revolutionized pest control in maize cultivation by reducing the need for external pesticide applications. The insecticidal proteins produced by Bt maize disrupt the digestive system of target pests, causing paralysis and death while being harmless to humans and most non-target organisms (Osman et al., 2015). Bt maize has been highly effective in reducing pest populations and protecting maize crops from significant damage. However, the long-term use of transgenic crops has led to concerns about pest resistance. Some insect populations, such as the corn rootworm, have developed resistance to the Bt toxins, diminishing the effectiveness of transgenic crops over time. To counteract this, newer varieties of transgenic maize have been developed that express multiple Bt toxins or combine Bt traits with other pest management strategies to delay resistance development (Gassmann and Clifton, 2017). Transgenic maize also offers benefits beyond pest control, such as reducing the environmental impact of chemical pesticide use and lowering production costs for farmers. By incorporating biopesticidal traits directly into the crop, the need for chemical pesticide applications is significantly reduced. However, the adoption of transgenic crops is met with regulatory and market challenges in some regions, where concerns over genetically modified organisms (GMOs) persist. Despite these challenges, Bt maize continues to be a cornerstone of modern maize IPM programs and offers significant potential for the future of sustainable agriculture (Nyangau et al., 2020). 2 Mechanisms of Action 2.1 How microbial biopesticides affect pest populations Microbial biopesticides are derived from organisms such as bacteria, fungi, and viruses, and their mode of action involves various biological mechanisms. For instance, Bacillus thuringiensis (Bt) produces toxins that disrupt the gut of lepidopteran pests like the corn borer, leading to their death. These toxins are highly specific, only affecting certain insect species while being harmless to humans and non-target organisms (Kulkarni, 2015). Another mechanism involves fungal biopesticides, such as Metarhizium rileyi, which penetrate the insect's cuticle and proliferate inside the host, eventually causing the pest to die. This fungus has shown high efficacy against pests like the fall armyworm, a major threat to maize crops (Grijalba et al., 2018). These microbial biopesticides can also work by inducing systemic resistance in plants, helping crops to better defend themselves against future pest attacks.Some microbial biopesticides, particularly bacteria, compete with pests for resources such as nutrients or space, reducing the ability of harmful organisms to establish themselves on the plant. For example, some strains of beneficial bacteria produce antimicrobial substances that inhibit the growth of harmful pathogens or compete for iron by producing siderophores, making the environment less favorable for pest growth (Roca-Couso et al., 2021). 2.2 Mode of action of botanical biopesticides Botanical biopesticides, derived from plant extracts, affect pests through multiple pathways. Neem (Azadirachta
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