Bt Research 2024, Vol.15, No.5, 248-256 http://microbescipublisher.com/index.php/bt 250 encapsulation methods, such as spray drying, coacervation, and supercritical fluid technology, have been explored to produce micro- and nanoparticulate systems (Junior et al., 2021). For example, spray drying can be optimized to produce microspheres with controlled release properties, enhancing the long-term efficacy of the biopesticides. The use of Pickering emulsions for single-cell encapsulation has shown promise in improving the distribution and stability of Bt formulations, leading to higher pest control activity (Yaakov et al., 2018). The development of micro-emulsions has also been effective in reducing the diameter of microcapsules, thereby increasing the insecticidal activity of Bt formulations (Barrera-Cortés et al., 2017). 3 Improving Bt Biopesticide Stability 3.1 Strategies to prevent degradation in harsh environments Bt biopesticides are susceptible to degradation by environmental factors such as ultraviolet (UV) radiation, temperature, and humidity. One effective strategy to prevent degradation is the use of microencapsulation techniques. For instance, encapsulating Bt in materials that provide a protective barrier can significantly reduce the impact of UV radiation and other environmental stressors. A novel formulation technology involving the microencapsulation of baculoviruses in ENTOSTAT wax combined with titanium dioxide (TiO2) has been shown to protect the viral DNA from UV degradation, thereby extending the efficacy of the biopesticide (Wilson et al., 2020). The use of nanotechnology has been explored to enhance the stability of biopesticides. Nanoencapsulation can provide controlled release kinetics and prevent the premature degradation of active ingredients under harsh environmental conditions (Kumar et al., 2019). 3.2 Enhancing shelf life through additives The shelf life of Bt biopesticides can be significantly improved by incorporating various additives into the formulation. Additives such as antioxidants, stabilizers, and UV protectants can help maintain the bioactivity of Bt over extended periods. For example, the use of tea polyphenols as antioxidants has been shown to effectively inhibit the degradation of bioactive substances in microencapsulated formulations, thereby enhancing their stability and shelf life (Meng et al., 2022). Moreover, the incorporation of natural quaternary ammonium ionic liquids in microcapsules has demonstrated improved stability and prolonged effectiveness of the encapsulated biopesticides (Zhou et al., 2021). 3.3 Microencapsulation for controlled release Microencapsulation is a promising strategy for the controlled release of Bt biopesticides. This technique involves encapsulating the active ingredients in a protective matrix, which can be designed to release the biopesticide in a controlled manner over time. Various microencapsulation techniques, such as spray drying, coacervation, and electrospraying, have been employed to create micro- and nanoparticulate systems for Bt formulations (Oliveira et al., 2021). For instance, the use of double-shelled mesoporous silica microcapsules has been shown to provide pH-responsive release properties and good stability in soil, thereby extending the duration of the biopesticide's effectiveness. The development of enzyme-responsive nanoparticles containing botanical compounds has demonstrated increased selectivity and specificity in pest management, contributing to more sustainable agricultural practices (Monteiro et al., 2021). 4 Enhancing Efficacy of Bt-based Biopesticides 4.1 Synergistic additives The efficacy of Bt-based biopesticides can be significantly enhanced through the use of synergistic additives. For instance, the addition of boric acid has been shown to increase the activity of Bacillus thuringiensis (Bt) by 2.9-fold against Spoladea recurvalis larvae, demonstrating a substantial increase in larval mortality. Similarly, the combination of Bt with gold nanoparticles and deltamethrin has been explored to address resistance issues, showing promising results in stabilizing the biopesticide complex and enhancing pest control efficacy (Narkhede et al., 2016). The compatibility of Bt biopesticides with adjuvants such as LI has been found to increase growth and sporulation, further improving the effectiveness against pests like Spodoptera frugiperda(Santos et al., 2021).
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