Journal of Mosquito Research 2024, Vol.14, No.2, 67-75 http://emtoscipublisher.com/index.php/jmr 68 1Bti Application Strategies in Aquaculture 1.1 Application methods of Bti in aquaculture environment Bacillus thuringiensis var. israelensis (Bti) in aquaculture environments requires careful planning of its application time, concentration and frequency to achieve optimal mosquito larvae control. Generally, Bti applications should be timed to match the mosquito's life cycle, especially during peak larval hatching. In addition, the application concentration should be sufficient to kill most mosquito larvae but not have a negative impact on aquaculture organisms or the environment. The frequency of application needs to be determined based on the mosquito's breeding cycle and the continued activity of Bti in a specific water environment. In most cases, periodic application of Bti can effectively interrupt the mosquito life cycle, thereby reducing the number of adult mosquitoes. Ângelo et al. (2015) used response surface methodology to optimize the culture medium for Bti in their study. This optimization process not only increased the production of Bti, but also provided a basis for the development of effective application strategies. The optimized culture medium can support Bti to produce higher concentrations of toxins, thereby achieving lower LC50 values in practical applications, that is, a lower concentration of toxin required to kill half of the target organisms. Schneider et al. (2015) developed a specific PCR method for Bti, providing an effective tool for monitoring the distribution and concentration of Bti in aquaculture environments. This method can help researchers and farm managers accurately determine the presence of Bti and evaluate the effectiveness of its application methods, ensuring that the application concentration and frequency achieve the desired mosquito larval control effect while avoiding potential negative impacts on the environment and non-target organisms. Melo et al. (2018) further emphasized the importance of cultivating Bti in bioreactors to improve its application in aquaculture. By cultivating Bti on a large scale under controlled conditions, researchers were able to obtain high-density, high-activity Bti cultures, which is essential for achieving effective mosquito larvae control. In addition, bioreactor cultivation also provides more precise experimental conditions for studying the optimal application time, concentration and frequency of Bti, making the application strategy of Bti more scientific and effective. 1.2 Effect of different Bti formulations on the effect Different formulations of Bti, such as suspended particles and solutions, have a significant impact on its effectiveness. Planktonic formulations are particularly suitable for use in static or slow-moving water bodies due to their longer duration and ability to form a coating on the surface of the water. This formula effectively attracts and kills surface-feeding mosquito larvae. In contrast, solution formulas are more suitable for fast action and are suitable for fast-moving water bodies or situations where mosquito larvae populations need to be reduced immediately. The adaptability of different formulas to specific water types and mosquito larvae densities determines their effectiveness and economy in practical applications. Iors et al. (2015) emphasized the importance of formulation to improve Bti activity by using multiple carbon sources to develop a new Bti feed batch method. This study shows that by optimizing the carbon source, Bti production and toxicity can be significantly improved, thereby reducing the required Bti concentration in practical applications and achieving increased cost-effectiveness. This is particularly important for large-scale application of Bti for mosquito larvae control, especially in resource-constrained aquaculture sites. Zghal et al. (2018) improved the yield and effectiveness of Bti biopesticides by optimizing culture media based on agricultural by-products. Their study not only demonstrated the impact of different formulations on the effectiveness of Bti, but also highlighted the impact of environmental factors, such as culture medium composition, on the expression of Bti toxicity. By optimizing the composition of the culture medium, a significant increase in Bti toxin production was achieved, which is of great significance for achieving effective mosquito larvae control.
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