Journal of Mosquito Research 2024, Vol.14, No.2, 67-75 http://emtoscipublisher.com/index.php/jmr 69 Gopinathan and Shalini (2022) further demonstrated the potential of formulation improvement to enhance Bti activity. By chemically pretreating rice straw as a cost-effective Bti culture medium, they found that the pretreated rice straw not only provided a rich source of nutrients but also enhanced the growth and toxicity expression of Bti by improving the physical and chemical properties of the culture medium. This approach provides a feasible strategy for developing new, efficient, and low-cost Bti formulations. 1.3 Influence of environmental conditions The activity of Bti is affected by a variety of environmental conditions, including water type, temperature, and pH. The type of water, such as ponds, ditches, or rice fields, affects the uniformity and duration of Bti distribution. Temperature is another key factor. Too high or too low temperatures may affect the activity of Bti toxins. Generally, warm environments help Bti to be active, but extreme high temperatures may reduce its effectiveness. pH also has an important impact on Bti. Overly acidic or alkaline water environments can destroy the stability of Bti spores, thereby affecting their insecticidal effects. Therefore, when planning a Bti application strategy, these environmental conditions must be taken into account, and the application plan must be adjusted as much as possible to adapt to these conditions to ensure that Bti is optimally effective. Allgeier et al. (2018) revealed the important impact of temperature on Bti activity through research on European common frog larvae. This study found that although Bti exposure did not significantly affect the survival rate and metamorphosis completion time of larvae, it caused a significant increase in the activities of detoxifying enzymes and antioxidant enzymes, suggesting that environmental temperature may regulate the effects of Bti by affecting metabolic activities. Brühl et al. (2020) shows that Bti, as an environmentally friendly and effective biopesticide for specific targets, may behave differently in different types of water bodies depending on the complexity of the ecosystem. For example, static or slow-flowing water bodies, such as ponds and rice fields, are more suitable for Bti's floating particle formula, because this formula can form a stable covering layer on the water surface, effectively targeting surface-feeding mosquito larvae. However, characteristics of this ecosystem may also lead to impacts at the food web level, and further assessment of the long-term ecological effects of Bti use is needed. Gutierrez-Villagomez et al. (2021) indirectly reflected the possible impact of pH value on Bti activity by evaluating the impact of Bti commercial formulations on tadpoles. Research shows that although Bti has little effect on the survival rate, body length, weight and other indicators of tadpoles, it causes significant changes in the composition of the intestinal microbial community. This change may reflect the potential impact of Bti on interactions among ecosystem members under different pH conditions. 2 Ecological and Environmental Impacts of Bti 2.1 The control effect of Bti on target mosquito larvae populations Bacillus thuringiensis var. israelensis (Bti) has been widely recognized in controlling target mosquito larval populations, especially against important disease-transmitting mosquito species such as Aedes aegypti. Begum et al. (2015) showed that the use of Bti aqueous suspension for the third and fourth instar larvae of Aedes aegypti reared in the laboratory can achieve the highest lethality rate of 96.66%, with an LC50 of 1.0 μl/ml. The value is 0.0097. This result highlights that Bti has a significant control effect on the target mosquito larvae population at a specific concentration (Figure 1). Additionally, Bti-CECIF is a biopesticide designed and developed in solid tablet form for the control of disease vector mosquitoes. An evaluation of the effectiveness and residual activity of Aedes aegypti larvae by Wilber Gómez-Vargas et al. (2018) in semi-field and field conditions in two Colombian municipalities showed that the highest tested dose showed the greatest residual activity after 15 days, with Postlarval mortality is 80%. Suwito et al. (2021) examined the effectiveness of Bti H-14 biopesticide in controlling (Aedes spp.) larval density. Continuous observation of 3171 containers in household containers found that Bti H-14 was highly effective in controlling larval density over a 6-month period. These research results not only confirm the efficient killing
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