Bt Research 2025, Vol.16, No.6, 251-258 http://microbescipublisher.com/index.php/bt 254 4 Application Models of Bt in Vector Control 4.1 Environmental release strategies using liquid and granular formulations When using Bt to control mosquitoes, the choice of dosage form is not arbitrary. There are two common types: liquid and granular. They look similar, but in fact, the usage and effects are quite different. Liquid preparations are suitable for rapid diffusion, especially in water areas such as puddles and ponds where mosquito larvae tend to gather. They are effortless to use and show quick results (Huang, 2025). Granular preparations are different. They are more suitable for use in soil or still water, can be released slowly, and have a longer duration of action. These two strategies do not replace each other but each has its own division of labor according to the scenario. Some large-scale vector control projects will be used in combination with the aim of extending the effective time of Bt in the environment as much as possible while minimizing harm to other innocent organisms (Xie et al., 2025). 4.2 Application techniques of Bt biopesticides in aquatic, agricultural, and urban environments The method of spraying pesticides is not the same everywhere. How to use Bt depends on where it is scattered. For instance, in places like ponds, rice fields and irrigation canals, it is usually directly poured into the water, with the main feature being "targeting the larvae". However, in farmlands, especially near livestock breeding areas, the control of other vectors such as midges also needs to be taken into account. Usually, the surface of crops is treated by spraying. But in the city, the situation becomes even more complicated. All kinds of plastic buckets, old tires and drainage ditches may be breeding grounds for mosquitoes. At this point, it is necessary to rely on precise manual spraying or targeted spraying. For instance, when dealing with "old urban residents" like Aedes aegypti mosquitoes, the actions must be quick and the positions accurate. This type of application technique focuses not on large dosage, but on timing and precision control. The aim is to enhance the efficacy of the drug and also reduce environmental stress and drug resistance problems (De Klerk et al., 2024). 4.3 Integrated strategies combining Bt with other control measures (chemical insecticides, biological control agents) Relying solely on Bt to get through is not realistic, especially in some high-incidence areas. So, nowadays, more and more places are adopting a combination of measures. When Bt is used in combination with chemical insecticides, if used properly, it not only enhances the effect but also slows down the emergence of drug resistance. Besides, biological natural enemies are not just for show. Fish that feed on mosquito larvae and predatory insects, once introduced properly, can form a "pincer attack from both inside and outside" situation with Bt. These combinations are not merely aimed at suppressing pests in the short term, but rather at optimizing the medium control effect from a systematic perspective. The comprehensive strategy also means no longer relying solely on insecticides to support the situation, but emphasizing the use of multiple means and moving towards an environmentally friendly and sustainable direction. These concepts have begun to be put into practice in many vector control projects (Huang et al., 2021; Xie et al., 2025). 5 Advantages and Limitations of Bt 5.1 High ecological safety for non-target organisms Not all pesticides are treated equally. Some, once scattered, cause pests to die and beneficial insects to suffer as well. But Bt is not like that. It only targets specific pests and has almost no effect on humans, animals, or even some beneficial insects. For this reason, it is increasingly used in organic agriculture and integrated pest management. Many farmers prefer to choose it not because of its strength, but because it doesn't offend the "innocent". The mode of action of Bt toxin is rather "picky", specifically targeting the intestinal structure of pests, which allows other species to "escape". So from an ecological perspective, it is indeed milder than those broad-spectrum chemical pesticides and more beneficial for protecting biodiversity (Ma, 2024). 5.2 Slow development of resistance and low environmental residues Insects can become smarter, which is almost an unavoidable problem for all pesticides. However, Bt has been much slower in this regard, especially under the premise of rational use. The development speed of its drug resistance is far slower than that of chemical agents. Even if it needs to be applied multiple times, it is unlikely to
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