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Bt Research 2025, Vol.16 http://microbescipublisher.com/index.php.bt © 2025 MicroSci Publisher, an online publishing platform of Sophia Publishing Group. All Rights Reserved. Sophia Publishing Group (SPG), founded in British Columbia of Canada, is a multilingual publisher. MicroSci Publisher is an international Open Access publisher specializing in microbiology, bacteriology, mycology, molecular and cellular biology and virology registered at the publishing platform that is operated by Sophia Publishing Group (SPG), founded in British Columbia of Canada. Publisher MicroSci Publisher Edited by Editorial Team of Bt Research Email: edit@bt.microbescipublisher.com Website: http://microbescipublisher.com/index.php/bt Address: 11388 Stevenston Hwy, PO Box 96016, Richmond, V7A 5J5, British Columbia Canada Bt Research (ISSN 1925-1939) is an open access, peer reviewed journal published online by MicroSciPublisher. The journal is publishing high quality original research on all aspects of Bacillus thuringiensis and their toxins affecting the living organisms, as well as environmental risk and public policy relevant to Bt modified organisms. Topics include (but are not limited to) Bt strain identification, novel Bt toxin discovery and bioassay, transgenic Bt plants, insecticidal mechanism of Bt toxin as well as resistant mechanisms of target-insect to Bt toxin. All the articles published in Bt Research are Open Access, and are distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. MicroSciPublisher uses CrossCheck service to identify academic plagiarism through the world’s leading plagiarism prevention tool, iParadigms, and to protect the original authors’ copyrights.
Bt Research (online), 2025, Vol. 16, No. 6 ISSN 1925-1939 http://microbescipublisher.com/index.php/bt © 2025 MicroSci Publisher, an online publishing platform of Sophia Publishing Group. All Rights Reserved. Sophia Publishing Group (SPG), founded in British Columbia of Canada, is a multilingual publisher. Latest Content Overcoming Insect Resistance to Bt Toxins: Strategies and Innovations Jia Xing, Wenzhong Huang Bt Research, 2025, Vol. 16, No. 6, 234-241 Applications of Remote Sensing and GIS in Monitoring the Use of Bt Bioinsecticides Lin Liu, Dandan Huang Bt Research, 2025, Vol. 16, No. 6, 242-250 Bt as a Tool for Controlling Vector-Borne Diseases Jun Wang, Qikun Huang Bt Research, 2025, Vol. 16, No. 6, 251-258 Regulatory Framework and Risk Assessment of Bt Transgenic Crops Zhonggang Li, Xiaojie Liu Bt Research, 2025, Vol. 16, No. 6, 259-268 The Role of Plasmids in the Metabolic Diversity of Bt Chengxi Wang, Qiangsheng Qian, Danyan Ding Bt Research, 2025, Vol. 16, No. 6, 269-277
Bt Research 2025, Vol.16, No.6, 234-241 http://microbescipublisher.com/index.php/bt 234 Review Article Open Access Overcoming Insect Resistance to Bt Toxins: Strategies and Innovations Jia Xing 1, Wenzhong Huang 2 1 Tropical Animal Resources Research Center, Hainan Institute of Tropical Agricultural Resources, Sanya, 572025, Hainan, China 2 Biomass Research Center, Hainan Institute of Tropical Agricultural Resouces, Sanya, 572025, Hainan, China Corresponding email: wenzhong.huang@hitar.org Bt Research, 2025, Vol.16, No.6 doi: 10.5376/bt.2025.16.0026 Received: 05 Sep., 2025 Accepted: 10 Oct., 2025 Published: 18 Nov., 2025 Copyright © 2025 Xing and Huang, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Xing J., and Huang W.Z., 2025, Overcoming insect resistance to Bt toxins: strategies and innovations, Bt Research, 16(6): 234-241 (doi: 10.5376/bt.2025.16.0026) Abstract Bacillus thuringiensis (Bt) toxin, which is widely used in genetically modified crops, has significantly reduced pest damage and the use of chemical pesticides worldwide. However, the rapid evolution of insect resistance to Bt toxins has become the main obstacle restricting the sustainability of Bt technology, seriously threatening the long-term stability of the integrated pest management system. This study systematically reviews the currently revealed resistance mechanisms, including receptor gene mutations, enhanced detoxification metabolic pathways, and behavioral adaptations, discusses field population resistance monitoring methods and resistance evolution dynamics, and summarizes multiple molecular and biotechnological strategies for overcoming resistance. This includes the "gene pyramid" technology of superimposing multiple Bt genes, the combined use of Bt toxins and RNA interference (RNAi) to enhance insecticidal effects, and the use of gene editing tools such as CRISPR to target and destroy genes related to insect resistance. By analyzing typical cases from the United States, China, India and other places, this study evaluated the successful experiences and failure reasons of resistance management strategies, highlighting the importance of comprehensive governance and scientific supervision. This research holds significant theoretical and practical value for extending the effective lifespan of Bt crops, reducing pesticide dependence, and promoting the construction of a green agricultural system. Keywords Bt toxin; Resistance mechanism; Gene pyramid technology; RNA interference; Resistance management strategy 1 Introduction In the mid-1990s, Bt crops were officially launched on the market. Since then, Cry proteins, especially the type secreted by Bacillus thuringiensis (Bt), have appeared more and more frequently in cotton, corn and soybeans. These crops rely on the Bt toxins they express to deal with the stubborn Lepidoptera and Coleoptera pests in the fields, indeed saving a lot of trouble with chemical pesticides. The second-generation Bt crops composed of multiple Cry proteins have also been used to deal with a wider range of pest populations while delaying the emergence of resistance (Tabashnik, 2015). They not only increased crop yields, but also demonstrated obvious advantages in environmental protection and pesticide reduction. In addition, Bt toxins have a relatively small impact on non-target organisms, and they have become an indispensable part of the global integrated Pest management (IPM) system. However, to be fair, this "pest control tool" of Bt crops is not without flaws. As time went by, some insects gradually "figured out the tricks" of Bt toxins. In many countries, it has been confirmed that several pest varieties have developed resistance to Bt. This situation has been particularly prominent in the past two decades, especially in crops that express only one Cry protein (Jurat-Fuentes et al., 2021). Where is the problem? At present, resistance may be related to receptor mutations (such as cadherin, ABC transporter). Some studies have also found that changes in proteases affecting toxin activation and alterations in midgut structure may play a certain role (Soberon et al., 2007; Tay et al., 2015; Badran et al., 2016). Particularly worthy of attention are the mutations of ABC transporters such as ABCA2, which are highly correlated with the resistance of pests like cotton bollworms to Cry2Ab toxins, indicating that the resistance mechanism may be more complex than expected. Although the multi-toxin expression strategy has achieved certain effects in delaying resistance, some field resistance phenomena still persist. This also reminds us that the resistance issue cannot be ignored, and continuous monitoring and dynamic management are imperative.
Bt Research 2025, Vol.16, No.6, 234-241 http://microbescipublisher.com/index.php/bt 235 The objective of this study is to sort out the molecular mechanisms, coping strategies and the latest technological advancements of Bt toxin resistance. We will focus on introducing how to enhance the binding force between toxins and receptors by modifying their structures, how to optimize the design of multi-toxin crops, and how to promote a more adaptive integrated management system in the context of the continuous evolution of resistance. It is hoped that these contents can provide a theoretical basis for the continuous and safe application of Bt crops and biopesticides, and also offer technical reserves for the stable development of future agriculture and global food security. 2 Mechanisms of Insect Resistance to Bt Toxins 2.1 Mutations in toxin receptors and reduced binding affinity (e.g., CAD, APN, ALP) Not all insects are naturally resistant to Bt toxins, but in some populations, when some key protein structures change, trouble follows. Midgut receptors such as cadmucin (CAD), aminopeptidase N (APN), and alkaline phosphatase (ALP) are originally the "targets" of toxins. Once these proteins mutate or their expression levels decline, Bt toxins are difficult to accurately "hit", and the effect is reduced (Jurat-Fuentes et al., 2021; Liu et al., 2022; Hu et al., 2025). For instance, some studies have found that Cry2Ab toxin is significantly less effective against cotton bollworms with ABCA2 mutations, indicating that receptor proteins play a crucial role in resistance formation (Tay et al., 2015). Of course, this does not mean that every resistance is related to receptor mutations, but this mechanism of "toxins not hitting the target" has indeed been widely observed, and the inhibition of Bt toxins is also very obvious. 2.2 Activation of detoxification and efflux mechanisms Even if the toxin can successfully enter the insect's body at the beginning, it doesn't mean that it can successfully complete the "task". Some insects activate another set of defense mechanisms - allowing toxins to be dismantled or expelled before they even take effect. For instance, in some insects, the activity of intestinal protease has increased, and the Bt pretoxin has been decomposed before it is activated. In addition, the levels of detoxifying enzymes or excretion transport proteins will also rise, making it difficult for toxins to accumulate to lethal concentrations. The small cabbage moth is a typical example. They can regulate the expression of these "detoxification factors" in the midgut through the MAPK signaling pathway (Guo et al., 2020). Moreover, this regulation has little impact on the survival of insects themselves. That is to say, they "make very little effort but have strong resistance". Therefore, such biochemical countermeasures not only increase the complexity of the resistance mechanism but also make the prevention and control of Bt resistance more challenging (Wang et al., 2025). 2.3 Behavioral adaptations and physiological barriers Sometimes, insects do not rely on complex molecular regulation; they simply "bypass the problem". For instance, some insects will change their feeding patterns. They no longer eat plants containing Bt toxins in large quantities but instead consume them in small amounts, at different times, and try to minimize their intake. Moreover, when the pH value of the midgut or the composition of the peristaltic membrane changes, the solubility and penetration ability of toxins will also be affected, directly reducing the effect of toxins. Furthermore, some insects can enhance their own immune levels, such as secreting more antimicrobial peptides and releasing reactive oxygen species, to counter the attack of Bt toxins (Xiao et al., 2023). Although these behavioral and physiological changes may not seem so "high-end", when combined with molecular mechanisms, they often cause considerable interference to the control effect of Bt, making continuous pest management more challenging. 3 Resistance Monitoring and Evolutionary Trends 3.1 Laboratory and field-based resistance assessment methods Whether insects develop resistance to Bt toxins cannot be determined solely by the naked eye in the field. Laboratory tests often detect early signs earlier. For instance, in a controlled environment, expose pests to a standard concentration of Bt toxin to see what the mortality rate is, or test the allele frequencies that may cause resistance. Field investigations are of course indispensable, such as whether the pest density in the area where Bt
Bt Research 2025, Vol.16, No.6, 234-241 http://microbescipublisher.com/index.php/bt 236 crops are grown has changed and whether the degree of pest infestation has worsened (Hughes and Andersson, 2017; Blanquart, 2019). However, the effects of these assessment methods may not be the same on different crops and different pests. How to unify the standards and how to interpret the data are quite tricky in actual operation. 3.2 Population genetics underlying resistance development Why are some pests becoming increasingly "indestructible"? The problem might lie in their genes. Under the long-term cultivation of Bt crops, some originally rare resistance genes (such as those controlling toxin receptors or metabolic detoxification) will gradually accumulate (Toprak et al., 2011; Furusawa et al., 2018). However, there are exceptions - some resistance alleles are retained even without the selection pressure of Bt due to the compensation mechanism generated during the population adaptation process (Yu et al., 2025). This makes the evolution of resistance not develop in a single line, but is interwoven and influenced by multiple factors such as mutation rate, gene flow and adaptation cost. Understanding these mechanisms from a genetic perspective does indeed help us determine whether resistance will spread and at what rate. 3.3 Resistance dynamics prediction models and decision-making support To truly intervene in the spread of resistance in advance, it is difficult to be thorough merely by relying on experience. Many teams have attempted to combine mathematical modeling with actual data to simulate the path of resistance development. These models incorporate variables such as mutation sources, selective stress intensity, refuge strategies, and pest migration patterns to assist in designing planting strategies for Bt crops and even the timing of policy intervention (Figure 1) (Spohn et al., 2019). Of course, it doesn't mean that the model can precisely calculate when resistance will occur. After all, there are too many uncontrollable factors such as genetic superiority and environmental changes. However, when combined with the existing observational data, the reference value of the model is still quite significant (Hughes and Andersson, 2017; Blanquart, 2019). For adversarial management, these simulation tools have become increasingly important "auxiliary brains". Figure 1 Mutational profiles of 38 AMP-resistant lines (Adopted from Spohn et al., 2019) 4 Molecular and Biotechnological Approaches to Delay or Overcome Resistance 4.1 Gene pyramiding strategies: stacking multiple Bt genes When it comes to dealing with pests, relying on just one type of Bt toxin is often not sufficient. Over time, pests will always be able to "figure out the pattern" and develop resistance. But what if multiple Bt genes are combined into one crop? This is what is called the "gene pyramid" strategy. Different Bt proteins act on different targets. It is
Bt Research 2025, Vol.16, No.6, 234-241 http://microbescipublisher.com/index.php/bt 237 much more difficult for insects to develop resistance to multiple toxins simultaneously (Li et al., 2016). In fact, this approach has been adopted by many genetically modified crops and has achieved good results. Not only is the toxicity range wider, but insects also cannot evolve resistance mechanisms so easily when facing these crops, and the development of resistance has been significantly slowed down. 4.2 RNA interference (RNAi) to enhance Bt toxin efficacy If Bt toxins are a "direct strike", then RNA interference is like "dismantling the enemy's weapons" behind the scenes. This technology can silence some key genes in pests, such as those that control detoxification, transport and detoxification, or toxin recognition. In this way, toxins are more likely to take effect and the resistance of pests is weakened (Li et al., 2016). The application methods of RNAi are quite flexible. Some use genetic engineering to make plants produce interference fragments on their own, while others directly apply them locally. Importantly, it has high precision and little impact on non-target organisms, and can be regarded as an environmentally friendly and efficient resistance countermeasure. 4.3 Gene editing (e.g., CRISPR/Cas) targeting insect resistance-related genes Nowadays, when people talk about resistance, more and more people are beginning to pay attention to CRISPR. Although most of these gene editing technologies are still being tested in laboratories at present, their potential should not be ignored. The CRISPR/Cas system can precisely modify the genes of insects, such as directly disrupting those key pathways or proteins that make them "immune" to Bt toxins (Li et al., 2016). If these resistance genes can be "invalidated", the insecticidal effect of Bt toxin may be enhanced again. Of course, there are still many problems to be solved for this technology to be widely applied in the fields. However, as an innovative means to supplement the existing Bt control system, its prospects are still worth looking forward to. 5 Development of Next-Generation Bt Toxins and Alternative Proteins 5.1 Screening and application of novel Bt toxin families (e.g., Vip, Cry51) Traditional Cry protein is not a panacea, especially when it comes to those resistant pests that have already been "trained". So, scientists began to pay attention to another batch of "players" - new Bt toxins like Vip and Cry51, whose structures and insecticidal methods are different from those of the older generation of Cry toxins. For instance, Vip protein is produced during the vegetive growth period of Bacillus thuriensis, which is different from the classic secretion mechanism of Cry and does not act on the same receptor. This makes it particularly effective in dealing with CR-resistant pests (Gupta et al., 2021). Especially Vip3, which has a very obvious effect on lepidoptera insects, has been combined with Cry protein into genetically modified crops such as cotton, corn and rice (Figure 2). Although these new toxins are not "substitutes", as supplementary measures, they do broaden the thinking of pest control and add an extra line of defense to the issue of resistance. 5.2 Synthetic Bt toxins and innovations in directed evolution Sometimes, ready-made Bt toxins are not effective, especially when dealing with pests that have evolved resistance. The original "routine" no longer works. At this point, some "surgery" is needed, which relies on protein engineering. Classic toxins like Cry1Ac, after undergoing directed evolution treatment, have their receptor recognition range broadened, allowing them to "see" targets that were previously unrecognized, and their insecticidal effect has also been enhanced (Badran et al., 2016). The principle behind this type of technology is actually not complicated. To put it simply, it is to "modify and upgrade" the old toxins to make them more suitable for the new resistance state of pests. Not only phage-assisted continuous evolution, but also screening methods such as phage display and ribosome display have gradually become routine operations in laboratories. They can quickly identify the best-performing ones among a bunch of toxin variants (Pacheco et al., 2015). Of course, in the final analysis, these methods are still a bit far from being widely used in the fields at present. But at least in terms of tool reserves, the "Arsenal" of Bt toxins is becoming increasingly flexible and targeted. 5.3 Development of non-Bt bioinsecticidal proteins (e.g., lectins, plant-derived proteins) If one keeps revolving around Bt, it is inevitable to encounter a bottleneck. So researchers have also begun to explore alternative approaches, attempting to find new insecticidal proteins from plants or other microorganisms.
Bt Research 2025, Vol.16, No.6, 234-241 http://microbescipublisher.com/index.php/bt 238 Plant proteins like Lectin are considered to have the potential to be involved in pest management. Although current research on them is not as mature as that on Bt, some experiments have shown that if these proteins are used in combination with Bt toxins, they can complement each other and even slow down the rate at which pests develop resistance (Jurat-Fuentes et al., 2021). Given the continuous changes in pest resistance, relying on a single Bt strategy is clearly insufficient. Introducing these "non-BT players" into transgenic systems or biological agents may open up more options for pest management. Figure 2 Model representing Vip3A proteins-insecticidal mechanism through pore formation and apoptosis (Adopted from Gupta et al., 2021) 6 Case Studies: Successes and Failures in Resistance Management Strategies 6.1 Evolution of resistance in Helicoverpa armigera to Bt cotton in the U.S. and crop rotation strategies At the beginning, Bt cotton did perform very well in the United States. The occurrence of cotton bollworms has significantly decreased, and a lot of pesticides have been saved. People have high expectations for this genetically modified technology. But the good times didn't last long. A few years later, more and more "untouchable" insects began to appear in the fields. It's not that Bt technology has failed, but that the cotton bollworms are constantly adapting. Where is the problem? In fact, the technology itself is not wrong; the key lies in over-reliance. No matter how good the effect is, if one toxin is used to the end, it won't last long. If the IPM measures are not implemented thoroughly, it is almost only a matter of time before resistance emerges. Crop rotation has also been attempted in the United States - alternating Bt cotton with conventional non-GMO crops. Theoretically, this can disrupt the reproduction rhythm of pests and slow down their resistance rate. However, whether the effect of this approach
Bt Research 2025, Vol.16, No.6, 234-241 http://microbescipublisher.com/index.php/bt 239 can last does not solely depend on the strategy itself. Whether farmers are willing to cooperate and whether the monitoring mechanism can keep up are equally crucial. Some regions perform well, but the development of resistance is a bit slower. But as long as any one link fails to keep up, problems will still arise (Khudhair et al., 2025). 6.2 Monitoring of fall armyworm resistance and Bt maize deployment in China China's strategy is slightly different, with the focus placed on "prediction" and "monitoring". Against the backdrop of the intensifying threat from the fall armyworm, genetically modified Bt corn has been gradually introduced. However, this is not blind promotion but is being advanced in tandem with a set of resistance monitoring systems. Monitoring methods include on-site observation and molecular detection techniques, which are specifically used to track resistance-related genes. In this way, once a problem is identified, management measures can be adjusted immediately. Although a lot of preparations have been made at the technical and policy levels, what really works is this "one step ahead" approach - not waiting for problems to erupt before responding, but rather planting, observing, investigating and adjusting simultaneously. Meanwhile, the construction of refuge areas and diversified pest control measures are also important components. It can be seen from this case that relying solely on genetically modified crops themselves is far from enough. Resistance monitoring is an indispensable part for maintaining their long-term effects (Khudhair et al., 2025). 6.3 Analysis and reflection on the failure of Bt resistance strategies in whiteflies in India Not all resistance management programs can succeed. India's Bt management of whiteflies serves as a negative example. At first, BT-related technologies and some traditional pesticides were also used, but problems soon emerged. This type of pest has strong adaptability by itself. If management is slightly negligent, its resistance will accumulate rapidly. During this process, several loopholes were particularly fatal: farmers lacked relevant knowledge, the refuge areas were not well built, and the pest control methods were too monotonous. As a result, the control effect of Bt was greatly reduced. Compared with other countries, India is much weaker in terms of supervision and grassroots training. This incident reminds us that resistance management cannot be supported by a single method; it must be accompanied by an overall strategy, including the combination of genetics, farming, and chemical control, and it is even more necessary for farmers to truly participate. Otherwise, even with technologies like Bt, it would be very difficult to withstand the complex and ever-changing challenges of pests (Khudhair et al., 2025). 7 Conclusion and Future Perspectives Controlling pest resistance is both easy and difficult. Although we have tried many methods, such as combining Bt proteins with different mechanisms, modifying the toxin structure through directed evolution, or introducing some non-BT biological insecticidal proteins, in the hope of alleviating the resistance pressure brought by a single toxin, or multi-target strikes to make it less easy for insects to "adapt". These strategies are indeed helpful in targeting different receptors, especially after clarifying the molecular mechanisms like ABC transporter mutations, we have more direction to design the next generation of toxins. Furthermore, not only the toxins themselves, but also new methods such as RNA interference are being considered for introduction. At the same time, combined with management strategies such as shelter cultivation, these remain key means to maintain the effectiveness of Bt crops. But to be honest, the path to stopping resistance is still far from being blocked. The evolution rate of some pest populations is much faster than the pace at which we update toxins, and up to now, our understanding of resistance mechanisms is still not comprehensive. What is even more challenging is that there may be cross-resistance among different Bt toxins. Some resistance alleles may even bring adaptive advantages in specific environments, which makes the management work somewhat difficult. Moreover, monitoring resistance in the field is inherently labor-intensive and resource-intensive, and it is hard to say whether the shelter strategy can be truly implemented effectively. Moreover, it is not yet fully clarified whether the large-scale deployment of the new toxin will cause interference to the ecosystem and whether non-BT proteins will lead to new resistance issues.
Bt Research 2025, Vol.16, No.6, 234-241 http://microbescipublisher.com/index.php/bt 240 If we truly want to take control of this situation in the future, we may have to rely more on the integration of multiple disciplines. Protein engineering can help us quickly produce new Bt toxins and enhance their ability to resist variant receptors. Meanwhile, finding breakthroughs from hormone signals and the relationship between pests and hosts may also bring about new target resources. From a broad perspective, the sustainability of pest management does not only rely on technological upgrades, but also on detailed management regulations, farmer training and policy coordination - in other words, while laboratories should take the lead, the coordination at the field level should not be neglected. Only by truly integrating biotechnology, ecological thinking and socio-economic factors can Bt crops possibly gain a firm foothold in the long term and replace more traditional chemical control roles. Acknowledgments Thank you to Dr. Zhang for his technical support in data analysis and visualization, and also thank the members of the research team for their discussions and suggestions during the paper writing. Conflict of Interest Disclosure The authors affirms that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest. References Badran A., Guzov V., Huai Q., Kemp M., Vishwanath P., Kain W., Nance A., Evdokimov A., Moshiri F., Turner K., Wang P., Malvar T., and Liu D., 2016, Continuous evolution of B. thuringiensis toxins overcomes insect resistance, Nature, 533: 58-63. https://doi.org/10.1038/nature17938 Blanquart F., 2019, Evolutionary epidemiology models to predict the dynamics of antibiotic resistance, Evolutionary Applications, 12: 365-383. https://doi.org/10.1111/eva.12753 Furusawa C., Horinouchi T., and Maeda T., 2018, Toward prediction and control of antibiotic-resistance evolution, Current Opinion in Biotechnology, 54: 45-49. https://doi.org/10.1016/j.copbio.2018.01.026 Guo Z., Kang S., Sun D., Gong L., Zhou J., Qin J., Guo L., Zhu L., Bai Y., Ye F., Wu Q., Wang S., Crickmore N., Zhou X., and Zhang Y., 2020, MAPK-dependent hormonal signaling plasticity contributes to overcoming Bacillus thuringiensis toxin action in an insect host, Nature Communications, 11: 1-14. https://doi.org/10.1038/s41467-020-16608-8 Gupta M., Kumar H., and Kaur S., 2021, Vegetative insecticidal protein (Vip): a potential contender from Bacillus thuringiensis for efficient management of various detrimental agricultural pests, Frontiers in Microbiology, 12: 659736. https://doi.org/10.3389/fmicb.2021.659736 Hu D., Wang D., Pan H., and Liu X., 2025, Molecular mechanisms underlying resistance to Bacillus thuringiensis cry toxins in lepidopteran pests: an updated research perspective, Agronomy, 15(1): 155. https://doi.org/10.3390/agronomy15010155 Hughes D., and Andersson D., 2017, Evolutionary trajectories to antibiotic resistance, Annual Review of Microbiology, 71: 579-596. https://doi.org/10.1146/annurev-micro-090816-093813 Jurat-Fuentes J., Heckel D., and FerréJ., 2021, Mechanisms of resistance to insecticidal proteins from Bacillus thuringiensis, Annual Review of Entomology, 66: 121-140. https://doi.org/10.1146/annurev-ento-052620-073348 Khudhair I., Abbood N., and El-Amier Y., 2025, Insecticide resistance in agricultural pests: mechanisms case studies and future directions, University of Thi-Qar Journal of Science, 12(1): 245-250. https://doi.org/10.32792/utq/utjsci/v12i1.1381 Li W., Zhang H., Assaraf Y., Zhao K., Xu X., Xie J., Yang D., and Chen Z., 2016, Overcoming ABC transporter-mediated multidrug resistance: molecular mechanisms and novel therapeutic drug strategies, Drug Resistance Updates : Reviews and Commentaries in Antimicrobial and Anticancer Chemotherapy, 27: 14-29. https://doi.org/10.1016/j.drup.2016.05.001 Liu L., Xu P., Liu K., Wei W., Chang Z., and Cheng D., 2022, Advances in receptor-mediated resistance mechanisms of Lepidopteran insects to Bacillus thuringiensis toxin, Chinese Journal of Biotechnology, 38(5): 1809-1823. https://doi.org/10.13345/j.cjb.210834 Pacheco S., Cantón E., Zúñiga-Navarrete F., Pecorari F., Bravo A., and Soberón M., 2015, Improvement and efficient display of Bacillus thuringiensis toxins on M13 phages and ribosomes, AMB Express, 5: 73. https://doi.org/10.1186/s13568-015-0160-1
Bt Research 2025, Vol.16, No.6, 234-241 http://microbescipublisher.com/index.php/bt 241 Soberón M., Pardo-López L., López I., Gómez I., Tabashnik B., and Bravo A., 2007, Engineering modified Bt toxins to counter insect resistance, Science, 318: 1640-1642. https://doi.org/10.1126/science.1146453 Spohn R., Daruka L., Lázár V., Martins A., Vidovics F., Grézal G., Méhi O., Kintses B., Számel M., Jangir P., Csörgő B., Györkei Á., Bódi Z., FaragóA., Bodai L., Földesi I., Kata D., Maróti G., Pap B., Wirth R., Papp B., and Pál C., 2019, Integrated evolutionary analysis reveals antimicrobial peptides with limited resistance, Nature Communications, 10: 4538. https://doi.org/10.1038/s41467-019-12364-6 Tabashnik B., 2015, ABCs of insect resistance to Bt, PLoS Genetics, 11(11): e1005646. https://doi.org/10.1371/journal.pgen.1005646 Tay W., Mahon R., Heckel D., Walsh T., Downes S., James W., Lee S., Reineke A., Williams A., and Gordon K., 2015, Insect Resistance to Bacillus thuringiensis Toxin Cry2Ab is conferred by mutations in an ABC transporter subfamily a protein, PLoS Genetics, 11(11): e1005534. https://doi.org/10.1371/journal.pgen.1005534 Toprak E., Veres A., Michel J., Chait R., Hartl D., and Kishony R., 2011, Evolutionary paths to antibiotic resistance under dynamically sustained drug selection, Nature Genetics, 44: 101-105. https://doi.org/10.1038/ng.1034 Wang D.L., Yan P.P., and Wang S.J., 2025, Stacking of multiple resistance genes in wheat via transgenic approaches, Triticeae Genomics and Genetics, 16(3): 120-129. https://doi.org/10.5376/tgg.2025.16.0013 Xiao Z., Yao X., Bai S., Wei J., and An S., 2023, Involvement of an enhanced immunity mechanism in the resistance to Bacillus thuringiensis in lepidopteran pests, Insects, 14(2): 151. https://doi.org/10.3390/insects14020151 Yu F., Wang D., Zhang H., Wang Z., and Liu Y., 2025, Evolutionary trajectory of bacterial resistance to antibiotics and antimicrobial peptides in Escherichia coli, mSystems, 10(3): e01700-24. https://doi.org/10.1128/msystems.01700-24
Bt Research 2025, Vol.16, No.6, 242-250 http://microbescipublisher.com/index.php/bt 242 Feature Review Open Access Applications of Remote Sensing and GIS in Monitoring the Use of Bt Bioinsecticides Lin Liu 1, Dandan Huang 2 1 Tropical Microbial Resources Research Center, Hainan Institute of Tropical Agricultural Resources, Sanya, 572025, Hainan, China 2 Hainan Institute of Biotechnology, Haikou, 570206, Hainan, China Corresponding email: dandan.huang@hibio.org Bt Research, 2025, Vol.16, No.6 doi: 10.5376/bt.2025.16.0027 Received: 08 Sep., 2025 Accepted: 15 Oct., 2025 Published: 21 Nov., 2025 Copyright © 2025 Liu and Huang, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Liu L., and Huang D.D., 2025, Applications of remote sensing and GIS in monitoring the use of Bt bioinsecticides, Bt Research, 16(6): 242-250 (doi: 10.5376/bt.2025.16.0027) Abstract The wide application of Bacillus thuringiensis (Bt) biopesticide in modern agriculture has significantly improved the efficiency of pest control and reduced the reliance on chemical pesticides. However, the spatio-temporal dynamic monitoring of Bt application still faces many challenges, which limit its sustainable development in precise pesticide application and environmentally friendly agriculture. This study systematically explores the integrated application of remote sensing and geographic information system (GIS) in the monitoring of Bt biopesticide use, proposes a technical path based on high spatial accuracy and data fusion, introduces the mechanism of action of Bt toxins and their common application methods, and then analyzes the remote sensing platform and GIS technology suitable for agricultural monitoring. The health status of crops and the occurrence of pests can be monitored through vegetation indices such as NDVI and EVI. Represented by India, China and the Midwestern United States, this study selected typical regional cases to demonstrate the practical application effects of this technical system in the deployment of Bt crops and ecological response monitoring. The research results show that the integration of remote sensing and GIS has significant advantages in the supervision of Bt biopesticide use. It not only improves the accuracy of pesticide application but also provides decision support for the green control of pests in intelligent agriculture. This study aims to promote the development of eco-friendly agriculture, reduce the abuse of pesticides, and provide a scientific basis for data-driven pest management in the context of precision agriculture. Keywords Bt Biological pesticide; Remote sensing technology; Geographic information system; Precision agriculture; Pest monitoring 1 Introduction The fact that Bacillus thuringiensis (Bt) can kill insects has actually been exploited for a long time, relying on a type of protein called Cry toxin produced in its body. Once these toxins are ingested by the insects, they will cause trouble in the intestines, damage the cell structure and eventually lead to the death of the pests. Common agricultural pests such as caterpillars, beetles and mosquitoes are all sensitive to it. The key point is that it has little effect on non-target organisms, which is very popular (El-Ghany et al., 2020; Weiss et al., 2020). Therefore, Bt preparations are widely spread in the fields to control pests, reduce yield losses, and also save a considerable amount of chemical pesticides. But problems do exist. For instance, after Bt is applied, how effective it is, whether the environment is affected, and whether pests will develop drug resistance - all these need to be closely monitored by someone. Traditionally, it relied on manual sampling and record-keeping in the fields. Not only was it quite tiring, but the coverage was also limited. The result is that data often comes slowly and the information is incomplete (Zhou and Li, 2021). This reveals a reality: to accurately know the effect of Bt application on a large scale, a more efficient monitoring method needs to be adopted. Remote sensing and geographic information system (GIS) technologies have shown great potential in this regard. These two tools, one can "look up at the sky" and the other can "manage the map", together can do quite a few things. From the growth of crops, the spread of pests to the spatial distribution of Bt application, they can all grasp key clues. These technologies can also stitch information across regions and time periods, incorporating areas that traditional monitoring cannot cover into the analysis scope.
Bt Research 2025, Vol.16, No.6, 242-250 http://microbescipublisher.com/index.php/bt 243 This study reviews the application of remote sensing and geographic information System (GIS) technologies in monitoring the use of Bt biopesticides, with a focus on their potential to overcome the limitations of traditional methods. It explores how remote sensing can detect crop and pest conditions related to Bt application, and how GIS can integrate spatial data for monitoring and decision-making. And evaluate the benefits of these technologies for sustainable pest and disease management. This study aims to emphasize that remote sensing and GIS provide powerful tools for enhancing the accuracy, efficiency and environmental safety of Bt biopesticides in agriculture, thereby supporting sustainable crop protection and ecological conservation. 2 Mechanisms of Bt Bioinsecticides in Pest Control 2.1 Insecticidal mechanisms of Bt toxins and target pest species Not all insects will be "hit in the flesh" by Bt toxins, but for those pests with specific receptors in the midintestine, such as Lepidoptera, Coleoptera, diptera, etc., the effects of Cry toxins and Vip toxins are quite obvious. The principle behind them is actually not complicated: After the larvae eat them, the alkaline environment in the intestines activates the pretoxins, which then run to bind to the receptors on the intestinal cells. Eventually, the cells rupture and the worms die. Many Cry toxins have specific selectivity for particular insect species, which is also the basis for their "precise strikes". Interestingly, sometimes when several Bt toxins are used in combination, the effect is even stronger. They not only enhance the efficiency of pest control but also slow down the rate at which pests like the beet armyworm develop resistance (Baranek et al., 2021; Pinos et al., 2021). 2.2 Application methods of Bt formulations (sprays, granules, transgenic crops) How to use Bt? There is more than one way. The common spraying method used by farmers nowadays also requires advanced techniques. For instance, adding microcapsule coating can resist ultraviolet rays and extend the "service life" in the field. Granular agents are more suitable for being scattered into the soil to deal with pests that hide at the roots or underground. In contrast, genetically modified crops are like "armed with their own weapons", directly expressing Cry proteins within the plants. This way, even internal pests that cannot be reached by spraying can be prevented. However, no matter how good these genetically modified Bt crops are, one issue cannot be ignored - the risk of resistance. It is necessary to cooperate with management strategies, such as crop rotation or shelters, to avoid the situation where the disease is incurable after a few years (Duraisamy et al., 2023). 2.3 Environmental behavior and degradation characteristics after application Bt toxins are not always effective when they reach the fields. It is greatly influenced by the environment. For instance, it will decompose when exposed to too much sunlight, and soil microorganisms may also "eat" it. Although this makes it more environmentally friendly and reduces the impact on non-target insects, it also means that it needs to be resprayed or simply some protective agents should be selected to prolong the efficacy. Therefore, the application time must be calculated accurately. Studying the degradation patterns of Bt toxins is not only for safety but also helps farmers use fewer pesticides and take more pest control measures. After all, its characteristic of being both degradable and selective makes it a popular type of green pesticide in integrated pest management (Sanchis, 2011; Aswathi et al., 2024; Ragasruthi et al., 2024). 3 Fundamentals of Remote Sensing in Agricultural Monitoring 3.1 Principles and advantages of multispectral and hyperspectral remote sensing Remote sensing technology may sound rather sophisticated, but in fact, it has long permeated every corner of agricultural monitoring, especially in the two types of multispectral and hyperspectral monitoring. The crops in the farmland may look similar on the surface, but as long as these sensors are used to illuminate them, the trick can be seen. Multispectrum usually covers several wide bands, while hyperspectrum can obtain reflection data of hundreds of consecutive narrow bands. This also means that it can "see more precisely" and can capture some crop differences or early manifestations of diseases that are completely indistinguishable to the naked eye. It is worth mentioning that this technology does have advantages in monitoring the health and nutritional status of crops, especially in identifying physiological changes and biochemical reactions (Sishodia et al., 2020; Weiss et al., 2020). Of course, it is unrealistic to say that it can completely replace traditional methods, but it does have its place in assisting judgment and providing early warnings.
Bt Research 2025, Vol.16, No.6, 242-250 http://microbescipublisher.com/index.php/bt 244 3.2 Image processing and crop classification techniques Whether remote sensing images can be used or not still depends on the processing method. For instance, when images are brought back, they first need to undergo radiation correction, and then they might also need to be "merged" with other images. Only in this way can the data quality be improved. It was only then that the classification algorithm came into play. Many methods determine the species or growth stage of different crops based on their spectral performance differences, while others track changes through time series. There are also many classification methods, such as supervised classification and unsupervised classification, each with its own usage. When encountering complex plots, the combined use of different data sources, such as combining hyperspectral data with liDAR or thermal imaging data, can sometimes significantly improve the accuracy of recognition (Figure 1) (Omia et al., 2023; Allu and Mesapam, 2025). However, not every crop is suitable for the same processing procedure. In practical application, specific problems still need to be analyzed specifically. Figure 1 The electromagnetic spectrum, different wavelengths and regions, bands’ energy levels, and some examples of their use in agricultural remote sensing applications (Adopted from Omia et al., 2023) 3.3 Vegetation health and pest detection indicators (e.g., NDVI, EVI) based on remote sensing When evaluating the growth of crops, you may have heard of vegetation indices such as NDVI and EVI to some extent. These indices are not calculated out of thin air. They rely on the reflection of crops to different wavelengths of light, especially the differences between near-infrared and visible light. Simply put, the greener the leaves are, the higher the index is usually. Conversely, once the index shows abnormal fluctuations, it may be a sign of pest or disease, even earlier than the yellowing of leaves as seen by the human eye. This ability to issue early warnings is of great value to agricultural management. Furthermore, if these indices can be combined with time series data, the changing trend of the entire field can be tracked, such as when pests and diseases start to spread and to what stage they have developed, facilitating timely measures to be taken, such as precise application of Bt biopesticides (Segarra et al., 2020). Of course, all of this is predicated on the fact that the remote sensing data is detailed enough and someone knows how to use it.
Bt Research 2025, Vol.16, No.6, 242-250 http://microbescipublisher.com/index.php/bt 245 4 Application of GIS in Spatial Analysis of Bt Use 4.1 Construction and integration of GIS systems for agricultural data management Nowadays, agricultural information is becoming increasingly diverse, and how to manage it has become a considerable problem. GIS, or Geographic Information System, can integrate various agricultural-related data, such as terrain, climate, soil, crop distribution, etc., into a unified platform. Many people initially think that the data sources are too diverse - such as remote sensing images, field investigations, and sensor networks, all integrated together, which is indeed quite complicated. However, as long as the system is well set up, these data can be combined into an interoperable database. Especially in the application of Bt biological insecticides, GIS can integrate spatial data such as crop distribution, application records, and the occurrence of pests and diseases to form a panoramic map. It's not just about looking at the pictures. Some systems have directly integrated decision support tools, enabling farmers and experts to share data and respond quickly, thus achieving more sustainable pest and disease management strategies (Martins and Rocha, 2012; Sadoun et al., 2015; Akindele et al., 2023). 4.2 Spatial distribution modeling and visualization of Bt application areas Not all places are suitable for applying pesticides, especially genetically modified insecticides like Bt pesticides, which require more emphasis on "using them correctly". At this point, the GIS system comes in handy. It can help draw the specific areas where pesticides are applied, making it clear at a glance which areas have been sprayed and which have not. It can even be seen whether the drug effect is in place. Through some methods, such as weighted analysis or multi-criteria decision-making tools, GIS can also create a "suitable map" that takes into account environmental conditions and agricultural demands, indicating where the most suitable place for pesticide application is. Not only that, it can also help identify "blind spots" - that is, those areas that are easily overlooked, and at the same time, it can see whether these measures have a restraining effect on the number of pests. These maps and models look like "navigation", but in fact, they are designed to deliver pesticides more precisely and ensure that resources are used where they are most needed (Dossow et al., 2025). 4.3 Decision support functions of GIS combined with field parcel information Sometimes, relying solely on large-scale data is not enough; decisions need to be made at the level of farmland. Combining GIS with specific plot information can make it closer to the actual situation. Details such as the stage at which the crops on which plot of land have grown, what pests and diseases have occurred, and how many times pesticides have been sprayed before can all be recorded in the system. With this information, when to spray the pesticide and how much to spray can be more reasonable. More importantly, in this way, it can prevent the situation where too much medicine is scattered or there is no need to sprinkle it at all, and the environmental pressure can also be reduced. In fact, such GIS support systems have long been attempting to integrate spatial analysis, predictive models, and real-time monitoring to assist farmers and agricultural technicians in making more targeted decisions. Especially in the same field, the differences in various locations can also be taken into account, achieving true "treating the symptoms with the right medicine". In this way, the use of Bt pesticides is both efficient and more environmentally friendly (Sadoun et al., 2015; Akindele et al., 2023). 5 Technical Framework for Integrated Monitoring of Bt Application Using Remote Sensing and GIS 5.1 Data source integration: satellites, UAVs, and ground observations When it comes to monitoring Bt biological insecticides, relying on a single data source is often insufficient. Satellite images, drone aerial photography, and ground surveys - these data may seem scattered, but as long as they are properly integrated, the information density and accuracy can be significantly improved. For instance, although satellites have a wide coverage and are relatively continuous in terms of time, their resolution is limited and they may not be suitable for fine monitoring of small plots of land. Drones are much more flexible. They can not only fly to the places they want to see, but also have high image resolution. Even if the aerial data is as clear as possible, the ground layer cannot be ignored. On-site observation of the growth of crops and the distribution of pests and diseases is often an important basis for correcting remote sensing data. After integrating these data through fusion technology, when observing Bt application patterns and environmental changes, the images will be more detailed and the judgments will be more reliable (Guo et al., 2025).
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