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.
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 Editedby 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. 3 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 Bt and Climate Change: Impacts on Efficacy and Distribution Guanli Fu, Zhen Li Bt Research, 2025, Vol. 16, No. 3, 86-94 Bt Application Strategies to Minimize Environmental Impact Gao Fumin, Jiong Fu Bt Research, 2025, Vol. 16, No. 3, 95-102 Bt Bioengineering for Enhanced Environmental Stability and Persistence Xiaoyan Chen, Qibin Xu Bt Research, 2025, Vol. 16, No. 3, 103-109 Transcriptomic Responses of Bacillus thuringiensis to Environmental Stress Kai Chen, Jia Xuan Bt Research, 2025, Vol. 16, No. 3, 110-117 Epigenetic Modifications in Bt and Their Impact on Gene Expression Sibin Wang, Zhonggang Li Bt Research, 2025, Vol. 16, No. 3, 118-124
Bt Research 2025, Vol.16, No.3, 86-94 http://microbescipublisher.com/index.php/bt 86 Review Article Open Access Bt and Climate Change: Impacts on Efficacy and Distribution Guanli Fu , Zhen Li Hainan Institute of Biotechnology, Haikou, 570206, Hainan, China Corresponding author: guanli.fu@hibio.org Bt Research, 2025, Vol.16, No.3 doi: 10.5376/bt.2025.16.0011 Received: 08 Mar., 2025 Accepted: 23 Apr., 2025 Published: 05 May, 2025 Copyright © 2025 Fu and Li, 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: Fu G.L., and Li Z., 2025, Bt and climate change: impacts on efficacy and distribution, Bt Research, 16(3): 86-94 (doi: 10.5376/bt.2025.16.0011) Abstract Climate change is affecting the efficacy and distribution of Bt crops. Environmental stress such as high temperatures, drought and increased carbon dioxide can reduce the production of insecticidal proteins by Bt crops and lower their ability to control pests. There is still a lack of research on the performance mechanism of Bt crops under extreme climates, so it is difficult to accurately predict future effects. Some pests around the world have developed obvious resistance to Bt crops, which has reduced the pest control effect of many crops in the field. Climate change will also affect the distribution, reproduction rate and drug resistance of pests and vector insects, thereby altering the applicable regions and control plans for Bt crops. In the future, to ensure the long-term effectiveness of Bt crops, it is necessary to combine resistance management, ecological adaptation and the application of new technologies. The aim of this study is to explore strategies for enhancing the pest control effect of Bt crops in the context of climate change. Keywords Bt crop; Climate change; Resistance evolution; Environmental stress; Distributed expansion 1 Introduction Bt (Bacillus thuringiensis) technology is a genetic engineering method. It is widely used in agriculture, especially for cotton and corn. Crops can express Bt protein to kill major pests. This way, less pesticides are used, yields can be increased, and it is also more environmentally friendly. Since the end of the 20th century, Bt crops have been regarded as an important part of agricultural modernization and the green revolution. Many small-scale peasant economies hope that it can reduce poverty, increase income and help solve the pest problem in agriculture (Veettil et al., 2017). Now, global climate change is affecting agricultural ecosystems. The rise in temperature, changes in precipitation and the increasing number of extreme weather conditions will all affect crop growth, pests and diseases as well as farmers' lives. Some policymakers and technology promoters believe that Bt technology can help agriculture cope with these changes. They believe that the insect resistance and adaptability of Bt can enable crops to maintain yield under conditions such as high temperature and drought (Giron-Calva et al., 2020). However, the long-term performance of Bt crops under climate change is increasingly being questioned. Studies have found that although Bt crops can initially reduce pesticides and alleviate environmental stress (Veettil et al., 2017), with climate fluctuations, increased pest resistance, and complex changes in the ecosystem, its effects vary greatly in different regions and stages (Wang et al., 2022; Karamchedu, 2023). In some areas, pests have become more resistant to Bt protein, and pesticides have been used more frequently, even increasing the economic risks and debts of farmers. Moreover, environmental stresses such as high temperature and drought may also affect the expression of Bt protein and the pest resistance of crops, ultimately affecting ecological benefits and sustainability. This study aims to systematically sort out the impact and performance of Bt technology under climate change, and examine its advantages and limitations under different environmental and social conditions. We will search for and analyze relevant literature, with a focus on several aspects: the performance of different climate zones, the changing trends of pest resistance, ecological and environmental impacts, farmers' lives and economic outcomes, as well as sustainability and policy recommendations under future climate scenarios.
Bt Research 2025, Vol.16, No.3, 86-94 http://microbescipublisher.com/index.php/bt 87 2 Bt Technology: Mechanisms and Current Applications 2.1 Mode of action In the current literature, no direct data specifically studying the mechanism of action of Bt insecticidal protein has been found. Generally speaking, Bt technology enables crops to produce specific insecticidal proteins, such as Cry protein. After pests consume these proteins, the proteins will be activated in their intestines, destroying the intestinal epithelial cells and eventually leading to their death. Most of the data available now is about another field abbreviated as "BT", such as Blockchain Technology (BT), rather than the detailed molecular mechanism of Bt insecticidal proteins. 2.2 Current adoption patterns Regarding the adoption model of Bt technology in global agriculture, there is no direct data available in the current search results. It is generally believed that Bt cotton and Bt corn are widely cultivated in the Americas, Asia and other places. Their adoption rate will be influenced by a variety of factors such as policies, markets and farmers' perception. However, many existing literatures focus on the application and adoption models of blockchain technology in supply chains and agricultural informatization. For instance, blockchain is regarded in the agricultural supply chain as capable of enhancing traceability, increasing transparency and efficiency, and promoting sustainable development (Liu et al., 2021; Zkik et al., 2022). 2.3 Performance under conventional climate conditions At present, no literature has been found directly studying the field performance of Bt crops or Bt preparations under conventional climatic conditions. The general view is that Bt crops can effectively control target pests, reduce the use of chemical pesticides, increase yields and be more environmentally friendly in normal climates. Many existing studies discuss the performance of blockchain technology in agricultural supply chain management, such as improving data transparency, reducing transaction costs, and enhancing traceability, etc. (Kamble et al., 2020; Taş and Aylak, 2022). 3 Climate Change Effects on Pest Dynamics 3.1 Shifts in pest ranges Climate change will affect the distribution of pests, especially global warming and precipitation changes. Many agricultural and forest pests are spreading to higher latitudes and altitudes. The increase in temperature raises the survival rate of pests over the winter and also increases their reproduction frequency. In this way, they can establish populations in places that were originally unsuitable. For instance, in the case of climate warming, the European corn borer may move several hundred kilometers northward and add additional breeding generations in new areas, and the risk of crop damage will also increase (Pureswaran et al., 2018; Malhi et al., 2021; Skend and ICet al., 2021). Climate change will also reduce the barriers to the invasion and spread of alien pests, accelerate the invasion rate, and allow local pests to spread even faster (Schneider et al., 2022). However, some heat-sensitive pests may have a reduced distribution in the south or low-altitude areas due to high temperatures and drought (Netherer and Schopf, 2010). 3.2 Altered pest phenology Climate change will significantly alter the life cycle rhythm of pests, such as earlier emergence, faster development and more reproduction. An increase in temperature will lead to an increase in the number of generations of pests, a longer development period, and a change in the time matching with host plants, which may make crops more vulnerable to damage (Karuppaiah and Sujayanad, 2012; Malhi et al., 2021; Nitta et al., 2024). Phenological changes may also staggerize the timing of pests with their natural enemies or host plants, thereby affecting the effectiveness of biological control (Thomson et al., 2010; Jactel et al., 2019). The responses of different pests and regions vary. Some pests may grow more slowly or even have fewer generations due to high temperature and pressure. 3.3 Emergence of secondary pests Climate change not only affects major pests but may also turn pests that were originally less harmful into major
Bt Research 2025, Vol.16, No.3, 86-94 http://microbescipublisher.com/index.php/bt 88 threats. Changes in temperature and precipitation can alter the competition among pests, affecting the resistance of host plants and the number of natural enemies. Some minor pests have strong adaptability, or when natural enemies decrease, they may suddenly break out (Bajwa et al., 2020; Malhi et al., 2021; Subedi et al., 2023). In addition, climate change will also accelerate the spread of invasive pests, increase the emergence frequency of new pests and pathogens, and bring new challenges to agriculture and ecosystems (Pureswaran et al., 2018; Linnakoski et al., 2019). 4 Climate Change Effects on Bt Efficacy 4.1 Direct impacts on Bt proteins Climate change, especially the increase in temperature and carbon dioxide, may affect the stability, degradation rate and residence time of Bt protein in the environment. These changes will directly or indirectly reduce its insecticidal ability. The adsorption, decomposition and residue time of Bt protein in soil can be affected by environmental factors. Climate change may cause Bt protein to decompose more rapidly in the environment or combine with soil components, thereby affecting its activity and duration and reducing the field insecticidal effect (Li et al., 2022). In addition, the Bt proteins in genetically modified crops and those in natural Bt strains are inherently different in structure and function. Climate change may amplify the impact of these differences on environmental performance and insecticidal efficacy (Figure 1). Figure 1 Environmental behaviors of Bt protein (A) and its three-dimensional structures (B). I, II, and III: domains I, II, and III (Adopted from Li et al., 2022) 4.2 Plant physiology changes Climate change can affect the physiological processes of plants, such as growth rate, nutrient distribution and defense mechanisms, which will also indirectly influence the content and distribution of Bt protein. Some seasonal changes or environmental stresses may reduce the Bt protein in Bt crops, thereby reducing their ability to control pests. The responses of plants to climate stress, such as enhancing stress resistance or adjusting the growth cycle, may also change the distribution and concentration of Bt protein in different parts, which will affect the dose consumed by pests and thereby affect the insecticidal effect (Matzrafi, 2018). 4.3 Pest physiology and resistance evolution Climate change can also affect the physiological state, metabolic capacity and generation cycle of pests, thereby accelerating their adaptation and resistance evolution to Bt protein. High temperatures and increased carbon dioxide levels may enhance the detoxification ability of pests, making them less sensitive to Bt protein in specific environments. This situation is known as "conditional resistance" (Matzrafi, 2018). Meanwhile, climate change may accelerate the generational replacement of pests, accelerate the accumulation of resistance genes, and
Bt Research 2025, Vol.16, No.3, 86-94 http://microbescipublisher.com/index.php/bt 89 ultimately promote the earlier formation of resistance populations (Van Den Berg et al., 2022). At present, a variety of pests have developed actual resistance to Bt crops worldwide, and climate change is regarded as an important external factor accelerating this process. In addition, the physiological changes of plants in different seasons can also affect the adaptability and resistance gene frequencies of pests on Bt crops. Appropriate establishment of sheltered areas for non-BT crops can delay the formation of resistance (Carriere et al., 2017). 5 Climate Change and Distribution of Bt Use 5.1 Geographic shifts in demand Climate warming and the increasing number of extreme weather events are driving changes in the location of agricultural production areas. For instance, rising temperatures and droughts will cause crop-growing areas to move towards higher latitudes or altitudes, which will also affect the distribution of demand for pest control technologies, such as Bt crops. Take rice, wheat and corn as examples. Long-term high temperatures and water shortage will significantly reduce the accumulation of biomass. Crops that were originally suitable for cool climates, such as wheat, have been more affected. This means that under climate change conditions, their suitable planting areas will shift (Perdomo et al., 2015). Such geographical changes will directly affect the promotion area and demand size of Bt crops. The impact of climate change on the distribution of pests will also alter the demand for Bt crops. Climate warming may allow some pests to enter new areas, thereby increasing the demand for Bt crops in these areas (Wittmann and Baylis, 2000). However, at present, there is still a lack of empirical studies directly measuring the changes in the geographical distribution of Bt crops. 5.2 Economic and regulatory drivers Climate change will not only alter the areas where crops are grown, but also indirectly drive changes in the economic and policy environment of Bt crops by influencing land use, carbon balance and agricultural sustainability goals. The changes in land use structure, the increase in carbon emission pressure, and the policy demand for sustainable development may make decision-makers more willing to promote efficient and environmentally friendly Bt crops. Meanwhile, the new pest threats and crop loss risks brought about by climate change may also make Bt crops more economically attractive, promoting their application in high-risk areas. From a regulatory perspective, climate change will prompt policymakers to enhance land management and agricultural planning, providing policy support for the promotion of Bt crops. However, it should also be noted that the impact of climate change on the ecological security of Bt crops, such as on soil organisms, still requires long-term monitoring and assessment (Wang et al., 2022). 6 Integrated Pest Management (IPM) in the Climate Change Era 6.1 Bt in combination with other control methods The large-scale promotion of Bt crops has greatly reduced the reliance on chemical pesticides. This restores and enhances the role of biological control factors such as natural enemies, thereby improving the overall effect of integrated Pest management (IPM) (Lu et al., 2018; Romeis et al., 2019). For instance, in China, the use of Bt cotton not only controls cotton bollworms, but also indirectly helps control the natural enemies of aphids by reducing the use of pesticides, thereby reducing the damage caused by aphids. However, if only Bt crops are used, it may also cause a large number of non-target pests (such as stink bugs) to occur, which indicates that a diversified IPM strategy is very important. Therefore, Bt is best combined with biological control, agronomic measures (such as intercropping, rotation), behavioral regulation (such as pheromones), etc., so as to sustainably control pests in the long term (Figure 2) (Heeb et al., 2019; Angon et al., 2023; Zanzana et al., 2024). 6.2 Resistance management Climate change will accelerate the evolution of pest resistance, and the emergence of BT-resistant pests has become a global concern. Effective resistance management methods include: increasing the proportion of non-BT crop "shelters", rotating different Bt toxins, using in combination with other control methods, and strengthening resistance monitoring (Ziska et al., 2018; Gassmann and Reisig, 2022; Aswathi et al., 2024). In Africa, the United
Bt Research 2025, Vol.16, No.3, 86-94 http://microbescipublisher.com/index.php/bt 90 States and other places, the effectiveness of resistance management is closely related to the implementation by farmers, policy support and technology promotion (Van Den Berg et al., 2022). In addition, climate change may accelerate the spread of resistance genes by altering the generations and distribution of pests. Therefore, resistance management strategies also need to be adjusted at any time. Figure 2 The PRISMA diagram depicts the search, screening for inclusion, exclusion, and accepted studies for the IPM review (Adopted from Angon et al., 2023) 6.3 Modeling future deployment Facing the uncertainties of climate change, modeling tools are becoming increasingly important in predicting pest dynamics, evaluating the effects of IPM and guiding the deployment of Bt crops. These models can combine various data such as climate, crops, pests and natural enemies to predict the distribution of pests, the development trend of resistance, and the long-term effect of IPM measures. For instance, by using GIS and the coupled model of climate - pests - crops, targeted Bt deployment and IPM strategies can be formulated for different regions (Ziska et al., 2018). Furthermore, real-time monitoring and big data analysis, such as citizen science and mobile data collection, also provide new tools for the dynamic optimization of IPM (Ziska et al., 2018; Skend and ICet al., 2021). 7 Case Study: Take European Corn as an Example 7.1 Background Europe is one of the important application regions of Bt crops. Bt corn can produce Bacillus thuringiensis (Bt) toxin, which effectively controls major pests such as the corn borer. This not only reduces the use of chemical pesticides but also increases the output. However, environmental changes and the development of pest resistance pose challenges to the long-term sustainability of Bt crops (Giron-Calva et al., 2020). 7.2 Observed climate change trends Over the past few decades, temperatures in Europe have risen significantly and precipitation patterns have also changed, especially in Western and Southern Europe. The increase of high temperature and extreme weather has prolonged the activity period of pests, expanded their distribution range northward, and also changed the relationship between pests and crops. 7.3 Impacts on Bt efficacy Climate change will affect the performance of Bt crops in multiple ways. Environmental stress such as high
Bt Research 2025, Vol.16, No.3, 86-94 http://microbescipublisher.com/index.php/bt 91 temperatures and drought may cause a decrease in the Bt protein content within crops, thereby reducing their lethality to pests. Climate change will also accelerate the evolution of pests' resistance to Bt toxins. In some areas, it has been found that pests such as corn borer have developed practical resistance to Bt corn, resulting in weakened control effects (Giron-Calva et al., 2020). In addition, climate change may also indirectly reduce the control ability of Bt crops by affecting the physiology and behavior of pests (Guis et al., 2011). 7.4 Adaptation strategies implemented To address climate change and pest resistance, Europe has adopted a variety of measures. For instance, promoting multi-toxin (multi-gene) Bt crops, increasing the sheltered area of non-BT crops to delay the development of resistance, strengthening resistance monitoring and management, and optimizing field management methods (such as crop rotation and diversified planting), etc. In addition, researchers are also attempting to enhance the stability and utilization rate of Bt protein by using nanotechnology and additives to adapt to more complex climates in the future (Matzrafi, 2018). 7.5 Outcomes and lessons learned These measures have to some extent slowed down the spread of resistance and also enhanced the sustained effectiveness of Bt crops in the context of climate change. However, studies have found that under extreme climatic conditions, the performance of Bt crops remains highly uncertain, and the current data are not sufficient to accurately predict the effects under such circumstances. Therefore, continuous resistance monitoring, conducting multi-dimensional research on climate, crops and pests, and maintaining flexible management strategies are important experiences for ensuring the sustainable utilization of Bt crops. 8 Research Gaps and Future Directions 8.1 Data deficiencies At present, there is still a significant lack of data in studying the effect and distribution of Bt under the background of climate change. First of all, data collection in many regions and for many species is unbalanced. There are few relevant studies in some biogeographic regions, such as islands, coastal areas and reptile groups, which leaves us with very limited understanding of the adaptability and ecological impact of Bt in these areas (Sarkar et al., 2024). Secondly, approximately 60% of the species distribution model studies did not adequately explain or quantify the data gap, nor did they analyze the uncertainty of the model parameters in detail. This would affect the reproducibility of the research results and the policy reference value. In addition, the underrepresentation of research in the Global South and developing countries also limits our comprehensive assessment of the application prospects of Bt in different climate zones (Zhou et al., 2023). 8.2 Technological innovations Technological progress is of great significance in making up for the insufficiency of data and enhancing the adaptability of Bt applications. Nowadays, the methods of climate change adaptation assessment are constantly improving, but there are still many challenges in the formulation of adaptation indicators, the acquisition of fine-scale data, and the collaborative assessment of adaptation measures and mitigation measures. In the future, the standardization of species distribution Modeling (SDM) methods should be strengthened, and uncertainty analysis should be given due attention. Meanwhile, it is necessary to promote the application of new technologies such as remote sensing, big data and artificial intelligence in Bt distribution prediction and efficacy evaluation (Singh et al., 2020; Sarkar et al., 2024). Furthermore, interdisciplinary and cross-border cooperation also contributes to enhancing the efficiency of data sharing and technology transformation. 8.3 Policy and extension needs Improving the policy and promotion system is the key to making Bt work in tandem with climate change management. At present, cross-regional and cross-institutional cooperation is insufficient, and the participation of developing countries in research and policy-making is also relatively low (Zhou et al., 2023). In the future, the assessment of climate change adaptation measures should be strengthened at the policy level, evidence-based decision-making should be promoted, and resource input to vulnerable and vulnerable regions should be increased. Meanwhile, emphasis should also be placed on promotion and popular science to enhance farmers' and relevant
Bt Research 2025, Vol.16, No.3, 86-94 http://microbescipublisher.com/index.php/bt 92 stakeholders' awareness of Bt application and climate risks, thereby promoting the implementation of the technology and enhancing adaptability at the community level (Bi et al., 2020; Baidya and Saha, 2024). 9 Conclusion This review summarizes the main impacts of climate change on the effects and distribution of Bt crops. Firstly, environmental stress such as high temperatures, drought and elevated carbon dioxide levels will reduce the production of insecticidal proteins by Bt crops, thereby lowering their ability to control target pests. However, at present, there are still few studies on the mechanism of Bt crop performance under extreme climates, so it is difficult to make accurate predictions. Secondly, on a global scale, the resistance of some pests to Bt crops is increasing. Climate change can affect the physiological and ecological processes of pests, which may accelerate the evolution of resistance and pose a greater threat to the sustainability of Bt crops. In addition, climate change will also alter the distribution range of pests and vector insects, exposing some new regions to the risks of BT-related diseases and pests. In the face of these uncertainties and challenges, an active adaptation strategy is very important. The field performance monitoring of Bt crops under various environmental pressures can be strengthened, multi-toxin compound Bt crops can be cultivated, non-BT crop isolation belts can be rationally configured, and new adjuvants and nanotechnology can also be used to enhance the insecticidal effect. At the same time, it is necessary to attach importance to pest resistance management, integrate ecological regulation with biodiversity conservation, and enhance the overall resilience of the agricultural system. To effectively address the complex challenges faced by Bt crops under climate change, close collaboration among entomologists, climatologists, agronomists and policymakers is required. Only through interdisciplinary integration can we better understand the multiple relationships among climate, crops, pests and the environment, formulate scientific and forward-looking management and policy plans, and ensure the long-term efficacy of Bt crops and global food security. Acknowledgments The authors extend sincere thanks to two anonymous peer reviewers for their feedback on the manuscript. Conflict of Interest Disclosure The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest. References Angon P.B., Mondal S., Jahan I., Datto M., Antu U.B., Ayshi F.J., and Islam M.S., 2023, Integrated pest management (IPM) in agriculture and its role in maintaining ecological balance and biodiversity, Advances in Agriculture, 2023(1): 5546373. https://doi.org/10.1155/2023/5546373 Aswathi N., Balakrishnan N., Srinivasan T., Kokiladevi E., and Raghu R., 2024, Diversity of Bt toxins and their utility in pest management, Egyptian Journal of Biological Pest Control, 34(1): 40. https://doi.org/10.1186/s41938-024-00803-6 Baidya A., and Saha A., 2024, Exploring the research trends in climate change and sustainable development: a bibliometric study, Cleaner Engineering and Technology, 18: 100720. https://doi.org/10.1016/j.clet.2023.100720 Bajwa A., Farooq M., Al‐Sadi A., Nawaz A., Jabran K., and Siddique K., 2020, Impact of climate change on biology and management of wheat pests, Crop Protection, 137: 105304. https://doi.org/10.1016/j.cropro.2020.105304 Bi P., Shi X., and Liu Q., 2020, Climate change and population health research in China: knowledge gaps and further directions, Advances in Climate Change Research, 11: 273-278. https://doi.org/10.1016/j.accre.2020.07.001 Carrière Y., Degain B., Unnithan G., Harpold V., Heuberger S., Li X., and Tabashnik B., 2017, Effects of seasonal changes in cotton plants on the evolution of resistance to pyramided cotton producing the Bt toxins Cry1Ac and Cry1F in Helicoverpa zea, Pest Management Science, 74(3): 627-637. https://doi.org/10.1002/ps.4746 Gassmann A.J., and Reisig D.D., 2022, Management of insect pests with Bt crops in the United States, Annual Review of Entomology, 68(1): 31-49. https://doi.org/10.1146/annurev-ento-120220-105502
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Bt Research 2025, Vol.16, No.3, 95-102 http://microbescipublisher.com/index.php/bt 95 Research Insight Open Access Bt Application Strategies to Minimize Environmental Impact FuminGao 1, JiongFu2 1 Tropical Microbial Resources Research Center, Hainan Institute of Tropical Agricultural Resources, Sanya, 572025, Hainan, China 2 Hainan Provincial Key Laboratory of Crop Molecular Breeding, Sanya, 572025, Hainan, China Corresponding author: jiong.fu@hitar.org Bt Research, 2025, Vol.16, No.3 doi: 10.5376/bt.2025.16.0012 Received: 28 Mar., 2025 Accepted: 18 May, 2025 Published: 30 May, 2025 Copyright © 2025 Gao and Fu, 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: Gao F.M., and Fu J., 2025, Bt application strategies to minimize environmental impact, Bt Research, 16(3): 95-102 (doi: 10.5376/bt.2025.16.0012) Abstract This review mainly discusses the usage methods of Bt (Bacillus thuringiensis), with a focus on how to reduce its impact on the environment. The emergence of Bt technology, especially the application of Bt genetically modified crops, has significantly reduced the usage of chemical pesticides. In this way, not only is the damage to the ecosystem reduced, but also the risk to human health is lowered. The article summarizes the basic modes of action of Bt toxins and several common application methods, such as foliar spraying, genetically modified crops and seed treatment. It also introduces the types of pests it can control and the limitations encountered during use. Bt has also played a significant role in integrated pest management. Research has found that Bt not only effectively kills pests but also further enhances the sustainability of agriculture through high-quality seeds and reasonable resistance management. In the future, if the application mode of Bt can be optimized and resistance management can be done well, it will be possible to better promote the development of green agriculture. This article aims to summarize the application experience of Bt, analyze its advantages and disadvantages, and provide references for future sustainable agriculture. Keywords Bt toxin; Environmental impact; Genetically modified crops; Pest management; Sustainable agriculture 1 Introduction Bacillus thuringiensis (Bt) is a common biological agent used to control agricultural pests. It is effective, highly targeted and relatively safe for humans and non-target organisms, so it is often regarded as an important alternative to chemical pesticides. Since the end of the 20th century, Bt has not only been used in fields in the form of sprays and granules, but also introduced into major crops such as cotton and corn through genetic engineering, thus forming Bt crops. These practices have accelerated the sustainable development of global agriculture (Glaser and Matten, 2003). The use of Bt crops and Bt formulations reduces chemical pesticides, lowers environmental toxicity, and also decreases health risks. For example, among small-scale farmers in India, Bt cotton significantly reduces the Environmental Impact Index (EIQ), has less negative effects than ordinary cotton, and the efficiency of high-quality Bt seeds is higher. In the United States, large-scale cultivation of Bt corn not only increased the yield but also reduced the frequency and dosage of pesticide use. However, the promotion of Bt technology has also encountered problems, such as pest resistance, ecological security and social acceptance (Glaser and Matten, 2003). In sustainable pest management, how to better apply Bt to reduce environmental impact is currently the focus of agricultural management. The scientific and reasonable use can slow down the resistance of pests, reduce ecological risks and promote the transformation of agriculture towards a green direction. The purpose of this review is to sort out and evaluate the latest research on the environmental impact of Bt applications. The focus is on the application of Bt crops and Bt preparations, their environmental effects and risks, as well as measures for sustainable management. By analyzing relevant literature, it is hoped to provide references for the green application and policy-making of Bt technology in the future. 2 Mechanism of Action and Scope of Use 2.1 How Bt toxins work against insect pests Bt (Bacillus thuringiensis) can produce three main insecticidal proteins: Cry, Vip and Cyt. All of them will act on
Bt Research 2025, Vol.16, No.3, 95-102 http://microbescipublisher.com/index.php/bt 96 the intestinal cells of insects, eventually leading to the death of pests. Cry toxin is activated in the alkaline environment of the insect's intestinal tract. It first binds to receptors on the surface of epithelial cells, such as cadherin, aminopeptidase N and alkaline phosphatase. Then it inserts into the cell membrane, makes holes, disrupts the osmotic balance, causes the cell to rupture, and the insect dies. The Vip toxin works in different ways. After binding to other receptors, it can induce apoptosis or open ion channels. Cyt toxin does not rely on receptors. It directly binds to lipids on the membrane and kills pests by destroying the membrane (Deist et al., 2014; Heckel, 2020; Liu et al., 2022; Li et al., 2024) (Figure 1). Figure 1 Cry toxin mode of action (Adopted from Aswathi et al., 2024) 2.2 Major applications: foliar sprays, transgenic crops, seed treatments There are mainly three application methods of Bt toxin. The first type is the traditional foliar spraying of Bt preparations, which is often used for various types of crops. The second type is genetic engineering, which involves introducing the Bt gene into crops to enable them to continuously express toxins on their own, such as Bt cotton and Bt corn. The third type is seed treatment, which involves coating the surface of the seeds with Bt protein, providing protection during the seedling stage. These methods have expanded the application scope of Bt and also improved the prevention and control efficiency (Chougule et al., 2013; Deist et al., 2014; Bravo et al., 2015). 2.3 Spectrum of target pests and limitations Bt toxin is effective against many pests, such as cotton bollworms and corn borers of Lepidoptera, corn root worms of Coleoptera, as well as some pests of diptera and hemiptera. But it is safe for non-target insects, mammals and humans. The targets of action of different Bt toxins are also different. Some pests, such as certain hemiptera and homoptera, are naturally insensitive to Bt. The development of pest resistance, differences in receptors and changes in intestinal enzyme activity also limit the application of Bt. Nowadays, through protein engineering, toxin modification and multi-toxin superposition, the range of action can be expanded and the development of resistance can also be delayed (Abdullah et al., 2009; Aswathi et al., 2024). 2.4 Role in integrated pest management (IPM) frameworks Because Bt toxins have strong selectivity and are relatively environmentally friendly, they are very important in integrated pest management (IPM). Bt crops and Bt preparations can be used in combination with biological control, chemical pesticides and agricultural measures. This can reduce the use of chemical pesticides and also protect natural enemies and the environment. In IPM, common methods include rotating or superimposing
Bt Research 2025, Vol.16, No.3, 95-102 http://microbescipublisher.com/index.php/bt 97 different Bt toxins, setting up non-BT crop shelters, and monitoring pest resistance. These measures can extend the service life of Bt technology and help achieve sustainable pest management (Bravo and Soberon, 2008; Bravo et al., 2015; Soberon et al., 2015; Afzal et al., 2024). 3 Environmental Concerns Associated with Bt 3.1 Ecological risks Bt crops and sprays are highly targeted and have little direct impact on non-target organisms. Many field and laboratory studies have shown that Bt protein has no obvious toxicity to invertebrates, mammals and birds. Compared with chemical pesticides, Bt crops have lower negative effects on the ecology (Koch et al., 2015; Twardowski et al., 2022). Some negative effects occasionally found in the laboratory mostly do not occur in the field (Koch et al., 2015). In addition, the use of Bt crops reduces broad-spectrum pesticides, helps protect natural enemies, and also promotes biodiversity (Lu et al., 2012). However, it is still necessary to track the potential impact of Bt proteins on non-target organisms over the long term (Manjunath, 2020; Peterson et al., 2020). 3.2 Resistance development in target pests Although Bt crops can delay the development of resistance, pests may still develop resistance to Bt proteins. There have been reports of pests developing resistance to a single Bt protein both in the laboratory and in the field, especially when there is no "high-dose/sanctuary" strategy. To slow down resistance, comprehensive management is required, such as planting sheltered areas, superimposing different toxins and continuous monitoring. 3.3 Gene flow and biodiversity concerns from transgenic Bt crops The genes of Bt crops may be transmitted to wild relatives through pollen, which poses a risk of gene mobility. Most studies suggest that this risk is very low in crops such as corn and soybeans. However, in areas with wild relatives such as cotton, sales and cultivation need to be restricted to avoid gene outflow (Then and Bauer-Panskus, 2017; Peterson et al., 2020). In addition, the large-scale cultivation of Bt crops may also change the structure of field biodiversity, so it is necessary to continuously assess its role in the ecosystem. 3.4 Persistence in soil and water ecosystems Bt protein decomposes rapidly in the soil and is not easy to accumulate. Its impact on non-target organisms in the soil is limited. However, spray components such as Bt spores may persist in the soil for many years and sometimes have certain impacts on soil ecology. Compared with traditional pesticides, Bt protein poses a much lower risk of pollution to water and soil. However, attention still needs to be paid to long-term accumulation and persistence in extreme environments. 4 Strategies to Minimize Environmental Impact 4.1 Resistance management Resistance management is very important to ensure the long-term use of Bt crops. A common approach is the "high-dose/sanctuary" strategy. It is to grow some non-BT crops around Bt crops to provide living space for BT-sensitive pests, which can slow down the accumulation of resistance genes (Shelton et al., 2000; Carriere et al., 2016; Arends et al., 2021). Research has found that the size, location and distance of the sheltered area from Bt crops all affect the effect. If multi-toxin Bt crops are used together with sanctuary areas, resistance can be better delayed (Carriere et al., 2016; Arends et al., 2021) (Figure 2). In addition, some scholars have proposed releasing individual pests sensitive to Bt as a new approach, which may help reverse the trend when resistance increases. 4.2 Application practices The rational application of Bt crops can alleviate environmental pressure. Its promotion has greatly reduced the usage of chemical pesticides and also lowered the harm to the environment and human health (Cannon, 2000; Chatla and SumanthKumar, 2017). Through crop rotation, intercropping and diversified planting, resistance pressure can be dispersed and secondary pest outbreaks can also be avoided. Combining field monitoring and precise pesticide application, and adjusting according to the characteristics of local pests, can also improve the efficacy of Bt crops and reduce the impact on non-target organisms (Macintosh, 2010; Manjunath, 2020).
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