Global Pest Research Articles

The Effects of Global Climate Warming on the Developmental Parameters of Helicoverpa armigera (Hübner, 1808) (Lepidoptera: Noctuidae)

Helicoverpa armigera (Hübner, 1808) is a significant global agricultural pest, particularly posing a major threat during the boll-forming stage of cotton. In recent years, the severity of its damage has increased markedly, and its population dynamics and biological characteristics may be profoundly affected by global climate change. This study conducted a systematic meta-analysis to evaluate the life history traits of H. armigera under conditions of rising global temperatures, different photoperiods, and humidity levels. A comprehensive analysis of 26 related studies revealed that different developmental stages of H. armigera have distinct temperature requirements. When the temperature is within an optimal range (32 °C to 35 °C), the development rate of H. armigera accelerates, the life cycle shortens, and the reproductive capacity of female moths increases. However, when the temperature exceeds 35 °C, development slows, mortality rates increase, and the oviposition of female moths decreases significantly, indicating a negative impact of high temperatures on growth and reproduction. Overall, as the temperature rises above 20 °C, various physiological indicators of H. armigera significantly improve, and at 32 °C, the larval development period and overall life cycle reach their shortest duration. This meta-analysis provides new insights into the biological responses of H. armigera in the context of climate change and offers a scientific basis for future control strategies.

Biological performance of Bollgard II® Bt-resistant vs susceptible population of pink bollworm, Pectinophora gossypiella (Saunders) on non-toxic diet

BackgroundThe pink bollworm, Pectinophora gossypiella (Saunders), is a devastating global pest of cotton that has caused substantial economic damage to Bt Bollgard-II® cotton plants in recent years due to the evolution of Bt resistance. The associated fitness cost is assumed to be one of the factors delaying the development of resistance against Bt transgenic crops. Hence, the present study was undertaken to assess the biological performance of pink bollworms by comparing the life history and demographic parameters of a resistant (Field-R) and susceptible (Lab-S) population.ResultsProlonged larval duration (23.40 days in Field-R vs 18.80 days in Lab-S population), total life cycle (male = 50.00 vs 42.80 days; female = 53.60 vs 46.20 days), reduced fecundity (100.60 vs 154.20 eggs/female) and fertility (88.00 vs 138.00 fertile eggs/female) was observed. The demographic parameters indicated a significant reduction in the net reproductive rate (184.27 vs 276.72), innate capacity for increase in number (0.11 vs 0.15), finite rate of increase in number (1.12 vs 1.16 female progenies produced/female/day), weekly multiplication rate (2.16 vs 2.86), potential fecundity (545.06 vs 634.11 eggs), number of hypothetical F2 females (33 955.65 vs 76 572.41), but longer mean length of generation (47.54 vs 37.74 days) and population doubling time (6.30 vs 4.62 days) in Field-R compared with Lab-S population. A stage-specific life table demonstrated the differences in survival rates between susceptible and resistant populations at various life stages, with the resistant population having higher generation mortality (0.22 vs 0.19).ConclusionsThe study confirms the involvement of fitness costs associated with Bt resistance in P. gossypiella. Despite reduced reproductive fitness, the resistant population tried prolonging the larval stage as a compensatory mechanism to repair the damaged host tissues due to Bt intoxication and for accumulation of enough nutrient reserves for normal pupation and adult emergence. Presence of a high proportion of double Bt-resistant larvae in the field coupled with continued noncompliance with refug planting certainly favours the flaring up of this monophagous pest despite the observed fitness costs. The resistance cannot be effectively reversed unless suitable alternative management strategies are deployed.

Impact of transinfection of Wolbachia from the planthopper Laodelphax striatellus on reproductive fitness and transcriptome of the whitefly Bemisia tabaci.

The whitefly Bemisia tabaci is critical global pest threatening crops and leading to agricultural losses. Wolbachia is an intracellular symbiotic bacterium in insects, which can regulate the growth and development of the host through various ways. In a prior study, Wolbachia was found to be transferred to whitefly and induce fitness changes. However, little is known about the underlying mechanisms of host-Wolbachia interactions in B. tabaci. In this study, a Wolbachia strain wStri was isolated from the small brown planthopper, Laodelphex striatellus, and transferred to B. tabaci. The distribution of Wolbachia in whiteflies was determined using fluorescence in situ hybridization. Reciprocal crossing experiments demonstrated that wStri did not induce cytoplasmic incompatibility phenotypes in B. tabaci, but prolonged the developmental duration of the offspring. We performed transcriptomic analysis of Wolbachia-infected female and male adults using Illumina-based RNA-Seq. A total of 843 differentially expressed genes (DEGs) were identified in infected females, among them 141 were significantly up-regulated and 702 were down-regulated by Wolbachia infection. In infected males, of 511 gene sets, 279 host genes were significantly up-regulated, and 232 were down-regulated by Wolbachia infection. KEGG analysis of DEGs demonstrated significant differences in gene pathway distribution between up-regulated and down-regulated genes. These genes are involved in various biological processes, including, but not limited to, detoxification, oxidation-reduction, metabolic processes, and immunity. The transcriptomic profiling of this study offers valuable information on the differential expression of genes in whiteflies following Wolbachia infection, and enhances our understanding of this host-symbiotic interaction.

Enhancing cotton whitefly (Bemisia tabaci) detection and counting with a cost-effective deep learning approach on the Raspberry Pi.

The cotton whitefly (Bemisia tabaci) is a major global pest, causing significant crop damage through viral infestation and feeding. Traditional B. tabaci recognition relies on human eyes, which requires a large amount of work and high labor costs. The pests overlapping generations, high reproductive capacity, small size, and migratory behavior present challenges for the real-time monitoring and early warning systems. This study aims to develop an efficient, high-throughput automated system for detection of the cotton whiteflies. In this work, a novel tool for cotton whitefly fast identification and quantification was developed based on deep learning-based model. This approach enhances the effectiveness of B. tabaci control by facilitating earlier detection of its establishment in cotton, thereby allowing for a quicker implementation of management strategies. We compiled a dataset of 1200 annotated images of whiteflies on cotton leaves, augmented using techniques like flipping and rotation. We modified the YOLO v8s model by replacing the C2f module with the Swin-Transformer and introducing a P2 structure in the Head, achieving a precision of 0.87, mAP50 of 0.92, and F1 score of 0.88 through ablation studies. Additionally, we employed SAHI for image preprocessing and integrated the whitefly detection algorithm on a Raspberry Pi, and developed a GUI-based visual interface. Our preliminary analysis revealed a higher density of whiteflies on cotton leaves in the afternoon and the middle-top, middle, and middle-down plant sections. Utilizing the enhanced YOLO v8s deep learning model, we have achieved precise detection and counting of whiteflies, enabling its application on hardware devices like the Raspberry Pi. This approach is highly suitable for research requiring accurate quantification of cotton whiteflies, including phenotypic analyses. Future work will focus on deploying such equipment in large fields to manage whitefly infestations.

Stability, Inheritance, Cross-Resistance, and Fitness Cost of Resistance to λ-Cyhalothrin in Cydia pomonella.

Insecticides are commonly utilized in agriculture and forestry for pest control, but their dispersal can pose hazards to humans and environment. Understanding resistance, inheritance patterns, and fitness costs can help manage resistance. A λ-cyhalothrin-resistant population (LCR) of Cydia pomonella, a global pest of pome fruits and walnuts, was obtained through selective insecticide breeding for 15 generations, showing stable moderate resistance (23.85-fold). This population was cross-resistant to deltamethrin (4.26-fold) but not to β-cypermethrin, chlorantraniliprole, chlorpyrifos, and avermectin. Genetic analysis revealed the resistance was autosomal, incompletely dominant, and controlled by multiple genes. Increased activity of glutathione S-transferases and cytochrome P450 monooxygenases (P450s) played a primary role in resistance, with specific genes up-regulated in LCR, and exhibited significant expression in midgut. LCR also exhibited fitness costs, including delays in development, reduced fecundity, and slower population growth. These findings contribute to understanding λ-cyhalothrin resistance in C. pomonella and can guide resistance management strategies.

How do global forest pests respond to increasing temperatures? – a meta‐analysis

Biotic disturbances caused by insects and pathogens have a major impact on forests in the Northern Hemisphere. Knowledge of the effects of increasing temperature on the performance of these forest pests will thus be crucial for predicting future disturbance risks. Here, we systematically review the direct effects of increasing temperatures on four functional subgroups of forest pests, including leaf chewers, sap suckers, bark and wood borers, and pathogens. We considered 118 studies (2003–2022) representing 72 pest species feeding on 33 host genera from sub‐tropical, temperate and boreal forests in Asia, Europe and North America. Based on a subset of 89 studies reporting the required data, we conducted a meta‐analysis 1) distinguishing the functional subgroups, and 2) considering the main life‐history traits, i.e. development, fitness and survival. A temperature corresponding to the expected mean temperature during the growing season in the years 2081–2100 had a significant positive effect on the overall performance of leaf chewers (+18%) and bark and wood borers (+10%), while sap suckers and pathogens remained unaffected. In contrast, performance was not or even significantly negatively affected when a more pronounced temperature increase, i.e. corresponding to the temperature maxima in 2081–2100, was considered. This finding reflects the non‐linear temperature–performance relationship beyond currently evolved temperature optima in insects and pathogens. Furthermore, we showed that differential responses of life‐history traits to increased temperatures may counterbalance each other (e.g. development versus survival), highlighting the importance of a multi‐trait approach to assessing the impact of global warming on pest performance. By quantifying the effects of increasing temperatures on forest pest performance, our results facilitate the prediction of biotic disturbance impacts in a future climate. For instance, they could provide a valuable contribution to the parameterization of large‐scale ecosystem models, which often do not explicitly consider the response of biotic disturbances to climate change.

Generation and characterization of a novel ovariole cell line derived from Spodoptera frugiperda in China with sensitivity to both SfMNPV and AcMNPV

Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV), belonging to the species Alphabaculovirus spofrugiperdae, has been recently registered as an insecticide in China. This virus has a specific effect on the global major agricultural pest Spodoptera frugiperda. To gain insights into viral infection, replication processes, and the complex formation of viral particles, in vitro studies using cell lines are essential tools. Although the IPLB-Sf9 and IPLB-Sf21 cell lines derived from S. frugiperda are widely used for studies on the infection and replication mechanisms of Autographa californica multiple nucleopolyhedrovirus (AcMNPV), their capacity to produce viral polyhedra after SfMNPV infection is not optimal. To address this limitation, a novel cell line named IOZCAS-Sf-1 has been developed from a S. frugiperda population sourced Yunnan, China. The mitochondrial COX1 gene analysis confirmed the species origin of the IOZCAS-Sf-1 cell line. Furthermore, a comparative study was carried out to contrast the COX1 gene sequence of this novel cell line with that of IPLB-Sf9, highlighting the distinctions between the two. Importantly, the IOZCAS-Sf-1 cells exhibited a remarkable ability to generate polyhedra when infected with AcMNPV and SfMNPV, respectively. Consequently, this cellular lineage is considered a promising and valuable resource. It serves not only to investigate the molecular mechanisms of viral replication and its impact on host cells, but also to explore the transfection efficiency of SfMNPV DNA. This exploration further expands into its potential application in recombinant DNA experiments, laying a theoretical groundwork for the advancement of more effective biopesticides and sustainable agricultural practices.

Carvacrol acts on the larval midgut of Spodoptera frugiperda by destroying the tissue structure and altering the bacterial community

The fall armyworm, Spodoptera frugiperda, has become a global invasive pest in recent years, threatening agricultural production. Carvacrol (CAR) is a multifunctional plant-derived compound and exhibited significant bioactivities against many pests. Our previous study found that CAR inhibited growth and development in S. frugiperda. However, the effects of CAR on the midgut of this pest remain unknown. In this study, the actions of CAR on the larval midgut of S. frugiperda were investigated. The results found that 1.0 and 2.0 g/kg CAR treatments destroyed the structure of the larval midgut based on hematoxylin-eosin staining and transmission electron microscope observation. In addition, 2.0 g/kg CAR exposure significantly altered the larval midgut bacterial community composition and structure. The results of the linear discriminant analysis effect size (LEfSe) analysis suggest that six bacterial genera contributed to the different structures of the larval bacterial community. Furthermore, PICRUSt2 analysis found that 16 bacterial function categories were altered by CAR treatment, of which 8 were significantly increased. Our results provided new insight into the toxicological mechanisms of CAR against S. frugiperda larvae and laid the foundation for the field application of S. frugiperda control.

Transcriptome-Wide Evaluation Characterization of microRNAs and Assessment of Their Functional Roles as Regulators of Diapause in Ostrinia furnacalis Larvae (Lepidoptera: Crambidae).

microRNAs (miRNAs) function as vital regulators of diapause in insects through their ability to post-transcriptionally suppress target gene expression. In this study, the miRNA of Ostrinia furnacalis, an economically important global crop pest species, was characterized. For the included analyses, 9 small RNA libraries were constructed using O. furnacalis larvae in different diapause states (non-diapause, ND; diapause, D; diapause-termination, DT). The results identified 583 total miRNAs, of which 256 had previously been identified, whereas 327 were novel. Furthermore, comparison analysis revealed that 119 and 27 miRNAs were differentially expressed in the D vs. ND and DT vs. D, respectively. Moreover, the expression patterns of their miRNAs were also analyzed. GO and KEGG analysis of the target genes of differentially expressed miRNAs highlighted the importance of these miRNAs as diapause regulators in O. furnacalis, especially through metabolic processes, endocrine processes, 20-hydroxyecdysone, and circadian clock signaling pathways. In summary, this study highlighted the involvement of specific miRNAs in the control of diapause in O. furnacalis. To the best of our knowledge, this is the first study to identify miRNA expression patterns in O. furnacalis, thereby providing reference and novel evidence enhancing our current understanding of how small RNAs influence insect diapause.

Dominant strain shift in the invasive fall armyworm (Lepidoptera: Noctuidae) populations in Thailand as inferred from mitochondrial COI and nuclear Tpi genes.

The fall armyworm, Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae), is a significant global pest, that exhibits 2 discernible strains, corn strain (CS) and rice strain (RS). After initial detection in the eastern hemisphere in 2016, the dominant strain was identified as RS based only on cytochrome C oxidase subunit I (COI) mitochondrial gene from limited samples from various countries, including Thailand. This study aimed to assess strain and haplotype variation in the S. frugiperda populations in Thailand using both mitochondrial COI and nuclear triosephosphate isomerase (Tpi) genes. Analyses of COI sequences (n = 105) revealed 2 predominant haplotypes, COICSh4 (82.86%) and COIRSh1 (17.14%), and the analyses of Tpi sequences (n = 99) revealed 6 haplotypes, with TpiCa1a (53.53%) being the most prevalent. Of the 98 caterpillar samples, the majority exhibited true CS (83.67%) for both genes. Meanwhile, interstrain hybrids, indicated by gene discordance, accounted for the minority (16.33%). Interestingly, despite the initial dominance of RS during the 2018 outbreak, the current study identified CS as the prevalent strain across all localities in Thailand. These findings suggested a shift in S. frugiperda dynamics in Thailand that was possibly influenced by factors, such as competitive exclusion principle, pesticide usage in rice cultivation, and preferences for corn over rice. Our study suggests a need to reexamine the previous reports of rice-strain dominance in various countries in the eastern hemisphere after the initial invasion.

Design the fusion double-strand RNAs to control two global sap-sucking pests

RNA interference (RNAi) is an effective pest management strategy through silencing the crucial genes in target organisms. However, the effectiveness of targeting a single gene is often limited by the silencing efficiency due to tissue or developmental stage-specific gene expression. Moreover, multiple pests often infest the same crop simultaneously under current ecological conditions. Therefore, a combined strategy of “targeting multiple genes” and “controlling multiple pests” is expected to yield better management results. In this study, homologous genes from two globally sap-sucking pests, the peach aphid (Myzus persicae) and the whitefly (Bemisia tabaci), were screened on a genome-wide scale. Subsequently, RNAi bioassays showed silencing the genes (MpAbd-A, MpH3, MpRpL27a, and MpScr) exhibited high mortalities in both species, which were further selected for designing fusion dsRNAs. These fusion dsRNAs resulted in higher mortalities in both pests than single gene silencing and posed a minimal off-target risk to the predator ladybeetle (Propylaea japonica) based on the sequence analysis. Finally, the tobacco plants expressing the fusion dsRNAs through virus-induced gene silencing (VIGS) technology enhanced the resistance to both pests. In conclusion, this study proposes a novel RNAi-based approach for managing two sap-sucking pests simultaneously.

Carboxylesterase α-EST5 is required for the red flour beetle to metabolize mugwort essential oil

The red flour beetle (Tribolium castaneum) is a global agricultural grain storage pest that seriously jeopardizes the food safety of wheat, corn, and other grains. Carboxylesterases belong to a family of multifunctional enzymes that can participate in the metabolism of toxic substances ingested by T. castaneum, conferring drug resistance. In this study we have cloned from T. castaneum a gene encoding carboxylesterase, α-EST5, which is expressed mainly in T. castaneum late larvae and late adults. Tissue expression pattern analysis showed that α-EST5 was mainly expressed in the larval gut and adult head. Moreover, α-EST5 was able to be induced to be expressed by mugwort essential oils and significantly increased the enzymatic activity of carboxylesterase in T. castaneum after mugwort essential oil treatment. The sensitivity of T. castaneum to mugwort essential oils was significantly increased after knockdown the expression of α-EST5 using RNAi (RNA interference) technology. Through our study, we demonstrated that the carboxylesterase α-EST5 plays an important role in the detoxification of mugwort essential oils by T. castaneum. This study results provide a reference for understanding the detoxification mechanism of T. castaneum to external toxic substances.

Establishing the distribution of Carpophilus truncatus in Australia using an integrative approach for an emerging global pest

The nitidulid beetle Carpophilus truncatus is rapidly becoming a major pest of nut crops around the world. This insect first infested Australian almonds in 2013 and has since escalated to be the preeminent insect pest for the industry. Data pertaining to C. truncatus distribution are scant, but without awareness of its origin, distribution, and ecological factors that influence distribution, efforts to understand and manage the insect as a pest are stymied. Here, we employ an integrative approach to gain a multifaceted understanding of the distribution of C. truncatus in Australia. Methods employed were (1) reviewing historical records in insect collections to establish the presence of C. truncatus prior to commercial almond horticulture, (2) field trapping of insects to establish presence in regions of interest, (3) laboratory trials to determine the thermal limits of the organism, and (4) correlative species distribution modelling to describe its current distribution. We find that C. truncatus is more widespread across Australia than was previously known, with historical records preceding commercial almond production in Australia by a century. The methods developed in this study can be applied elsewhere in the world where C. truncatus is an emerging pest, or to novel pest species as they arise with increasing frequency in a globalised and warming world.

Sex dimorphism in pupae and adults of the specialist Ipomoea batatas defoliator Bedellia somnulentella (Lepidoptera: Bedelliidae).

Bedellia somnulentella Zeller, 1847 (Lepidoptera: Bedelliidae), a global pest of the sweet potato Ipomoea batatas, was recorded in Brazil, but morphological information on the sexual dimorphism of this insect is scarce. The objective was to evaluate morphological characters of sexual dimorphism of B. somnulentella pupae and adults. External structures with sexual dimorphism were not detected in the last abdominal segments of B. somnulentella pupae. The females of this insect are heavier, which could be a distinctive sex characteristic. A pair of frenulum on the hind wings of females and only one on those of males, in addition to elongated cerci and bipartite genitalia in the latter and smaller cerci involving the last abdominal segment and an ovipositor in females, differentiate sexes of B. somnulentella.

Challenges in Assessing Repellency via the Behavioral Response by the Global Pest Tribolium castaneum to Protect Stored Grains.

Food security is an increasingly pressing global issue, and by 2050, food production will not be sufficient to feed the growing population. Part of global food insecurity can be attributed to post-harvest losses, including quantity and quality losses caused by stored-product pests like insects. It is thus timely to find management strategies to mitigate these losses and counteract food insecurity. The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), a global stored-product pest with a wide range of food sources, was used in this study to assess repellency to a selection of essential oils. Multiple behaviorally relevant methods were used to determine the efficacy of the essential oils in assays to pinpoint the most promising repellents. Experiments were used to assess individual and group behaviors with or without airflow and examined the behavioral variation in distance moved and the time spent away from the oil. It was found that exposure to essential oils and conditions of experimentation considerably influenced T. castaneum's behavioral response, but a clear candidate for repellency could not be chosen based on the collected data. Follow-up research is needed to pinpoint repellents for integrated pest management practices to protect grains from stored-product pests and to justify their use in and around commodities.

Population Dynamics of Bactrocera dorsalis (Diptera: Tephritidae) in Four Counties of Yunnan, China, by Electronic Monitoring System.

Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) is a global economic pest that poses a serious threat to the fruit industry. In the southwest of China, Yunnan Province sustains a severe infestation of B. dorsalis. An automated monitoring system designed for B. dorsalis was employed in this study to elucidate the annual population dynamics of B. dorsalis in four counties: Yuanjiang, Huaping, Guangnan, and Ludian in Yunnan. The system utilizes sex parapheromone and image recognition technology. The data uploaded by the device are used to analyze the annual population dynamics of B. dorsalis in different regions. The results showed that the populations of adult B. dorsalis in all four counties peaked twice annually, with Yuanjiang experiencing the earliest peak periods, followed by Huaping, Guangnan, and Ludian. Adult B. dorsalis occurred in Yuanjiang throughout the year, and Yuanjiang had the highest number of B. dorsalis monitored. In Huaping, adult B. dorsalis occurred in March-December and was highly active, with a high population density in 2019. Bactrocera dorsalis did not occur in December in Guangnan but only in May-October in Ludian. Bactrocera dorsalis abundance was correlated with temperature in all four areas. The outcomes of this experiment provide a practical foundation for developing control strategies targeting B. dorsalis in various orchards across each county.

Modeling human activity-related spread of the spotted lanternfly (Lycorma delicatula) in the US.

The spotted lanternfly (Lycorma delicatula) has recently spread from its native range to several other countries and forecasts predict that it may become a global invasive pest. In particular, since its confirmed presence in the United States in 2014 it has established itself as a major invasive pest in the Mid-Atlantic region where it is damaging both naturally occurring and commercially important farmed plants. Quarantine zones have been introduced to contain the infestation, but the spread to new areas continues. At present the pathways and drivers of spread are not well-understood. In particular, several human activity related factors have been proposed to contribute to the spread; however, which features of the current spread can be attributed to these factors remains unclear. Here we collect county level data on infestation status and four specific human activity related factors and use statistical methods to determine whether there is evidence for an association between the factors and infestation. Then we construct a network model based on the factors found to be associated with infestation and use it to simulate local spread. We find that the model reproduces key features of the spread 2014 to 2021. In particular, the growth of the main infestation region and the opening of spread corridors in the westward and southwestern directions is consistent with data and the model accurately forecasts the correct infestation status at the county level in 2021 with 81% accuracy. We then use the model to forecast the spread up to 2025 in a larger region. Given that this model is based on a few human activity related factors that can be targeted, it may prove useful to incorporate it into more elaborate predictive forecasting models and in informing management efforts focused on interstate highway transport and garden centers in the US and potentially for current and future invasions elsewhere globally.

Effect of critical temperatures on mortality and cuticle composition of Plodia interpunctella larvae: Insights from GC–MS analysis and SEM imaging

The Indian meal moth, Plodia interpunctella Hübner (Lep.: Pyralidae), is a significant global pest of stored products, particularly in temperate regions. This study investigated the impact of various temperatures (25, 50, 55, and 60 °C) over different durations (5, 10, 15 and 20 min) on the mortality and cuticle layer of third instar P. interpunctella larvae. Hexane solvent separated the cuticle layer of 3rd instar larvae treated at critical temperatures; Bis (trimethylsilyl) acetamide and Trimethylsilyl chloride were added for derivatization before injection into the GC–MS. Additionally, SEM imaging was used to observe the epicuticle surface of treated larvae under critical temperatures. The findings showed a direct relationship between increasing temperatures and the mortality rate of 3rd instar larvae, with complete mortality occurring in 20 min at 50 °C, in 15 min at 55 °C, and in just 10 min at 60 °C. Moreover, with an increase in temperature and exposure time, the weight of the larvae decreased significantly. GC–MS analysis unveiled that the waxy layer contained sixteen fatty acids within P. interpunctella cuticles; it was observed that as temperatures increased, there was a significant reduction in fatty acid levels. SEM imaging also revealed that rising temperatures led to a dramatic decrease in cohesion within the epicuticle layer; altering its physical and chemical structure caused dehydration, ultimately leading to death. These results suggest that utilizing critical temperatures for short durations can effectively control P. interpunctella populations.

Receptor interactions of protoxin and activated Vip3Aa structural conformations in Spodoptera exigua.

The Vip3Aa insecticidal protein, produced by Bacillus thuringiensis, has been effectively used in commercial Bt-crops to manage lepidopteran pests. Upon ingestion by larvae, the protoxin is processed by midgut proteases into the activated protein and binds specifically to its receptors in the midgut, leading to insect mortality. Cryo-EM resolution of the trypsin-processed Vip3Aa protein unveiled structural remodelling of the N-terminal region during the transition from protoxin to activated protein. This conformational change has been demonstrated to be crucial for toxicity against Spodoptera exigua larvae, a major global lepidopteran pest. In this study, we investigated the relevance of the structural remodelling for the specific binding to midgut receptors. We conducted in vitro binding assays with radiolabelled proteins and brush border membrane vesicles (BBMV) from S. exigua, employing structural mutants that lock the protein in either its protoxin or its activated conformation. Our results indicate that both structural stages of the protein share binding sites in the midgut epithelium. Moreover, in vivo competition assays revealed that Vip3Aa is able to bind to functional receptors in S. exigua larvae both as protoxin and as activated protein. Altogether, our findings point to both structural conformations contributing to receptor binding. In vivo, either spontaneous structural shift upon proteolytic cleavage or receptor-mediated remodelling could be occurring. However, the timing and context in which the conformational change occurs could influence membrane insertion and toxicity. Our results show the complex interplay between proteolytic processing, protein structure and receptor interactions in Vip3Aa's toxicity. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Host Preference and Developmental Dynamics of Fall Armyworm <i>Spodoptera frugiperda</i> (J E Smith)

The invasive fall army worm Spodoptera frugiperda (J E Smith) is a major global agricultural pest, originally from tropical and subtropical America, now affecting over 80 plant species across Africa, Asia, and beyond. This study examines its host preferences and developmental dynamics, focusing on four host plants: Zea mays L., Glycine max L., Carica papaya L., and Brassica oleraceae var. acephala L. Using a complete randomized design, mortality and developmental rates of larvae were evaluated. These results revealed that C. papaya and B. oleraceae leaves resulted in maximum larval mortality (80 and 65%, respectively). This can be attributed to the presence of secondary metabolites like tannins, terpenoids, flavonoids, and alkaloids, which exhibit toxic and antifeedant properties. This study highlights the armyworm's ability to adapt to alternative hosts like G. max and B. oleraceae, even surviving on C. papaya leaves, typically used as a botanical pesticide.