Establishment of RNAi-Mediated Pest Control Method for Red Imported Fire Ant, Solenopsis invicta.

RNAi plays a crucial role in insect gene function research and pest control field. Nonetheless, the variable efficiency of RNAi across diverse insects and off-target effects also limited its further application. In this study, we cloned six essential housekeeping genes from Solenopsis invicta and conducted RNAi experiments by orally administering dsRNA. Then, we found that mixing with liposomes significantly enhanced the RNAi efficiency by targeting for SiV-ATPaseE. Additionally, we observed a certain lethal effect of this dsRNA on queens by our established RNAi system. Furthermore, no strict sequence-related off-target effects were detected. Finally, the RNAi effect of large-scale bacteria expressing dsRNA was successfully confirmed for controlling S. invicta. In summary, this study established an RNAi system for S. invicta and provided a research template for the future development of nucleic acid drugs based on RNAi.

The Diversity of Wolbachia and Other Bacterial Symbionts in Spodoptera frugiperda.

Bacterial symbionts associated with insects can be crucial in insect nutrition, metabolism, immune responses, development, and reproduction. However, the bacterial symbionts of the fall armyworm Spodoptera frugiperda remain unclear. S. frugiperda is an invasive polyphagous pest that severely damages many crops, particularly maize and wheat. Here, we investigated the infection, composition, abundance, and diversity of bacterial symbionts, especially Wolbachia, in different tissues of S. frugiperda female adults. The infection prevalence frequencies of Wolbachia in five provinces of China, namely Pu'er, Yunnan; Nanning, Guangxi; Sanya, Hainan; Yunfu, Guangdong; and Nanping, Fujian, were assessed. The results indicated that Proteobacteria, Firmicutes, and Bacteroidetes were the three most dominant bacterial phyla in S. frugiperda adults. At the genus level, the abundant microbiota, which included Enterobacter and Enterococcus, varied in abundance between tissues of S. frugiperda. Wolbachia was found in the ovaries and salivary glands of S. frugiperda adults, and was present in 33.33% of the Pu'er, Yunnan, 23.33% of the Nanning, Guangxi, and 13.33% of the Sanya, Hainan populations, but Wolbachia was absent in the Yunfu, Guangdong and Nanping, Fujian populations. Further phylogenetic analyses revealed that all of the Wolbachia strains from the different S. frugiperda populations belonged to the supergroup B and were named the wFru strain. Since there were Wolbachia strains inducing cytoplasmic incompatibility in supergroup B, these findings may provide a foundation for developing potential biocontrol techniques against S. frugiperda.

Integrated approaches for Solenopsis invicta (Hymenoptera: Formicidae) management: insights from laboratory studies with entomopathogenic nematodes and insecticides.

BACKGROUND: In agricultural pest management, especially in combatting the invasive red imported fire ant (RIFA, Solenopsis invicta), significant challenges emerge as a consequence of the constraints of solely depending on chemical insecticides or entomopathogenic nematodes (EPNs). The utilization of chemical insecticides carries environmental and ecological hazards, whereas EPNs, when applied independently, might not offer the immediate effectiveness necessary for adequate RIFA suppression. Acknowledging these hurdles, our study investigates a synergistic method that integrates EPNs with chemical insecticides, aiming to fulfill the urgent demand for more efficient and environmentally friendly pest control solutions. RESULTS: Our evaluation focused on the interaction between the highly pathogenic Steinernema riobrave 7-12 EPN strain and prevalent insecticides, specifically beta-cypermethrin and a mixture of bifenthrin and clothianidin, applied at highly diluted recommended concentrations. The findings revealed a notable increase in RIFA mortality rates when EPNs and these insecticides were used together, outperforming the results achieved with each method individually. Remarkably, this enhanced efficacy was especially evident at lower concentrations of the bifenthrin-clothianidin mixture, indicating a valuable approach to minimizing reliance on chemical insecticides in agriculture. Furthermore, the high survival rates of EPNs alongside the tested insecticides indicate their compatibility and potential for sustained use in integrated pest management programs. CONCLUSION: Our research underscores the effectiveness of merging EPNs with chemical insecticides as a powerful and sustainable strategy for RIFA management. This combined approach not only meets the immediate challenges of pest control in agricultural settings, but also supports wider environmental objectives by reducing the dependency on chemical insecticides. © 2024 Society of Chemical Industry.

Histone Acetylation Enhancing Host Melanization in Response to Parasitism by an Endoparasitoid Wasp.

Endoparasitoids are insects that develop within other insects, employing unique strategies to enhance their offspring's survival. They inject polydnavirus and/or venom into their hosts along with eggs, effectively suppressing the host's immune system. Polydnavirus from Braconidae and Ichneumonidae wasps can integrate into the host's genome to express viral genes using the host's transcription systems. However, the ability of parasitoids without polydnavirus to manipulate host gene expression remains unclear. Lysine acetylation (LysAc), a post-translational modification critical for gene regulation, is hypothesized to be used by endoparasitoids lacking polydnavirus. We utilized the Chalcidoidea wasp Tetrastichus brontispae, which lacks polydnavirus, as an idiobiont endoparasitoid model to test this hypothesis, with pupae of the nipa palm hispid beetle Octodonta nipae as the host. Parasitism by T. brontispae resulted in the reduced expression of histone deacetylase Rpd3 and elevated levels of LysAc modification at histones H3.3K9 and H3.3K14 through proteomics and LysAc modification omics. The knockdown of Rpd3 increased the expression level of OnPPAF1 and OnPPO involved in the phenoloxidase cascade, leading to melanization in the host body whereby it resembled a mummified parasitized pupa and ultimately causing pupa death. This study enhances our understanding of how endoparasitoids employ histone acetylation to regulate immunity-related genes, offering valuable insights into their survival strategies.

A C-Type Lectin, RfCTL27, Activates the Immune Defense in the Red Palm Weevil Rhynchophorus ferrugineus (A.G. Olivier, 1791) (Coleoptera: Curculionidae: Dryophthorinae) by the Recognition of Gram-Negative Bacteria.

Red palm weevil, Rhynchophorus ferrugineus (Olivier), is a palm tree insect pest that causes significant damage in the many countries from the Indian sub-continent and southeast Asia into date palm-growing countries of Africa, the Middle East, and the Mediterranean Basin. This study is aimed at determining the role of a C-type lectin, RfCTL27, in the immune defense of RPW larvae. RfCTL27 is a secreted protein that possesses a QPD motif, being integral for the discrimination of Gram-negative bacteria. The abundance of RfCTL27 transcripts in the gut and fat body was significantly higher than that in other tissues. Six hours after injection of Escherichia coli, the expression level of RfCTL27 in the gut of RPW larvae was significantly elevated compared with other groups. At 12 h after injection of E. coli, the expression of RfCTL27 in fat body was dramatically induced in contrast with other treatments. More interestingly, the ability of RPW larvae to clear the pathogenic bacteria in the body cavity and gut was markedly impaired by the silencing of RfCTL27. Additionally, the expression levels of two antimicrobial peptide genes, RfCecropin in the gut and RfDefensin in fat body of RPW larvae, were significantly decreased. Taken together, these data suggested that RfCTL27 can recognize the Gram-negative bacterium and activate the expression of antimicrobial peptides to remove the invaded bacterial pathogens. This study provides a new scientific basis for improving the control efficiency of pathogenic microorganisms against red palm weevils in production practice.

Development of a Safe and Effective Bacillus thuringiensis-Based Nanobiopesticide for Controlling Tea Pests.

Mg(OH)2 was used as the nanocarrier of the Bacillus thuringiensis (Bt) Cry1Ac protein, and the synthesized Cry1Ac-Mg(OH)2 composites were regular and uniform nanosheets. Nano-Mg(OH)2 could effectively improve the insecticidal effect of the Cry1Ac protein toward Ectropis obliqua. It could enhance the damage degree of the Cry1Ac protein to intestinal epithelial cells and microvilli, induce and enrich the production of reactive oxygen species (ROS) in the midgut, and enhance the degradation of the Cry1Ac protein into active fragments. Furthermore, an anti-rinsing assay showed that the Cry1Ac-Mg(OH)2 composites were bound to the notch structure of the tea leaf surface. The retention of the Cry1Ac protein increased by 11.45%, and sprayed nano-Mg(OH)2 was rapidly absorbed by different tissues of tea plants. Moreover, nano-Mg(OH)2 and composites did not significantly affect non-target organisms. These results show that nano-Mg(OH)2 can serve as a safe and effective biopesticide carrier, which provides a new approach for stable and efficient Bt preparation.

Host-Encoded Aminotransferase Import into the Endosymbiotic Bacteria Nardonella of Red Palm Weevil.

Symbiotic systems are intimately integrated at multiple levels. Host-endosymbiont metabolic complementarity in amino acid biosynthesis is especially important for sap-feeding insects and their symbionts. In weevil-Nardonella endosymbiosis, the final step reaction of the endosymbiont tyrosine synthesis pathway is complemented by host-encoded aminotransferases. Based on previous results from other insects, we suspected that these aminotransferases were likely transported into the Nardonella cytoplasm to produce tyrosine. Here, we identified five aminotransferase genes in the genome of the red palm weevil. Using quantitative real-time RT-PCR, we confirmed that RfGOT1 and RfGOT2A were specifically expressed in the bacteriome. RNA interference targeting these two aminotransferase genes reduced the tyrosine level in the bacteriome. The immunofluorescence-FISH double labeling localization analysis revealed that RfGOT1 and RfGOT2A were present within the bacteriocyte, where they colocalized with Nardonella cells. Immunogold transmission electron microscopy demonstrated the localization of RfGOT1 and RfGOT2A in the cytosol of Nardonella and the bacteriocyte. Our data revealed that RfGOT1 and RfGOT2A are transported into the Nardonella cytoplasm to collaborate with genes retained in the Nardonella genome in order to synthesize tyrosine. The results of our study will enhance the understanding of the integration of host and endosymbiont metabolism in amino acid biosynthesis.

A ScWIP5 gene confers fall armyworm resistance by reducing digestive enzyme activities in sugarcane.

BACKGROUND: The fall armyworm, Spodoptera frugiperda, is one of the most dangerous pests to various crops. As the most crucial sugar crop, sugarcane is also constantly threatened by these pests. Plant wound-induced proteinase inhibitors (WIP) are natural defense proteins that play important roles in the defense system against insect attack. Breeding for resistance would be the best way to improve the variety characteristics and productivity of sugarcane. Screening and verification for potential plant endogenous insect-resistant genes would greatly improve the insect-resistant breeding progress of sugarcane. RESULTS: A sugarcane WIP5 gene (ScWIP5) was up-regulated 536 times after insect feeding treatment on previous published transcriptome databases. ScWIP5 was then cloned and its potential role in sugarcane resistance to fall armyworm evaluated by construction of transgenic Nicotiana benthamiana. The toxicity of ScWIP5 transgenic N. benthamiana to fall armyworm showed lower weight gain and higher mortality compared to wild-type N. benthamiana feeding group. Furthermore, the concentration of JA and NbAOC, NbAOS, and NbLOX from the Jasmin acid biosynthesis pathway was significantly induced in ScWIP5 transgenic N. benthamiana compared to the control. In addition, digestive enzyme actives from the insect gut were also evaluated, and trypsin and cathepsin were significantly lower in insects fed with ScWIP5 transgenic N. benthamiana. CONCLUSION: These results indicate that ScWIP5 might enhance insect resistance by increasing JA signal transduction processes and reducing insect digestive enzyme activities, thus impacting insect growth and development. © 2023 Society of Chemical Industry.

Host plant recognition by two odorant-binding proteins in Rhynchophorus ferrugineus (Coleoptera: Curculionidae).

BACKGROUND: Rhynchophorus ferrugineus, the red palm weevil (RPW), is a key pest that attacks many economically important palm species and that has evolved a sensitive and specific olfactory system to seek palm hosts. Odorant-binding proteins (OBPs) not only play crucial roles in its olfactory perception process but are also important molecular targets for the development of new approaches for pest management. RESULTS: Analysis of the tissue expression profiles of RferOBP8 and RferOBP11 revealed that these two Rhynchophorus ferrugineus odorant binding proteins (RferOBPs) exhibited high expression in the antennae and showed sexual dimorphism. We analyzed the volatiles of seven host plants by gas chromatography-mass spectrometry and screened 13 potential ligands by molecular docking. The binding affinity of two recombinant OBPs to aggregation pheromones and 13 palm odorants was tested by fluorescence competitive binding assays. The results revealed that eight tested palm volatiles and ferrugineol have high binding affinities with RferOBP8 or RferOBP11. Behavioral trials showed that these eight odor compounds could elicit an attraction response in adult RPW. RNA interference analysis indicated that the reduction in the expression levels of the two RferOBPs led to a decrease in behavioral responses to these volatiles. CONCLUSION: These results suggest that RferOBP8 and RferOBP11 are involved in mediating the responses of RPW to palm volatiles and to aggregation pheromones and may play important roles in RPW host-seeking. This study also provides a theoretical foundation for the promising application of novel molecular targets in the development of new behavioral interference strategies for RPW management in the future. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Exogenously applied zinc improves sugar-acid profile of loquat (Eriobotrya japonica Lindl.) by regulating enzymatic activities and expression of their metabolism-related genes.

Soluble sugars and organic acids are the most abundant components in ripe fruits, and they play critical roles in the development of fruit flavor and taste. In this study, loquat trees were sprayed with 0.1, 0.2 and 0.3% zinc sulphate. The contents of soluble sugars and organic acids were determined using HPLC-RID and UPLC-MS, respectively. The activities of key enzymes involved in sugar-acid metabolism were measured and expression profiling of related genes was done using RT-qPCR. The results revealed that 0.1% zinc sulphate was a promising treatment among other Zn applications with respect to the increased levels of soluble sugars and decreased acid contents in loquats. Correlation analysis showed that the enzymes i.e., SPS, SS, FK, and HK were may be involved in the regulation of fructose and glucose metabolism in the fruit pulp of loquat. While, the activity of NADP-ME showed negative and NAD-MDH showed a positive correlation with malic acid content. Meanwhile, EjSPS1-4, EjSS2-4, EjHK1-3, and EjFK1-6 may play an important role in soluble sugar metabolism in the pulp of loquat fruits. Similarly, EjPEPC2, EjPEPC3, EjNAD-MDH1, EjNAD-MDH3-5, EjNAD-MDH6 and EjNAD-MDH13 may have a vital contribution to malic acid biosynthesis in loquat fruits. This study provides new insights for future elucidation of key mechanisms regulating soluble sugars and malic acid biosynthesis in loquats.

Potential of entomopathogenic nematode-infected insect cadavers for the biocontrol of the red imported fire ant Solenopsis invicta.

BACKGROUND: Entomopathogenic nematodes (EPNs) in an aqueous suspension treatment showed potential in the biocontrol of the red imported fire ant Solenopsis invicta, whereas colony relocation following this inundative application had restricted overall effectiveness. As a novel strategy, EPN pre-infected insect cadavers carrying the next generation of nematode-infective juveniles (IJs) might be used to efficiently manage insect pests. However, this strategy has not been tested on S. invicta. This study evaluated EPNs emerging from wax moth Galleria mellonella cadavers to facilitate infection of S. invicta compared to those used in aqueous suspensions. RESULTS: Among seven EPN species, Steinernema riobrave and Heterorhabditis bacteriophora had the highest insecticidal efficiency in aqueous treatment. Cadavers of G. mellonella colonized by either one of two EPN species were not damaged by worker ants, ensuring that the IJs could develop within and emerge successfully from the cadavers. Likewise, compared to an aqueous suspension treatment with an equivalent number of IJs, treatment with an S. riobrave-infected cadaver increased the mortality of S. invicta by ≈10%, whereas infection by H. bacteriophora did not differ between treatments. However, the coexistence of S. riobrave- and H. bacteriophora-infected cadavers adversely affected the control of S. invicta, likely as a result of competition resulting from the increased dispersal of each emerging EPN species. CONCLUSION: Using EPN-infected G. mellonella cadavers as a strategy increased the mortality of S. invicta in the laboratory. This study provides positive evidence for the future applications of S. riobrave-infected cadavers in the biocontrol of red imported fire ants. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A peptidoglycan recognition protein regulates the immune response of Rhynchophorus ferrugineus Olivier (Coleoptera: Dryophthoridae) during exposure to pathogenic Gram-positive bacteria and fungi.

Red palm weevil (RPW), Rhynchophorus ferrugineus Olivier, is a tremendously destructive insect pest of palm trees worldwide. Although some biological agents have been used to fight against RPW larvae, the control efficiency is still dissatisfactory. This study aimed to determine the role of a peptidoglycan recognition protein (PGRP), RfPGRP-S3, in RPW immunity. RfPGRP-S3 is a secreted protein with a DF (Asp85-Phe86) motif, implying that it can discriminate Gram-positive bacteria. The abundance of RfPGRP-S3 transcripts in the hemolymph was significantly higher than that in other tissues. The expression of RfPGRP-S3 can be markedly induced by challenge with Staphylococcus aureus and Beauveria bassiana. After RfPGRP-S3 was silenced, the ability of individuals to clear the pathogenic bacteria in the body cavity and gut was significantly compromised. Furthermore, silencing RfPGRP-S3 dramatically impaired the survival rate of RPW larvae upon challenge with S. aureus. RT‒qPCR revealed that the expression levels of RfDefensin in the fat body and gut were decreased by RfPGRP-S3 silencing. Taken together, these results demonstrated that RfPGRP-S3 acts as a circulating receptor to promote the expression of the antimicrobial peptide gene upon the discrimination of pathogenic microbes.

The Symbiotic Bacteria-Xenorhabdus nematophila All and Photorhabdus luminescens H06 Strongly Affected the Phenoloxidase Activation of Nipa Palm Hispid, Octodonta nipae (Coleoptera: Chrysomelidae) Larvae.

Symbiotic bacteria form a mutualistic relationship with nematodes and are pathogenic to many insect pests. They kill insects using various strategies to evade or suppress their humoral and cellular immunity. Here we evaluate the toxic effects of these bacteria and their secondary metabolites on the survival and phenoloxidase (PO) activation of Octodonta nipae larvae using biochemical and molecular methods. The results show P. luminescens H06 and X. nematophila All treatments caused significant reductions in the number of O. nipae larvae in a dose-dependent manner. Secondly, the O. nipae immune system recognizes symbiotic bacteria at early and late stages of infection via the induction of C-type lectin. Live symbiotic bacteria significantly inhibit PO activity in O. nipae whereas heat-treated bacteria strongly increase PO activity. Additionally, expression levels of four O. nipae proPhenoloxidase genes following treatment with P. luminescens H06 and X. nematophila All were compared. We found that the expression levels of all proPhenoloxidase genes were significantly down-regulated at all-time points. Similarly, treatments of O. nipae larvae with metabolites benzylideneacetone and oxindole significantly down-regulated the expression of the PPO gene and inhibited PO activity. However, the addition of arachidonic acid to metabolite-treated larvae restored the expression level of the PPO gene and increased PO activity. Our results provide new insight into the roles of symbiotic bacteria in countering the insect phenoloxidase activation system.

The Cellular Immunological Responses and Developmental Differences between Two Hosts Parasitized by Asecodes hispinarum.

This study aims to investigate the developmental interactions of Asecodes hispinarum Boucek on Brontispa longissima Gestro and Octodonta nipae Maulik, as well as the cellular immune responses of B. longissima and O. nipae larvae in response to parasitism by A. hispinarum, with the hope of determining the reason for the difference in larval breeding of A. hispinarum in B. longissima and O. nipae. The effects of parasitism by A. hispinarum on the larval development, hemocyte count, and proportion of the hemocyte composition of the two hosts were carried out through selective assay and non-selective assay using statistical analysis and anatomical imaging. There was no significant difference in parasitic selection for A. hispinarum on the larvae of these two beetles; however, more eggs were laid to B. longissima larvae than to O. nipae larvae after parasitism by A. hispinarum. The eggs of A. hispinarum were able to grow and develop normally inside the larvae of B. longissima, and the parasitism caused the larvae of B. longissima become rigid within 7 d, with a high larval mortality rate of 98.88%. In contrast, the eggs of A. hispinarum were not able to develop normally inside the O. nipae larvae, with a high encapsulation rate of 99.05%. In addition, the parasitism by A. hispinarum caused a 15.31% mortality rate in O. nipae larvae and prolonged the larval stage by 5 d and the pupal stage by 1 d. The number of hemocytes during the 12, 24, 48, 72, and 96 h of the four instars from O. nipae larvae was 6.08 times higher than from B. longissima larvae of the same age. After 24 h of being parasitized by A. hispinarum, the total number of hemocytes and granulocyte proportion of B. longissima larvae increased significantly. However, the total number of hemocytes and plasmatocyte proportion of O. nipae increased significantly after 24, 72, and 96 h, and the proportion of granulocytes increased significantly after 12 h post-parasitism. The results in the present study indicated that A. hispinarum was unable to successfully reproduce offspring in O. nipae, but its spawning behavior had an adverse effect on the larval development of its host. In addition, the adequate number of hemocytes and more pronounced changes in the hemocyte count and hemocyte composition ratio in the larvae after parasitization may be important factors for the successful encapsulation in O. nipae larvae.

Sugar and acid profile of loquat (Eriobotrya japonica Lindl.), enzymes assay and expression profiling of their metabolism-related genes as influenced by exogenously applied boron.

Soluble sugars and organic acids are the most abundant components in ripe fruits, and they play critical roles in the development of fruit flavor and taste. Some loquat cultivars have high acid content which seriously affect the quality of fruit and reduce the value of commodity. Consequently, studying the physiological mechanism of sugar-acid metabolism in loquat can clarify the mechanism of their formation, accumulation and degradation in the fruit. Minerals application has been reported as a promising way to improve sugar-acid balance of the fruits. In this study, loquat trees were foliar sprayed with 0.1, 0.2 and 0.3% borax, and changes in soluble sugars and organic acids were recorded. The contents of soluble sugars and organic acids were determined using HPLC-RID and UPLC-MS, respectively. The activities of enzymes responsible for the metabolism of sugars and acids were quantified and expressions of related genes were determined using quantitative real-time PCR. The results revealed that 0.2% borax was a promising treatment among other B applications for the increased levels of soluble sugars and decreased acid contents in loquats. Correlation analysis showed that the enzymes i.e., SPS, SS, FK, and HK were may be involved in the regulation of fructose and glucose metabolism in the fruit pulp of loquat. While the activity of NADP-ME showed negative and NAD-MDH showed a positive correlation with malic acid content. Meanwhile, EjSPS1, EjSPS3, EjSS3, EjHK1, EjHK3, EjFK1, EjFK2, EjFK5, and EjFK6 may play an important role in soluble sugars metabolism in fruit pulp of loquat. Similarly, EjPEPC2, EjPEPC3, EjNAD-ME1, EjNAD-MDH1, EjNAD-MDH5-8, EjNAD-MDH10, and EjNAD-MDH13 may have a vital contribution to malic acid biosynthesis in loquat fruits. This study provides new insights for future elucidation of key mechanisms regulating soluble sugars and malic acid biosynthesis in loquats.

One-Step Construct Responsive Lignin/Polysaccharide/Fe Nano Loading System Driven by Digestive Enzymes of Lepidopteran for Precise Delivery of Pesticides.

A strategy that relies on the differences in feeding behavior between pests and natural enemies to deliver insecticides precisely was proposed. After proving that the digestive enzymes in Lepidopteran pests can act as triggers for lignin-based controlled-release carriers, a novel multiple-enzyme-responsive lignin/polysaccharide/Fe nanocarrier was constructed by combining the electrostatic self-assembly and chelation and loaded with lambda-cyhalothrin (LC) to form a nanocapsule suspension loading system. The nanocapsules were LC@sodium lignosulfonate/chitosan/Fe (LC@SL/CS/Fe) and LC@sodium lignosulfonate/alkyl polyglycoside quaternary ammonium salt/Fe (LC@SL/APQAS/Fe). LC@SL/APQAS/Fe was more stable than LC@SL/CS/Fe because it adsorbs more Fe3+, and the half-lives of LC in LC@SL/APQAS/Fe under UV irradiation were prolonged at 4.02- and 6.03-folds than those of LC@SL/CS/Fe and LC emulsifiable concentrate (LC EC), respectively. Both LC@SL/APQAS/Fe and LC@SL/CS/Fe have responsive release functions to laccase and cellulase, and the release rate of the former was slower. The insecticidal activity of LC@SL/APQAS/Fe against Agrotis ipsilonis was similar to those of LC@SL/CS/Fe and LC EC, while the toxicity of LC@SL/APQAS/Fe to the natural enemy was 2-3 times less than those of LC@SL/CS/Fe and LC EC. Meanwhile, the organic solvent component in the nanocapsule suspension was 94% less than that in the EC preparation. Therefore, the nano loading system based on SL/APQAS/Fe is a promising nanoplatform with the advantages of high efficiency, low toxicity, and environmental friendliness.

The Entomopathogenic Nematodes H. bacteriophora and S. carpocapsae Inhibit the Activation of proPO System of the Nipa Palm Hispid Octodonta nipae (Coleoptera: Chrysomelidae).

Entomopathogenic nematodes are biocontrol agents of invasive insect pests in soil and cryptic habitats. Nipa palm hispid, Octodonta nipae, is a pest of palm trees in Sothern China. To address its increasing damage, environmentally friendly control methods are required. This study aimed to test efficacy of Heterorhabditis bacteriophora and Steinernema carpocapsae on O. nipae and investigated the influence of secondary metabolites, nematodes, and their isolated cuticles on the activation of O. nipae's prophenoloxidase system using qPCR analysis. Our data revealed that O. nipae were less susceptible to H. bacteriophora than S. carpocapsae and penetrations of infective juveniles were higher with S. carpocapsae treatment than H. bacteriophora. Moreover, expression levels of the serine protease P56, prophenoloxidase activation factor 1, PPO and serine protease inhibitor 28 upon S. carpocapsae and H. bacteriophora infections were generally downregulated at all times. However, upon heating, the cuticles lost their inhibitory effects and resulted in upregulation of the PPO gene. Similarly, the addition of arachidonic acid reversed the process and resulted in the upregulation of the PPO gene compared to the control. Further work is needed to identify toxic substances secreted by these EPNs to evade O. nipae's immune system.

Multiple dsRNases Involved in Exogenous dsRNA Degradation of Fall Armyworm Spodoptera frugiperda.

RNAi is regarded as a promising technology for pest control. However, not all insects are sensitive to RNAi. Studies have confirmed that insect dsRNases are one of key factors affecting RNAi efficiency. In the current study, we identified four genes coding for dsRNases from the Spodoptera frugiperda genome. Spatial and temporal expression analysis showed that those dsRNases were highly expressed in the midgut and old larvae. Then a delivery method was applied for inducing efficient RNAi based on dsRNA encapsulated by liposome. Furthermore, we assessed degradation efficiency by incubation with dsRNA with gut juice or hemocoel to characterize potential roles of different SfdsRNases after suppression of SfdsRNase. The result showed that interferenced with any sfdsRNase reduced the degradation of exogenous dsRNA in midgut, interfered with sfdsRNase1 and sfdsRNase3 slowed down the degradation of exogenous dsRNA in hemolymph. Our data suggest the evolutionary expansion and multiple high activity dsRNase genes would take part in the RNAi obstinate in S. frugiperda, besides we also provide an efficient RNAi method for better use of RNAi in S. frugiperda.

Phytopathogens Increase the Preference of Insect Vectors to Volatiles Emitted by Healthy Host Plants.

Phytopathogen infections not only affect the physiology of host plants but also the preference of insect vectors; these modifications may increase the spread of infection. For this, we determined the effects of "Candidatus Liberibacter asiaticus" (CLas) infection on the preference of an insect vector (Diaphorina citri) for its uninfected or CLas-infected host (Citrus sinensis) and found that the infected vector preferred uninfected citrus, while the uninfected vector preferred infected citrus. We identified two compounds, (Z)-3 hexenyl and methyl salicylate, that were differentially abundant in the volatiles emitted by infected and uninfected citrus and two odorant-binding protein (OBP) genes differentially expressed between infected and uninfected vectors. The results of receptor-ligand binding assays indicated that CLas upregulated OBP A10 expression in the infected vector to target (Z)-3 hexenyl acetate emitted by uninfected citrus and induced citrus to emit more methyl salicylate for binding to OBP2 in the uninfected vector. Our results might be useful for the effective control of CLas infections.

A specific primed immune response in red palm weevil, Rhynchophorus ferrugineus, is mediated by hemocyte differentiation and phagocytosis.

Red palm weevil, Rhynchophorus ferrugineus, is an invasive and destructive pest that causes serious damages to palm trees. Like other invertebrates, red palm weevil relies solely on its innate immune response to fight invading microbes; by definition, innate immunity lacks adaptive characteristics. However, we show here that priming the red palm weevil larvae with heat-killed Bacillus thuringiensis specifically increased survival of the larvae during a secondary lethal infection with live bacteria, and B. thuringiensis primed larvae also showed a higher clearance efficiency for this bacterium, which indicated that the red palm weevil larvae possessed a strong immune priming response. The degree of enhanced immune protection was positively correlated with hemocyte proliferation and the level of phagocytic ability of hemocytes. Moreover, the red palm weevil larvae primed by B. thuringiensis induced the continuous synthesis of serotonin in the hemolymph, which in turn enhanced the phagocytic ability and pathogen clearance ability of the host, representing an important mechanism for the red palm weevil to achieve priming protection. Our findings reveal a specific immune priming of the red palm weevil larvae mediated by the continuous secretion of serotonin, and provide new insights into the mechanisms of invertebrates immune priming.