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The beet armyworm, Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae), has become a significant pest of chickpea in recent years. The polyphagous nature allows it to survive on various hosts during the off-season, creating a great menace to the crop in the following season. To assess the incidence and document the alternate hosts of S. exigua, a rapid roving survey was conducted in 11 chickpea-growing areas of Prakasam district, Andhra Pradesh, India. Additionally, the life history traits of S. exigua were studied on major alternate host plants under laboratory conditions (27 ± 1 °C and 70 ± 2% RH) to understand the survival, life expectancy and potential contribution to future populations. The results show that, among the different crops surveyed, the maximum larval incidence was noticed in maize (1.93 larvae/plant), cowpea (1.73 larvae/plant), and sunflower (1.68 larvae/plant) during the off-season. Life history studies of S. exigua showed that highest larval survival percentage was observed on chickpea (83.6%), while the lowest was on maize (44.5%). The mean developmental time for larvae was longest on maize (27.1 days) and shortest on chickpea (14.9 days). Larvae did not develop beyond the third instar when fed with chilli. The growth index statistics showed chickpea (9.2) was the most suitable host plant, whereas maize (0.9) was the least suitable host. The age-stage-specific survival rate (Sxj) varied across developmental stages, and the survival curves overlapped, indicating different growth rates among individuals. The life expectancy (exj) at age zero was highest on groundnut (37.06 days). The intrinsic rate of increase (r) of S. exigua was lowest on maize (0.10 ± 0.0013) and highest on chickpea (0.22 ± 0.0010). Similarly, the net reproductive rate (R0) was highest on chickpea (846.39 ± 18.22) and lowest on maize (59.50 ± 2.06). The population doubled every 3.08 ± 0.011 days on chickpea compared to 7.22 ± 0.80 days on maize. The study conclusively indicates that chickpea and sunflower, primarily cultivated during the rabi season in India, are the most preferred hosts for S. exigua. In contrast, maize and cotton, mainly grown during the kharif season, are less preferred and merely support the pest's survival. Consequently, S. exigua switches hosts between different crops growing seasons, so effective management of S. exigua during the kharif season can help prevent pest outbreaks during the rabi season. [ABSTRACT FROM AUTHOR]

Viral infection can regulate the cell cycle, thereby promoting viral replication. Hijacking and altering the cell cycle are important for the virus to establish and maintain a latent infection. Previously, Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV)-latently infected P8-Se301-C1 cells, which grew more slowly than Se301 cells and interfered with homologous SeMNNPV superinfection, were established. However, the effects of latent and superinfection with baculoviruses on cell cycle progression remain unknown. In this study, the cell cycle profiles of P8-Se301-C1 cells and SeMNPV or Autographa californica multiple nucleopolyhedrovirus (AcMNPV)-infected P8-Se301-C1 cells were characterized by flow cytometry. The results showed that replication-related genes MCM4, PCNA, and BAF were down-regulated (p < 0.05) in P8-Se301-C1 cells, and the S phase of P8-Se301-C1 cells was longer than that of Se301 cells. P8-Se301-C1 cells infected with SeMNPV did not arrest in the G2/M phase or affect the expression of Cyclin B and cyclin-dependent kinase 1 (CDK1). Furthermore, when P8-Se301-C1 cells were infected with SeMNPV after synchronized treatment with hydroxyurea and nocodazole, light microscopy and qRT-PCR analysis showed that, compared with unsynchronized cells and S and G2/M phase cells, SeMNPV-infected P8-Se301-C1 cells in G1 phase induced G2/M phase arrest, and the amount of virus adsorption and intracellular viral DNA replication were significantly increased (p < 0.05). In addition, budded virus (BV) production and occlusion body (OB)-containing cells were both increased at 120 h post-infection (p < 0.05). The expression of Cyclin B and CDK1 was significantly down-regulated at 48 h post-infection (p < 0.05). Finally, the arrest of SeMNPV-infected G1 phase cells in the G2/M phase increased BV production (p < 0.05) and the number of OB-containing cells. In conclusion, G1 phase infection and G2/M arrest are favorable to SeMNPV proliferation in P8-Se301-C1 cells, thereby alleviating the homologous superinfection exclusion. The results contribute to a better understanding of the relationship between baculoviruses and insect cell cycle progression and regulation. [ABSTRACT FROM AUTHOR]

Gut microbiota plays a functional role in nutrition among several insects. However, the situation is unclear in Lepidoptera. Field studies suggest the microbiome may not be stable and is determined by diet, while in the laboratory, Lepidoptera are routinely reared on diet containing antibiotics with unknown effects on microbial communities. Furthermore, molecular approaches for the characterization of lepidopteran microbiomes rarely describe the metabolically active gut bacteria. The aim of this study was to evaluate how diet and antibiotics affect Spodoptera exigua (Hübner) growth and the diversity and activity of the gut bacteria community. We assessed how alfalfa and wheat germ-based diets affected larval growth, in the presence and absence of streptomycin. Alfalfa diet improved larval growth, pupal mass, and survival, but antibiotic was only beneficial in the wheat germ diet. We observed diet-driven changes in the gut bacterial communities. In the active community, the alfalfa colony was dominated by Enterococcus and Rhodococcus whereas in the wheat germ colony, only Enterococcus was present. In contrast, spore-forming Bacilli species were very common members of the DNA community. In both cases, streptomycin had a selective effect on the relative abundance of the taxa present. Our study highlights the importance of characterizing both the diversity and activity of the gut microbiota community. DNA-derived communities may include environmental DNA, spores, or non-viable bacteria, while RNA-derived communities are more likely to give an accurate representation of the diversity of active members that are potentially directly involved in the metabolic processes of the host. [ABSTRACT FROM AUTHOR]

Various studies have addressed the impact of microbial inoculants on the composition of the resident microbiome. How microbial inoculants impact plant metabolism and interact with the resident rhizobiota under herbivory stress remains elusive. Here, we investigated the impact of two bacterial and two fungal inoculants, inoculated as single species and as a synthetic community, on the rhizosphere microbiome and volatilome of tomato plants (Solanum lycopersicum) comparing nonstress conditions to exposed to leaf herbivory by Spodoptera exigua. Based on amplicon sequencing analysis, rhizobacterial community composition was significantly affected by all four inoculants and the magnitude of this effect was dependent on herbivory stress. Fungal community composition was altered by the microbial inoculants but independent of herbivory stress. The rhizosphere volatilome was impacted by the microbial inoculation and differences between treatments were evened under herbivory stress. Each microbial inoculant caused unique changes in the volatilome of stressed plants but also shared similar responses, in particular the enhanced production of dimethyl disulfide and benzothiazole. In conclusion, the introduction of microbial inoculants in the tomato rhizosphere caused unique as well as common changes in the rhizosphere microbiome and volatilome, but these changes were minor compared to the microbiome changes induced by herbivory stress. [ABSTRACT FROM AUTHOR]

In order to evaluate the effect of different weed management treatments on weeds, pest and natural enemies populations in sesame (Sesamum indicum L.), a 2-year study was conducted in East Azarbaijan, Iran in 2020–2021. The study was conducted based on randomized complete block design with four replications. The weed management treatments consisted of trifluralin use (960 g ai ha−1), wheat straw mulch (WSM), living mulches of fenugreek (Trigonella foenum-graecum L.) (FLM), bitter vetch (Vicia ervilia L.) (VLM), calendula (Calendula officinalis L.) (CLM) and one-time hand weeding (OHW). The effect of weed management treatment was significant on densities of insect pests, natural enemies and weed and also weed biomass and sesame seed yield. The lowest densities of insect pests including Myzus persicae, Brevicoryne brassicae, Helicoverpa armigera and Spodoptera exigua were observed in CLM treatment. Also, the highest densities of natural enemies Coccinella septompunctata, Coccinella undecimpunctata and Orius niger were observed in CLM treatment. The highest reductions in grass (51.0%), broadleaf (72.0%), and total (62.6%) weed biomasses and highest seed yield (1456 kg ha−1) were obtained in OHW. The seed yields in CLM and WSM treatments were not significantly different with trifluralin treatment and could be recommended in sustainable production of sesame. [ABSTRACT FROM AUTHOR]

Cruciferous plants manufacture glucosinolates (GSLs) as special and important defense compounds against insects. However, how insect feeding induces glucosinolates in Brassica to mediate insect resistance, and how plants regulate the strength of anti-insect defense response during insect feeding, remains unclear. Here, mustard (Brassica juncea), a widely cultivated Brassica plant, and beet armyworm (Spodoptera exigua), an economically important polyphagous pest of many crops, were used to analyze the changes in GSLs and transcriptome of Brassica during insect feeding, thereby revealing the plant–insect interaction in Brassica plants. The results showed that the content of GSLs began to significantly increase after 48 h of herbivory by S. exigua, with sinigrin as the main component. Transcriptome analysis showed that a total of 8940 DEGs were identified in mustard challenged with beet armyworm larvae. The functional enrichment results revealed that the pathways related to the biosynthesis of glucosinolate and jasmonic acid were significantly enriched by upregulated DEGs, suggesting that mustard might provide a defense against herbivory by inducing JA biosynthesis and then promoting GSL accumulation. Surprisingly, genes regulating JA catabolism and inactivation were also activated, and both JA signaling repressors (JAZs and JAMs) and activators (MYCs and NACs) were upregulated during herbivory. Taken together, our results indicate that the accumulation of GSLs regulated by JA signaling, and the regulation of active and inactive JA compound conversion, as well as the activation of JA signaling repressors and activators, collectively control the anti-insect defense response and avoid over-stunted growth in mustard during insect feeding. [ABSTRACT FROM AUTHOR]

Numerous nematodes in the genus Oscheius possess entomopathogenic abilities. These nematodes also kill their insect hosts by releasing their symbiotic bacteria within 48–72 h. In this study, 12 indigenous isolates of Oscheius myriophilus based on molecular, morphological, and morphometric studies were recovered from different undisturbed soils in Thailand. Moreover, the virulence of 12 O. myriophilus at a rate of 25 IJs/cm2 against fifth‐instar larvae of Galleria mellonella ranged from 56%–86% after 72 h of exposure. Oscheius myriophilus EPNKU40 exhibited the highest efficacy in causing mortality in the insect larvae. It also killed third‐instar larvae of Spodoptera litura and Spodoptera exigua up to 60% after 72 h of exposure. The median lethal concentration (LC50) values of O. myriophilus EPNKU40 against G. mellonella larvae after 48 and 72 h of exposure were 11 and 4 IJs/cm2, respectively. The discovery of O. myriophulus is the first record in Thailand characterized using morphological, morphometric, and molecular diagnostic tools, which have shown lethal effects against insect pests and can later be utilized as biocontrol agents after several comprehensive assessments. [ABSTRACT FROM AUTHOR]

Plant and soil biodiversity can have significant effects on herbivore resistance mediated by plant metabolites. Here, we disentangled the independent effects of plant diversity and soil legacy on constitutive and herbivore‐induced plant metabolomes of three plant species in two complementary microcosm experiments. First, we grew plants in sterile soil with three different plant diversity levels. Second, single plant species were grown on soil with different plant diversity‐induced soil legacies. We infested a subset of all plants with Spodoptera exigua larvae, a generalist leaf‐chewing herbivore, and assessed foliar and root metabolomes. Neither plant diversity nor soil legacy had significant effects on overall foliar, root, or herbivore‐induced metabolome composition. Herbivore‐induced metabolomes, however, differed from those of control plants. We detected 139 significantly regulated metabolites by comparing plants grown in monocultures with conspecifics growing in plant or soil legacy mixtures. Moreover, plant–plant and plant–soil interactions regulated 141 metabolites in herbivore‐induced plants. Taken together, plant diversity and soil legacy independently alter the concentration and induction of plant metabolites, thus affecting the plant's defensive capability. This is a first step toward disentangling plant and soil biodiversity effects on herbivore resistance, thereby improving our understanding of the mechanisms that govern ecosystem functioning. [ABSTRACT FROM AUTHOR]

Cruciferous plants produce sulforaphane (SFN), an inhibitor of nuclear histone deacetylases (HDACs). In humans and other mammals, the consumption of SFN alters enzyme activities, DNA-histone binding, and gene expression within minutes. However, the ability of SFN to act as an HDAC inhibitor in nature, disrupting the epigenetic machinery of insects feeding on these plants, has not been explored. Here, we demonstrate that SFN consumed in the diet inhibits the activity of HDAC enzymes and slows the development of the generalist grazer Spodoptera exigua, in a dose-dependent fashion. After consuming SFN for seven days, the activities of HDAC enzymes in S. exigua were reduced by 50%. Similarly, larval mass was reduced by 50% and pupation was delayed by 2–5 days, with no additional mortality. Similar results were obtained when SFN was applied topically to eggs. RNA-seq analyses confirm that SFN altered the expression of thousands of genes in S. exigua. Genes associated with energy conversion pathways were significantly downregulated while those encoding for ribosomal proteins were dramatically upregulated in response to the consumption of SFN. In contrast, the co-evolved specialist feeder Trichoplusia ni was not negatively impacted by SFN, whether it was consumed in their diet at natural concentrations or applied topically to eggs. The activities of HDAC enzymes were not inhibited and development was not disrupted. In fact, SFN exposure sometimes accelerated T. ni development. RNA-seq analyses revealed that the consumption of SFN alters gene expression in T. ni in similar ways, but to a lesser degree, compared to S. exigua. This apparent resistance of T. ni can be overwhelmed by unnaturally high levels of SFN or by exposure to more powerful pharmaceutical HDAC inhibitors. These results demonstrate that dietary SFN interferes with the epigenetic machinery of insects, supporting the hypothesis that plant-derived HDAC inhibitors serve as "epigenetic weapons" against herbivores. [ABSTRACT FROM AUTHOR]

Several herbivorous insects consume certain metabolites from plants for other purposes than nutrition, such as defence. Adults of the turnip sawfly, Athalia rosae take up specific terpenoids, called clerodanoids, from Ajuga reptans. These metabolites are slightly modified by the sawflies and influence their mating behaviour and defence against predators. We characterised these metabolites and investigated their localisation in the insect and the specificity of the uptake and metabolite modification. Therefore, we performed feeding assays with adults and larvae of A. rosae as well as larvae of Spodoptera exigua, followed by chemical analyses. Two main clerodanoid-derived metabolites were detected in the abdomen and thorax but also on the surface of the adults. Small amounts were also found in larvae of the sawfly, while they were not detectable in S. exigua. Our findings provide new insights into the peculiarities of pharmacophagy and specialised metabolism in A. rosae. [ABSTRACT FROM AUTHOR]

In the conditions of Khoronk settlement of Armavir marz, Armenia, Helicoverpa armigera (syn. Chloridea armigera Hübner) and Spodoptera exigua (syn. Caradrina exigua Hübner) are the chief pests damaging the pepper plants in their larval stage. In crop season 2022, experiments on these pests in pepper fields tested the insecticides that mainly control the insects. The insecticides tested against Helicoverpa armigera and Spodoptera exigua included Eforia, Belt, Decis F-Lux, and Spintor. The Arrivo served as standard, and the experiment also had a control. As a result of the conducted research, the insecticides Belt, Decis F-Lux, and Eforia showed the highest biological and economic efficiency in controlling Helicoverpa armigera and Spodoptera exigua. The study also ran a biochemical analysis of the pepper harvest to know the effects of the applied insecticides on the peppers' quality indicators. [ABSTRACT FROM AUTHOR]

Plant-plant signalling via volatile organic compounds (VOCs) has been studied intensively, but its contingency on abiotic conditions (e.g., soil nutrients, drought, warming) is poorly understood. To address this gap, we carried out a greenhouse experiment testing whether soil nutrients influenced signalling between potato (Solanum tuberosum) plants in response to insect leaf herbivory by the generalist caterpillar Spodoptera exigua. We placed pairs of plants in plastic cages, where one plant acted as a VOC emitter and the other as a receiver. We factorially manipulated soil nutrients for both emitter and receiver plants, namely: unfertilized (baseline soil nutrients) vs. fertilized (augmented nutrients). Then, to test for signalling effects, half of the emitters within each fertilization level were damaged by S. exigua larvae and the other half remained undamaged. Three days after placing larvae, we collected VOCs from emitter plants to test for herbivory and fertilization effects on VOC emissions and placed S. exigua larvae on receivers to test for signalling effects on leaf consumption and larval mass gain as proxies of induced resistance. We found that herbivory increased total VOC emissions and altered VOC composition by emitter plants, but these effects were not contingent on fertilization. In addition, bioassay results showed that receivers exposed to VOCs from herbivore-damaged emitters had lower levels of herbivory compared to receivers exposed to undamaged emitters. However, and consistent with VOC results, fertilization did not influence herbivore-induced signalling effects on receiver resistance to herbivory. In sum, we found evidence of S. exigua-induced signalling effects on resistance to herbivory in potato plants but such effects were not affected by increased soil nutrients. These results call for further work testing signalling effects under broader range of nutrient concentration levels (including nutrient limitation), teasing apart the effects of specific nutrients, and incorporating other abiotic factors likely to interact or covary with soil nutrients. [ABSTRACT FROM AUTHOR]

The soil-derived Bacillus toyonensis HSY140 strain was found to produce parasporal crystalline inclusions. Genome sequencing and annotation did not find the three-domain Cry (3d-Cry) and Cyt toxins, but a novel mpp23-like gene (918 bp) containing an ETX/MTX2 domain was detected. Alignment and phylogenetic analysis revealed that the translated Mpp23-like protein had the highest homology to Cry23Aa1 (now named Mpp23Aa1, AAA22333.1). Cloning and expression of the mpp23-like gene into the acrystalliferous Bacillus thuringiensis BMB171 (cry-) generated a recombinant strain able to produce elliptical parasporal crystals with the same shape as those of the HSY140 strain. Finally, bioassay experiments indicated that the expressed Mpp23-like protein did not exhibit any activity to the lepidopteran insects of Plutella xylostella, Helicoverpa armigera, and Spodoptera exigua and the dipteran insect of Aedes aegypti. Altogether, we have characterized for the first time a new toxin, Mpp23-like protein, responsible for the formation of crystalline inclusions in B. toyonensis HSY140 strain. [ABSTRACT FROM AUTHOR]

Onion is an important crop in the province of Nueva Ecija, Philippines. Currently, its production is being constrained by onion armyworm (OAW; Spodoptera exigua). The impact of planting dates and distance on the infestation of OAW was studied across two productions. The aim is to evaluate the influence of different combinations of planting dates (November, December, and January) and row spacing [5 cm x 10 cm, 8 cm x 10 cm, 10 cm x 10 cm, and farmer's practice or waray (6-10 cm x 6-10 cm)] on the damage and population density of OAW. The count of observed OAW larvae from the earliest month (November) and during the month of the usual production period (November-December) was negligible to minimal. However, a significant increase in the OAW population during late planting (January). In terms of leaf damage caused by the OAW feeding, November, December, and January planting had an increasing percentage as the OAW population also increased. There was an increase in bulb diameter as the row spacing widens (10 cm x 10 cm), as well as an increase in the number of marketable bulb onions when it is narrow (5 cm x 10 cm). This study showed that planting dates and distances should be one of the major considerations in onion production and insect pest management. [ABSTRACT FROM AUTHOR]

Spodoptera exigua (Hübner), a highly destructive pest of agricultural crops, is often managed through the use of chemical pesticides. However, the use of chemical pesticides can have negative impacts on human health and the environment, making it important to find sustainable and alternative approaches to effectively manage this pest. One promising solution is the use of inhibitors that hinder the activity of proteases in the insect's digestive tract. Many digestive proteases, such as chymotrypsin, are produced as inactive zymogens with N-terminal pro-regions, which act as intramolecular chaperones and inhibitors of cognate catalytic regions. The present study aimed to utilize various bioinformatics tools to identify the physicochemical properties, secondary structures, and topology of chymotrypsin from S. exigua. Furthermore, we evaluated the potential of peptide inhibitors derived from the pro-region of zymogens that could be utilized as mimetic inhibitors for chymotrypsin in S. exigua. Homology molecular modeling was performed using SWISS-MODEL, with the predicted model validated by various programs. Molecular docking studies between five homologous species-derived protease inhibitors and the predicted model following by molecular dynamics (MD) simulation coupled with Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA) calculations were also applied. The analysis of peptides/enzyme interactions revealed the antagonistic capacity of two screened inhibitors against S. exigua chymotrypsin. Protein-protein interaction networks demonstrated that chymotrypsin from S. exigua interacted with eleven other proteins in a high confidence score. Active site analysis revealed that S219, D230, and H232 serve as catalytic residues. These findings demonstrate a central role for computational methods in designing a potent inhibitor peptide that is highly specific and selective to its mature enzyme. Our study could be promising for future insecticide designs used in S. exigua control. [ABSTRACT FROM AUTHOR]

Here, we provide mechanistic support for the involvement of the CYP9A subfamily of cytochrome P450 monooxygenases in the detoxification of host plant defense compounds and chemical insecticides in Spodoptera exigua and Spodoptera frugiperda. Our comparative genomics shows that a large cluster of CYP9A genes occurs in the two species but with significant differences in its contents, including several species-specific duplicates and substantial sequence divergence, both between orthologs and between duplicates. Bioassays of CRISPR-Cas9 knockouts of the clusters show that, collectively, the CYP9As can detoxify two furanocoumarin plant defense compounds (imperatorin and xanthotoxin) and insecticides representing three different chemotypes (pyrethroids, avermectins, and oxadiazines). However, in vitro metabolic assays of heterologously expressed products of individual genes show several differences between the species in the particular CYP9As with activities against these compounds. We also find that the clusters show tight genetic linkage with high levels of pyrethroid resistance in field strains of the two species. We propose that their divergent amplifications of the CYP9A subfamily have not only contributed to the development of the broad host ranges of these species over long evolutionary timeframes but also supplied them with diverse genetic options for evolving resistance to chemical insecticides in the very recent past. [ABSTRACT FROM AUTHOR]

Baculoviruses are successful microbial control agents used in the biological control of agricultural pest species, especially in the order Lepidoptera. The beet armyworm, Spodoptera exigua is a popular agricultural pest in the world. S exigua larvae, which are active in the all-summer period, cause economic losses by damaging many crops in agricultural production areas. This article aims to analyze the full genome of Spodoptera exigua multiple nucleopolyhedroviruses from Iran (SeMNPV-IR) and to determine the geographical difference between the strains at the genomic level. The full genome of SeMNPV-IR is 135.764 base pairs in length that contained 136 open reading frames (ORFs), and 43.92% G + C content. The seven homologous repeated (hr) regions were identified. In the results of genome-wide phylogenetic analysis, it was determined that the SeMNPV-IR genome isolated from Iran was interestingly close to the genome of the US and Korea isolates. However, there are significant differences in the two hypothetical (Orf 83 and Orf 104) genes. The SeMNPV-IR has a unique homolog repeat region (hr1, 96 bp) that is not found in other SeMNPV genomes, and it also differs in terms of the hr2 region. In silico restriction endonuclease analysis by StuI and SacII enzymes show that there were significant differences between all geographic isolates of SeMNPV. [ABSTRACT FROM AUTHOR]

Various plant species contain terpene secondary metabolites, which disrupt insect growth and development by affecting the activity of juvenile hormone-degrading enzymes, and the juvenile hormone (JH) titers maintained in insects. Nerolidol, a natural sesquiterpenol belonging to the terpenoid group, exhibits structural similarities to insect JHs. However, the impact of nerolidol on insect growth and development, as well as its underlying molecular mechanism, remains unclear. Here, the effects of nerolidol on Spodoptera exigua were investigated under treatment at various sub-lethal doses (4.0 mg/mL, 1.0 mg/mL, 0.25 mg/mL). We found that a higher dose (4.0 mg/mL) of nerolidol significantly impaired the normal growth, development, and population reproduction of S. exigua, although a relatively lower dose (0.25 mg/mL) of nerolidol had no significant effect on this growth and development. Combined transcriptome sequencing and gene family analysis further revealed that four juvenile hormone esterase (JHE)-family genes that are involved in juvenile hormone degradation were significantly altered in S. exigua larvae after nerolidol treatment (4.0 mg/mL). Interestingly, the juvenile hormone esterase-like (JHEL) gene Sexi006721, a critical element responsive to nerolidol stress, was closely linked with the significant augmentation of JHE activity and JH titer in S. exigua (R2 = 0.94, p < 0.01). Taken together, we speculate that nerolidol can function as an analog of JH by modulating the expression of the enzyme genes responsible for degrading JH, resulting in JH disorders and ultimately disrupting the development of insect larvae. This study ultimately provides a theoretical basis for the sustainable control of S. exigua in the field whilst proposing a new perspective for the development of novel biological pesticides. [ABSTRACT FROM AUTHOR]

Baculovirus infection induces apoptosis in host cells, and apoptosis significantly affects virus production. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) can regulate apoptosis, but the regulatory mechanism is unclear. Here, we found that AcMNPV infection induced different apoptosis responses in different Spodoptera exigua cell lines. In the early stages of viral infection (1–6 h), Se-1 cells underwent severe apoptosis, while Se-3 cells underwent very slight apoptosis. In the late stages of viral infection (12–72 h), Se-1 cells continued to undergo apoptosis and formed a large number of apoptotic bodies, while the apoptosis of Se-3 cells was inhibited and no apoptotic bodies were formed. To determine the reasons for the apoptosis differences in the two cell lines, we measured the expression of the six S. exigua cysteine-dependent aspartate specific protease genes (SeCaspase-1 to -6) and the three AcMNPV antiapoptotic protein genes (iap1, iap2 and p35) during viral infection. We found that SeCaspase-1 to -6 were all activated in Se-1 cells and inhibited in Se-3 cells, whereas iap1, iap2 and p35 were all inhibited in Se-1 cells and normally expressed in Se-3 cells. And p35 was expressed earlier than iap1 and iap2 in Se-3 cells. Otherwise, Se-1 and Se-3 cells would all be apoptotic when infected with the recombinant p35 knockout AcMNPV, whereas only Se-1 cells were apoptotic, but Se-3 cells were not apoptotic when infected with the recombinant p35 repair AcMNPV. Combined with the fact that the expression of P35 protein is inhibited in Se-1 cells but normally expressed in Se-3 cells during the infection of recombinant p35 repair AcMNPV, we proposed that the different expression of P35 is an important reason for the apoptosis differences between the two cell lines. We also found that some genes associated with apoptosis can probably regulate the expression of P35. However, the major upstream regulators of P35 and their mechanisms are still unclear and will be studied in the future. [ABSTRACT FROM AUTHOR]

Foliage-feeding fall armyworm (FAW; Spodoptera frugiperda) and root-feeding western corn rootworm (WCR; Diabrotica virgifera virgifera) are maize (Zea mays L.) pests that cause significant yield losses. Jasmonic acid (JA) plays a pivotal defense role against insects. 12-oxo-phytodienoic acid (12-OPDA) is converted into JA by peroxisome-localized OPDA reductases (OPR). However, little is known about the physiological functions of cytoplasmic OPRs. Here, we show that disruption of ZmOPR2 reduced wound-induced JA production and defense against FAW while accumulating more JA catabolites. Overexpression of ZmOPR2 in Arabidopsis enhanced JA production and defense against beet armyworm (BAW; Spodoptera exigua). In addition, lox10opr2 double mutants were more susceptible than either single mutant, suggesting that ZmOPR2 and ZmLOX10 uniquely and additively contributed to defense. In contrast to the defensive roles of ZmOPR2 and ZmLOX10 in leaves, single mutants did not display any alteration in root herbivory defense against WCR. Feeding on lox10opr2 double mutants resulted in increased WCR mortality associated with greater herbivory-induced production of insecticidal death acids and ketols. Thus, ZmOPR2 and ZmLOX10 cooperatively inhibit the synthesis of these metabolites during herbivory by WCR. We conclude that ZmOPR2 and ZmLOX10 regulate JA-mediated resistance in leaves against FAW while suppressing insecticidal oxylipin synthesis in roots during WCR infestation. [ABSTRACT FROM AUTHOR]

Peptidoglycan recognition proteins (PGRPs) are a class of molecules that play a critical role in insect immunity. Understanding the function of PGRPs is important to improve the efficiency of microbial insecticides. In this study, we investigated the role of PGRP‐LB (a long type PGRP) in insect immunity against viruses using Spodoptera exigua and Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) as an insect–virus model. We cloned and identified a PGRP‐LB gene from S. exigua; the gene consisted of 7 exons that encoded a polypeptide of 234 amino acids with a signal peptide and a typical amidase domain. Expression analysis revealed that the abundance of SePGRP‐LB transcripts in the fat body was greater than in other tissues. Overexpression of SePGRP‐LB resulted in a significant decrease of 49% in the rate of SeMNPV‐infected cells. In addition, the multiplication of SeMNPV was significantly decreased: a decrease of 79% in the production of occlusion‐derived virion (ODV), and a maximum decrease of 50% in the production of budded virion (BV). In contrast, silencing of SePGRP‐LB expression by RNA interference resulted in a significant 1.65‐fold increase in the rate of SeMNPV‐infected cells, a significant 0.54‐fold increase in ODV production, a maximum 1.57‐fold increase in BV production, and the larval survival dropped to 21%. Our findings show that SePGRP‐LB has an antiviral function against SeMNPV, and therefore this gene may provide a target for lepidopteran pest control using virus insecticides. [ABSTRACT FROM AUTHOR]

To clarify the insecticidal activity and field efficacy of seven insecticides （IRAC 28group： chlorantraniliprole, cyantraniliprole, tetrachlorantraniliprole, tetraniliprole and thiotraniliprole, IRAC 30 group： broflanilide and isocycloseram）on lepidopterous pests, the bioactivity assays against Plutella xylostella, Spodoptera exigua, Helicoverpa armigera and Chilo suppressalis were performed by immersion method, and the field trials were conducted to evaluate the control efficacy on P. xylostella and S. exigua. The bioassay showed that the toxicities of isocycloseram against P. xylostella, S. exigua and C. suppressalis were the highest, with LC50 values of 0.0040, 0.0521 and 0.0078 mg/L, respectively. Followed by broflanilide, the LC50 values were 0.0198, 0.0584 and 0.0339 mg/L, respectively. The LC50 values of the other five insecticides against P. xylostella, S. exigua and C. suppressalis were 0.0212-0.1378 mg/L, 0.2577-0.8080 mg/L and 0.2886-1.2277 mg/L, respectively. The toxicity of thiotraniliprole against H. armigera was an highest with the LC50 value of 0.0218 mg/L, which was significantly higher than that of the other 6 insecticides (LC50 values were 0.0694-0.2747 mg/L). The field trials for controlling P. xylostella showed that the control efficacy of IRAC 30 group insecticides at a dose of 30 a.i. g/hm2 was 95.60%-96.68% at 7 d after treatment, significantly higher than that of IRAC 28 group insecticides at the dose of 30 a.i. g/hm2 and 60 a.i. g/hm2 (49.07%-81.77% and 57.47%-85.90%). The control efficacy of thiotraniliprole, cyantraniliprole and tetrachlorantraniliprole was over 80% at the dose of 60 a.i. g/hm2, which was higher than that of chlorantraniliprole (57.47%). The control efficacy of broflanilide against S. exigua was 96.45% after 7 d treatment at a dose of 22.5 a.i. g/hm², which was higher than that of the other six insecticides at a dose of 22.5 and 45 a.i. g/hm2 (62.34%-86.75% and 68.06%-85.56%). Chlorantraniliprole showed the weakest effect on S. exigua (62.34%). The research showed that the seven insecticides tested had high activity against four lepidopterous pests, but variations of control effect existed under field trials. Field populations of P. xylostella and S. exigua were likely to have developed different levels of resistance to insecticides in IRAC 28 group. Corresponding resistance management strategies need to be launched timely and the development and application of insecticides in IRAC 30 group need to be accelerated. [ABSTRACT FROM AUTHOR]

Spodoptera exigua Hubner (Lepidoptera: Noctuidae) is the main pest of shallot causing significant economic losses. The continuous use of insecticides has resulted S. exigua to develop resistant against them. This study aims to determine the level of S. exigua resistance of Nganjuk and Bantul populations against methomyl, chlorfenapyr, and emamectin benzoate and temporal resistance of S. exigua of Nganjuk population to methomyl. Nganjuk population were sampled in June, September, and December. First instar larvae from the first generation were used tested using the leaf-dipping method. Temporal resistance test was carried out using the same concentrations. The resistance ratios of Nganjuk population to the insecticides methomyl, chlorfenapyr, and emamectin benzoate were 58.8; 8.8; and 2.5 fold respectively. The LC50 values of S. exigua of Nganjuk population collected in June, September, and December were 1127.44; 50.62; and 366.76 mg [AI] liter-1, respectively. The results of this study indicated that the S. exigua of Nganjuk population was highly resistant to methomyl and its level has changed over time. Resistance management by rotating the type of insecticide is not sufficient but should also consider its change of resistance pattern over time. [ABSTRACT FROM AUTHOR]

The use of chemical insecticides to control Spodoptera exigua is currently the main choice for farmers. The continuous use of chemical insecticides will cause many problems including resistance, food safety and environmental damage. alternative use of organic insecticides needs to be applied for the control system of Spodoptera exigua on shallot plants. The experiment was carried out in Playangan Village, Gebang District, Cirebon Regency, in Oktober-Desember 2022. The research method used a randomized block design with 3 replications, consisting of 9 treatment combinations of three cultivars: Bima, Ilokos, Sumenep, organic insecticides: neem seed extract, Bauveria bassiana, Bacillus thuringiensis. The results of the experiment showed that the combination of treatment of 3 cultivars of shallots and organic insecticides had a significant effect on the components of the intensity of the attack of Spodptera exigua pests (plants aged 43, 50 and 57 DAP). The best treatment was obtained, namely the treatment of Ilokos cultivar and neem seed extract insecticide with tuber yields of 6.60 kg / plot or equivalent to 28.57 tonnes / ha. [ABSTRACT FROM AUTHOR]

GATA transcription factor is crucial for plant growth and development, physiological metabolism, and environmental response, which has been reported in many plants. Although the identification of maize GATA genes has been reported previously, the number of maize GATA genes was incomplete, and the expression patterns of maize GATA genes were not analyzed. Therefore, in this study, the GATA gene family of maize (Zea mays L.) was systematically analyzed. Forty-one GATA family genes were identified in the maize and were divided into four groups. The gene structure of each subgroup was basically consistent with that of the motif. The maize GATA genes were distributed on 10 chromosomes, including 3 and 17 pairs of tandem and segmental duplication genes, respectively. Fourteen types of cis-acting elements were identified in the promoter sequences of maize GATA family genes, involving four categories: light response, stress, hormone, and growth and development. The tissue-specific expression analysis of maize GATA family genes revealed that 4 GATA genes were highly expressed in almost all the maize tissues, and 11 GATA genes were not expressed in almost all tissues. The other maize GATA family genes showed a tissue-specific expression pattern. The results of RNA-seq reanalysis of publicly available transcriptome sequencing big data revealed that the gene ZmGATA37 was significantly down-regulated in response to abiotic stresses including high temperature, low temperature, drought, waterlogging, and salt, and significantly up-regulated in response to biotic stresses including smut disease, Maize Iranian mosaic virus infection, beet armyworm and aphid infestations. This indicated that the ZmGATA37 gene plays an important role in maize growth and development. Our findings offer new insight into the potential role of GATA transcription factors in abiotic and biotic stresses and provide a theoretical groundwork for the molecular mechanisms underlying maize adaptation to such stress. [ABSTRACT FROM AUTHOR]

Anti-oviposition induced by Cordyceps fumosorosea FG340 to Spodoptera exigua and its persistence had been assessed on the Chinese cabbage seedlings sprayed with 0, 106, 107 and 108 conidia per mL in greenhouse and laboratory. In a randomized complete block, four couples (males and females) of moths were released in each cage. In the laboratory, the percentage of egg laid varied significantly between treatments with 59.8, 14.8, 11.9, and 13.5% on 0, 106, 107 and 108 conidia per mL; respectively. Similarly, in the greenhouse, the percentage of eggs laid differed significantly between suspensions with 88.18, 8.7, 0, and 3.13% on 0, 106, 107, and 108 conidia per mL; respectively. Repellence study showed that there is a major difference between suspensions with average 34.55, 35.21 and 40.02% for 106, 107 and 108 conidia per mL; respectively. Endophytic C. fumosorosea and its culture fluid affect the behavior of armyworm larvae. The concentration of 108 conidia per mL can affect the oviposition of the armyworm. [ABSTRACT FROM AUTHOR]

Simple Summary: When an insect pest outbreak occurs, it is crucial to quickly assess the damage to manage the outbreak effectively. This study investigated a serious outbreak of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), that occurred in soybean fields in South Korea. We conducted an aerial survey of 31 soybean blocks within the outbreak region using drones. The aerial images were analyzed to quantify soybean defoliation and to investigate the spatial patterns of the soybean damage by S. exigua. The results of this study showed that the aerial survey was an effective and rapid method for estimating the defoliation of soybeans caused by S. exigua. Moreover, it was found that the aerial survey followed by image analysis was more economical and required less time than a conventional ground survey, especially when the number of target soybean blocks subject to the survey was more than 15 blocks. Overall, the study demonstrated the effectiveness of using an autonomous drone and image analysis to conduct a low-cost aerial survey of soybean damage caused by S. exigua during its outbreak. Rapid assessment of crop damage is essential for successful management of insect pest outbreaks. In this study, we investigated the use of an unmanned aircraft system (UAS) and image analyses to assess an outbreak of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), that occurred in soybean fields in South Korea. A rotary-wing UAS was deployed to obtain a series of aerial images over 31 soybean blocks. The images were stitched together to generate composite imagery, followed by image analyses to quantify soybean defoliation. An economic analysis was conducted to compare the cost of the aerial survey with that of a conventional ground survey. The results showed that the aerial survey precisely estimated the defoliation compared to the ground survey, with an estimated defoliation of 78.3% and a range of 22.4–99.8% in the 31 blocks. Moreover, the aerial survey followed by image analyses was found to be more economical than the conventional ground survey when the number of target soybean blocks subject to the survey was more than 15 blocks. Our study clearly demonstrated the effectiveness of using an autonomous UAS and image analysis to conduct a low-cost aerial survey of soybean damage caused by S. exigua outbreaks, which can inform decision-making for S. exigua management. [ABSTRACT FROM AUTHOR]

Lufenuron (LUF) and Methoxyfenozide (MET) as Insect Growth Regulators (IGRs) contribute to the current control of the catastrophic crop pest, Spodoptera exigua (Lepidoptera, Noctuidae). Yet S. exigua has evolved resistance to LUF and MET, which is possibly mediated by cytochrome P450 monooxygenases (P450s), particularly from the CYP3 clade family, as it plays a key role in the detoxification of insecticides. However, a mixture of LUF and MET (MML) (optimal ratio: 6:4) remains highly insecticidal. Here, we analysed the response of S. exigua to sublethal concentrations of LUF, MET, and MML via transcriptomics. Twelve differentially expressed genes (DEGs) encoding CYP3 clade members were observed in transcriptomes and CYP9A9 was significantly upregulated after treatment with LUF, MET, and MML. Further, CYP9A9 was most highly expressed in the midgut of L4 S. exigua larvae. RNAi‐mediated knockdown of CYP9A9 reduced the activity of CYP450 and increased the susceptibility of S. exigua larvae to LUF, MET, and MML. Thus, CYP9A9 plays a key role in the detoxification of LUF, MET, and MML in S. exigua. These findings provide new insights into insecticidal actions of IGRs, which can be applied to the establishment of novel pest management strategies. [ABSTRACT FROM AUTHOR]

In order to delay the development of the insecticide resistance and screen the highly efficient mixtures against Spodoptera exigua (Hübner)，the interaction assay and co-toxicity coefficient method were used to evaluate the synergistic effects of different mixtures on S. exigua, and the field efficacy trial was conducted to verify the synergistic mixtures. The results of initial screening by interaction assay and rescreening by co-toxicity coefficient method showed that the proportion of chlorfenapyr and beta-cypermethrin at 7 : 3-12 : 1 (mass ratio of active ingredients at 1.20 : 1.00-6.23 : 1.00) had the synergistic effect on S. exigua, and the proportion of 9 : 1 (mass ratio of active ingredients at 4.63 : 1.00) had the highest co-toxicity coefficient of 314.72, and the synergistic effect was the greatest. The three mixtures with the proportion of 7 : 3, 9 : 1 and 11 : 1 (mass ratio of active ingredients at 1.20 : 1.00, 4.63 : 1.00 and 5.71 : 1.00) were selected for the field efficacy test. Compared with the single insecticides, the control efficacies of these three mixtures were improved at middle dosage (75.0 g a.i./hm² ) and high dosage (100.5 g a.i./hm² ) on each day after treatment against S. exigua, and the highest control efficacy reached 93.58% on the third day after treatment. According to the above results, the mass ratio of active ingredients of chlorfenapyr and beta-cypermethrin at 1.20 : 1.00-6.23 : 1.00 had the synergistic effect on S. exigua, which could be used for the control of S. exigua in Wuhan, and the recommended dosage was 75.0-100.5 g a.i./hm². [ABSTRACT FROM AUTHOR]

Noctuidae is known to have high species diversity, although the genomic diversity of Noctuidae species has yet to be studied extensively. Investigation of transposable elements (TEs) in this family can improve our understanding of the genomic diversity of Noctuidae. In this study, we annotated and characterized genome-wide TEs in ten noctuid species belonging to seven genera. With multiple annotation pipelines, we constructed a consensus sequence library containing 1038–2826 TE consensus. The genome content of TEs showed high variation in the ten Noctuidae genomes, ranging from 11.3% to 45.0%. The relatedness analysis indicated that the TE content, especially the content of LINEs and DNA transposons, is positively correlated with the genome size (r = 0.86, p-value = 0.001). We identified SINE/B2 as a lineage-specific subfamily in Trichoplusia ni, a species-specific expansion of the LTR/Gypsy subfamily in Spodoptera exigua, and a recent expansion of SINE/5S subfamily in Busseola fusca. We further revealed that of the four TE classes, only LINEs showed phylogenetic signals with high confidence. We also examined how the expansion of TEs contributed to the evolution of noctuid genomes. Moreover, we identified 56 horizontal transfer TE (HTT) events among the ten noctuid species and at least three HTT events between the nine Noctuidae species and 11 non-noctuid arthropods. One of the HTT events of a Gypsy transposon might have caused the recent expansion of the Gypsy subfamily in the S. exigua genome. By determining the TE content, dynamics, and HTT events in the Noctuidae genomes, our study emphasized that TE activities and HTT events substantially impacted the Noctuidae genome evolution. [ABSTRACT FROM AUTHOR]

Understanding plant-insect interactions requires the uncovering of the host plant use of insect herbivores, but such information is scarce for most taxa, including nocturnal moth species, despite their vital role as herbivores and pollinators. In this study, we determined the plant species visited by an important moth species, Spodoptera exigua, by analyzing attached pollen on migratory individuals in Northeast China. Pollen grains were dislodged from 2334 S. exigua long-distance migrants captured between 2019 and 2021 on a small island in the center of the Bohai Strait, which serves as a seasonal migration pathway for this pest species, and 16.1% of the tested moths exhibited pollen contamination, primarily on the proboscis. Subsequently, 33 taxa from at least 23 plant families and 29 genera were identified using a combination of DNA barcoding and pollen morphology, primarily from the Angiosperm, Dicotyledoneae. Moreover, the sex, inter-annual, and seasonal differences in pollen adherence ratio and pollen taxa were revealed. Notably, compared to previously reported pollen types found on several other nocturnal moths, we found that almost all of the above 33 pollen taxa can be found in multiple nocturnal moth species, providing another important example of conspecific attraction. Additionally, we also discussed the indicative significance of the pollen present on the bodies of migratory individuals for determining their migratory route. Overall, by delineating the adult feeding and pollination behavior of S. exigua, we advanced our understanding of the interactions of the moths with their host plants, and its migration pattern, as well as facilitated the design of (area-wide) management strategies to preserve and optimize ecosystem services that they provide. [ABSTRACT FROM AUTHOR]

Juvenile hormone (JH) controls almost every aspect of an insect, especially metamorphosis. Since RNA interference works on transcripts and is often insufficient in Lepidoptera, how JH affects larval development in these insects is not well studied. Using the CRISPR/Cas9 technique, we knocked out Spodoptera exigua methoprene‐tolerant 1 (SeMet1) gene of beet armyworm by modifying two sites in the coding region. However, SeMet1 knockout did not affect egg hatch rate or larval development at L1–L3 stages. In contrast to the consistent five larval instars of the control group, L4 SeMet1 mutants began to show signs of precocious metamorphosis, that is, small patches of pupal cuticle. Most L4 and all L5 SeMet1 mutants died for failing to shed their mosaic cuticles. RNA‐seq indicated that most genes encoding pupal cuticle proteins and chitinase genes were altered in SeMet1 mutant L4 larvae. SeKr‐h1, a key transcription factor in JH action was significantly down‐regulated in L3‐L5 larvae, while SeBR‐C, a pupal indicator was only upregulated in L4‐L5 larvae. These results suggested that S. exigua larvae may initially develop independently of JH, and involve SeMet1 in transducing JH signalling, leading to controlled larval metamorphosis at the late larval stage. We believe our findings will enhance better understanding of JH regulation of larval development. [ABSTRACT FROM AUTHOR]

The high fitness cost of predation selects prey capable of detecting risk cues and responding in ways that reduce their vulnerability. While the impacts of auditory predator cues have been extensively researched in vertebrate prey, much less is known about invertebrate species' responses and their potential to affect the wider food web. We exposed larvae of Spodoptera exigua, a slow‐moving and vulnerable herbivore hunted by aerial predators, to recordings of wasp buzzing (risk cue), mosquito buzzing (no‐risk cue), or a no‐sound control in both laboratory and field settings. In the laboratory, wasp buzzing (but not mosquito buzzing) reduced survival relative to the control; there was, however, no effect on time to or weight at pupation in survivors. In the field, wasp buzzing reduced caterpillar herbivory and increased plant biomass relative to the control treatment. In contrast, mosquito buzzing reduced herbivory less than wasp buzzing and had no effect on plant biomass. The fact that wasp cues evoked strong responses in both experiments, while mosquito buzzing generally did not, indicates that caterpillars were responding to predation risk rather than sound per se. Such auditory cues may have an important but largely unappreciated impacts on terrestrial invertebrate herbivores and their host plants. [ABSTRACT FROM AUTHOR]

In order to explore the occurrence regularity of sesame diseases and insect pests in Shanxi and improve the yield and economic benefit of sesame, in this study, a locally grown sesame variety of Fenzhi 2 was taken as the test material, the occurrence regularity of sesame diseases and insect pests was investigated and studied by establishing a systematic observation garden of diseases and insect pests. The experiment of high yield and efficient green control technologies for sesame was carried out. The results showed that there was no disease in seedling stage, full-bloom stage was the stage when diseases occurred severely, the main diseases in this stage were fusarium wilt, stem spot blight, and leaf spot. The main insect pests in the seedling stage were black cutworm and beet armyworm, and cotton bollworm and aphid were mainly harmful to sesame in initial-bloom stage and full-bloom stage. By utilizing the high yield and efficient green control technologies, the control efficacy of fusarium wilt, stem spot blight, leaf spot, and bacterial wilt were respectively 68.6%, 65.6%, 73.2% and 85.7%. The control efficacy of black cutworm, aphid, beet armyworm, and cotton bollworm were respectively 87.8%, 95.0%, 100% and 100%. Compared with the control, the production of demonstration area increased by 33.6%, and the economic benefit improved by 54.8%. In conclusion, applicaiton of the high yield and efficient green control technologies for sesame could not only significantly improve the control effect of diseases and insect pests, reduce the impact of natural disasters on sesame and planting risks, but also significantly improve the economic benefits of sesame. [ABSTRACT FROM AUTHOR]

This study was carried out in Silopi and Cizre districts of Şırnak province in order to determine the Lepidopteran species that cause damage to maize and their population densities in 2016-2017. The most common species in maize fields were Sesamia cretica (Lederer) and Spodoptera exigua (Hubner). Helicoverpa armigera (Hubner), Ostrina nubilalis (Hubner) and Agrotis ipsilon (Hufnagel) were determined at lower rates as harmful other species. It was found out that especially S. cretica was seriously harmful on maize ears and it caused yield loses. [ABSTRACT FROM AUTHOR]

Chitin deacetylase (CDA) can accelerate the conversion of chitin to chitosan, influencing the mechanical properties and permeability of the cuticle structures and the peritrophic membrane (PM) in insects. Putative Group V CDAs SeCDA6/7/8/9 (SeCDAs) were identified and characterized from beet armyworm Spodoptera exigua larvae. The cDNAs of SeCDAs contained open reading frames of 1164 bp, 1137 bp, 1158 bp and 1152 bp, respectively. The deduced protein sequences showed that SeCDAs are synthesized as preproteins of 387, 378, 385 and 383 amino acid residues, respectively. It was revealed via spatiotemporal expression analysis that SeCDAs were more abundant in the anterior region of the midgut. The SeCDAs were down-regulated after treatment with 20-hydroxyecdysone (20E). After treatment with a juvenile hormone analog (JHA), the expression of SeCDA6 and SeCDA8 was down-regulated; in contrast, the expression of SeCDA7 and SeCDA9 was up-regulated. After silencing SeCDAV (the conserved sequences of Group V CDAs) via RNA interference (RNAi), the layer of intestinal wall cells in the midgut became more compact and more evenly distributed. The vesicles in the midgut were small and more fragmented or disappeared after SeCDAs were silenced. Additionally, the PM structure was scarce, and the chitin microfilament structure was loose and chaotic. It was indicated in all of the above results that Group V CDAs are essential for the growth and structuring of the intestinal wall cell layer in the midgut of S. exigua. Additionally, the midgut tissue and the PM structure and composition were affected by Group V CDAs. [ABSTRACT FROM AUTHOR]

Simple Summary: The beet armyworm Spodoptera exigua (Hübner) is a polyphagous pest of numerous cultivated crops including potatoes, beans, asparagus, cotton, etc., causing considerable economic losses in crop production worldwide. Currently, the use of chemical insecticides is the most commonly used method to control this pest, however, the overuse of them results in insecticide resistance, environmental pollution and toxicity to other non-target organisms. Our results indicated that S. exigua field populations had developed resistance to almost half of the eleven commonly used insecticides with different modes of action. Thus, it is extremely urgent to seek an efficient strategy for insecticide resistance management. We found that the combined application of the specific entomopathogen of S. exigua (Spodoptera exigua multiple nucleopolyhedrovirus, SeMNPV) reduced insecticide resistance or even recovered the susceptibility to insecticides and enhanced the toxicity obviously in both laboratory experiments and field trials. These findings are valuable to provide a promising efficient way for improving insecticide resistance management strategy and an environmentally friendly approach for pest management with the combined application of nucleopolyhedroviruses and insecticides. Spodoptera exigua is a polyphagous pest of diverse crops and causes considerable economic losses. The overuse of chemical insecticides for controlling this pest results in insecticide resistance, environmental pollution and toxicity to other non-target organisms. Therefore, a sustainable and efficient way for pest management is urgently required. In this study, laboratory bioassays of eleven commonly used insecticides, the specific entomopathogen of S. exigua (Spodoptera exigua multiple nucleopolyhedrovirus, SeMNPV), and SeMNPV-insecticide combinations against the S. exigua laboratory population and two field populations were tested. Our results indicated that the two field populations had developed resistance to almost half of the tested insecticides, while SeMNPV had good virulence in all populations. Interestingly, the combined use of SeMNPV enhanced the toxicity of the tested insecticides against all populations to a different extent and considerably reduced the insecticide resistance of S. exigua field populations or even recovered the susceptibility to above insecticides. Furthermore, the field trial showed that the combined application of SeMNPV contributed to promoting the control efficacy of emamectin benzonate and chlorfenapyr. These results provide a promising efficient way for pest resistance management and an environmentally friendly approach for controlling S. exigua with the combined application of nucleopolyhedroviruses and insecticides. [ABSTRACT FROM AUTHOR]

Bacillus thuringiensis (Bt) is a biological agent for insect pest management. Its toxins effectively control Spodoptera exigua Hübner (Lepidoptera: Noctuidae) larvae, but it is sensitive to ultraviolet (UV) radiation from the sunlight. This study aimed to investigate the effect of sericin extract from Samia ricini Boisduval (Lepidoptera: Saturniidae) cocoons as a UV protectant for Bt after exposure under direct sunlight for 1, 2, 3, and 4 weeks. After being exposed to sunlight, the Bt formulae were tested against 20 larvae of 24 hr old, the first larval instar in the laboratory. The larval mortality was observed 72 hr after the treatment. The results indicated that the mortality of S. exigua in Bt + sericin extract treatment was significantly different compared with Bt alone. For the first week, the mortality of S. exigua in exposed Bt + sericin exposed Bt alone, unexposed (Bt + sericin, and unexposed Bt alone were 80, 61, 85, and 97%, respectively. Scanning electron microscopy analysis revealed that Bt + sericin, after being exposed to sunlight, still showed the presence of spore and crystal protein comparable to the unexposed Bt. Based on the results, sericin provides good protection against sunlight and prevents the Bt spores from light-induced damage. [ABSTRACT FROM AUTHOR]

Ascoviruses are insect-specific viruses that are thought to utilize the cellular apoptotic processes of host larvae to produce numerous virion-containing vesicles. In this study, we monitored the in vivo infection processes of Heliothis virescens ascovirus 3h (HvAV-3h) to illustrate the regulated cell death (RCD) of host cells. Transmission electron microscopic observations did not reveal any morphological markers of apoptosis in the fat bodies or hemocytes of HvAV-3h-infected Helicoverpa armigera or Spodoptera exigua larvae. However, several hemocytes showed the morphological criteria for necrosis and/or pyroptosis. Further in vitro biochemical tests were performed to confirm the RCD type of host cells after infection with HvAV-3h. Different morphological characteristics were found between the early (prior to 24 hours post-infection, [hpi]) and later (48 to 120 hpi) stages in both HvAV-3h infected larval fat bodies and hemocytes. In the early stages, the virions could only be found in several adipohemocytes, and the fat bodies were cleaving their contained lipid inclusions into small lipid dots. In the later stage, both fat bodies and hemocytes were filled with numerous virions. According to the morphological characteristics of HvAV-3h infected larval fat bodies or hemocytes, the pathogenic characteristics and infection patterns of HvAV-3h in the host larvae were described, and the systematic pathogenic mode of ascovirus infection was refined in this study. This study details the complete infection process of ascoviruses, which provides insights into the relationship between a pathogenesis of an insect virus and the RCD of different host tissues at different stages of infection. IMPORTANCE Viruses and other pathogens can interrupt host cellular apoptosis to gain benefits, such as sufficient resources and a stable environment that enables them to complete their replication and assembly. It is unusual for viruses to code proteins with homology to caspases, which are commonly recognized as apoptosis regulators. Ascoviruses are insect viruses with special cytopathology, and they have been hypothesized to induce apoptosis in their host larvae via coding a caspase-like protein. This enables them to utilize the process of cellular apoptosis to facilitate vesicle formation and replication. However, our previous studies revealed different trends. The fat bodies and hemocytes of Heliothis virescens ascovirus 3h (HvAV-3h)-infected larvae did not show any morphological markers of apoptosis but did display necrosis and/or pyroptosis morphological characteristics. The pathogenic characteristics and infection patterns of HvAV-3h in the host larvae were described, which can help us understand the relationship between the pathogenesis of an insect virus and host RCD. [ABSTRACT FROM AUTHOR]

Simple Summary: Spodoptera exigua (Hübner) is a common agricultural pest that can harm hundreds of crops. Carbohydrates and proteins are the two key nutrients affecting the development of insect populations. To study the development of the S. exigua population under different carbohydrate and protein nutrition conditions, we constructed a life table of S. exigua under different nutrient conditions: high nitrogen, medium nitrogen–medium sugar, and high sugar. The results showed that there was no significant difference in net reproductive rate among the three nutritional conditions. S. exigua on medium nitrogen–medium sugar diets had the shortest generation time and significantly higher intrinsic rate of increase, finite rate of increase, fecundity, and predicted population at 100 days. These results suggested that an appropriate protein:carbohydrate ratio was beneficial to the rapid development of Spodoptera exigua on farmland. These findings are important for scientifically predicting the population dynamics of S. exigua and constructing a system for controlling the insect population. Spodoptera exigua (Hübner) is a common agricultural pest that can harm hundreds of crops. Nutrition conditions can significantly affect the development of insects, especially carbohydrates (C) and proteins (P), which are the two most critical nutrients. To study the development of the S. exigua population under different carbohydrate and protein nutrition conditions, we constructed a life table of both sexes of an S. exigua population under three artificial diets: high nitrogen (P:C = 7:1), medium nitrogen, medium sugar (P:C = 1:1), and high sugar (P:C = 1:7). The results showed that the generation time of S. exigua was 26.38 ± 0.54 d under the medium nitrogen–medium sugar diet, which was the shortest among the three nutrition conditions. The intrinsic rate of increase (0.18 ± 0.01), finite rate of increase (1.20 ± 0.01), fecundity (605.42 ± 36.33 eggs/female), and predicted population at 100 days (8,840,000) were significantly higher under the medium nitrogen–medium sugar condition. There was no significant difference in the net reproductive rate among the three conditions. These results suggested that an appropriate protein:carbohydrate ratio is beneficial to the rapid development of S. exigua on farmland. These findings are important for scientifically predicting the population dynamics of S. exigua from the perspective of nutritional ecology, understanding its catastrophic mechanism, and constructing a prevention and control system. [ABSTRACT FROM AUTHOR]

The management of economically important lepidopteran pests has relied heavily on chemical and Bt-bio pesticides since 1940s, which has led to multiple recurring issues in resistance and environment. In this study, to search for a genetic-based control alternative with a distinctively different mode of action, we carried out a toxicological characterization of miR-34-5p, a highly conserved lepidopteran microRNA targeting EcR. Integrating target site prediction, co-localization of miRNA and EcR by fluorescence in situ hybridization, luciferase reporter assays as well as the gain-of-function and loss-of-function experiments, we comprehensively examined the physiological function and insecticidal properties of miR-34-5p among three representative lepidopteran pests, including Helicoverpa armigera, Spodoptera exigua, and Plutella xylostella. The combined results confirm a conserved role of miR-34-5p in the regulation of EcR in multiple lepidopteran pests. Overexpression or knocking down of miR-34-5p through both injection and feeding leads to insecticidal phenotypes, including high mortality, low fecundity, and developmental defects, suggesting that miRNAs can be considered as novel molecular targets in general, miR-34-5p for lepidopteran pests in particular. These results highlight the importance of miR-34-5p in the regulation of EcR expression in lepidopteran insects and provide a solid foundation for development of miRNA-based green pest control technology. [ABSTRACT FROM AUTHOR]

This study provides a promising controlled release form of nuclear polyhedrosis virus (NPV) for targeted control of lepidopteran pests. However, the application of NPV is limited due to its sensitivity to UV inactivation. This study investigated the anti-UV properties of microcapsules of SeMNPV occlusion bodies (OBs) encapsulated by calcium alginate (CA), and also the influence of the modification of CA by chitosan (CS), whey protein (WP), and polydopamine (PDA). These capsules were used to deliver, in a controlled release manner virions under alkaline pH conditions. Characterization of the structure, morphology, particle size, encapsulation efficiency, contact angle, insecticidal activity, UV resistance and in vitro release of the microcapsules was conducted. The modified microcapsules had better sphericity, and were devoid of SeMNPV OBs on the surface. The encapsulation rate was 84.76 ± 0.59%. PDA@CA-NPV had the highest wettability and the contact angle was 74.51 ± 0.53°. The 50% lethal concentration values (LC50) of CA-NPV, CS@CA-NPV, WP@CA-NPV and PDA@CA-NPV were 11.5, 10.7, 10.5 and 1.2 times that of SeMNPV OBs alone. The modified microcapsules all improved the anti-UV performance of the virus, and PDA@CA-NPV was the most UV-resistant. Using qPCR, it was observed that under alkaline conditions, a large number of virions were released from PDA@CA-NPV, CA-NPV and SeMNPV OBs. Microencapsulated virus under alkaline conditions did not change the release pattern of virions. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) symbiosis modulates plant‐herbivore interactions. Still, how it shapes the overall plant defence strategy and the mechanisms involved remain unclear. We investigated how AM symbiosis simultaneously modulates plant resistance and tolerance to a shoot herbivore, and explored the underlying mechanisms. Bioassays with Medicago truncatula plants were used to study the effect of the AM fungus Rhizophagus irregularis on plant resistance and tolerance to Spodoptera exigua herbivory. By performing molecular and chemical analyses, we assessed the impact of AM symbiosis on herbivore‐triggered phosphate (Pi)‐ and jasmonate (JA)‐related responses. Upon herbivory, AM symbiosis led to an increased leaf Pi content by boosting the mycorrhizal Pi‐uptake pathway. This enhanced both plant tolerance and herbivore performance. AM symbiosis counteracted the herbivore‐triggered JA burst, reducing plant resistance. To disentangle the role of the mycorrhizal Pi‐uptake pathway in the plant's response to herbivory, we used the mutant line ha1‐2, impaired in the H+‐ATPase gene HA1, which is essential for Pi‐uptake via the mycorrhizal pathway. We found that mycorrhiza‐triggered enhancement of herbivore performance was compromised in ha1‐2 plants. AM symbiosis thus affects the defence pattern of M. truncatula by altering resistance and tolerance simultaneously. We propose that the mycorrhizal Pi‐uptake pathway is involved in the modulation of the plant defence strategy. [ABSTRACT FROM AUTHOR]

Silicon (Si) fertilization alleviates biotic stresses in plants. Si enhances plant resistance against phytophagous insects through physical and biochemical mechanisms. In particular, Si modifies jasmonic acid levels and the emissions of herbivore-induced plant volatiles (HIPVs). Here, we investigated whether Si accumulation in the tissues of maize leaves modifies the emissions of constitutive and herbivore-induced plant volatiles, with cascade deterrent effects on oviposition site selection by Spodoptera exigua Hübner (Lepidoptera: Noctuidae). Maize plants were cultivated in a hydroponic system under three Si concentrations, resulting in three groups of plants expressing different Si concentrations in their tissues (0.31 ± 0.04, 4.69 ± 0.49, and 9.56 ± 0.30 g Si. Kg− 1 DW). We collected volatiles from undamaged and caterpillar-infested plants, and found that Si concentration in plant tissues had no significant impact. Jasmonic acid content was high in insect-infested plants, but was similar across all Si treatments. Oviposition site selection bioassays using fertilized S. exigua females showed that Si concentration in plant tissues did not affect the number of eggs laid on Si-treated plants. In conclusion, our study shows that the Si content in maize tissues does not impact the semiochemical interactions with S. exigua. [ABSTRACT FROM AUTHOR]

Mycorrhizal symbiosis influences plant growth and nutrition and can affect the performance of insect herbivores, but these effects are context-dependent. This study aims to investigate the influence of nitrogen fertilization and mycorrhizal symbiosis on maize and Spodoptera exigua performance and to explore the potential underlying mechanisms. Mycorrhiza promoted maize growth and reduced S. exigua performance, but these effects were dependent on nitrogen availability. We then assessed whether the consequences for S. exigua were mediated by its gut microbiota. Neither nitrogen nor mycorrhization affected S. exigua gut bacterial community. Reduced herbivore performance was instead potentially due to the effects of nitrogen-mycorrhiza interaction on the plant nutritional value. [ABSTRACT FROM AUTHOR]

Background: In nature and in cultivated fields, plants encounter multiple stress factors. Nonetheless, our understanding of how plants actively respond to combinatorial stress remains limited. Among the least studied stress combination is that of flooding and herbivory, despite the growing importance of these stressors in the context of climate change. We investigated plant chemistry and gene expression changes in two heirloom tomato varieties: Cherokee Purple (CP) and Striped German (SG) in response to flooding, herbivory by Spodoptera exigua, and their combination. Results: Volatile organic compounds (VOCs) identified in tomato plants subjected to flooding and/or herbivory included several mono- and sesquiterpenes. Flooding was the main factor altering VOCs emission rates, and impacting plant biomass accumulation, while different varieties had quantitative differences in their VOC emissions. At the gene expression levels, there were 335 differentially expressed genes between the two tomato plant varieties, these included genes encoding for phenylalanine ammonia-lyase (PAL), cinnamoyl-CoA-reductase-like, and phytoene synthase (Psy1). Flooding and variety effects together influenced abscisic acid (ABA) signaling genes with the SG variety showing higher levels of ABA production and ABA-dependent signaling upon flooding. Flooding downregulated genes associated with cytokinin catabolism and general defense response and upregulated genes associated with ethylene biosynthesis, anthocyanin biosynthesis, and gibberellin biosynthesis. Combining flooding and herbivory induced the upregulation of genes including chalcone synthase (CHS), PAL, and genes encoding BAHD acyltransferase and UDP-glucose iridoid glucosyltransferase-like genes in one of the tomato varieties (CP) and a disproportionate number of heat-shock proteins in SG. Only the SG variety had measurable changes in gene expression due to herbivory alone, upregulating zeatin, and O-glucosyltransferase and thioredoxin among others. Conclusion: Our results suggest that both heirloom tomato plant varieties differ in their production of secondary metabolites including phenylpropanoids and terpenoids and their regulation and activation of ABA signaling upon stress associated with flooding. Herbivory and flooding together had interacting effects that were evident at the level of plant chemistry (VOCs production), gene expression and biomass markers. Results from our study highlight the complex nature of plant responses to combinatorial stresses and point at specific genes and pathways that are affected by flooding and herbivory combined. [ABSTRACT FROM AUTHOR]

Host plants have an effect on the susceptibility of lepidopteran insects to nucleopolyhedrovirus (NPV), but the role of the protein in peritrophic membrane (PM) of larvae has not been investigated. We determined a key PM gene (SeIIM8 gene) in Spodoptera exigua (Hübner), which plays a role in protecting against NPV infection. Then we quantified the activity of chitin synthase (SeCHS), the content of insect intestinal mucin (SeIIM) and the expression of their genes in S. exigua fed one of four foods (artificial diet, Brassica oleracea (L.), Glycine max (L.), or Ipomoea aquatica (Forsskal)) with or without inoculation of Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV). Our results showed that the larval mortality was highest for NPV-infected with siRNA-injected larvae, intermediate for NPV-infected larvae, and lowest for uninfected larvae. The SeCHS activity, SeIIM content, and their relative gene expressions of S. exigua fed G. max or artificial diet were lower compared to caterpillars fed other diets. The relative SeCHS and SeIIM8 gene expression levels of larvae depended on the interaction of NPV treatment, diet, and time. This study concluded that plants affected the susceptibility of insects to NPV by altering the enzyme activity and gene expression of insects. [ABSTRACT FROM AUTHOR]

Airborne plant communication is a widespread phenomenon in which volatile organic compounds (VOCs) from damaged plants boost herbivore resistance in neighbouring, undamaged plants. Although this form of plant signalling has been reported in more than 30 plant species, there is still a considerable knowledge gap on how abiotic factors (e.g. water availability) alter its outcomes.We performed a greenhouse experiment to test for communication between potato plants Solanum tuberosum in response to herbivory by the generalist insect Spodoptera exigua and whether communication was affected by water availability. We paired emitter and receiver potato plants, with half of the emitters damaged by S. exigua larvae and half serving as undamaged controls. Both emitter and receiver plants were factorially subjected to one of two watering treatments: high (i.e. well‐watered) vs. low (i.e. reduced watering) availability, thus effectively teasing apart water availability effects on the emission and reception components of signalling. After 4 days of herbivore feeding, we collected emitter VOCs and receivers were subjected to feeding by S. exigua to test for effects of signalling on induced resistance.Herbivory by S. exigua led to increased VOCs emissions as well as changes in VOCs composition in emitter plants. Furthermore, emitters subjected to low water availability exhibited a weaker induction of VOCs in response to herbivory relative to well‐watered emitters. Results from the feeding bioassay indicated that receivers exposed to VOCs from herbivore‐induced emitters showed lower S. exigua damage (i.e. induced resistance) compared to receivers exposed to undamaged emitters. However, we did not observe a significant effect of water availability in either emitters or receivers on plant signalling effects on receiver resistance.Overall, our study contributes to understanding how the abiotic context affects plant communication by providing evidence of water availability effects on the induction of VOCs that act as airborne signals between plants. The observed changes in induced VOCs due to the water treatment had no detectable consequences for plant communication. Accordingly, the induction of key compounds mediating communication was apparently not compromised by our experimental conditions. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Simple Summary: An entomopathogen, Bacillus thuringiensis (Bt), has been used to control insect pests. On the other hand, insect immune responses defend the bacterial pathogenicity. An idea to enhance the Bt virulence was to inhibit insect immune defense using immunosuppressant. Secondary metabolites from another entomopathogen, Xenorhabdus hominickii, are known to inhibit the insect immune responses, but they alone give little virulence against insects. The addition of the bacterial culture broth containing the secondary metabolites to Bt spores significantly enhanced the Bt virulence in laboratory and field trials. This study demonstrates an integrated biological control by ideally combining two entomopathogenic bacteria. Insect immunity defends against the virulence of various entomopathogens, including Bacillus thuringiensis (Bt). This study tested a hypothesis that any suppression of immune responses enhances Bt virulence. In a previous study, the entomopathogenic bacterium, Xenorhabdus hominickii (Xh), was shown to produce secondary metabolites to suppress insect immune responses. Indeed, the addition of Xh culture broth (XhE) significantly enhanced the insecticidal activity of Bt against S. exigua. To analyze the virulence enhanced by the addition of Xh metabolites, four bacterial secondary metabolites were individually added to the Bt treatment. Each metabolite significantly enhanced the Bt insecticidal activity, along with significant suppression of the induced immune responses. A bacterial mixture was prepared by adding freeze-dried XhE to Bt spores, and the optimal mixture ratio to kill the insects was determined. The formulated bacterial mixture was applied to S. exigua larvae infesting Welsh onions in a greenhouse and showed enhanced control efficacy compared to Bt alone. The bacterial mixture was also effective in controlling other Spodopteran species such as S. litura and S. frugiperda but not other insect genera or orders. This suggests that Bt+XhE can effectively control Spodoptera-associated pests by suppressing the immune defenses. [ABSTRACT FROM AUTHOR]

Vip3 proteins are produced by Bacillus thuringiensis and are toxic against lepidopterans, reason why the vip3Aa gene has been introduced into cotton and corn to control agricultural pests. Recently, the structure of Vip3 proteins has been determined and consists of a tetramer where each monomer is composed of five structural domains. The transition from protoxin to the trypsin‐activated form involves a major conformational change of the N‐terminal Domain I, which is remodelled into a tetrameric coiled‐coil structure that is thought to insert into the apical membrane of the midgut cells. To better understand the relevance of this major change in Domain I for the insecticidal activity, we have generated several mutants aimed to alter the activity and remodelling capacity of this central region to understand its function. These mutants have been characterized by proteolytic processing, negative staining electron microscopy, and toxicity bioassays against Spodoptera exigua. The results show the crucial role of helix α1 for the insecticidal activity and in restraining the Domain I in the protoxin conformation, the importance of the remodelling of helices α2 and α3, the proteolytic processing that takes place between Domains I and II, and the role of the C‐t Domains IV and V to sustain the conformational change necessary for toxicity. [ABSTRACT FROM AUTHOR]