Climate warming impacts chewing Spodoptera litura negatively but sucking Corythucha marmorata positively on native Solidago canadensis.

Insect-plant interactions are among importantly ecological processes, and rapid environmental changes such as temperature and resource fluctuations can disrupt long-standing insect-plant interactions. While individual impacts of climate warming, atmospheric nitrogen (N) deposition, and plant provenance on insect-plant interactions are well studied, their joint effects on insect-plant interactions are less explored in ecologically realistic settings. To this end, we performed five experiments with native and invasive Solidago canadensis populations from home and introduced ranges and two insect herbivores (leaf-chewing Spodoptera litura and sap-sucking Corythucha marmorata) in the context of climate warming and N deposition. We determined leaf defensive traits, feeding preference, and insect growth and development, and quantified the possible associations among climate change, host-plant traits, and insect performance with structural equation modeling. First, native S. canadensis populations experienced higher damage by S. litura but lower damage by C. marmorata than invasive S. canadensis populations in the ambient environment. Second, warming decreased the leaf consumption, growth, and survival of S. litura on native S. canadensis populations, but did not affect these traits on invasive S. canadensis populations; warming increased the number of C. marmorata on native S. canadensis populations via direct facilitation, but decreased that on invasive S. canadensis populations via indirect suppression. Third, N addition enhanced the survival of S. litura on native S. canadensis populations, and its feeding preference and leaf consumption on invasive S. canadensis populations. Finally, warming plus N addition exhibited non-additive effects on insect-plant interactions. Based on these results, we tentatively conclude that climate warming could have contrasting effects on insect-plant interactions depending on host-plant provenance and that the effects of atmospheric N deposition on insects might be relatively weak compared to climate warming. Future studies should focus on the molecular mechanisms underlying these different patterns.

Involvement of Sep38ß in the Insecticidal Activity of Bacillus thuringiensis against Beet Armyworm, Spodoptera exigua (Lepidoptera).

The p38 mitogen-activated protein kinases (MAPKs) are associated with insect immunity, tissue repair, and the insecticidal activity of Bacillus thuringiensis (Bt). Here, a p38 MAPK family gene (Sep38ß) was identified from Spodoptera exigua. Among the developmental stages, the transcription level of Sep38ß was the highest in egg, followed by that in prepupa and pupa. Sep38ß expression peaked in Malpighian tubules and the hemolymph of fifth instar larvae. Knockdown of Sep38ß or injection of SB203580 (a p38 MAPK inhibitor) significantly downregulated the SeDUOX expression and reactive oxygen species (ROS) level in the midgut, accounting for deterioration of the midgut to scavenge pathogens and enhancement of Bt insecticidal activity. In conclusion, all the results demonstrate that Sep38ß regulates the immune-related ROS level in the insect midgut, which suppresses the insecticidal activity of Bt against S. exigua by 17-22%. Our study highlights that Sep38ß is essential for insect immunity and the insecticidal activity of Bt to S. exigua and is a potential target for pest control.

Cowpea volatiles induced by beet armyworm or fall armyworm differentially prime maize plants.

Exposure to herbivore-induced plant volatiles (HIPVs) is known to enhance the defense responses in plants. This so-called priming effect has only been marginally studied in intercropping systems. We tested whether HIPVs from cowpea, which often serves as an intercrop alongside maize, can prime herbivore-induced volatile emissions in maize. Conventional volatile collection assays and real-time mass spectrometry revealed that maize plants that were exposed to HIPVs from cowpea infested with Spodoptera exigua caterpillars emitted more than control plants when they themselves were subsequently damaged by the same pest. The enhanced emission was only evident on the first day after infestation. Maize plants that were exposed to HIPVs from cowpea infested by S. frugiperda larvae showed no priming effect and released considerably less upon S. frugiperda infestation than upon S. exigua infestation. The latter may be explained by the fact that S. frugiperda is particularly well adapted to feed on maize and is known to suppress maize HIPV emissions. Our results imply that HIPVs from cowpea, depending on the inducing insect herbivore, may strongly prime maize plants. This deserves further investigation, also in other intercropping systems, as it can have important consequences for tritrophic interactions and crop protection.

Characterization and transcriptomic analyses of the toxicity induced by toosendanin in Spodoptera frugipreda.

The fall armyworm, Spodoptera frugiperda, is a destructive agricultural pest that seriously threatens global food security. Insecticide resistance of this pest has gradually formed in recent years due to improper usage, and alternative methods are badly needed. Toosendanin (TSN) is a botanical compound with broad-spectrum insecticidal activities against many pests. However, the effects of TSN on S. frugiperda are still unclear. In this study, the growth inhibition phenomenon, including weight loss and prolonged developmental duration, in the larvae with TSN exposure was clearly observed. Compared to the control group, a total of 450 and 3314 differentially expressed genes (DEGs) were identified by RNA-Seq in the larvae groups treated with 10 and 20 mg/kg TSN, respectively. Furthermore, the DEGs involved in the juvenile hormone and ecdysone signal pathways and downstream processes, including detoxifying enzyme genes, chitin synthesis and metabolism genes, and cuticular protein genes, were found. Our findings suggest that TSN regulates the expression of key genes in juvenile hormone and ecdysone signal pathways and a series of downstream processes to alter the hormone balance and cuticle formation and eventually inhibit larval growth, which laid the foundation for the molecular toxicological mechanism research of TSN on S. frugiperda larvae.

Transcriptome Dynamics of Brassica juncea Leaves in Response to Omnivorous Beet Armyworm (Spodoptera exigua, Hübner).

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.

Eco-friendly approaches of zinc oxide and silver nitrate nanoparticles along with plant extracts against Spodoptera litura (Fabricius) under laboratory conditions.

The tobacco cutworm (Spodoptera litura) is a widespread pest that inflicts severe damage on various crops, including cotton, tobacco, and vegetables, with a particular preference for solanaceous plants. Traditional control methods often rely heavily on synthetic insecticides, leading to adverse effects on the environment, human health, and the development of insecticide resistance. In light of these challenges, this study explores the potential of nanotechnology as an innovative and sustainable approach to combat this notorious pest. Bioassays were conducted using laboratory-reared 3rd instar S. litura larvae. Eight different plant extracts coated with zinc oxide and silver nitrate nanoparticles were tested, with concentrations in both distilled water and ethanol at 3, 5, and 7 ml. Data were collected at 24, 48, and 72-h intervals. The results revealed that the highest larval mortality, reaching 98%, was observed in the group treated with silver nitrate nanoparticles derived from Cymbopogon citratus. In comparison, the group treated with zinc oxide nanoparticles dissolved in ethanol exhibited a larval mortality rate of 90%. Ethanol is a polar solvent that is widely used in the synthesis of nanocomposites. It is capable of forming strong hydrogen bonds with oxygen atoms, making it a good dispersant for zinc oxide nanoparticles. Additionally, ethanol has a low boiling point and a non-toxic nature, which makes it a safe and effective option for the dispersion of nanoparticles. Notably, the study concluded that silver nanoparticles combined with ethanol exhibited prolonged and more potent toxic effects against S. litura when compared to zinc oxide nanoparticles. Overall, this research underscores the potential of nanotechnology as a valuable component of Integrated Pest Management (IPM) strategies. By integrating nanotechnology into pest management practices, we can promote sustainable and environmentally friendly approaches that benefit both farmers and the ecosystem.

Insecticidal efficacy and possibility of Combretum trifoliatum Vent. (Myrtales: Combretaceae) extracts in controlling Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae).

BACKGROUND: The fall armyworm Spodoptera frugiperda (J.E. Smith), is an important pest of agronomical crops. It is interesting to discover secondary metabolites in plants that are environmentally safer than synthetic pesticides. For this purpose, Combretum trifoliatum crude extract and its isolated compounds were investigated for their insecticidal activities against S. frugiperda. RESULTS: The median lethal dose (LD50 ) was evaluated in the second-instar larvae using the topical application method. The isolated compounds, apigenin and camphor, demonstrated a highly toxic effect on larvae at a lower LD50 dose than crude extract. Moreover, when the larvae were exposed to crude extract concentrations, the development to pupa and adult stages was reduced by more than 50%. The ovicidal toxicity was examined using a hand sprayer. The extract concentration 5, 10, and 20 µg/egg significantly decreased the egg hatchability. In addition, crude extract showed a significant difference in inhibiting acetylcholinesterase (AChE) activity while crude extract and camphor showed significant inhibitory effects on carboxylesterase (CE) and glutathione-S-transferase (GST) activities. CONCLUSION: The crude ethanol extract of Combretum trifoliatum was toxic to S. frugiperda in terms of larval mortality, negatively affecting biological parameters, and decreasing egg hatchability. Additionally, the activities of cholinergic and detoxifying enzymes were affected by crude extract and its isolated compounds. These results highlight that Combretum trifoliatum might be efficient as a bioinsecticide to control S. frugiperda. © 2023 Society of Chemical Industry.

In Vitro and Molecular Docking Evaluation of Larvicidal Effects of Essential Oils of Five Aromatic Plants on the Fall Armyworm Spodoptera frugiperda JE. Smith (Lepidoptera: Noctuidae) from Ivory Coast.

Faced with the serious consequences resulting from the abusive and repeated use of synthetic chemicals, today rethinking crop protection is more than necessary. It is in this context that the essential oils of the Lamiaceae Ocimum gratissimum and Ocimum canum, the Poaceae Cymbopogon citratus and nardus and a Rutaceae Citrus sp. of known chemical compositions were experimented. The evaluation of the larvicidal potential of the essential oils was done by the method of topical application of the test solutions, on the L1-L2 stage larvae from the first generation of S. frugiperda obtained after rearing in an air-conditioned room. Lethal concentrations (LC10 , LC50 and LC90 ) were determined after 48 h. After assessing the larvicidal potential of essential oils, molecular docking was carried out to study protein-ligand interactions and their propensity to bind to insect enzyme sites (AChE). The essential oil of O. gratissimum was the most effective with the lowest lethal concentrations (LC10 =0.91 %, LC50 =1.91 % and LC90 =3.92 %). The least toxic oil to larvae was Citrus sp. (LC10 =5.44 %, LC50 =20.50 % and LC90 =77.41 %). Molecular docking revealed that p-cymene and thymol from O. gratissimum essential oil are structurally similar and bind to the AChE active site via predominantly hydrophobic interactions and a H-bond with Tyr374 in the case of thymol. The essential oil of O. gratissimum constitutes a potential candidate for the development of biological insecticides for the fight against insect pests and for the protection of the environment.

Potential insecticidal extracts from Artocarpus lacucha against Spodoptera litura (Lepidoptera: Noctuidae) larvae.

Artocarpus lacucha, a plant in the Moraceae family, has traditionally been used in Southeast Asian medicine to treat various ailments. This study investigated the insecticidal potential against Spodoptera litura of several compounds extracted from A. lacucha using a topical application method. A sequential extraction method was employed with A. lacucha stems to identify the most toxic crude extract by using hexane, dichloromethane, ethyl acetate, and methanol solvents. Subsequently, the most toxic crude extract was analyzed for chemical composition by HPLC, followed by the isolation process. Among these crude extracts, the ethyl acetate crude extract was the most toxic to second-instar S. litura larvae (24-h LD50 value of ~9.07 µg/larva). Our results showed that the catechin isolated from the ethyl acetate crude extract exhibited the highest toxicity against this insect (24-h LD50 value of ~8.37 µg/larva). Additionally, catechin significantly decreased the activities of acetylcholinesterase, carboxylesterases, and glutathione S-transferase in the larvae. These findings suggest that catechin isolated from A. lacucha could be a potential insecticidal agent against S. litura. However, the toxicity and persistence of catechin under field conditions need to be further investigated to develop this novel insecticide.

Synergism and toxicity of iron nanoparticles derived from Trigonella foenum-graecum against pyrethriod treatment in S. litura and H. armigera (Lepidoptera: Noctuidae).

The tobacco cutworm, Spodoptera litura and cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae) are important pests of various agricultural crops that cause sevier economic loses throughout the world. Indiscriminate and frequent use of insecticide may lead to development of resistance in these pests. Nanotechnology has given an alternative to manage and overcome insecticide resistance for pest management strategies. In the present study the iron nanoparticles derived from Trigonella foenum-graecum leaf extract (FeNPs) was investigated for its ecofriendly management of pyrethroid resistance in two lepidopteron pest species at 24 h, 48 h and 72 h post treatment. The result showed high mortality (92.83% and 91.41%) of S. litura and H. armigera at 72 h treatment upon FeNPs and fenvalerate (Fen + FeNPs) teratment. Probit analysis revealed high LC50 upon Fen + FeNPs treatment (130.31 and 89.32 mg/L) with a synergism ratio of 1.38 and 1.36. Antifeedant activity of six dofferent concentration of FeNPs revelaed increased antifeedant activity with respect to increasing concentration of nanoparticles ranging from 10 to 90% and 20-95% againt both insects (p<0.05). Detoxification activity of carboxylesterase was elevated at 630 µmol/mg protein/min (p<0.05) in fenvalerate treatment, whereas decreased activity was found (392umole/mg protein/min) in FeNPs and Fen + FeNPs treatment (P<0.001). GST and P450 activity was also increased in fenvalerate treatment, whereas decreased activity was observed in FeNPs and Fen + FeNPs. Esterase isoenzyme banding pattern revealed four bands in fenvalerate treatment and two bans (E3 and E4) in Fen + FeNPs combination. Hence the present study concludes that T. foenum-graecum synthesized iron nanoparticles could be an effective alternate for ecofriendly management of S. litura and H. armigera.

Pollen Molecular Identification from a Long-Distance Migratory Insect, Spodoptera exigua, as Evidenced for Its Regional Pollination in Eastern Asia.

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.

Ingestion and effects of green synthesized cadmium sulphide nanoparticle on Spodoptera Litura as an insecticidal and their antimicrobial and anticancer activities.

The current study investigated the multifunctional properties of Cadmium Sulphide Nanoparticles synthesized using a green synthesis method (CdS NPs) using a green feedstock, Nopal Cactus fruit extract. The biological activities of the CdS NPs were thoroughly investigated, including their insecticidal, antibacterial, and anticancer activities. The different concentrations (0.005-0.04%) of CdS NPs were fed to the larvae of Spodoptera litura, and their ingestion effects were observed on the different biological, biochemical, and oxidative stress markers. There are significant dose-dependent changes in the biochemical parameters like superoxide dismutase (SOD), Catalase (CAT), Glutathione-S-transferase (GST), and MDA level as a marker of lipid peroxidation in the treated larvae were studied. In the highest concentration (0.04%), significant larval mortality (46.66%), malformation (pupae and adult) (27.78%), inhibition of adult emergence (43.87%), as well as reduced fecundity (25.28%), and fertility (22.74%) as compared to control was observed. CdS NPs have been investigated for antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus bacterial strains. In vitro anticancer activities were carried out to decrease the viability of the Pancreatic cancer cell line. The cells showed 18% and 12% viability at a 200 µg/ml concentration when incubated with CdS NPs for 24 and 48 h, respectively, confirming its potent anticancer property. The lack of cytotoxicity against the (RBC) endorses the biocompatible nature of synthesized CdS NPs. It was observed that green synthesized CdS NPs could be used as a promising insecticidal, antibacterial, and anticancer agent.

A chromosome-level genome assembly of the beet armyworm Spodoptera exigua.

BACKGROUND: The beet armyworm Spodoptera exigua is a polyphagous caterpillar that causes serious damage to many species of crops and vegetables. To gain insight into how this polyphagous insect differs from less harmful oligophagous species, we generated a chromosome-level assembly and compared it to closely related species with the same or different feeding habits. RESULTS: Based on Illumina and Pacific Biosciences data and Hi-C technology, 425.6 Mb of genome sequences were anchored and oriented into 31 linkage groups, with an N50 length of 14.8 Mb. A total of 24,649 gene models were predicted, of which 97.4% were identified in the genome assembly. Chemosensory genes are vital for locating food: of the four main families, odorant-binding proteins, chemosensory proteins and olfactory receptors showed little difference, whereas gustatory receptors are greatly expanded in S. exigua. Examination of other polyphagous insects confirmed this difference from oligophagous congeners and further identified the bitter receptor subfamily as being particularly affected. CONCLUSION: Our high-quality genome sequence for beet armyworm identified a key expansion of the bitter gustatory receptor subfamily in this and other pests that differs crucially from more benign relatives and offers insight into the biology and possible future means of control for these economically important insects.

Group V Chitin Deacetylases Influence the Structure and Composition of the Midgut of Beet Armyworm, Spodoptera exigua.

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.

Limonoids and insecticidal activity on Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) of Trichilia catigua A. Juss. (Meliaceae).

The aim of the study was to evaluate the effects of the seeds, exocarp and aril extracts from Trichilia catigua A. Juss. (Meliaceae) against Spodoptera frugiperda and present the phytochemical study carried out with the aril extract of T. catigua. Limonoids were isolated from the aril of T. catigua through chromatographic techniques and their structures were proposed by spectroscopic analysis and comparison with literature data. The effects of the seeds, exocarp and aril extracts from T. catigua against S. frugiperda were evaluated considering as parameters the duration and mortality of the larval phase, in addition to the pupal weight. Phytochemical investigation of the aril extracts of T. catigua has led to the identification of the limonoids 6α-O-acetyl-7-deacetyl-14,15-dihydro-15-oxo-nimocinol (1), cedrelone (2) and 6α-O-acetyl-7-deacetylnimocinol (3). The hexane and CH2Cl2 extracts of the aril showed a high rate of larval mortality (100 and 90%, respectively). In addition, a prolongation of larval phase and a reduction in the pupal weight were observed for insects treated with hexane, CH2Cl2 and methanol extracts of seeds and with CH2Cl2 extract of exocarp of T. catigua.

Eco-friendly biosynthesis of TiO2 nanoparticles using Desmostachya bipinnata extract: Larvicidal and pupicidal potential against Aedes aegypti and Spodoptera litura and acute toxicity in non-target organisms.

The resistance to insecticides among insects, including mosquitoes and agricultural pests, and the impact of these compounds' environmental risks and health issues have motivated the proposition of eco-friendly alternatives. Thus, we aimed to explore the potential use of Desmostachya bipinnata for the biosynthesis of TiO2NPs and evaluate their larvicidal and pupicidal activity of target (Aedes aegypti and Spodoptera litura) and acute toxicity in non-target organisms (Toxorhynchites splendens and Eisenia fetida), at distinct concentrations, after 24 h of exposure. The characterization of the biosynthesized TiO2NPs was carried out by FT-IR, XRD, SEM, and EDX analysis. Under the UV-vis spectrum analysis, a sharp peak was recorded at 200 to 800 nm, which indicated the production of TiO2NPs by the plant extract. The SEM analysis revealed that the synthesized TiO2NPs were spherical with a diameter of 36.4 nm and were detected in the XRD spectrum analysis related to the TiO2NPs. The highest percentage of mortality recorded at 900 µg/mL was 96 % and 94 % in the 2nd instar of A. aegypti and S. litura larvae, respectively, and exhibited the LC50 and LC90 values 5 of 458.79 and 531.01 µg/mL, respectively. The biosynthesized TiO2NPs showed concentration-dependent increased pupal lethality for both A. aegypti and S. litura. We also observed increased detoxification enzyme activity (α esterase, ß esterase, and glutathione-S-transferase) of A. aegypti and S. litura exposed to different concentrations of biosynthesized TiO2NPs as histopathological changes in the midgut region of these animals. On the other hand, the mortality rate of non-target organisms (T. splendens and E. fetida) was lower when exposed to TiO2NPs, compared to the high lethality induced by synthetic pesticides (cypermethrin and monocrotophos for E. fetida; and cypermethrin and temphos for T. splendens). Thus, our study provides pioneering evidence on the potential use of D. bipinnata-mediated TiO2NPs for controlling mosquito vectors and agricultural pest management.

Antifeedant and larvicidal activity of bioactive compounds isolated from entomopathogenic fungi Penicillium sp. for the control of agricultural and medically important insect pest (Spodoptera litura and Culex quinquefasciatus).

The use of chemical insecticides in agriculture has posed several challenges to environment and ecosystem health. Pesticides of biological origin are considered to be suitable for sustainable environment. In the present study bioactive compounds from Penicillium sp. was isolated and tested for insecticidal activity on Spodoptera litura and Culex quinquefasciatus larvae. Ethyl acetate extract of Penicillium sp. were characterized using GC-MS and FT-IR analysis. GC-MS analysis showed 20 different bioactive compounds namely, Propanoic acid, ethyl ester, Acetic Acid, Propyl Ester, Isopentyl Acetate, Acetic Acid, 2-Methylpropyl Ester, Behenic alcohol, 1-Hexadecene, 1-Octadecene, 1-Hexacosanol, n-Hexadecanoic acid, 1-Tetradecanol, 1-Dodecene, Tetrydamine, and Octadecanoic acid. The presence of functional groups such as, chloroalkanes, sulfonates, phosphines, amines, carboxylic acid, alkanes, and isocyanates was identified by using FTIR. Ethyl acetate extract of Penicillium sp., were tested for larvicidal activity on Spodoptera litura and Culex quinquefasciatus larvae showed significant larval mortality after 48 h of exposure with LC50: 72.205 mg/ml: LC90: 282.783 mg/ml and LC50: 94.701 mg/ml: LC90:475.049 mg/ml respectively. High antifeedant activity was observed in 300 µg/ml at 48 h of crude extract exposure. The present study concludes that Penicillium sp., secondary metabolites are effective for control of Spodoptera litura and Culex quinquefasciatus larvae.

Insecticidal activity of isolated gingerols and shogaols from Zingiber officinale Roscoe rhizomes against Spodoptera spp. (Lepidoptera: Noctuidae).

The discovery of eco-friendly plant-based insecticides is currently booming in research with an attempt to replace synthetic chemical insecticides causing tremendous adverse effects. The present work studied the insecticidal potential of ginger, an important medicinal plant. Four crude extracts from Zingiber officinale rhizomes were evaluated for their contact toxicity against second instars of Spodoptera litura, Spodoptera exigua and Spodoptera frugiperda using the topical application. The hexane extract exhibited the strongest toxicity to S. exigua with the LD50 of 9.92 and 8.40 µg/larva at 24 and 48 h posttreatment, respectively, followed by S. frugiperda. Comparative toxicity of the most abundant secondary metabolites from the hexane extract, gingerols and shogaols, against both insects concluded that 8-shogaol (5) was identified as the most active compound against S. frugiperda with the LD50 of 7.68 and 3.96 µg/larva at 24 and 48 h posttreatment, respectively.

Plant genetic relatedness and volatile-mediated signalling between Solanum tuberosum plants in response to herbivory by Spodoptera exigua.

It has been proposed that plant-plant signalling via herbivore-induced volatile organic compounds (VOCs) should be stronger between closely related than unrelated plants. However, empirical tests remain limited and few studies have provided detailed assessments of induced changes in VOCs emissions across plant genotypes to explain genetic relatedness effects. In this study, we tested whether airborne signalling in response to herbivory between Solanum tuberosum (potato) plants was contingent on plant genetic relatedness, and further investigated genotypic variation in VOCs potentially underlying signalling and its contingency on relatedness. We carried out a greenhouse experiment using 15 S. tuberosum varieties placing pairs of plants in plastic cages, i.e. an emitter and a receiver, where both plants were of the same genotype or different genotype thereby testing for self-recognition, an elemental form genetic relatedness effects. Then, for half of the cages within each level of relatedness the emitter plant was damaged by Spodoptera exigua larvae whereas for the other half the emitter was not damaged. Three days later, we placed S. exigua larvae on receivers to test for emitter VOC effects on leaf consumption and larval weight gain (i.e. induced resistance). In addition, we used a second group of plants subjected to the same induction treatment with the same S. tuberosum varieties to test for herbivore-induced changes in VOC emissions and variation in VOC emissions among these plant genotypes. We found that herbivory drove changes in VOC composition but not total emissions, and also observed quantitative and qualitative variation in constitutive and induced VOC emissions among varieties. Results from the bioassay showed that the amount of leaf area consumed and larval weight gain on receiver plants exposed to damaged emitters were significantly lower compared to mean values on receivers exposed to control emitters. However, and despite genotypic variation in induced VOCs, this signalling effect was not contingent on plant genetic relatedness. These findings provide evidence of VOCs-mediated signalling between S. tuberosum plants in response to S. exigua damage, but no evidence of self-recognition effects in signalling contingent on variation in VOC emissions among S. tuberosum varieties.

CRISPR/Cas9-mediated methoprene-tolerant 1 knockout results in precocious metamorphosis of beet armyworm (Spodoptera exigua) only at the late larval stage.

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.