Spodoptera Exigua Research Articles

Management Technique Against Spodoptera Exigua (Hübner) in the Different Elevation of Shallot

Spodoptera exigua (Hübner) (beet armyworm) as the destructive insect pest in shallot. The purpose of the research is to determine difference of S. exigua management techniques based elevation in two different plantation. The research was conducted by collected primary data from shallot farmers in Anggeraja District (Mataran 650 m asl and Pekalobean 840 m asl) and Baraka District (Perarian 1.014 m asl and Parinding 638 m asl). The two places used in research is the center of shallot plantation in Enrekang Regency, South Sulawesi. The data was obtained by survey used 15 shallot farmers in each village. The results showed the control techniques different according to the elevation. S. exigua controlled by nylon nets only in areas < 700 m asl (Mataran 53% and Parinding 27%). In areas with elevation > 700 m asl (result of light trap in Mataran by 87% and Parinding by 80%). In the elevation > 700 m asl (result of light trap in Pekalobean about 100% and Perangian 0%). The mechanical control techniques by squeezing insect pest eggs at elevation of > 700 m asl (Pekalobean 93% and Perangian 6%), elevation of < 700 m asl (Mataran and Parinding both showed 60%). Conclusion of research, the control techniques different based on the elevation of shallot plantation.

Efektifitas Tanaman Refugia Kacang-Kacangan Menangkal Intensitas Serangan Hama Ulat Grayak (spodoptera exigua Hubner.) Pada Bawang Merah

This experimental research aims to obtain the type of legume refugia plant that is most effective in preventing invasion, colonization and intensity of attack by the Spodoptera exigua Hubner pest on shallot. The experiment was designed with a randomized block design consisting of six treatments of various refugia plants, namely shallot plants without refugia treatment (Ro), shallot plants with refugia treatment peanuts (R1), soybeans (R2), green beans (R3), red beans (R4) and cowpeas (R5), which are planted in two rows on the side of the bund at a distance of 10 cm from the outermost row of shallot plants. Observation parameters were egg population, larvae, intensity of S. exigua pest attack and weight of fresh shallot bulbs. The variety of refugia plants from the legume group influences invasion, colonization and the intensity of Spodoptera exigua Hubner pest attacks. on red onions. Peanut and cowpea refugia plants planted in two rows on the sides of the shallot mounds, are very effective in preventing invasion, colonization and the intensity of Spodoptera exigua Hubner pest attacks, so that the shallot plants experience very light disturbance with an attack intensity of 2,522% – 4,432 %, which is in the very low category. As a result, the yield of fresh shallot tubers obtained was significantly higher compared to shallot plants without refugia plants and with refugia plants of soybeans, green beans and red beans. Soybean, green bean and red bean refugia plants are not effective in preventing Spodoptera exigua Hubner pest attacks on shallots because the plants experience attack intensity from the age of 49 HST – 63 HST of 21.86% - 23.34% with the attack intensity being in the medium category.

Resistance of Spodoptera exigua Population from Nganjuk against Methomyl, Chlorfenapyr, and Emamectin Benzoate

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.

Design and Synthesis of a Water-Based Nanodelivery Pesticide System for Improved Efficacy and Safety.

Developing an environmentally friendly and safe nanodelivery system is crucial to improve the efficacy of pesticides and minimize environmental and health risks. However, preparing a completely water-based nanopesticide without using harmful solvents is a technical challenge. In this study, a water-based nanodelivery pesticide system was constructed to improve the efficacy and safety of Emamectin Benzoate (EB). A specific surfactant, 29-(4-(5-hydroxynonan-5-yl)phenoxy)-3,6,9,12,15,18,21,24,27-nonaoxanonacosan-1-ol (SurEB) was designed and synthesized to form a water-based nanodelivery system (EBWNS) with EB. Molecular dynamics simulations revealed the self-assembly and interaction forces between SurEB and EB in water, providing insights into the formation mechanism of EBWNS nanoparticles. The nanodelivery system showed the prolonged effectivity of EB with reduced degradation and demonstrated a good control efficacy for multiple target pests, such as red spider mite, beet armyworm larvae (Lepidoptera: Noctuidae), and rice stem borers (Chilo suppressalis). Toxicology tests on various objects demonstrated that the EBWNS has low toxicity for seeds, HaCaT cells, zebrafish, earthworm, and E. coli. This study provides a distinctive perspective for developing environmentally friendly nanopesticide formulations, which clarified a water-based treatment method for specific lipid-soluble pesticides. The water-based nanodelivery pesticide system has the potential to improve the efficacy and safety of pesticides in the process of field applications.

Insectivorous bats provide more pest suppression services than disservices - a case study in China

Many studies have investigated the role of insectivorous bats as natural enemies of agricultural pests. However, insectivorous bats have a broad diet, and whether their prey species are beneficial or harmful is unknown; thus, accurately assessing the services provided by bats is challenging. In China, most people, including farmers and plant protection workers, have an insufficient understanding of the ecological value of bats in biological control. Therefore, we collected the fecal samples of 10 bat species from three different sampling sites located in Guizhou Province, China, and conducted DNA metabarcoding to determine the diet composition of bats. We also categorized the prey species from the diet of bats as harmful or beneficial, based on previous studies, and recorded the industries they affect. Our results showed that the 10 bat species consumed prey from 19 orders and 96 families; most of them being lepidopterans. Among 564 total prey species recorded, 390 (69.15%) were pests and 28 (4.96%) were beneficial insects. Among them, 326 (57.80%) were agriculture or forestry pests, such as globally present Cotton bollworm (Helicoverpa armigera) and Beet armyworm (Spodoptera exigua). These results indicated that insectivorous bats have more beneficial effects than harmful effects, especially in the context of agriculture and forestry, as they suppressed very few beneficial arthropod mesopredators. By comparing the differences in the diet of I. io in different regions, we found that bats present in different regions can provide different predation services. Our study showed that insectivorous bats provide excellent pest suppression services in various industries and regions. It might be helpful for increasing awareness among people and bat conservation in China and other regions.

Manipulation of GameXPeptide synthetase gene expression by a promoter exchange alters the virulence of an entomopathogenic bacterium, Photorhabdus temperata temperata, by modulating insect immune responses.

An entomopathogenic bacterium, Photorhabdus temperata subsp. temperata, is mutualistic to its host nematode, Heterorhabditis megidis. The infective juvenile nematodes enter target insects through natural openings and release the symbiotic bacteria into the insect hemocoel. The released bacteria suppress the insect immune responses and cause septicemia through their secondary metabolites. GameXPeptide (GXP) is one of the common secondary metabolites of most Photorhabdus species and is produced by the catalytic activity of a specific non-ribosomal peptide synthetase called GxpS encoded by the gxpS gene. This study confirmed gxpS to be encoded in the P. temperata temperata genome and analyzed its expression during bacterial growth. LC-MS/MS analysis of the bacterial culture broth contained at least four different GXPs (GXP-A to GXP-D), in which GXP-A was the most abundant. To investigate GXP synthesis following gxpS expression, the gxpS promoter of P. temperata temperata was replaced with an inducible arabinose promoter by homologous recombination. The gxpS transcript levels in the mutant were altered by the addition of l-arabinose. Without the inducer, the gxpS transcript level was significantly lower compared to the wild type and produced significantly lower amounts of the four GXPs. The addition of the inducer to the mutant significantly increased gxpS expression and produced significantly higher levels of the four GXPs compared to the wild type. The metabolite extracts obtained from wild-type and mutant bacteria showed differential immunosuppressive activities according to their GXP contents against the cellular and humoral immune responses of a lepidopteran insect, Spodoptera exigua. Interestingly, the gxpS-mutant bacteria showed less insecticidal activity compared to the wild type, whereas the addition of GXP to the mutant significantly restored insecticidal activity. These results suggest that the gxpS gene encoded in P. temperata temperata is responsible for the production of at least four different GXPs, which play crucial roles in bacterial virulence.

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.

Suppression of weed and insect populations by living and straw mulches in sesame (Sesamum indicum L.)

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.

Preparation of zein-grafted mesoporous silica nanoparticles for improving Lambda-cyhalothrin insecticidal activity and biosafety

Currently, stimuli-responsive pesticide carriers can effectively enhance the insecticidal effectiveness against target pests and safety to nontarget organisms, and further reduce environmental pollution. In this work, a pesticide delivery system (LCN@MSN-SS-Zein) based on pH and redox dual-stimuli-responsive was prepared by loading Lambda-cyhalothrin (LCN) onto biodegradable disulfide-functionalized mesoporous silica nanoparticles and combining with gatekeeper zein. The results showed that LCN@MSN-SS-Zein had a high pesticide loading (24.7%, w/w). The nanoparticles have excellent pH and redox dual response behavior and have significant controlled release characteristics. Under the stimulation of pH and glutathione, the disulfide bond and zein structure of the nanoparticles are decomposed to release LCN on demand. Compared with LCN technical, the stability of LCN@MSN-SS-Zein nanoparticles under ultraviolet light was significantly enhanced, and the adhesivity of these nanoparticles on the cabbage leaf surface was significantly improved. Biological activity tests showed that LCN@MSN-SS-Zein nanoparticles had higher insecticidal activity against Spodoptera exigua than Lambda-cyhalothrin emulsion oil in water (LCN@EW), and the control effect was more lasting, while the toxicity to zebrafish was significantly reduced. In addition, MSN-SS-Zein nanoparticles were safe for the growth of cabbage and had good biocompatibility. Therefore, LCN@MSN-SS-Zein nanoparticles provide a new strategy for effective pest control and have broad application prospects.

Controlling Armyworm (Spodoptera exigua) (Lepidoptera: Noctuidae) on Shallot using Nano Husk Ash

The Beet Armyworm (Spodoptera exigua) is a polyphagous defoliator that poses a significant threat to cultivated plants, particularly shallot crops. Its attacks during the vegetative phase cause substantial damage. To control this pest, farmers often resort to synthetic pesticides, leading to negative consequences such as resistance development. To address consequences, internal control measures, like enhancing plant resistance through beneficial nutrients like silica, are crucial. Silica has been known to improve plant resistance against pest attacks. This study aims to investigate the effects of various methods of applying nano-sized rice husk ash fertilizer on the growth and resistance of Biru Lancor cultivar of shallots against S. exigua. Nano-rice husk ash fertilizer with an average particle size of 65,326 nm was produced and applied using three methods: placement, foliar, and seed coating. The results demonstrated that all methods of nano-rice husk ash application increased plant resistance, reducing leaf damage and pest mortality. The foliar application yielded the best results, enhancing plant height and epidermal cell wall thickness. Furthermore, nano-rice husk ash application positively influenced shallot productivity. This study highlights the potential of nano-sized rice husk ash as a sustainable and effective internal control measure against S. exigua, complementing synthetic pesticides for shallot pest management.

Botanical biopesticides have an influence on tomato quality through pest control and are cost-effective for farmers in developing countries.

Synthetic insecticides heavily applied to manage agricultural pests are highly hazardous to the environment and non-target organisms. Their overuse through repeated treatments in smallholder farming communities is frequent. Botanical biopesticides are ideal for sustainable pest management in agricultural environments by keeping synthetic insecticide use at a minimum. Here we evaluated a locally prepared neem seed extract (NSE) alongside emamectin benzoate against both lepidopteran pests Helicoverpa armigera (Hübner) and Spodoptera exigua (Hübner) on tomato Lycopersicon esculentum Mill under natural field conditions in Pakistan. We compared pest severity, fruit injury, quality, marketability, and cost:benefit ratio (CBR) between treatments. The concentration of azadirachtin A in the NSE was 26.5 ppm. NSE at 2% (20 mL/L) and the emamectin benzoate at the recommended field rate in Pakistan were sprayed weekly throughout the fruiting stage. The pest larvae were significantly more abundant on fruits than on flowers and leaves. Fruit injury and losses were significantly more important in untreated control compared to NSE and emamectin benzoate treatments. NSE efficacy varied with respect to the cultivars used and the seasons. Cultivar Eden harboured more pests than Adventa, and emamectin benzoate suppressed more pest individuals than NSE. Both the insecticidal treatments were comparable in terms of marketable yield productions as well as unmarketable, uninjured, and recovered fruit yields. NSE generated a higher CBR (1: 9.26) than emamectin benzoate (1: 3.23). NSE suppressed pests by acting as an antifeedant, similar to its synthetic counterpart. Smallholder growers can thus use NSE as a cost-effective solution in tomato pest management in Pakistan.

Overexpression of the F116V allele of CYP9A186 in transgenic Helicoverpa armigera confers high-level resistance to emamectin benzoate

Insect cytochrome P450s play important roles in the detoxification of xenobiotics and the metabolic resistance to insecticides. However, the approach for in vivo validation of the contribution of specific candidate P450s to resistance is still limited in most non-model insect species. Previous studies with heterologous expression and in vitro functional assays have confirmed that a natural substitution (F116V) in the substrate recognition site 1 (SRS1) of the CYP9A186 of Spodoptera exigua is a gain-of-function mutation, which results in detoxification capability of and thus high-level resistance to both emamectin benzoate (EB) and abamectin. In this study, we established an effective piggyBac-based transformation system in the serious agricultural pest Helicoverpa armigera and overexpressed in vivo a resistance P450 allele, CYP9A186-F116V, from another lepidopteran pest Spodoptera exigua. Bioassays showed that transgenic H. armigera larvae expressing CYP9A186-F116V obtained 358-fold and 38.6-fold resistance to EB and abamectin, respectively. In contrast, a transgenic line of Drosophila melanogaster overexpressing this P450 variant only confers ∼20-fold resistance to the two insecticides. This bias towards the resistance level revealed that closely related species might provide a more appropriate cellular environment for gene expression and subsequent toxicokinetics of insecticides. These results not only present an alternative method for in vivo functional characterization of P450s in H. armigera and other phylogenetically close species but also provide a valuable genetic engineering toolkit for the genetic manipulation of H. armigera.

Vegetable waste extracts as enhancers of baculovirus infections

Vegetable waste extracts (VWE) contain a great variety of antioxidants such as polyphenols, which have shown to potentiate baculovirus infections, making them ingredients for pest control ingredients. In the present study, the mortality enhancement of different vegetable extracts obtained from food residues when combined with baculoviruses was evaluated. Extracts from spent coffee (E2), rosehip (E17), asparagus (E28), artichoke (E29), beet stalks (E32) and banana peel (E37) were selected as they increased mortality of Spodoptera littoralis nucleopolyhedrovirus (SpliNPV) in second instar S. littoralis larvae, when comparing with the virus inoculation alone. Extracts were assayed at 1 % w/v. In S. littoralis-SpliNPV system, the selected extracts reduced the median lethal concentration (LC50) of SpliNPV against second instar larvae. The E37 extract presented the highest potentiation, as it reduced the LC50 13.61 times, while the rest of the extracts presented LC50 reductions from 3.71 to 7.72-fold. In Spodoptera exigua-SeMNPV (Spodoptera exigua multiple nucleopolyhedrovirus) system, none of the extracts decreased the LC50 of SeMNPV. In contrast, in Spodoptera frugiperda-SfMNPV (Spodoptera frugiperda multiple nucleopolyhedrovirus) system, E2 showed the greatest potentiating effect. In the heterologous systems, none of the extracts tested increased the effective host range of SfMNPV, AcMNPV (Autographa californica multiple nucleopolyhedrovirus), and MbMNPV (Mamestra brassicae multiple nucleopolyhedrovirus) in second instar S. littoralis larvae. Thus, the viral enhancing effect of VWE was host-pathogen and instar dependent. However, the potentiation effect of the extracts could not be directly related with the antioxidants content of the extracts.

The Lrp transcriptional factor of an entomopathogenic bacterium, Xenorhabdus hominickii, activates non-ribosomal peptide synthetases to suppress insect immunity

Two bacterial genera, Xenorhabdus and Photorhabdus, are mutually symbiotic to the entomopathogenic nematodes, Steinernema and Heterorhabditis, respectively. The infective juveniles deliver the symbiotic bacteria to the hemocoel of target insects, in which the bacteria proliferate and help the development of the host nematode. The successful parasitism of the nematode-bacterial complex depends on host immunosuppression by the bacteria via their secondary metabolites. Leucine-responsive regulatory protein (Lrp) is a global bacterial transcriptional factor that plays a crucial role in parasitism. However, its regulatory targets to suppress insect immunity are not clearly understood. This study investigated the bacterial genes regulated by Lrp and the subsequent production of secondary metabolites in Xenorhabdus hominickii. Lrp expression occurred at the early infection stage of the bacteria in a target insect, Spodoptera exigua. A preliminary in silico screening indicated that 3.7% genes among 4075 predicted genes encoded in X. hominickii had the Lrp-response element on their promoters, including two non-ribosomal peptide synthetases (NRPSs). Eight NRPS (NRPS1-NRPS8) genes were predicted in the bacterial genome, in which six NRPS (NRPS3-NRPS8) expressions were positively correlated with Lrp expression in the infected larvae of S. exigua. Exchange of the Lrp promoter with an inducible promoter altered the production of the secondary metabolites and the NRPS expression levels. The immunosuppressive activities of X. hominickii were dependent on the Lrp expression level. The metabolites produced by Lrp expression included the eicosanoid-biosynthesis inhibitors and hemolytic factors. A cyclic dipeptide (=cPF) was produced by the bacteria at high Lrp expression and inhibited the phospholipase A2 activity of S. exigua in a competitive inhibitory manner. These results suggest that Lrp is a global transcriptional factor of X. hominickii and plays a crucial role in insect immunosuppression by modulating NRPS expression.

Plant diversity and soil legacy independently affect the plant metabolome and induced responses following herbivory.

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.

The effectiveness of various insecticide active ingredients against the intensity of armyworm (Spodoptera exigua) attacks on onion plants (Allium ascalonicum L.) Varieties of Bima Brebes

Shallots (Allium ascalonicum L.) are one of the leading commodities in agriculture. Shallots are commonly used as a seasoning for cooking, besides that shallots are also useful as traditional medicine because they have antiseptic substances contained in them. The productivity of onion plants often decreases as a result of pest attacks. Armyworm (Spodoptera exigua) is one of the obstacles in the cultivation of onion plants (Allium ascalonicum L.), high caterpillar attack rates can reduce onion productivity, even causing crop failure. One way to control this pest is to control by using insecticides with certain active ingredients. This study aims to determine the effectiveness of various insecticide active ingredients to control armyworm pests (Spodoptera exigua) on onion plants (Allium ascalonicum L.). The design in this study was a Group Randomized Design (RAK) with 4 treatments of insecticide active ingredients and controls, namely A (Profenofos), B (Emamectin benzoate), C (Metomil), D (Cipermethrin) and E (control). Each treatment was repeated 5 times so that there were 25 experimental units. The research was conducted in Gagasari Village, Gebang District, Cirebon Regency, West Java. The trial research time starts from June - September 2023. The results showed that the application of insecticides active ingredients Profenofos, Emamectin benzoate, Metomil and Sipermethrin did not cause phytotoxicity to onion plants. Insecticide, Profenofos has a relatively gentle attack and low when compared to other active ingredients. In general, it is seen that all active ingredients of insecticides tested are able to play a role in controlling pests well. Insecticide treatment has a significant effect on the yield of dry weight of shallots per plot when compared to treatment without insecticide control (control). Profenofos active ingredient insecticide treatment was seen to produce a higher dry tuber weight than other treatments even when compared to all insecticide active ingredients tested, reaching 24.92 kg or equivalent to 24.9 tons per hectare

CHEMICAL CONTROL OF HELICOVERPA ARMIGERA AND SPODOPTERA EXIGUA AND ITS EFFECTS ON THE QUALITATIVE INDICATORS OF PEPPERS

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.

Feeding Spodoptera exigua larvae with gut-derived Escherichia sp. increases larval juvenile hormone levels inhibiting cannibalism

Feed quality influences insect cannibalistic behavior and gut microbial communities. In the present study, Spodoptera exigua larvae were fed six different artificial diets, and one of these diets (Diet 3) delayed larval cannibalistic behavior and reduced the cannibalism ratio after ingestion. Diet 3-fed larvae had the highest gut bacterial load (1.396 ± 0.556 × 1014 bacteria/mg gut), whereas Diet 2-fed larvae had the lowest gut bacterial load (3.076 ± 1.368 × 1012 bacteria/mg gut). The gut bacterial composition and diversity of different diet-fed S. exigua larvae varied according to the 16S rRNA gene sequence analysis. Enterobacteriaceae was specific to the Diet 3-fed larval gut. Fifteen culturable bacterial isolates were obtained from the midgut of Diet 3-fed larvae. Of these, ten belonged to Escherichia sp. After administration with Diet 1- or 2-fed S. exigua larvae, two bacterial isolates (SePC-12 and -37) delayed cannibalistic behavior in both tested larval groups. Diet 2-fed larvae had the lowest Juvenile hormone (JH) concentration and were more aggressive against intraspecific predation. However, SePC-12 loading increased the JH hormone levels in Diet 2-fed larvae and inhibited their cannibalism. Bacteria in the larval midgut are involved in the stabilization of JH levels, thereby regulating host larval cannibalistic behavior.

Can low concentration flufenoxuron treatment increase the pathogenicity or production of nucleopolyhedrovirus occlusion bodies in Spodoptera exigua (Hübner) or Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae)?

Nucleopolyhedroviruses (Baculoviridae) are lethal pathogens that naturally infect lepidopteran larvae. The chitin synthesis inhibitor flufenoxuron has been reported to potentiate the insecticidal properties of nucleopolyhedrovirus occlusion bodies (OBs) by degrading the integrity of the peritrophic matrix in lepidopteran larvae. In the present study we examined the effect of flufenoxuron treatment on susceptibility of Spodoptera exigua (Hübner) and Spodoptera frugiperda (JE Smith) fifth instars to their homologous nucleopolyhedroviruses, SeMNPV and SfMNPV, respectively. Preliminary bioassays indicated that a 1 mg/l concentration of flufenoxuron resulted in 6.6 - 13.3% mortality of larvae, which could be used in combination with OB inoculum concentrations of 1.5 × 104 OBs/ml of SeMNPV OBs or 1.3 × 10⁶ OBs/ml of SfMNPV OBs. Treatment of larvae with flufenoxuron did not significantly affect virus-induced mortality of either S. exigua (16.7 - 17.2%) or S. frugiperda (28.9 - 34.4%) and had no significant effect on the mean yield of OBs from virus-killed insects of either species. The identity of both SeMNPV and SfMNPV in experimental insects was confirmed by examination of the restriction endonuclease profiles of each virus. These findings contrast with the results of previous studies in which high concentrations of flufenoxuron (100 mg/l) greatly potentiated virus-induced mortality in the silkworm Bombyx mori L., although insect mortality due to flufenoxuron treatment alone was not reported, for reasons that are unclear. We conclude that flufenoxuron (1 mg/l) failed to potentiate the insecticidal activity of SeMNPV or SfMNPV in their respective hosts.

Epigenetic weapons in plant-herbivore interactions: Sulforaphane disrupts histone deacetylases, gene expression, and larval development in Spodoptera exigua while the specialist feeder Trichoplusia ni is largely resistant to these effects.

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.