Xylostella Larvae Research Articles

Interactions between host plant quality and non‐consumptive predator effects on oviposition and larval behaviour of Plutella xylostella (Lepidoptera: Plutellidae)

Abstract The presence of predators can induce non‐consumptive effects on prey that result in subsequent changes to prey behaviour and defence. We investigate the interaction between top‐down non‐consumptive effects of various stages of the predator Coccinella septempunctata L.(Coleoptera: Coccinellidae) (larvae and adult) and bottom‐up effects of host nutrition on Plutella xylostella (L.) (Lepidoptera: Plutellidae) oviposition and larval host choice. We also compare the effect of presence of intact predators, predators without mandibles, confined predators and a no predator control treatment on P. xylostella larval growth, survival and herbivory. Host plant nutrition influenced the host choice of adult female P. xylostella; no interaction was observed between bottom‐up host plant nutrition and the presence of C. septempunctata adults or larvae on oviposition or larval host choice by P. xylostella. Predator presence impacted larval feeding and weight gain. The presence of free‐moving C. septempunctata adults without mandibles that could not predate P. xylostella reduced mean leaf consumption by P. xylostella larvae to 1.88 ± 0.21 cm2 and reduced weight gain to 2.12 ± 0.16 mg. Despite differences in leaf damage and larval weight gain, survival remained consistent across the non‐consumptive treatments. Intact C. septempunctata larvae reduced leaf damage and subsequent P. xylostella larval weight gain. The presence of larval predators across the non‐consumptive treatments, however, had no effect on feeding damage or weight gain. Results of our investigation indicate that C. septempunctata causes some non‐consumptive effects on P. xylostella that depend on predator life stage, level of confinement and prey life stage. It is likely that P. xylostella responds to multi‐modal cues in predator detection.

Characterization of larval gut microbiota of two endoparasitoid wasps associated with their common host, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae).

Insect gut microbes play important roles in digestion, metabolism, development, and environmental adaptation. Parasitoid wasps are one of the most important biological control agents in pest control, while the gut microbial species compositions and the associated functions have been poorly investigated. Two endoparasitoid wasps, Cotesia vestalis and Diadromus collaris, parasitize the larval stage and pupal stage of the diamondback moth, Plutella xylostella, respectively. Using whole-genome shotgun metagenomic sequencing, we characterized the gut microbial composition, diversity, and potential functional roles associated with the two parasitoid wasp larvae. The results reveal that Proteobacteria and Firmicutes are the dominant phyla in the gut of C. vestalis and D. collaris larvae, with Rhizobium and Enterococcus being the dominant genera. The putative microbial functions associated with the two parasitoid wasps might play a virtual role in assisting in consuming the host's nutritional composition. The enriched CAZymes family genes are primarily involved in the degradation and synthesis of chitin. Despite the richness of microbial species and communities, the microbes species and the microbial community structure exhibit significant similarity between the two parasitoid wasps and between the parasitoid wasp and the host P. xylostella. Notably, the prevalence of the genus Enterococcus shared among them suggests a possible link of gut microbes between the host and their associated parasitoids. Our study offers insights into the gut microbe-based interactions between the host and parasitoid wasps for the first time, potentially paving the way for the development of an ecologically friendly biocontrol strategy against the pest P. xylostella.IMPORTANCEEndoparasitoid wasps spend the majority of their lifespan within their host and heavily rely on the host's nutrition for survival. There is limited understanding regarding the composition and physiological impacts of gut microbial communities in parasitoid wasps, particularly during the larval stage, which is directly linked to the host. Based on a thorough characterization of the gut microbe and comprehensive comparative analysis, we found the microbial species of the larval parasitoid wasp Cotesia vestalis and the pupal parasitoid wasp Diadromus collaris were similar, sharing 159 genera and 277 species, as were the microbial community structure. Certain of the dominant microbial strains of the two parasitoid wasps were similar to that of their host Plutella xylostella larvae, revealing host insect may affect the microbial community of the parasitoid wasps. The putative microbial functions associated with the parasitoid wasp larvae play an important role in dietary consumption.

Redox-Responsive Nanopesticides Based on Natural Polymers for Environmentally Safe Delivery of Pesticides with Enhanced Foliar Dispersion and Washout Resistance.

Based on the modified cross-linking of the degradable natural polymers chitosan oligosaccharides (COS) and gelatin (GEL) via introduction of a functional bridge 3,3'-dithiodipropionic acid, this study constructed an environmentally responsive dinotefuran (DNF) delivery system (DNF@COS-SS-GEL). The introduction of the disulfide bond (-S-S-) endowed DNF@COS-SS-GEL with redox-responsive properties, allowing for the rapid release of pesticides when stimulated by glutathione (GSH) in the simulated insect. Compared with commercial DNF suspension concentrate (DNF-SC), DNF@COS-SS-GEL showed superior wet spreading and retention performance on cabbage leaves with a reduced contact angle (57°) at 180 s and 4-fold increased retention capacity after rainfall washout. Nanoencapsulation effectively improved the UV-photostability with only a 31.4% decomposition rate of DNF@COS-SS-GEL at 96 h. The small scale and large specific surface area resulted in excellent uptake and transportation properties in plants as well as higher bioactivity against Plutella xylostella larvae. This study will help promote sustainable agricultural development by reducing environmental pollution through improved pesticide utilization.

Synergism of Cry1 Toxins by a Fusion Protein Derived from a Cadherin Fragment and an Antibody Peptide.

Synergistic factors can enhance the toxicity of Bt toxins and delay the development of Bt resistance. Previous research has demonstrated that a Helicoverpa armigera cadherin fragment (HaCad-TBR) increased the toxicity of Cry1Ac in Plutella xylostella larvae but did not have a synergistic effect on Cry1B, Cry1C, and Cry1F toxins. In this study, a fusion protein (HaCad-TBR-2D3 VL) derived from HaCad-TBR and a Bt Cry1-specific antibody peptide was expressed in Escherichia coli. The HaCad-TBR-2D3 VL enhanced Cry1Ac toxicity more efficiently in insects and Sf9 cells than HaCad-TBR and also significantly increased the toxicity of Cry1B, Cry1C, and Cry1F toxins in insects. Further investigation indicated that the improved stability in insect midguts and higher binding capacity with Bt toxins contributed to the enhanced synergism of HaCad-TBR-2D3 VL over HaCad-TBR. This study suggested that Bt antibody fragments can potentially broaden the synergistic range of Bt receptor fragments, providing a theoretical foundation for developing broad-spectrum synergists for other biopesticides.

Susceptibility of Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) to cyantraniliprole and spinetoram

ABSTRACT Integrated pest management (IPM) uses a range of control strategies to diminish pest populations. Hence, the simultaneous utilisation of synthetic insecticides and biological control agents is desirable, although hindered by the possible impact of insecticides on non-target organisms. Plutella xylostella (L.) is a common target of several pesticides in Brassica crops. However, it can also be parasitised by Tetrastichus howardi (Olliff). This study examined the susceptibility of T. howardi to dry residue of cyantraniliprole and spinetoram on inert surfaces and treated kale (Brassica oleracea var. manteiga) leaf discs at field rates (FRs = 10 g a.i. ha−1 and 25 g a.i. ha−1, respectively), 50% of the FR, and at various time intervals (ranging from 2 h to 8 days after application). Survival of T. howardi remained unaffected by cyantraniliprole and spinetoram, regardless of the pesticide rate or spraying interval. Furthermore, the presence of cyantraniliprole and spinetoram in dry residue, when kale leaves were consumed by second-instar P. xylostella larvae at LC25 and LC50 levels, did not have any detrimental impact on the survival of the parasitoids. Similarly, the exposure of T. howardi to contaminated P. xylostella larvae did not have any impact on its ability to parasitise or on the emergence of the parasitoid. Given the minimal effect of cyantraniliprole and spinetoram on T. howardi, these control strategies appear to be suitable for incorporation into an integrated approach for the management of P. xylostella in Brassica crops.

Actinobacteria mediated synthesis of silver nanoparticles using Streptomyces diastaticus and their biological efficacy against human vector mosquitoes and agricultural insect pests

Mosquitoes and agricultural insects were harmful to both public health and crops. Prolonged use of synthetic chemical pesticides for insect pest control was associated with resistance development and negative human and ecological effects. This study investigates the larvicidal activity of Ag-NPs produced using Streptomyces diastaticus against Culex quinquefasciatus, Anopheles stephensi, Aedes aegypti, Spodoptera litura, and Plutella xylostella. UV-Vis spectroscopy, XRD, SEM-EDX, FT-IR, TEM, DLS, and Zeta potential analysis were used to characterize the biosynthesized Ag-NPs. The results showed that biosynthesized Ag-NPs were more toxic to, A. stephensi, C. quinquefasciatus, and A. aegypti with LC50 values of 15.70, 11.10, and 17.53 µg/mL, respectively. Biosynthesized Ag-NPs exhibited the highest antifeedant effects against S. litura (88.73 %) and P. xylostella (92.36 %) at 50 µg/mL concentration. The mortality bioassay revealed considerable larvicidal activity against S. litura and P. xylostella larvae at greater doses of 50 µg/mL, 80.67 and 84.05 %, respectively. Morphogenetic variations were observed on treated larvae of C. quinquefasciatus, A. aegypti, and A. stephensi, S. litura, and P. xylostella with Ag-NPs. In the present investigation the impact of Ag-NPs on the antioxidant enzymes (SOD, CAT, and GPx), the activity of each enzyme were dramatically increased with higher concentrations resulting in significant differences. The study also found that Ag-NPs inhibited the detoxifying enzyme (GST and AChE) activity of target organisms. The histological structure of the treated and untreated larvae revealed structural changes between the midgut epithelial cells. As a consequence of these findings, the S. diastaticus-mediated Ag-NPs serve as a possible, eco-friendly biopesticide and alternative to synthetic chemicals for the control of human vector mosquitoes and destructive arthropod insect pests.

Percentage Attacks of Plutella xylostella and Parasitization of the Parasitoid Diadegma semiclausum on Cabbage in Kintamani District

Cabbage plants are one of the horticultural commodities that many farmers cultivate in Indonesia because they have economic value, because apart from being able to meet domestic needs, cabbage also has the opportunity to become an export commodity. This study aims to determine the percentage of attacks by the cabbage leaf caterpillar Plutella xylostella and the level of parasitization of the parasitoid Diadegma semiclausum in Kintamani District. This research was carried out in Sekaan Village and Kedisan Village. The research method uses a survey method. Sampling of cabbage plants in the field was carried out diagonally so that 5 sample points were obtained, 10 plants were observed at each sample point. The research results showed that the percentage of P. xylostella pest attacks in Sekaan Village and Kedisan Village ranged from 12% to 28%. The average population of P. xylostella larvae in Sekaan Village ranges from 0.98 individuals/plant to 1.82 individuals/plant and the highest average population of P. xylostella larvae in Kedisan Village ranges from 0.7 individuals/plant to 1.66 individuals/plant. The level of parasitization of the parasitoid D. semiclausum in Sekaan Village ranges from 32% to 56% and the level of parasitization of the parasitoid D. semiclausum in Kedisan Village ranges from 24% to 48%. The highest peak of parasitization was found in the fourth observation (4 WAP).

Minimizing IP issues associated with gene constructs encoding the Bt toxin - a case study

BackgroundAs part of a publicly funded initiative to develop genetically engineered Brassicas (cabbage, cauliflower, and canola) expressing Bacillus thuringiensis Crystal (Cry)-encoded insecticidal (Bt) toxin for Indian and Australian farmers, we designed several constructs that drive high-level expression of modified Cry1B and Cry1C genes (referred to as Cry1BM and Cry1CM; with M indicating modified). The two main motivations for modifying the DNA sequences of these genes were to minimise any licensing cost associated with the commercial cultivation of transgenic crop plants expressing CryM genes, and to remove or alter sequences that might adversely affect their activity in plants.ResultsTo assess the insecticidal efficacy of the Cry1BM/Cry1CM genes, constructs were introduced into the model Brassica Arabidopsis thaliana in which Cry1BM/Cry1CM expression was directed from either single (S4/S7) or double (S4S4/S7S7) subterranean clover stunt virus (SCSV) promoters. The resulting transgenic plants displayed a high-level of Cry1BM/Cry1CM expression. Protein accumulation for Cry1CM ranged from 5.18 to 176.88 µg Cry1CM/g dry weight of leaves. Contrary to previous work on stunt promoters, we found no correlation between the use of either single or double stunt promoters and the expression levels of Cry1BM/Cry1CM genes, with a similar range of Cry1CM transcript abundance and protein content observed from both constructs. First instar Diamondback moth (Plutella xylostella) larvae fed on transgenic Arabidopsis leaves expressing the Cry1BM/Cry1CM genes showed 100% mortality, with a mean leaf damage score on a scale of zero to five of 0.125 for transgenic leaves and 4.2 for wild-type leaves.ConclusionsOur work indicates that the modified Cry1 genes are suitable for the development of insect resistant GM crops. Except for the PAT gene in the USA, our assessment of the intellectual property landscape of components presents within the constructs described here suggest that they can be used without the need for further licensing. This has the capacity to significantly reduce the cost of developing and using these Cry1M genes in GM crop plants in the future.

Comparative transcriptome analysis reveals disruption of Plutella xylostella immune system by fungal peptide cyclosporin C

The diamondback moth (Plutella xylostella), a major threat to crucifers across the globe, has developed resistance against the majority of insecticides enhancing the need for alternate control measures against this pest. Recently cyclosporin C, a secondary metabolite produced by the insect pathogenic fungus Purpeocillium lilacinum, has been reported to induce lethal and sub-lethal effects against P. xylostella. To date, little is known about the molecular mechanisms of interaction between cyclosporin C and P. xylostella immune systems. This study reports the transcriptome-based immune response of P. xylostella to cyclosprin C treatment. Our results showed differential expression of 322, 97, and 504 differentially expressed genes (DEGS) in P. xylostella treated with cyclosporin C compared to control 24, 48, and 72 h post-treatment, respectively. Thirteen DEGs were commonly expressed at different time intervals in P. xylostella larvae treated with cyclosporin C compared to control. Cyclosporin C treatment induced the down-regulated expression of majority of immune-related genes related to pattern recognition responses, signal modulation, Toll and IMD pathways, antimicrobial peptides and antioxidant responses confirming the ability to suppress immune response of P. xylostella. These results will further improve our knowledge of the infection mechanism and complex biochemical processes involved in interaction between cyclosporin C and insect immune systems.

Insecticidal action of mammalian galectin-1-transfected Arabidopsis thaliana.

Galectins (GALs) are a family of mammalian sugar-binding proteins specific for β-galactosides. Our previous studies have shown that the larval development of the diamondback moth (Plutella xylostella) is significantly disturbed when fed with recombinant mammalian galectin 1 (GAL1) derived from Escherichia coli. To further explore its applicability, two GAL1-overexpressed Arabidopsis [GAL1-Arabidopsis (whole plant) and GAL1-Arabidopsis-vas (vascular bundle-specific)] lines were established for insecticidal activity and mechanism studies. The expression level of GAL1 in transgenic Arabidopsis is 1-0.5% (GAL1-Arabidopsis) and 0.08-0.01% (GAL1-Arabidopsis-vas) of total leaf soluble protein. Survival, body weight, and food consumption significantly decreased in a time-dependent manner in P. xylostella larvae (with chewing mouthparts) fed on GAL1-Arabidopsis. The mortality of Kolla paulula (with piercing-sucking mouthparts and xylem feeder) fed on GAL1-Arabidopsis-vas was also significantly higher than that fed on wild-type Arabidopsis (WT-Arabidopsis), but was lower than that fed on GAL1-Arabidopsis. The histochemical structure and results of immunostaining suggested that the binding of GAL1 to the midgut epithelium of P. xylostella fed on GAL1-Arabidopsis was dose- and time-dependent. Ultrastructural studies further showed the disruption of microvilli, abnormalities in epithelial cells, and fragments of the peritrophic membrane (PM) in P. xylostella larvae fed on GAL1-Arabidopsis. The insecticidal mechanism of GAL1 involves interference with PM integrity and suggests that GAL1 is a potential candidate for bioinsecticide development. © 2024 Society of Chemical Industry.

Assessment of the insecticidal efficacy of ethanol extract of Millettia pachyloba Drake leaves against Plutella xylostella Linnaeus moth

Plutella xylostella (L.), a menacing threat to cruciferous crops, exhibits cross-resistance to various chemical agents. The exploration of plant-derived insecticides emerges as an intervention strategy for the successful management of P. xylostella. Millettia pachyloba Drake is renowned as a traditional remedy for diverse health issues and has insecticidal properties. Experimental investigations in both laboratory and greenhouse settings utilized M. pachyloba extract (EMPE) at concentrations ranging from 2 to 10% (w/v). The objectives included inducing toxicity and controlling P. xylostella larvae effectively, assessing nutritional impacts through parameters like relative consumption rate (RCR), relative growth rate of larvae (RGR), efficiency of conversion of digested food (ECD), efficiency of conversion of ingested food (ECI), approximate digestibility (AD), and assimilation ratio (AR), and evaluating leaf damage inflicted by P. xylostella larvae on Brassica juncea. In the laboratory, the application of EMPE on P. xylostella larvae and pupae for 24, 48, and 72 hours yielded markedly higher mortality rates than the water-treated control (p < 0.05). Significant reductions in RGR, RCR, ECD, ECI, AD, and AR were evident throughout the larval stage (p < 0.05). In the greenhouse, EMPE treatments demonstrated notable differences from the water control treatment. On the 15th day of treatment, the EMPE treatment at 10% (w/v) exhibited the highest mortality rate (p < 0.05). Significantly reduced leaf damage was observed with EMPE treatments, displaying an inverse correlation with escalating concentrations. Particularly, the highest enhancement across all surveyed parameters was observed in the EMPE 10% (w/v) treatment, which was comparable to the positive control with fipronil (p > 0.05). Noteworthy differences in damage reduction percentage (DRP) were identified between EMPE contact treatments and the water control group (p < 0.05), indicating the promising potential of Millettia pachyloba extract for pest control.

A flexible modulated pesticide release platform through poly(urethane-urea) microcapsules: effect of different crosslinkers compositions.

Polymeric microcapsules (MCs) have become an important issue and have attracted increasing attention because of their tunable physical and chemical properties. Diverse shell structures can confer multiple properties on MCs. Different polyols (1,4-butanediol and glycerin) and polyamines (triethylenetetramine and isophorondiamine) were selected as crosslinkers to obtain emamectin benzoate (EB)-loaded poly(urethane-urea) MCs (PU-MCs) by interfacial polymerization. The four obtained PU-MCs showed sphericity with different degrees of smoothness on their surfaces, and displayed a uniform size distribution ranging from 500 to 700 nm. Moreover, transmission electron microscopy showed that the shell thickness was roughly uniform, and was greatly influenced by the type and structure of the crosslinker. GI-MCs, prepared using glycerin and isophorondiamine, had the largest shell thickness. GT-MCs, obtained using glycerin and triethylenetetramine, had the highest encapsulation efficiency and drug-loading content, and BT-MCs, obtained using mixtures of 1,4-butanediol and triethylenetetramine, had the fastest release behavior. Thermogravimetric analysis revealed that the greater the degree of shell crosslinking, the higher decomposition temperature and the greater the thermal stability. A BT-MC suspension had the lowest viscosity and contact angle with the best wettability. Bioassay experiments showed that BT-MCs exhibited good insecticidal activity against Plutella xylostella larvae with a half-maximal lethal concentration of 4.19 mg/L. Furthermore, a BT-MC suspension showed good thermal and light stability, with potential applications in minimizing the toxicity of EB through sustained release. Various properties of EB-loaded PU-MCs were modulated through simple selection of different polyols and polyamines during fabrication, which might have an important role in constructing the pesticide delivery system and improving pesticide utilization. © 2024 Society of Chemical Industry.

Novel Cyclopenta[c]pyridine Derivatives Based on Natural Cerbinal as Potential Agrochemical Anti-TMV Agents and Insecticides.

Based on natural cerbinal, a series of novel 4-bit modified cyclopenta[c]pyridine derivatives containing a substituted amide or ester moiety were designed and synthesized for the first time. Their structures were systematically characterized by NMR and high-resolution mass spectra (HRMS). The anti-TMV activities, such as protection, inactivation, and curative effects in vivo, were evaluated methodically. The lethal activities of the target compounds against the agriculturally common pests Plutella xylostella larvae and Aphis laburni kaltenbach were evaluated by the immersion method. The bioassay results indicated that most of the target compounds exhibited good to excellent anti-TMV activity levels, good lethal activity against P. xylostella larvae at 600 μg/mL, and greater insecticidal activities against A. laburni Kaltenbach compared to the plant-derived insecticide rotenone. The binding mode of cerbinal and cyclopenta[c]pyridine derivatives 4b, 4p, and 4v with the TMV protein was studied with a molecular docking method, which indicated that the functional group of the 2- and 4-positions is vital for anti-TMV activity. The systematic research provides strong evidence that these novel 4-bit modified cyclopenta[c]pyridine derivatives could become potential agrochemical insecticides and anti-TMV agents.

Effects of frass from larvae of black soldier fly (Hermetia illucens) and yellow mealworm (Tenebrio molitor) on growth and insect resistance in field mustard (Brassica rapa): differences between insect species and frass treatments

AbstractFrass, a byproduct of insect rearing, has become popular for its potential use in sustainable agriculture. The rapid growth of insect production results in an increased frass output. This study examined the effects of frass as soil amendment on plant growth and resistance to insect herbivory. In greenhouse experiments, Brassica rapa L. (Brassicaceae), was grown in unamended soil (NoFrass; control) or soil amended with frass (2 g kg−1) from larvae of black soldier fly (BSFF), Hermetia illucens L. (Diptera: Stratiomyidae), or yellow mealworm (MWF), Tenebrio molitor L. (Coleoptera: Tenebrionidae). Frass was applied as raw, incubated, or composted frass before seed germination. Plant growth and performance were measured of larvae of root‐feeding Delia radicum L. (Diptera: Anthomyiidae) and shoot‐feeding Plutella xylostella L. (Lepidoptera: Plutellidae). Initially, raw BSFF and MWF reduced the growth of B. rapa and resulted in a smaller leaf area than NoFrass. However, over time, a notable trend emerged. Whereas the difference in leaf area between MWF and NoFrass disappeared, BSFF consistently resulted in a smaller leaf area than MWF and NoFrass. Raw BSFF reduced D. radicum larval survival and pupal biomass and larval survival of P. xylostella. In contrast, raw MWF increased larval survival and biomass of D. radicum and the survival of P. xylostella larvae. Interestingly, incubation of frass in the soil for 16 days before seed germination removed plant growth inhibition and increased plant leaf area, especially for MWF compared to NoFrass. In addition, composting MWF increased leaf growth. Therefore, frass may be used as a sustainable and natural alternative to conventional organic fertilisers, promoting plant growth and enhancing resistance to herbivory. Our results indicate that soil amendment with raw BSFF may negatively impact herbivore performance, whereas raw MWF may enhance herbivore performance.

Functional response of larval and adult Coccinella septempunctata to eggs and larvae of Plutella xylostella on canola

AbstractUnderstanding of functional responses (i.e., changes in predator feeding rates with prey density) of key predators to different crop pest stages is critical to strengthening biological control, particularly in view of climate change and temperature variation. We investigated prey preferences of Coccinella septempunctata L. (Coleoptera: Coccinelidae) to egg and larval stages of a key brassicaceous pest of canola (Brassica napus L., Brassicaceae), the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae). First, laboratory choice and no‐choice bioassays tested the hypotheses that C. septempunctata accepts and differentially prefers two prey developmental stages (eggs and larvae). Then, C. septempunctata larvae and adults were exposed to six densities of P. xylostella eggs over 24 h in functional response bioassays that determined the number of eggs consumed. Finally, the functional response bioassays were repeated with larval prey and extended with three temperature regimes: 10, 22 and 32 °C. In both choice and no‐choice assays, C. septempunctata adults and larvae consumed more P. xylostella larvae than eggs. The functional response of C. septempunctata depended on predator developmental stage and temperature, with reduced handling time and increased attack rates and consumption under warmer conditions. At 10 and 22 °C, the functional responses of both C. septempunctata larvae and adults were of Type II, i.e., rates of prey consumption increase at decelerating rates and then plateau with increasing prey density. Our study demonstrates that both larvae and adults of C. septempunctata can consume high numbers of eggs and early instar P. xylostella larvae; these responses are temperature‐dependent with increased consumption rates at higher temperatures. This may lead to improvements in management of P. xylostella in canola.

MiR-2b-3p Downregulated PxTrypsin-9 Expression in the Larval Midgut to Decrease Cry1Ac Susceptibility of the Diamondback Moth, Plutella xylostella (L.).

Crystal (Cry) toxins, produced by Bacillus thuringiensis, are widely used as effective biological pesticides in agricultural production. However, insects always quickly evolve adaptations against Cry toxins within a few generations. In this study, we focused on the Cry1Ac protoxin activated by protease. Our results identified PxTrypsin-9 as a trypsin gene that plays a key role in Cry1Ac virulence in Plutella xylostella larvae. In addition, P. xylostella miR-2b-3p, a member of the micoRNA-2 (miR-2) family, was significantly upregulated by Cry1Ac protoxin and targeted to PxTrypsin-9 downregulated its expression. The mRNA level of PxTrypsin-9, regulated by miR-2b-3p, revealed an increased tolerance of P. xylostella larvae to Cry1Ac at the post-transcriptional level. Considering that miR-2b and trypsin genes are widely distributed in various pest species, our study provides the basis for further investigation of the roles of miRNAs in the regulation of the resistance to Cry1Ac and other insecticides.

MicroRNA Targets PAP1 to Mediate Melanization in Plutella xylostella (Linnaeus) Infected by Metarhizium anisopliae.

MicroRNAs (miRNAs) play a pivotal role in important biological processes by regulating post-transcriptional gene expression and exhibit differential expression patterns during development, immune responses, and stress challenges. The diamondback moth causes significant economic damage to crops worldwide. Despite substantial advancements in understanding the molecular biology of this pest, our knowledge regarding the role of miRNAs in regulating key immunity-related genes remains limited. In this study, we leveraged whole transcriptome resequencing data from Plutella xylostella infected with Metarhizium anisopliae to identify specific miRNAs targeting the prophenoloxidase-activating protease1 (PAP1) gene and regulate phenoloxidase (PO) cascade during melanization. Seven miRNAs (pxy-miR-375-5p, pxy-miR-4448-3p, pxy-miR-279a-3p, pxy-miR-3286-3p, pxy-miR-965-5p, pxy-miR-8799-3p, and pxy-miR-14b-5p) were screened. Luciferase reporter assays confirmed that pxy-miR-279a-3p binds to the open reading frame (ORF) and pxy-miR-965-5p to the 3' untranslated region (3' UTR) of PAP1. Our experiments demonstrated that a pxy-miR-965-5p mimic significantly reduced PAP1 expression in P. xylostella larvae, suppressed PO activity, and increased larval mortality rate. Conversely, the injection of pxy-miR-965-5p inhibitor could increase PAP1 expression and PO activity while decreasing larval mortality rate. Furthermore, we identified four LncRNAs (MSTRG.32910.1, MSTRG.7100.1, MSTRG.6802.1, and MSTRG.22113.1) that potentially interact with pxy-miR-965-5p. Interference assays using antisense oligonucleotides (ASOs) revealed that silencing MSTRG.7100.1 and MSTRG.22113.1 increased the expression of pxy-miR-965-5p. These findings shed light on the potential role of pxy-miR-965-5p in the immune response of P. xylostella to M. anisopliae infection and provide a theoretical basis for biological control strategies targeting the immune system of this pest.

Evaluation of Insecticidal Performances of Jayanti Plant (Sesbania sesban) for Integrated Control of Cabbage Caterpillar (Plutella xylostella)

The study on the use of local natural materials as a source of insecticides is intended, among other things, to reduce farmers' dependency on using synthetic chemicals. This research was conducted to obtain the most selective insecticidal active ingredient from Sesbania sesban plant for controlling cabbage caterpillars, choose a target mode of action that has a safe impact on the environment, and determine insecticidal stability during storage of the material prior to application and its stability in water after application. The dried powder of S. sesban leaves was extracted in stages using a series of solvents, namely hexane, DCM, ethanol and water, respectively. Each of the extract fractions produced was tested for its lethal toxicity against Plutella xylostella larvae and Diadegma semiclausum imago. Each of mortality data were processed by probit analysis to produce LC50(s) to determine their insecticidal selectivity. Subsequent bioassays were carried out using extract-water of S. sesban leaves and the data were processed by probit analysis to determine their anti-ovipositor, ovicidal powers and anti-feedant properties against P. xylostella. The insecticidal stability of S. sesban was also studied according to variations in the storage time of the simplicia before extraction, the storage time of the extract before dissolution, and its stability in water during application. The data was processed using ANOVA. The results show that the insecticidal activity of the ethanol extract fraction of S. sesban leaves for controlling cabbage caterpillars was very selective, namely very toxic to P. xylostella but very less toxic to D. semiclausum. Against P. xylostella, S. sesban leaf extract has also been proven to significantly prevent oviposition, inhibit egg hatching and feeding activity. The insecticidal power of S. sesban did not decrease significantly during storage of the simplicia for less than three months and during storage of the extract for less than seven days. However, the toxicity of the extract solution decreased drastically after 24 hours of application

Insecticidal activity of extracts of handroanthus impetiginosus on Plutella xylostella (Lepidoptera: plutellidae) larvae

Plutella xylostella is considered the main pest of cabbage in Brazil and the world, causing damage of up to 100%. Thus, this study evaluated the insecticidal activity of extracts obtained from the fruits, seeds, bark, leaves, and flowers of Handroanthus impetiginosus against the diamondback moth, P. xylostella larvae. The seed extract showed the highest mortality (97.0%) compared to the control treatment. The LC50 values indicated that the seed and flower extracts (0.01003 and 0.01288 mg/L respectively) assumed the highest toxicity to P. xylostella larvae after 24 h of exposure. The results of this study indicated that the seeds extract is the most promising toxic extract, with measured mortality of approximately 97.0% for P. xylostella larvae after 144 h of exposure in kale plants. Seed extract showed the best insecticidal activity. Thus, this extract can be applied to develop an insecticide based on H. impetiginosus seed.

Discovery of Novel Thiazolyl Anthranilic Diamide Derivatives as Insecticidal Candidates.

Agricultural pests have caused huge losses in agricultural production and threaten global food security. Synthetic insecticides remain the major control method. However, with the rapid development of pest resistance and the increasingly stringent regulations on pesticide usage, the development of efficient insecticides with novel structures is particularly urgent. 26 novel anthranilic diamide derivatives containing thiazole moiety were designed based on the scaffold hopping strategy. Bioassay results indicated that compound 6e exhibited excellent insecticidal activity against a susceptible strain of diamondback moth (Plutella xylostella) with the median lethal concentration (LC50 ) being 0.65 mg/L, which was similar to chlorantraniliprole (LC50 = 0.53 mg/L). When treated on larvae of Plutella xylostella that were chlorantraniliprole-resistant, compound 6e showed marginally lower insecticidal activity than chlorantraniliprole (LC50 = 50.45 mg/L and 31.98 mg/L, respectively), suggesting a cross-resistance of compound 6e with chlorantraniliprole (resistance ratios, 77.6-fold and 60.3-fold, respectively). Compound 6e also showed good insecticidal activity against fall armyworm and beet armyworm with the mortalities of pests being 74% and 64%, respectively, at the concentration of 5 mg/L. In addition, compounds 6e and 12a showed delayed toxicity against red imported fire ant with mortality rates being 84% and 85% after 5 days of treatment at 1.0 mg/L, which was superior to chlorantraniliprole. The introduction of thiazole into anthranilic diamide scaffolds resulted in insecticidal leads 6e and 12a with excellent insecticidal activities and potential application in controlling red imported fire ants. The work also guides the discovery of insecticidal molecules with thiazole-containing anthranilic diamide scaffold. This article is protected by copyright. All rights reserved.