Diamondback moth ecology and management: problems, progress, and prospects

RNAi-mediated knockdown of fruitless in Plutella xylostella (Lepidoptera: Plutellidae) disrupts female sex pheromone biosynthesis and male courtship behavior

Strong fecundity is an important reason why the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), has become one of the most serious pests of cruciferous vegetables worldwide. Disrupting with courtship and mating behaviors has emerged as an important strategy for insect management. The fruitless (fru) gene encodes a transcription factor that contains a BTB (Broad-Complex, Tramtrack and Bric a brac) and a zinc finger pair related to the C2H2 class. It plays a crucial role in regulating insect courtship behavior. In this study, the fru gene of P. xylostella (Pxfru) was cloned, revealing 7 alternative splicing forms (Pxfru-1 to Pxfru-7). Pxfru-1 to Pxfru-3 were non-sex-specific transcripts, while the remaining forms were male-specific. Subcellular localization experiments demonstrated that the transcripts encoding proteins containing BTB and zinc finger domains (Pxfru-1 to Pxfru-3) localized to the cell nucleus, whereas Pxfru-4 and Pxfru-5, which contain only one BTB domain, were localized in the nucleus and cytoplasm, respectively. Knockdown the expression of fru in male moths delayed occurrence of mating and reduced their preference to female sex pheromones. Meanwhile, suppression of fru expression in female P. xylostella decreased their attractiveness to males. The results of GC-MS and Y-tube olfaction experiments indicated that this change may be attributed to alterations in the proportion of sex pheromones. This study represents the first report of the fru gene influencing pheromone ratios in female insects, and provides a new perspective for understanding the function of fru in the courtship behavior of non-model insects.

Battle between Gut Bacteria, Immune System, and Cry1Ac Toxin in Plutella xylostella

Research on Bacillus thuringiensis (Bt)-pest interactions has prioritized Cry toxin receptors, with limited attention to gut bacteria's role in modulating Bt sensitivity. This study identified two Enterobacter strains in Plutella xylostella with opposing effects on Cry1Ac susceptibility. Enterobacter hormaechei (PxG15) degraded Cry1Ac protoxin and activated the proPO-AS and JNK pathway, which reduced Cry1Ac's damage to the midgut while limiting the invasion of gut bacteria into the hemolymph. Although Enterobacter asburiae (PxG1) rapidly activated the proPO-AS, the JNK pathway was activated in a much slower and weaker mode when compared to PxG15, which attenuated the repairing efficiency of the midgut under the treatment of Cry1Ac, leading to death resulting from sepsis from the quick invasion of gut bacteria into the hemolymph. This study illustrates the intricate interrelationships among Cry1Ac, the pest's midgut bacteria, and its immune system, offering novel insights into how gut bacteria shape pest survival following Cry1Ac exposure.

A symbiotic gene stimulates aggressive behavior favoring the survival of parasitized caterpillars

Animals often exhibit increased aggression in response to starvation, while parasites often manipulate host behavior. In contrast, underlying molecular mechanisms for these behavioral changes are mostly unknown. The diamondback moth, Plutella xylostella, is an agricultural pest that feeds on cruciferous plants as larvae, while Cotesia vestalis is a parasitoid wasp that parasitizes diamondback moth larvae. In this study, we determined that unparasitized diamondback moth larvae exhibit increased aggression and cannibalism when starved, while starved larvae parasitized by C. vestalis were more aggressive than unparasitized larvae. C. vestalis harbors a domesticated endogenized virus named Cotesia vestalis bracovirus (CvBV) that wasps inject into parasitized hosts. Starvation increased octopamine (OA) levels in the central nervous system (CNS) of diamondback moth larvae while a series of experiments identified a CvBV-encoded gene product named Assailant that further increased aggression in starved diamondback moth larvae. We determined that Assailant increases OA levels by activating tyramine beta-hydroxylase (PxTβh), which is a key enzyme in the OA biosynthesis pathway. Ectopic expression of assailant in Drosophila melanogaster likewise upregulated expression of DmTβh and OA, which increased aggressive behavior in male flies as measured by a well-established assay. While parasitized hosts are often thought to be at a competitive disadvantage to nonparasitized individuals, our results uncover how a parasitoid uses an endogenized virus to increase host aggression and enhance survival of offspring when competing against unparasitized hosts.

Reverse engineering high-level resistance to Bt Cry1Ac toxin in Plutella xylostella reveals a hormonal regulatory feedback pathway

Decoding the molecular mechanisms of insect resistance to Bacillus thuringiensis (Bt) toxins is crucial for the sustainable utilization of Bt-based bioinsecticides and transgenic crops. Our previous studies showed that a hormone-responsive transcription factor FOXO binds to an inserted short interspersed nuclear element (SINE, named SE2), causing MAP4K4 overexpression and resistance to Bt Cry1Ac toxin in Plutella xylostella. Furthermore, titers of two upstream signaling hormones (20-hydroxyecdysone and juvenile hormone) were also found to be elevated in the resistant strain, but it was unclear whether this was due to natural variation or a feedback pathway. Here, we established a homozygous knock-in strain (SE2-KI) using a reverse genetic approach to insert the SE2 retrotransposon into the MAP4K4 promoter of a Cry1Ac-susceptible strain. The SE2 insertion induced MAP4K4 overexpression, which in turn caused a downregulation of midgut receptors and an identical resistance phenotype to that seen in the evolved resistant strain. Moreover, SE2 insertion significantly increased the levels of two insect hormones providing definitive evidence for a positive feedback regulatory pathway. This study unveils an as yet uncharacterized hormonal regulatory feedback pathway orchestrating Cry1Ac resistance in P. xylostella, providing new insights into the molecular basis of Bt resistance and informing suitable field resistance management strategies.

Discovery of multi-chitinase inhibitors cinnamyl thiazolidinone compounds as candidates for insect growth regulators via ligand-based optimization strategies

Chitinases are recognized as potential targets to develop novel insecticides to control lepidopteran pests. However, the design and development of effective multi-chitinase inhibitors remains a huge challenge. Based on the backgrounds, in this study, we designed and synthesized a series of cinnamyl-thiazolidinedione compounds as potential inhibitors against OfChtI, OfChtII and OfChi-h, for the first time, by integrating strategies including fragment replacement, 3D QSAR-guided design, and bioelectronic isosteric replacement. Among all synthesized compounds, those displayed substantial activities against three chitinases, such as 5f and 9m, simultaneously demonstrated significant larvicidal activities and growth regulation effects against various lepidopteran pests. Inhibition mechanism studies indicated that the π interactions, hydrophobic stacking, and electrostatic interactions between cinnamyl-thiazolidinone compounds and the conserved aromatic tryptophan and phenylalanine residues, as well as the polar asparagine residues in three chitinases, were crucial for their interactions. Furthermore, the qPCR experiment suggested that cinnamyl-thiazolidinone compounds could regulate the chitin metabolism pathway of Ostrinia furnacalis in vivo. This study provides the first successful example of developing novel multi-chitinase inhibitors through ligand-based optimization strategies, offering promising candidates for controlling lepidopteran pests.

Identification of seminal fluid proteins and reproductive function of trypsin-1 in male Plutella xylostella

Insect seminal fluid proteins (SFPs) are primary factors affecting physiology and behavior in both sexes, making them valuable targets for pest control. However, SFPs have not been fully characterized in the Plutella xylostella, a global pest that attacks cruciferous crops. Here, 75 putative SFPs were identified in P. xylostella, compared to 10 orthologs in Drosophila melanogaster, 10 in Nilaparvata lugens, 5 in Apis mellifera, and 43 in Heliconius melpomene. Analyses of Ka/Ks suggested that SFPs had high evolution rates. Proteases (22/75, 29.3 %) accounted for the highest proportion of P. xylostella SFPs, including 16 trypsins. The phylogenetic analysis showed that most trypsins from P. xylostella and H. melpomene belonged to the same cluster. SFP04 (trypsin-1) was orthologous to the SFP ADJ58550.1 in H. melpomene. PxTry1 was specifically expressed in adult males and their accessory glands but was also detected in females after mating. A CRISPR/Cas9-induced PxTry1 homozygous mutant strain with a 22-base pair nucleotides insertion was generated. PxTry1 deletion resulted in swollen testes, smaller spermatophores, and abnormal sperm, thus reducing the P. xylostella egg production and hatching. These results clarify the role of insect SFPs in evolution and reproduction and identify a promising target for pest control based on genetic regulation.

Symbiotic bracovirus of a parasite modulate host ecdysis process

Parasitoids modulate host development for the survival of their offspring, but the mechanisms underlying this phenomenon remain largely unknown. Here, we found that the endoparasitoid Cotesia vestalis disrupted the larval-larval ecdysis in its host Plutella xylostella by the 20-hydroxyecdysone (20E) synthesis pathway. After parasitization by C. vestalis, the 20E peak of host larvae disappeared before the onset of ecdysis and the expression of ecdysone synthesis genes was significantly downregulated. We further found that a Cotesia vestalis bracovirus (CvBV) gene CvBV_28 - 5 was transiently high-level expressed prior to the host's 20E peak, enabling the precise suppression of this critical developmental signal. Consistently, the knockdown of CvBV_28 - 5 affected the expression of 20E response transcription factors in the cuticle and several ecdysis-related genes. Furthermore, we found that CvBV_28 - 5 bound directly to the Raf, a MAP3K member of the MAPK pathwaythat functions as a critical regulator of ecdysone synthesis genes in hosts. Collectively, our results provide the first evidence that parasitoids modulate host ecdysis by affecting MAPK-20E signaling during a defined developmental window and provide novel insights into the mechanism of parasitoid regulation of host development.

Knockout of silk fibroin genes in Plutella xylostella results in decreased fitness and performance

BACKGROUND

The ability of insects to spin silk is crucial for their survival, reproduction, and interactions with the environment. The diamondback moth (DBM), Plutella xylostella, a serious agricultural pest, relies on silk production, which influences its behavior and population dynamics.

RESULTS

This study employed CRISPR/Cas9 technology to knock out three genes, that is, silk fibroin heavy chain (PxFibH), silk fibroin light chain (PxFibL), and fibrohexamerin (PxP25), to investigate their roles in silk gland development and related biological traits. We successfully generated PxFibH, PxFibL, and PxP25 knockout mutants, which displayed defective cocoon formation and developed into naked pupae. Further analysis revealed significant alterations in silk gland structure and various biological parameters, including increased larval mortality, prolonged developmental time, reduced pupal weight, and shortened adult lifespan.

CONCLUSIONS

These findings highlight the importance of silk fibroin genes in silk production and growth development in P. xylostella, positioning them as potential targets for innovative pest control strategies. © 2025 Society of Chemical Industry.

Electrophysiological Responses and Field Attractants of Plutella xylostella Adults to Volatiles from Brassica oleracea

The diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae), is a major pest of crucifers. Many volatile compounds emitted by cruciferous vegetables are known to mediate the attraction of DBM adults to host plant and oviposition sites. However, development of highly effective attractants for DBM management is still needed. Here, we first analyzed the volatile compounds emitted by macerated broccoli leaves with gas chromatographic-electroantennographic detection and gas chromatography/mass spectrometry. Eight compounds, including benzaldehyde, limonene, phenylacetaldehyde, acetophenone, linalool, 2-phenylethyl alcohol, methyl salicylate, and methyl 2-methoxybenzoate, elicited robust responses from the antennae. Then, we conducted multiple field trapping experiments involving the "addition approach" (individually adding components to the most abundant component, D-limonene) and the "subtraction approach" to evaluate the attractiveness of different blends. We found that a 3-component blend of D-limonene, 2-phenylethyl alcohol, and methyl 2-methoxybenzoate (3:2:1) is the most effective attractant. This blend holds great potential for monitoring and management of P. xylostella populations.

Whole genome sequencing reveals the genetic diversity and structure of Leptosphaeria maculans populations from the Western Cape province of South Africa

BACKGROUND

Leptosphaeria maculans is the causal agent of blackleg, a globally important disease of canola. Investigating the genetic diversity and structure of L. maculans populations can provide insight into its evolutionary potential and genetic variability, which is important to develop effective blackleg management strategies. In this study, whole genome sequence data was generated for 230 L. maculans isolates collected between 2020 and 2022 across the canola production regions of the Western Cape of South Africa. A total of 27 419 informative single nucleotide polymorphisms was used to investigate the genetic diversity and structure of the pathogen population.

RESULTS

Mating type distribution did not deviate statistically from a 1:1 ratio at any location, indicating no restriction on sexual reproduction. Genetic statistics calculated showed high genotypic diversity and evenness (Lambda and E.5 ≥ 0.98) and low linkage disequilibrium ( ≤ 2.71E-04) which is also associated with sexual reproduction. Discriminative analysis of principal components and sparse nonnegative matrix factorisation revealed genetic differentiation between the Swartland and Southern Cape canola production regions in the Western Cape. Analysis of molecular variance also indicated regions as the most important factor for population differentiation but suggested shallow population structure with only 3,71% of the total variation occurring between regions. To assess the phylogenomic position of South African isolates in the global context, data for 171 international isolates was included, and the clustering analyses repeated. Results showed a high similarity between Australian and Swartland isolates, while isolates from the Southern Cape formed a unique genetic cluster.

CONCLUSION

The results from this study provide the basis for blackleg research in South Africa and enhances understanding of the pathogen, which will assist in developing improved blackleg management strategies.

Development and survival of Plutella Xylostella in central Argentina: Estimating key parameters for local populations

Diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae), a globally distributed insect, is a major pest of crucifer crops due to its adaptability to diverse climates. In Argentina, its distribution spans three regions: a core area in the northeast and central-east where it persists year-round, a southwestern region with seasonal migrations, and an intermediate zone with variable year-round persistence. Across these areas, it is the primary pest of Brassica crops. In the central-east, the availability of year-round Brassicaceae crops and wild species indicates that seasonality is not linked to food scarcity. While studies have examined this relationship elsewhere, thermal thresholds vary among populations, and limited data on South American populations highlight the need for localised research. This study evaluated thermal thresholds for P. xylostella populations in central Argentina, focusing on temperature's effects on fecundity, fertility, development, and survival. We found that temperatures outside the optimal range (15-23°C) significantly reduced survival, with no individuals surviving at 5 or 30°C. Linear and non-linear models accurately described the relationship between temperature and pest development. Using cumulative degree-days, we mapped potential P. xylostella generations across central Argentina. This research provides the first comprehensive analysis of P. xylostella thermal biology in temperate Argentina, emphasising temperature's critical role in its development. The findings offer valuable insights for climate-specific pest management strategies and enhance understanding of insect population dynamics in agricultural ecosystems, contributing to more sustainable control practices.

A zinc finger protein shapes the temperature adaptability of a cosmopolitan pest

Global climate change is characterized by increased extreme temperatures affecting insects at all trophic levels. Zinc finger proteins (ZFPs) are key regulators of gene expression and cell differentiation in eukaryotes, essential for stress resistance in both animals and plants. Using CRISPR/Cas9 for gene deletion, this study predicted and examined the structure of ZFP320 in the diamondback moth (Plutella xylostella) and investigated its function in temperature stress response through a comprehensive age-stage, two-sex life table analysis. We found ZFP320 encodes a 387 amino acid protein (43 kDa) with no transmembrane domains, featuring a ZnF-C2H2 domain. Quantitative fluorescence analysis showed that ZFP320 expression increased under high temperatures. ZFP320 knockout altered antioxidant gene expression, resulting in higher levels of superoxide dismutase and catalase in mutant strains compared with wild-type strain. Life table analysis revealed that the mutant strains had shorter fecundity and oviposition periods under both normal and high temperatures. Additionally, mutant strains exhibited lower parameters (r, λ, R0), as well as reduced survival rates and critical thermal maxima. Notably, PxZFP320 plays a crucial role in temperature adaptation, paving the way for future investigations on the significance of ZFPs in P. xylostella's temperature tolerance.

Molecular and functional characterization of a β-tubulin gene in Plutella xylostella

The β-tubulin gene is essential for reproductive development, especially for male fertility, in different insects including Bombyx mori and Drosophila melanogaster. Targeting reproductive genes such as β-tubulin offers a promising approach to pest control that is more sustainable than chemical pesticides. However, there is limited research on the functional role of β-tubulin in Plutella xylostella, a highly damaging pest of vegetable crops. In the present study, we first identified and cloned the β-tubulin gene in P. xylostella (Pxβtubulin-1). Pxβtubulin-1 protein contains two conserved domains of Tubulin and Tubulin-C, and β-tubulin were conserved in the Lepidoptera. Spatiotemporal expression analysis revealed that Pxβtubulin-1 was highly expressed in male pupae, adult males, and testes, suggesting its testis-specific function. Using CRISPR/Cas9 technology, we generated two homozygous Pxβtubulin-1 mutant strains of P. xylostella. Mutant strains exhibited significantly lower egg production and hatching rates compared with the wild type. Dissection and measurement of reproductive organs revealed that the testes and bursa copulatrix in mutant strains were significantly reduced in size compared with the wild type. In conclusion, Pxβtubulin-1 is vital for male fertility as it influences the development of reproductive organs and can be a potential target for the control of P. xylostella.

Gut symbionts affect Plutella xylostella (L.) susceptibility to chlorantraniliprole

Plutella xylostella, a globally economically important pest of cruciferous crops, has varying degrees of resistance to almost all insecticides. Insect gut microbiotas have a variety of physiological functions, and recent studies have shown that they have some potential connection with insecticide resistance. Here, we use metagenomics to analyze the differences in gut microbiota among 5 different populations of P. xylostella resistant to chlorantraniliprole. Differential gene expression was enriched in various metabolic pathways including carbohydrate metabolism, amino acid metabolism, energy metabolism, metabolism of cofactors and vitamins, nucleotide metabolism and so on. Proteobacteria was the dominate phyla, and the relative abundance of common dominant genera in the treated group (CL, Bt, and BtCL) was higher than that in susceptible controls. We successfully isolated 15 species of bacteria, in which the Enterobacter hormaechei was associated with enhanced insecticide resistance. The population we isolated can metabolize chlorantraniliprole in vitro, with a metabolic rate of 34.8 % within 4 days. Our work advances understanding of the evolution of insecticide resistance and lays a foundation for the further exploration of symbiotic microbial associations of lepidopteran insects and their ecological consequences.

Impact of host switching at different larval instars on the performance of the polyphagous pest Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a highly adaptable and destructive pest of tomato crops, posing a significant threat to global agriculture due to its rapid spread and resistance to control measures. This study investigates the developmental rates and population parameters of T. absoluta larvae when transferred between three host plants-tomato, eggplant, and tobacco-across four distinct larval instars. Larvae were reared under controlled environmental conditions (25 ± 1 °C, 60 ± 5% RH, and 16L:8D photoperiod) and transferred between these hosts at the first to fourth instars. Life table analyses, including parameters such as net reproductive rate (R₀) and intrinsic rate of increase (r), were used to evaluate developmental times, survival, and reproductive potential across different hosts. The results showed that T. absoluta could complete its life cycle on all three host plants, although tobacco significantly prolonged the developmental periods, likely due to its high nicotine content, making it a less suitable host. In contrast, tomato supported the most optimal development, while third-instar larvae transferred to eggplant exhibited higher performance than those reared solely on tomato. These findings suggest that T. absoluta shows increased adaptability to eggplant at later developmental stages. The study highlights the pest's ability to exploit different hosts, particularly from the third instar onward, and underscores the importance of host selection in shaping pest management strategies. The results have implications for integrated pest management (IPM) approaches, emphasizing targeted interventions based on host plant suitability and developmental stage.

Pathogenicity and host-interacting mechanisms of enterogenic Enterobacter cancerogenus in silkworm

Introduction

Enterobacter cancerogenus (E. cancerogenus) is a facultative anaerobic, gram-negative bacterium that can be utilized for the biological control of pests. However, the molecular mechanisms underlying the pathogenicity of E. cancerogenus in insect hosts remain largely unexplored.

Methods

In this study, the Bombyx mori model was employed to investigate the pathogenicity of E. cancerogenus strain ECL7, a bacterium pathogenic to silkworms, through whole-genome sequencing, 16S rDNA sequencing, and transcriptome analysis.

Results

The results revealed that ECL7 harbors virulence genes associated with biofilm formation, adhesion, type III secretion system (T3SS), type VI secretion system (T6SS), and other factors, which collectively lead to damage to the peritrophic matrix (PM) and intestinal epithelial cells of the silkworm midgut following infection, and reduced silkworm larval survival rates and inhibited their growth and development. Additionally, ECL7 infection altered the composition and abundance of intestinal microorganisms, with Enterobacteriaceae and Enterobacteriales becoming dominant species. ECL7 also stimulated the expression of genes related to the Toll and IMD immune signaling pathways, resulting in the upregulation of antimicrobial peptide-related differentially expressed genes (DEGs). Furthermore, transcriptomic analysis revealed an upregulation of DEGs associated with oxidative stress in response to ECL7 infection.

Discussion

This study provides valuable insights into the molecular mechanisms underlying the interaction between E. cancerogenus and silkworms. The findings contribute to the prevention and control of infections caused by this bacterium in sericulture production and offer novel ideas for the potential application of E. cancerogenus in pest biological control.

Comprehensive Transcriptomic Analyses of Silk-Associated Genes and Functional Characterization of Key Silk Fibroins in Plutella xylostella

The diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae), is a serious agricultural pest that utilizes silk as a defensive mechanism, with silk fibroins playing a pivotal role in this process. Through comprehensive transcriptomic analyses, we identified 3452 differentially expressed genes (DEGs) co-expressed in the silk gland of P. xylostella and associated with silk production. The Gene Ontology (GO) analysis revealed enrichment in categories related to protein synthesis, secretion, and extracellular matrix organization, while Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis linked these genes to amino acid metabolism and protein processing pathways. Additionally, we identified three key silk fibroin genes: silk fibroin heavy chain (FibH), silk fibroin light chain (FibL), and fibrohexamerin (P25). We characterized the structure of these genes and analyzed the phylogenetic relationships, amino acid composition, hydrophilicity, and other physicochemical properties of the encoded silk fibroin proteins. The expression profiles revealed peak expression levels of these genes in the silk glands of fourth instar larvae. This integrative study enhances our understanding of the molecular mechanisms underlying silk production in P. xylostella and provides a foundation for future research into the biological roles, evolutionary trajectories, and potential applications of these silk fibroin genes in agricultural pest management and biotechnology.

Molecular Mechanism of λ-Cyhalothrin Detoxification by a Delta-Class Glutathione S-Transferase (PxGSTD3) from Plutella xylostella

The diamondback moth (Plutella xylostella) exhibits significant resistance to commonly used insecticides including λ-cyhalothrin. Delta-class glutathione S-transferases (GSTs) are crucial detoxification enzymes involved in insecticide detoxification and resistance. We demonstrate that PxGSTD3 is associated with the resistance to λ-cyhalothrin and contributes to λ-cyhalothrin detoxification. The transcription of PxGSTD3 was rapidly upregulated in response to λ-cyhalothrin exposure, and the recombinant protein exhibited significant metabolic activity against λ-cyhalothrin. Further investigation using computer-aided drug design revealed the binding and metabolic mechanism of PxGSTD3 toward λ-cyhalothrin. The results showed that λ-cyhalothrin binds to an active pocket through noncovalent interactions such as hydrogen bonds, π-π stacking, and hydrophobic interactions. Residues Arg36, Tyr115, and Phe119 were found to have a critical impact on the binding and metabolism of λ-cyhalothrin by PxGSTD3. These findings provide valuable insights into the metabolic role of GST in detoxifying insecticides and offer theoretical guidance for the design of novel pyrethroid-based insecticides.

Biological activity and field efficacy of Bacillus thuringiensis kurstaki strains with protein film adjuvants (PFAs) against Plutella xylostella (Lepidoptera: Plutellidae)

BACKGROUND

Diamondback moth (DBM), Plutella xylostella L. is a globally distributed insect pest with developed resistance to many insecticides such as Cry1Ac proteins of Bacillus thuringiensis (Bt). It is therefore urgent to develop novel Bt bacterial strains with biocontrol activity against the DBM population.

RESULTS

Nine Bt var. kurstaki (Btk) strains with high insecticidal activity against DBM larvae were selected, and three of them (B6, P2, and P6) had middle lethal concentrations (LC50) of 39.23 μg/mL, 3715.08 μg/mL, and 121.62 μg/mL, respectively, against 3rd instar DBM at 48 h. The three Btk strains were formulated with three different protein film adjuvants (PFAs) to perform insecticidal activity bioassays on laboratory potted cabbages. B6 and P6 formulations showed a faster insecticidal rate than the control insecticide (Emamectin benzoate, EB), and all caused approximately 100% mortality at 24 h after spraying. Interestingly, B6 demonstrated enhanced adhesion capacity to the leaf surface with the help of PFAs, while P6 showed reduced adhesion. Field control assays showed that B6 and P6 can effectively control the DBM population. However, they were not particularly effective against Pieris rapae larvae.

CONCLUSION

The present study identified two Btk strains with efficient insecticidal activity against DBM in both laboratory and field, as well as three PFAs allowing insecticide dose reduction while retaining efficacy. © 2025 Society of Chemical Industry.

Insecticidal activity of Psychotria spp., Vatairea spp. and Acosmium spp. on the biological parameters of Plutella xy-lostella L. 1758 (Plutellidae: Lepidoptera)

In recent years, several botanical species have been tested to determine their ability to reduce the damage caused by Plutella xylostella L. (Lepidoptera: Plutellidae) in brassica crops. Considering the insecticidal potential demonstrated by many botanical species, the effects of the aqueous extracts of Psychotria leiocarpa Cham. & Schltdl, Psychotria deflexa DC., Acosmium subelegans (Mohlenbr.) Yakovlev and Vatairea macrocarpa (Benth.) Ducke by infusion and maceration on the biological parameters of P. xylostella were evaluated. All extracts reduced P. xylostella larval duration and caused larval and egg mortality. In the larvae, the extracts resulted in 70% mortality. In addition, the botanical extracts affected the survival of P. xylostella eggs. The extracts of P. leiocarpa and P. deflexa, prepared by infusion, delayed the emergence of adults, while the extract of V. macrocarpa reduced pupal survival. The longevity of adults was also influenced by the extracts, where the maceration of V. macrocarpa and P. deflexa and infusion of A. subelegans reduced the longevity of P. xylostella females and the maceration of V. macrocarpa and P. leiocarpa reduced the longevity of P. xylostella males. We conclude that the studied extracts were toxic to P. xylostella, especially in the reproduction, of diamondback moth. Consequently, the botanical extracts reduced the number of individuals of the next generation.

PxSpätzle3 Regulates the Toll Pathway To Affect Bacillus thuringiensis Susceptibility of Plutella xylostella

Spätzle is an important messenger in the Toll pathway of the insect innate immune system. However, the function of Spätzle in regulating the Toll pathway in Bacillus thuringiensis (Bt) susceptibility of Plutella xylostella is unclear. In this study, we cloned the Spätzle3 gene of P. xylostella. Molecular docking and yeast two-hybrid experiments indicated that PxSpätzle3 combined with PxToll6 to regulate the Toll pathway. After knocking out PxSpätzle3, the expression of downstream Toll pathway genes and antimicrobial peptides (AMPs) decreased. Antibacterial assays showed that PxGloverin2 could inhibit Bt8010. Further bioassays revealed that the susceptibility of the mutant to Bt8010 was significantly higher than that of the wild type. Intriguingly, the gut bacteria Enterobacter sp. EbPXG5 enhanced the lethality of Bt8010 to the mutant P. xylostella. Our findings clarify that PxSpätzle3 activates the Toll pathway by binding with PxToll6, regulates AMP production, and affects the susceptibility of P. xylostella to Bt8010. Additionally, our study uncovers the role of gut bacteria in this process. These insights provide new ideas for the sustainable control of pests.

The role of GPI-anchored membrane-bound alkaline phosphatase in the mode of action of Bt Cry1A toxins in the diamondback moth

The insecticidal Cry proteins produced by the bacterium Bacillus thuringiensis (Bt) are extensively used for pest control in formulated sprays and in genetically modified crops, but resistance to Bt toxins threatens their sustainable use in agriculture. Understanding the molecular mechanisms involved in Bt pathogenesis is crucial for the development of effective resistance management strategies. Previously, we showed a strong correlation between Cry1Ac resistance in Plutella xylostella (L.) and down-regulation of the glycosylphosphatidylinositol (GPI)-anchored membrane-bound alkaline phosphatase (mALP) and aminopeptidase (APN) and members of the ATP-binding cassette (ABC) transporter subfamily C (ABCC), but we do not yet have a clear understanding of the relative contribution of each midgut receptor type. Here, a P. xylostella strain homozygous for the PxmALP gene knockout was generated using CRISPR/Cas9 and the results showed that this strain had a 294-fold resistance to Cry1Ac toxin and 394-fold cross-resistance to Cry1Ab. Moreover, a triple knockout strain lacking PxmALP, PxABCC2, and PxABCC3 exhibited 9,660-fold resistance to Cry1Ac and 5,662-fold cross-resistance to Cry1Ab. These resistance levels surpassed those observed in the previously described double PxABCC2 and PxABCC3 knockout mutant, revealing a functional redundancy between ABC transporters and PxmALP. In addition, the activity of Cry1A toxins against Sf9 cells expressing PxmALP, PxABCC2 or PxABCC3 confirmed that each of these can act as a functional receptor. Our findings are crucial for unraveling the relative role of multiple receptors and the molecular mechanisms underlying Bt resistance in insects.

Enhancing Bacillus thuringiensis Performance: Fertilizer-Driven Improvements in Biofilm Formation, UV Protection, and Pest Control Efficacy

This study investigated the effects of fertilizers on the biofilm formation, ultraviolet (UV) resistance, and insecticidal activity of Bacillus thuringiensis (Bt). Bacillus thuringiensis, a widely used microbial pesticide, has a minimal environmental impact and is highly effective against specific pests but is susceptible to environmental factors in field applications. Bacterial biofilms provide protection for Bt, enhancing its survival and functionality in the environment. However, the mechanisms by which fertilizers regulate the characteristics of microbial pesticides and enhance biofilm formation are not well understood. This study evaluated the effects of six fertilizers on the bacterial biofilm formation, the UV resistance, and the insecticidal activities of Bt wettable powders. The results demonstrated that fertilizers significantly enhanced the performance of three Bt preparations (Lv'an, Kang'xin, and Lu'kang). A compound fertilizer with 8.346 g/L of KCl, 2.751 g/L of ZnSO4·7H2O, and 25.681 μL/mL of humic acid was identified by response surface optimization, achieving the maximum BBF formation with OD595 value of 2.738. Furthermore, KH2PO4, HA, and ZnSO4·7H2O notably improved the survivability of Bt preparations under prolonged UV exposure, with the compound fertilizer providing the greatest protection. What's more, fertilizers reduced the LC50 values of all Bt preparations, with the compound fertilizer decreasing the LC50 of the Lv'an Bt wettable powder to 0.139 g/L, a 3.12-fold increase in efficacy. This study demonstrated that fertilizers significantly enhance the UV resistance and insecticidal activity of Bt wettable powders by promoting bacterial biofilm formation. Herein, this study provides new strategies and theoretical support for Bt applications in modern sustainable agriculture.

Adult Diel Locomotor Behaviour in the Agricultural Pest Plutella xylostella Reflects Temperature-Driven and Light-Repressed Regulation Rather than Coupling to Circadian Clock Gene Rhythms

The diamondback moth, Plutella xylostella, is arguably the most economically impactful and widespread lepidopteran pest. Though the larval P. xylostella life stage is responsible for most of this cost through the consumption of crops, it is the adult form that spreads the pest to fresh crops all around the world, seeking them out in a seasonally expanding range. It is therefore important to understand the activity rhythms of adult P. xylostella in response to environmental cues such as light and temperature. We analysed diel rhythms in both adult clock gene expression and locomotor behaviour for the ROTH P. xylostella strain. Real-time quantitative PCR analyses of P. xylostella demonstrated diel rhythms for transcripts of the clock genes period and timeless under both entrained and free-running conditions indicating the presence of a functional daily timekeeping mechanism. However, adult locomotor rhythms exhibited temperature-driven and light-repressed regulation rather than circadian control. Thus, our analyses show a lack of coupling between the P. xylostella circadian clock and adult locomotor behaviour, which may be relevant in predicting the activity patterns of this agricultural pest.

PxDorsal Regulates the Expression of Antimicrobial Peptides and Affects the Bt Susceptibility of Plutella xylostella

The insect NF-κB pathway is primarily constituted by nuclear factor κB (NF-κB) and the inhibitor of κB (IκB), which plays a crucial role in the innate immune response. Dorsal and Cactus, as NF-κB and IκB factors, are important downstream regulators of the Toll pathway in Plutella xylostella. In this study, the PxDorsal and PxCactus genes of P. xylostella were cloned, and the molecular docking demonstrated that PxDorsal and PxCactus can interact with each other. RT-qPCR results indicated that PxDorsal and PxCactus were expressed in all stages, and the expression of PxDorsal, PxCactus, and antimicrobial peptides PxGloverin2, PxMoricin3, and PxLysozyme2 were significantly down-regulated under Bacillus thuringiensis (Bt8010) infection. Interestingly, silencing the PxDorsal gene by RNA interference (RNAi) significantly down-regulated the expression of PxGloverin2 and PxMoricin3 and increased the epidermis melanization of P. xylostella larvae fed with Bt8010. Our findings indicate that PxDorsal and PxCactus may interact with each other, and silencing PxDorsal inhibits the expression of downstream antimicrobial peptides, thereby enhance the susceptibility of P. xylostella to Bt8010. This study contributes a theoretical basis for further research on the Toll pathway of P. xylostella to pathogens and offers insights for screening effective biological control targets from the perspective of the immune system.

Integrated physiological and transcriptomic data revealed the cold-resistant mechanisms in reproductive organs of the 'Jinguang' pear cultivar

The Pyrus spp. (pears) are crucial for the fruit industry; however, low spring temperatures can cause frost damage to their reproductive organs, which poses challenges to the final yields. In this study, we evaluated the response of the flowers and young fruits of the 'Jinguang' pear cultivar to low temperatures from integrated phenotypic, physiological, and molecular approaches. We found that the flowers were less sensitive to low temperatures than the young fruits, of which their over-cooling points were -5.6°C and -5.0°C, respectively. Transcriptomic data showed that the differentially expressed genes from flowers and young fruits compared to the control conditions were primarily involved in the biosynthesis of flavonoids, phenylalanine, and tyrosine. Further weighted gene co-expression network analysis uncovered the core transcription factors that may be potentially involved in the pear cold resistance, including MYB20, WRKY53, and WRKY30. Our findings provide valuable insights and candidate gene resources for further exploration of the molecular mechanisms underlying cold resistance in pear trees.

Nap1 is essential for eupyrene spermatogenesis and migration in Plutella xylostella

Spermatogenesis is a key process for the sexual reproduction species. In lepidopteran insects, spermatogenesis produces two different types of sperms, in which eupyrene sperm carry genomic DNA and fertilize eggs, whereas apyrene sperm are necessary for eupyrene sperm to enter eggs. However, functional genetic studies of spermatogenesis in Plutella xylostella remain a longstanding puzzle even though the phenomenon in lepidoptera has been widely documented more than a century. In this study, we particularly focus on the gene Nap1 which belongs to the Nucleosome assembly protein family. Our findings revealed that Nap1 was highly expressed in the testes, and the disruption of PxNap1 induced male sterility in P. xylostella, while the fertility of mutant females was comparable to wild-type females. Additionally, through immunofluorescence staining analysis, we found that the eupyrene sperm bundles presented diffusedly scattered nuclei in PxNap1 mutant males, while the nuclei in the wild-type were clustered together presented as needle shape. We also found that PxNap1 deficiency hinders the transfer of eupyrene sperm to the bursa copulatrix and spermatheca of females. However, the apyrene spermatogenesis was not affected in the PxNap1 mutant. RNA-seq analyses indicated that the defects of eupyrene sperm in PxNap1 mutants were related to energy metabolic such as pentose and glucuronate interconversions, biosynthesis of amino acids, and pentose phosphate pathway. Our study demonstrates that PxNap1 plays crucial function in eupyrene spermatogenesis and eupyrene sperm migration. Our research provides valuable insights for the genetic factors underlying reproductive processes in Lepidopteran insects.

Disruption of the odorant receptor co-receptor (Orco) reveals its critical role in multiple olfactory behaviors of a cosmopolitan pest

The olfactory system of insects plays a pivotal role in multiple, essential activities including feeding, mating, egg laying, and host localization. The capacity of odorant receptors to recognize odor molecules relies on odorant receptor co-receptors forming heterodimers. Here we report the successful engineering a homozygous mutant strain of diamondback moth (Plutella xylostella) in which the odorant receptor co-receptor PxOrco was silenced using CRISPR/Cas9. This insect is a globally important crop pest for which novel control methods are urgently required. Behavioral assays demonstrated that PxOrco knockout males exhibited abolished courtship behaviors, inability to mate, and loss of selective preference for P. xylostella's key sex pheromone components. Whilst female mating behavior and fecundity remained unaffected by PxOrco knockout, oviposition response to leaf alcohol, a key cue for normal oviposition behavior, was lost. Electroantennography revealed drastically reduced responses to sex pheromones and plant volatiles in PxOrco-deficient adults but food location by larvae was unaffected. Moreover, expression analysis of PxOrco-deficient pheromone receptors (PRs) indicated varied regulation patterns, with down-regulation observed in several PRs in both sexes. These findings underscore the critical role of PxOrco in regulating multiple olfactory aspects in P. xylostella, including feeding, mating, and host location. Our study identifies the potential of disrupting the Orco gene in this and other pest species to provide novel avenues for future pest control.

Characterization of an Ecdysone Oxidase from Plutella xylostella (L.) and Its Role in Bt Cry1Ac Resistance

Understanding the molecular mechanisms underlying insect resistance to Bacillus thuringiensis (Bt) pesticidal proteins is crucial for sustainable pest management. Here, we found that downregulation of the Plutella xylostella ecdysone oxidase gene (PxEO) in the normal feeding stages contributes to increased 20-hydroxyecdysone (20E) titer and mediates resistance to the Bt Cry1Ac toxin. The PxEO gene was cloned and its expression was significantly downregulated in the midgut of Bt-resistant and Cry1Ac-selected P. xylostella. Silencing of the PxEO gene significantly reduced Cry1Ac susceptibility, and downregulation of the PxEO gene is closely linked to Cry1Ac resistance in P. xylostella. The PxEO protein metabolized ecdysone (E) and 20E in vitro, and its reduction elevated 20E titers and activated the MAPK-mediated trans-regulatory mechanism known to directly cause the resistance phenotype. Together with our recently reported 20E-degrading glucose dehydrogenase, this finding highlights a robust, multipronged, approach developed by this insect in its 20E-mediated defense against harmful agents.

Zinc finger proteins facilitate adaptation of a global insect pest to climate change

BACKGROUND

Global climate change significantly impacts ecosystems, particularly through temperature fluctuations that affect insect physiology and behavior. As poikilotherms, insect pests such as the globally devastating diamondback moth (DBM), Plutella xylostella, are especially vulnerable to rising temperatures and extreme heat events, necessitating effective adaptive mechanisms.

RESULTS

Here we demonstrate the roles of zinc finger proteins (ZFPs) in mediating thermal adaptability in DBM. We utilized a comprehensive approach involving cloning and bioinformatics analysis of three ZFPs, PxZNF568, PxZNF93, and PxZNF266, measurement of their expression levels in hot-evolved and control strains, and assessment of catalase enzymatic activity and total antioxidant capacity. We also employed CRISPR/Cas9 technology to create five stable homozygous knockout strains to elucidate ZFP functions in high-temperature tolerance. Survival rates under high-temperature stress and the critical thermal maxima (CTMax) of the knockout strains were significantly lower than the wild-type strain, and exhibited marked decreases in antioxidant capacity.

CONCLUSION

Findings reveal the importance of ZFPs in thermal adaptability of DBM, contributing critical insights for future pest management strategies in the context of a warming climate and laying the foundation for further exploration of ZFP functionality in agricultural pest control.

Chlorantraniliprole resistance associated with diamondback moth (Lepidoptera: Plutellidae) outbreaks in Arizona Brassica crops

The diamondback moth, Plutella xylostella (Linnaeus), is one of the most important insect pests of Brassica crops worldwide. In October 2016, outbreaks of an invasive P. xylostella population and unexpected control failures occurred on broccoli and cauliflower crops throughout all vegetable-growing regions in Arizona. Nineteen populations of Plutella xylostella were collected from 2016 to 2021 from various commercial cauliflower fields in Yuma and Scottsdale, Arizona, and from experimental broccoli plots at the University of Arizona, Yuma Agricultural Center (UAYAC), Yuma, Arizona. Populations collected from the commercial cauliflower fields had been transplanted with seedlings produced in a local Yuma nursery in 2016 and Salinas, CA in 2017 to 2018, whereas experimental broccoli plots were direct seeded. These populations were evaluated for their susceptibility to chlorantraniliprole, spinetoram, emamectin benzoate, and cyantraniliprole. In this study, field rate laboratory bioassays, serial dilution laboratory bioassays, and field efficacy spray experiments were performed. The field rate laboratory bioassay results showed that spinetoram, emamectin benzoate, and cyantraniliprole remained effective at controlling P. xylostella, but chlorantraniliprole did not control P. xylostella at the field rate. Additionally, serial dilution bioassays confirmed significant levels of cyantraniliprole and chlorantraniliprole resistance in the P. xylostella populations collected from transplanted cauliflower fields. However, the results of the multiyear/growing-seasons study monitoring the susceptibility of P. xylostella populations collected from direct-seeded broccoli and field efficacy trials conducted at the UAYAC indicated that the resistance to diamide insecticides was neither uniform nor persistent following the 2016 outbreak. Nevertheless, the risk for P. xylostella resistance in Arizona vegetable-growing regions exists, particularly in Brassica transplants. Therefore, we recommend that Arizona Brassica growers remain vigilant and practice rigorous insecticide resistance management to offset the development of resistance.

Regional changes of maximum dose insecticide responses in diamondback moth (Lepidoptera: Plutellidae) populations from Georgia and Florida, USA

Maximum dose bioassays were conducted to assess the efficacy of multiple registered active ingredients for diamondback moth (DBM), Plutella xylostella (L.), control in Georgia and Florida from 2021 to 2023 as a follow-up to an earlier study. Low efficacy (<40% mortality) was recorded for the highest labeled rate of Bacillus thuringiensis var. kurstaki strain ATBS-351 in Georgia, as well as chlorantraniliprole, cyantraniliprole, and cyclaniliprole in Georgia and Florida. The active ingredients with the highest efficacy (>80% mortality) in both states were naled, emamectin benzoate, and spinetoram. Independent analysis of data by state indicated that the efficacy of bifenthrin, chlorantraniliprole, cyantraniliprole, tolfenpyrad, and methomyl was higher in Florida populations than in Georgia populations. In addition, a comparison of these data to a recent DBM maximum dose survey in the same region suggested that these DBM populations have rapidly developed high levels of resistance to cyantraniliprole and cyclaniliprole. This work provides growers in the region with a recent ranking of insecticide efficacy that documents the loss of control for certain active ingredients, which assists pest managers in the planning of ongoing insecticide rotations for DBM resistance management.

Transcriptomic analysis of male diamondback moth antennae: Response to female semiochemicals and allyl isothiocyanate

Female semiochemicals and allyl isothiocyanate (AITC) attract moths, and the moths use odorant-degrading enzymes (ODEs) to break down the excess odor. By identifying antennae-specific ODEs, researchers have established the molecular foundation for odorant degradation and signal inactivation in insects. This enables further exploration of new pest control methods. Currently, the degradation of female semiochemicals and AITC has received limited attention, inspiring this study to identify target ODEs in diamondback moths through transcriptome analysis. Sequencing of antennae from male adults (MA) exposed to female adults (FA) and AITC yielded a substantial 54.18 Gb of clean data, revealing 2276 differentially expressed genes (DEGs) between the MA and MA-FA treatments, and 629 DEGs between MA and MA-AITC treatments. The analysis of MAs exposed to FAs and AITC identified 29 and 17 ODEs, respectively, mainly involving aldehyde dehydrogenases (ALDHs), alcohol dehydrogenases (ADs), cytochrome P450s (CYPs), and UDP-glucuronosyltransferases (UGTs). Pathway analysis revealed primary enrichment in glycolysis/gluconeogenesis and fatty acid degradation in female adult treatments. In contrast, AITC treatments showed major enrichment in pathways related to pentose and glucuronate interconversions, retinol metabolism, and ascorbate and aldarate metabolism. Additionally, qRT-PCR analysis validated the expression patterns of 10 ODE genes in response to these treatments, with varying results observed among the genes. These findings indicate significant changes in ODE expression levels, providing a molecular foundation for identifying potential targets for behavioral inhibitors.

Tyrosine Hydroxylase Is Required for the Larval-Pupal Transformation and Immunity of Plutella xylostella: Potential for Pest Management

Plutella xylostella has developed high levels of resistance to many commonly used insecticides. Tyrosine hydroxylase (TH) is essential for insect survival; thus, we evaluated whether TH could be a potential target for controlling P. xylostella. In this study, PxTH was identified; further qPCR analysis showed that PxTH increased its expression during larval pupation and was highly expressed in the head and epidermis of prepupa in P. xylostella. Subsequently, we found a significant decrease in insect pupation and eclosion rates after injection of dsPxTH or a feeding diet supplemented with 3-iodo-tyrosine (3-IT) as a TH inhibitor in P. xylostella. Moreover, this study suggested that PxTH enzyme activity and dopamine concentrations were significantly decreased, agreeing with the blockage of larval-pupal cuticle tanning, with thinner puparium and less melanization after feeding 3-IT. In addition, expression levels of four antimicrobial peptide genes were significantly inhibited after P. xylostella feeding with 3-IT, and injection of Escherichia coli resulted in 73.3% mortality, indicating that PxTH was required for immune responses. In summary, these results confirmed that PxTH was involved in the development and immunity of P. xylostella, suggesting a critical potential novel insecticide target for RNAi-based pest control.

Comparative analysis of locomotor behavior and head diurnal transcriptome regulation by PERIOD and CRY2 in the diamondback moth

Earth's rotation shapes a 24-h cycle, governing circadian rhythms in organisms. In mammals, the core clock genes, CLOCK and BMAL1, are regulated by PERIODs (PERs) and CRYPTOCHROMEs (CRYs), but their roles remain unclear in the diamondback moth, Plutella xylostella. To explore this, we studied P. xylostella, which possesses a simplified circadian system compared to mammals. In P. xylostella, we observed rhythmic expressions of the Pxper and Pxcry2 genes in their heads, with differing phases. In vitro experiments revealed that PxCRY2 repressed monarch butterfly CLK:BMAL1 transcriptional activation, while PxPER and other CRY-like proteins did not. However, PxPER showed an inhibitory effect on PxCLK/PxCYCLE. Using CRISPR/Cas9, we individually and in combination knocked out Pxper and Pxcry2, then conducted gene function studies and circadian transcriptome sequencing. Loss of either Pxper or Pxcry2 eliminated the activity peak after lights-off in light-dark cycles, and Pxcry2 loss reduced overall activity. Pxcry2 was crucial for maintaining endogenous rhythms in constant darkness. Under light-dark conditions, 1 098 genes exhibited rhythmic expression in wild-type P. xylostella heads, with 749 relying on Pxper and Pxcry2 for their rhythms. Most core clock genes lost their rhythmicity in Pxper and Pxcry2 mutants, while Pxcry2 sustained rhythmic expression, albeit with reduced amplitude and altered phase. Additionally, rhythmic genes were linked to biological processes like the spliceosome and Toll signaling pathway, with these rhythms depending on Pxper or Pxcry2 function. In summary, our study unveils differences in circadian rhythm regulation by Pxper and Pxcry2 in P. xylostella. This provides a valuable model for understanding circadian clock regulation in nocturnal animals.

Functional analysis of dopa decarboxylase in the larval pupation and immunity of the diamondback moth, Plutella xylostella

The diamondback moth (Plutella xylostella L.), a notorious pest infesting cruciferous vegetables worldwide, has developed a high level of resistance to various commonly used chemical pesticides. In this paper, we explore whether dopa decarboxylase (DDC), which is essential for survival and development in insects, could be used as a potential target for the control of P. xylostella. Here, the full-length cDNA (PxDDC) of P. xylostella was identified, with a complete open reading frame of 1434 bp in length, encoding a protein of 477 amino acids. The temporal and spatial expression analysis showed a periodical expression pattern of PxDDC during molting, reaching a peak during the process of pupation, and it was found to be highly expressed in the epidermis of prepupal stage, indicating a crucial role of PxDDC in larval-pupal metamorphosis of P. xylostella. Subsequently, there was a significant decreasing in pupation and eclosion rates, and less production of melanin in P. xylostella after the disruption of PxDDC function by the injection of dsPxDDC (RNAi, RNA interference) or feeding a larval diet supplemented with L-α-methyl-DOPA (L-α-M-D) as DDC inhibitor. In addition, we found four antimicrobial peptide genes were significantly inhibited after feeding P. xylostella with L-α-M-D, and the injection of Escherichia coli could significantly increase insect mortality of enzyme inhibitor treated P. xylostella, suggesting PxDDC was involved in immune responses as well. In summary, these results confirm that PxDDC is required for larval-pupal metamorphosis and immunity of P. xylostella, suggesting a critical potential future novel insecticide target for RNAi based pest control.

A new species of Plutella Schrank (Lepidoptera, Plutellidae) from the Andes of northern Chile

Background

The moth genus Plutella Schrank, 1802 (Lepidoptera, Plutellidae) includes 26 described species. In addition to the diamondback moth, P.xylostella (Linnaeus, 1758), which is an important and widely distributed pest of cruciferous crops, only two species have been previously recorded in Chile, both with distribution ranges restricted to the southern temperate rainforests.

New information

Plutellacopaquillaensis sp. nov. is described and illustrated, based on adults reared from larvae collected on Neuontobotryslanata (Walp.) Al-Shehbaz (Brassicaceae) in the arid highlands of the Andes of northern Chile. The new species resembles P.xylostella in wing pattern, but clearly differs in genitalia morphology.

Novel "Phenyl-Pyrazoline-Oxadiazole" Ternary Substructure Derivatives: Synthesis, Insecticidal Activities, and Structure-Activity Relationship Study

In recent years, isoxazole insecticides or parasiticides targeting the γ-aminobutyric acid receptor, such as fluralaner or fluxametamide, featured a novel chemical structure and exhibited potent insecticidal activity with no-cross resistance. Thus, many research institutes have tried to modify the structures of these agents to find a new insecticide. Previously, the majority of researchers stuck to the "phenyl-isoxazole-phenyl" structure, making modifications only to other components. In this study, the "phenyl-isoxazole-phenyl" ternary motif was modified for the first time based on bioisosterism theory. A series of new derivatives carrying pyrazoline and 1,3,4-oxadiazole moieties were designed and synthesized to investigate their insecticidal activities against the diamondback moth (Plutella xylostella) and fall armyworm (Spodoptera frugiperda). Preliminary bioassay data showed that some of the target compounds exhibited good insecticidal activities against P. xylostella and S. frugiperda. Especially, compound A21 showed insecticidal activity against P. xylostella (LC50 = 1.2 μg/mL) better than commercial insecticide ethiprole (LC50 = 2.9 μg/mL) but worse than parasiticide fluralaner (LC50 = 0.5 μg/mL). Similarly, compound A21 exhibited insecticidal activity to S. frugiperda (LC50 = 13.2 μg/mL) better than commercial insecticide fipronil (LC50 = 78.8 μg/mL) but worse than fluralaner (LC50 = 0.7 μg/mL). Compound A21 could serve as a potential lead compound to control P. xylostella and S. frugiperda. The three-dimensional quantitative structure-activity relationship model revealed that the further introduction of an electron-donating group in the 2- or 3-site may increase the insecticidal activity of A21. Molecular dynamics simulations showed that the hydrogen bond of A21 and receptor was important for the binding receptor. This study has identified a new substructure called "phenyl-pyrroline-oxadiazole" instead of the previously known "phenyl-isoxazole-phenyl" substructure, offering a useful guide for the design of novel insecticide molecules.

Self-financing model for cabbage crops with pest management

Smallholder farmers rely on their farm earnings to cover operating costs and generate income. That is not an easy task because of the pests, which reduce yields and generate plant protection costs. The farm yield and plant protection depend on the budget capacity of the farmer. In this work, we want to explore conditions for a sustainable and self-financing cabbage farm. We propose then a non-linear mathematical model for cabbage crops by considering the current account of the plantation as a dynamic variable. We assume that this variable increases due to the sale of cabbages, and provides for the seedling purchase, the plant protection costs, and the grower's income. In the first part, we analyze the model without pest management. We determine how the budget must be spent and we show the existence of a double transcritical bifurcation. We quantify the seasonal yield and income, and estimate the damage due to pest herbivory. In the second part, we analyze a slightly simplified version of our model and obtain the existence of a backward bifurcation. Furthermore, we show that botanical pesticides can be used to prevent pest spread with relatively low plant protection costs.

Demography and predatory potential of Orius strigicollis on eggs of Plutella xylostella at two temperatures

Background

The polyphagous predatory bug Orius strigicollis Poppius (Heteroptera: Anthocoridae) is an active predator used to control many insect pests of agricultural crops. Orius species are significantly affected by the type of food and temperature.

Method

A study of O. strigicollis feeding on Plutella xylostella L. (Lepidoptera: Plutellidae) eggs in climate chambers at 28 and 32 °C, 70 ± 5% relative humidity, 16:8 photoperiod, was conducted to determine the effects of different temperatures on the predation activity, biological characteristics and demographic parameters of O. strigicollis. Twosex-MS Charts were used to determine the age-stages and characteristics of this species.

Results

The results showed that the daily consumption of pre-adults on eggs of P. xylostella was highest at 28 °C, and at this temperature, there was a greater probability that O. strigicollis would survive to adulthood (42.5%) than at 32 °C (25.0%). It has also been found that at 28 °C there was a long oviposition period (9.38 days) and the greatest female fecundity (44.2 eggs/female) In addition to the highest life expectancy of O. strigicollis (16.96 days) at 28 °C, the intrinsic rate of increase (0.087 d-1) was also highest. According to our results, O. strigicollis has the potential to grow and develop on the eggs of P. xylostella at 28 °C and, therefore, could potentially be used as a biological control agent in integrated pest management (IPM) programs.

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.

Phenotypic and genotypic characterization of fifty strains of Beauveria spp. (Ascomycota, Cordycipitaceae) fungal entomopathogens from diverse geographic origins against the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)

BACKGROUND

The diamondback moth (DBM) (Plutella xylostella) causes large losses to global crop production. Conventional insecticides are losing effectiveness due to resistance. Consequently, there is a growing interest in sustainable control methods like entomopathogenic fungi (EPF) in Integrated Pest Management. However, the field efficacy of fungi varies due to environmental influences. In this study, a group of 50 Beauveria strains sourced from different locations were characterized by genotype and phenotype with respect to their conidial production, temperature and UV-B radiation tolerance, and virulence against DBM.

RESULTS

Phylogenetic analysis revealed two distinct species: Beauveria bassiana (84%) and B. pseudobassiana (16%). Most strains showed optimal growth between 25 °C and 28 °C, with germination severely affected at 10 °C and 33 °C. Notably, 44% displayed high resistance to UV-B radiation (5.94 kJ  m-2), with germination rates between 60.9% and 88.1%. Geographical origin showed no correlation with temperature or UV radiation tolerance. In virulence experiments, 52% of strains caused mortality rates exceeding 80% in DBM second instars at 7 days after exposure to a 4 mL conidial suspension (107 conidia/mL).

CONCLUSION

Survival under environmental conditions is crucial for EPF-based commercial products against DBM. Results suggest strain tolerance to environmental stressors is more tied to specific micro-climatic factors than geographical origin. Each strain exhibited unique characteristics; for example, the most virulent strain (#29) was highly UV-sensitive. Therefore, characterizing diverse strains provides essential genotypic and phenotypic insights, which are fundamental for understanding their role as biocontrol agents while facilitating efficient biopesticide product development and uptake. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Functional types of long trichoid sensilla responding to sex pheromone components in Plutella xylostella

Sex pheromones, which consist of multiple components in specific ratios promote intraspecific sexual communications of insects. Plutella xylostella (L.) is a worldwide pest of cruciferous vegetables, the mating behavior of which is highly dependent on its olfactory system. Long trichoid sensilla on male antennae are the main olfactory sensilla that can sense sex pheromones. However, the underlying mechanisms remain unclear. In this study, 3 sex pheromone components from sex pheromone gland secretions of P. xylostella female adults were identified as Z11-16:Ald, Z11-16:Ac, and Z11-16:OH in a ratio of 9.4 : 100 : 17 using gas chromatography - mass spectrometry and gas chromatography with electroantennographic detection. Electrophysiological responses of 581 and 385 long trichoid sensilla of male adults and female adults, respectively, to the 3 components were measured by single sensillum recording. Hierarchical clustering analysis showed that the long trichoid sensilla were of 6 different types. In the male antennae, 52.32%, 5.51%, and 1.89% of the sensilla responded to Z11-16:Ald, Z11-16:Ac, and Z11-16:OH, which are named as A type, B type, and C type sensilla, respectively; 2.93% named as D type sensilla responded to both Z11-16:Ald and Z11-16:Ac, and 0.34% named as E type sensilla were sensitive to both Z11-16:Ald and Z11-16:OH. In the female antennae, only 7.53% of long trichoid sensilla responded to the sex pheromone components, A type sensilla were 3.64%, B type and C type sensilla were both 0.52%, D type sensilla were 1.30%, and 1.56% of the sensilla responded to all 3 components, which were named as F type sensilla. The responding long trichoid sensilla were located from the base to the terminal of the male antennae and from the base to the middle of the female antennae. The pheromone mixture (Z11-16:Ald : Z11-16:Ac : Z11-16:OH = 9.4 : 100 : 17) had a weakly repellent effect on female adults of P. xylostella. Our results lay the foundation for further studies on sex pheromone communications in P. xylostella.

microRNA-8514-5p regulates adipokinetic hormone/corazonin-related peptide receptor to affect development and reproduction of Plutella xylostella

BACKGROUND

Dicer1 plays a crucial role in regulating the development and reproduction of insects. Knockout of Dicer1 causes pupal deformity, low eclosion and low fecundity in Plutella xylostella, but the mechanism behind this phenomenon is not clear. This study aims to identify differentially-expressed genes and miRNAs in the Dicer1-knockout strain (ΔPxDcr-1) and assess their impact on the reproduction and development of P. xylostella.

RESULTS

The knockout of Dicer1 affected the expression of genes including the adipokinetic hormone/corazonin-related peptide receptor (PxACPR). The expression of PxACPR was upregulated, and the expression of miR-8514-5p was downregulated in ΔPxDcr-1 of P. xylostella. The dual luciferase reporter assay and pull-down assay showed that miR-8514-5p bound to PxACPR in vitro and in vivo. The expression profiles demonstrated a negative correlation between PxACPR mRNA and miR-8514-5p in different developmental stages of the wild-type strain. Both the miR-8514-5p agomir and double-stranded RNA of ACPR (dsPxACPR) injected into the pre-pupae inhibited the mRNA level of PxACPR, causing high mortality and deformity of pupae, and low fecundity and hatching rate, which were consistent with the phenotype of ΔPxDcr-1. The injection of miR-8514-5p antagomir caused a similar phenotype to the injection of miR-8514-5p agomir. Additionally, the injection of miR-8514-5p antagomir significantly rescued the phenotype caused by dsPxACPR.

CONCLUSION

These results indicate that miR-8514-5p affects the development and reproduction of P. xylostella by regulating PxACPR, and the homeostasis of PxACPR expression is essential for the development and reproduction of P. xylostella. © 2024 Society of Chemical Industry.

A midgut transcriptional regulatory loop favors an insect host to withstand a bacterial pathogen

Mounting evidence suggests that insect hormones associated with growth and development also participate in pathogen defense. We have discovered a previously undescribed midgut transcriptional control pathway that modulates the availability of 20-hydroxyecdysone (20E) in a worldwide insect pest (Plutella xylostella), allowing it to defeat the major virulence factor of an insect pathogen Bacillus thuringiensis (Bt). A reduction of the transcriptional inhibitor (PxDfd) increases the expression of a midgut microRNA (miR-8545), which in turn represses the expression of a newly identified ecdysteroid-degrading glucose dehydrogenase (PxGLD). Downregulation of PxGLD reduces 20E degradation to increase 20E titer and concurrently triggers a transcriptional negative feedback loop to mitigate 20E overproduction. The moderately elevated 20E titer in the midgut activates a MAPK signaling pathway to increase Bt tolerance/resistance. These findings deepen our understanding of the functions attributed to these classical insect hormones and help inform potential future strategies that can be employed to control insect pests.

Crofton weed derived isomers of ageraphorone as potent antifeedant against Plutella xylostella (L.)

Global agricultural production is significantly hampered by insect pests, and the demand for natural pragmatic pesticides with environmental concern remains unfulfilled. Ageratina adenophora (Spreng.) also known as Crofton weed, is an invasive perennial herbaceous plant that is known to possess multiple bioactive compounds. In our study, two isomers of ageraphorone metabolites i.e, 10 Hα-9-oxo-ageraphorone (10HA) and 10 Hβ-9-oxo-ageraphorone (10HB), were identified from Crofton weed, exhibiting potent antifeedant and larvicidal activities against Plutella xylostella. For antifeedant activity, the median effective concentration (EC50) values for 10HA and 10HB in the choice method were 2279 mg/L and 3233 mg/L, respectively, and for the no choice method, EC50 values were 1721 mg/L and 2394 mg/L, respectively. For larvicidal activity, lethal concentration (LC50) values for 10HA and 10HB were 2421 mg/L and 4109 mg/L at 48 h and 2101 mg/L and 3550 mg/L at 72 h. Furthermore, both in- vivo and in-vitro studies revealed that the isomers 10HA and 10HB exhibited potent detoxifying enzymes inhibition activity such as carboxylesterase and glutathione S-transferases. Molecular docking and MD simulation analysis provide insight into the possible interaction between isomers of ageraphorone metabolites and Carboxylic Ester Hydrolase protein (Gene: pxCCE016b) of P. xylostella, which led to a finding that CarEH protein plays a significant role in the detoxification of the two compounds in P. xylostella. Finally, our findings show that the primary enzymes undergoing inhibition by isomers of ageraphorone metabolites, causing toxicity in insects, are Carboxylesterase and glutathione S-transferase.

Insecticide resistance and characteristics of mutations related to target site insensitivity of diamondback moths in Taiwan

Diamondback moth (DBM, Plutella xylostella) is the most significant pest of cruciferous vegetables as they rapidly develop high-level resistance to many insecticides. Monitoring DBM susceptibility and target-site mutation frequency is essential for pest control. In this study, 10 insecticides were tested on 11 field populations. Frequencies of target-site mutations (including para, ace1, Rdl1, RyR1, and nAChRα6 genes) were estimated by pyrosequencing. Insecticides registered after 2007 for DBM control in Taiwan, i.e., spinetoram, chlorantraniliprole, chlorfenapyr, metaflumizone, and flubendiamide, showed >80% mortality toward several populations; Bacillus thurigiensis, emamectin benzoate, and chlorfluazuron showed medium to low efficacy in all populations; and tolfenpyrad and mevinphos were highly ineffective. Susceptibility to insecticides varied substantially among populations: eight out of nine populations were highly susceptible to spinetoram, but only one was susceptible to flubendiamide. Target-site mutations related to organophosphates, pyrethroids, fipronil, and diamides were detected in all populations, but there were few spinosad and spinetoram mutations. Our three-year field study demonstrated rapid efficacy loss for all insecticides tested, particularly for more toxic insecticides. Skipped-generation selection of a field DBM strain to emamectin benzoate, metaflumizone, chlorantraniliprole, and flubendiamide revealed that mortality rates dropped from 60 to 80% to <10% after 6 generations. Next-generation sequencing was performed to identify possible target gene mutations. A resistance management program that considers the instability of resistance to some chemicals and pertinent data on resistance mechanisms should be established. Identifying compounds to overcome high-frequency field DBM point mutations could be beneficial for pest control.

Comparative transcriptome analysis provides comprehensive insight into the molecular mechanisms of heat adaption in Plutella xylostella

Plutella xylostella is one of the most destructive pests for cruciferous vegetables, and is adaptability to different environmental stressors. However, we still know little about the molecular mechanisms of how P. xylostella adapt to thermal stress. Here, the comparative transcriptome analysis was conducted from the samples of control (27 °C, CK) and heat treatment (40 °C, 40 T) P. xylostella. The results showed 1253 genes were differentially expressed, with 624 and 629 genes up- and down-regulated respectively. The annotation analysis demonstrated that "Energy production and conversion", "Protein processing in endoplasmic reticulum", "Peroxisome" and "Tyrosine metabolism" pathways were significantly enriched. Additionally, we found the expression levels of heat shock protein genes (Hsps), cuticle related genes and mitochondrial genes were significantly up-regulated in 40 T insects, suggesting their vital roles in improving adaption to heat stress. Importantly, the SOD activity and MDA content of P. xylostella were both identified to be increased under high temperature stress, indicating the elevated antioxidant reactions might be involved in response to heat stress. In conclusion, the present study offered us an overview of gene expression changes after 40 °C treatments, and found some critical pathways and genes of P. xylostella might play the critical roles in resisting heat stress.

Combined Transcriptomics and Metabolomics Analysis Reveals Profenofos-Induced Invisible Injury in Pakchoi (Brassica rapa L.) through Inhibition of Carotenoid Accumulation

Profenofos insecticide poses risks to nontarget organisms including mammals and hydrobionts, and its effects on crops are not known. This study examined the invisible toxicity of profenofos on pakchoi (Brassica rapa L.), using transcriptome and metabolome analyses. Profenofos inhibited the photosynthetic efficiency and light energy absorption by leaves and severely damaged the chloroplasts, causing the accumulation of reactive oxygen species (ROS). Metabolomic analysis confirmed that profenofos promoted the conversion of β-carotene into abscisic acid (ABA), as evidenced by the upregulation of the carotenoid biosynthesis pathway genes: zeaxanthin epoxidase (ZEP), 9-cis-epoxycarotenoid dioxygenase (NCED3), and xanthoxin dehydrogenase (XanDH). The inhibitory effects on carotenoid accumulation, photosynthesis, and increased ABA and ROS contents of the leaves led to invisible injury and stunted growth of the pakchoi plants. The findings of this study revealed the toxicological risk of profenofos to nontarget crops and provide guidance for the safe use of insecticides.

In-Depth Structural Simplification of Celangulin V: Design, Synthesis, and Biological Activity

Celangulin V is a novel botanical insecticide with significant bioactivity and a unique molecular target, but its complex polyol ester structure hinders its broader application in agriculture. To discover new analogues of celangulin V with a simpler structure and enhanced biological activities, we initiated a research project aimed at simplifying its structure and assessing insecticidal efficacy. In this study, a series of novel 1-tetralone derivatives were designed via a structure-based rational design approach and synthesized by a facile method. The biological activities of the target compounds were determined against Mythimna separata (M. separata), Plutella xylostella, and Rhopalosiphum padi. The results revealed that most of the synthesized compounds exhibited superior activities compared to celangulin V. Remarkably, the insecticidal activity of compound 6.16 demonstrated 102-fold greater stomach toxicity than celangulin V against M. separata. In addition, certain compounds showed significant contact toxicity against M. separata, a finding not reported previously in the structural optimization studies of celangulin V. Molecular docking analysis illustrated that the binding pocket of compound 6.16 with the H subunit of V-ATPase was the same as celangulin V. This study presents novel insights into the structural optimization of botanical pesticides.