Plutella Xylostella Research Articles

Natural Glycyrrhizic Acid‐Tailored Nanoparticles toward the Enhancement of Pesticide Bioavailability

AbstractPesticide spraying serves as a prevalent segment in crop production for substantial economic and ecological benefits. Nevertheless, the existing pesticide formulations are often plagued by droplets rebounding during the spraying process, and the controlled‐release, photolysis protection, and non‐targeted bio‐friendliness are not inadequately considered. Herein, by combining spinosad (SSD, a model pesticide) with glycyrrhizic acid (GL) as an attractive building block, a supramolecular co‐assembly strategy is employed to elaborate pesticide formulations (GL‐SSD) simultaneously featuring high deposition, controlled‐release, and environmental friendliness. The resulting spherical GL‐SSD nanoparticles (NPs) have an average diameter of 207 nm and show an improved 5.2‐fold photostability compared with commercial spinosad suspension (SSD SC). Upon impacting on hydrophobic surfaces of polytetrafluoroethylene film and cabbage leaf, the droplets of GL‐SSD NPs exhibit superior affinity to the micro/nano structure of the surface. Consequently, the droplet rebounding is inhibited effectively, ensuring high deposition efficiency of droplets on surfaces. In addition, the release of SSD from GL‐SSD NPs can be controlled by pH variation. Indoor toxicity and pot experiments demonstrate that GL‐SSD NPs possess good control efficacy against Plutella xylostella. The work offers an alternative approach for the development of multi‐functional and sustainable pesticide formulations with promising potentials in actual agriculture production.

An odorant receptor mediates the avoidance of Plutella xylostella against parasitoid

BackgroundEcosystems are brimming with myriad compounds, including some at very low concentrations that are indispensable for insect survival and reproduction. Screening strategies for identifying active compounds are typically based on bioassay-guided approaches.ResultsHere, we selected two candidate odorant receptors from a major pest of cruciferous plants—the diamondback moth Plutella xylostella—as targets to screen for active semiochemicals. One of these ORs, PxylOR16, exhibited a specific, sensitive response to heptanal, with both larvae and adult P. xylostella displaying heptanal avoidance behavior. Gene knockout studies based on CRISPR/Cas9 experimentally confirmed that PxylOR16 mediates this avoidance. Intriguingly, rather than being involved in P. xylostella–host plant interaction, we discovered that P. xylostella recognizes heptanal from the cuticular volatiles of the parasitoid wasp Cotesia vestalis, possibly to avoid parasitization.ConclusionsOur study thus showcases how the deorphanization of odorant receptors can drive discoveries about their complex functions in mediating insect survival. We also demonstrate that the use of odorant receptors as a screening platform could be efficient in identifying new behavioral regulators for application in pest management.

Front Cover Image

The cover image is based on the Research Article Physiological and behavioral basis of diamondback moth Plutella xylostella migration and its association with heat stress by Fan Yang et al., https://doi.org/10.1002/ps.7904.image

Functional analysis of three odorant receptors in Plutella xylostella response to repellent activity of 2,3-dimethyl-6-(1-hydroxy)-pyrazine

Plutella xylostella is an important pest showing resistance to various chemical pesticides, development of botanical pesticides is an effective strategy to resolve above problem and decrease utilization of chemical pesticides. Previous study showed that 2,3-dimethyl-6-(1-hydroxy)-pyrazine has significant repellent activity to P. xylostella adult which mainly effect to the olfactory system, however the molecular targets and mechanism are still unclear. Based on the RNA-Seq and RT-qPCR data, eight ORs (Odorant receptor) in P. xylostella were selected as candidate targets response to repellent activity of 2,3-dimethyl-6-(1-hydroxy)-pyrazine. Here, most of the ORs in P. xylostella were clustered into three branches, which showed similar functions such as recognition, feeding, and oviposition. PxylOR29, PxylOR31, and PxylOR46 were identified as the potential molecular targets based on the results of repellent activity and EAG response tests to the adults which have been injected with dsRNA, respectively. Additionally, the three ORs were higher expressed in antenna of P. xylostella, followed by those in the head segment. Furthermore, it was found that the bindings between these three ORs and 2,3-dimethyl-6-(1-hydroxy)-pyrazine mainly depend on the hydrophobic effect of active cavities, and the binding to PxylOR31 was more stabler and easier with an energy of −16.34 kcal/mol, together with the π-π T-shaped interaction at PHE195 site. These findings pave the way for the complete understanding of pyrazine repellent mechanisms.

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.

Sulfonate derivatives bearing an amide unit: design, synthesis and biological activity studies

Pest disasters which occurs on crops is a serious problem that not only cause crop yield loss or even crop failure but can also spread a number of plant diseases.Sulfonate derivatives have been widely used in insecticide and fungicide research in recent years. On this basis, a series of sulfonate derivatives bearing an amide unit are synthesized and the biological activities are evaluated. The bioassay results showed that compounds A8, A13, A16, B1, B3, B4, B5, B10, B12 − 20, C3, C5, C9, C10, C14, C15, C17 and C19 showed 100% activity at a concentration of 500 µg/mL against the Plutella xylostella (P. xylostella). Among them, B15 which contains a thiadiazole sulfonate structure still shows 100% activity at 50 µg/mL concentration against P. xylostella and had the lowest median lethal concentration (LC50) (7.61 µg/mL) among the target compounds. Further mechanism studies are conducted on compounds with better insecticidal activity. Molecular docking results shows that B15 formed hydrophobic interactions π-π and hydrogen bonds with the indole ring of Trp532 and the carboxyl group of Asp384, respectively, with similar interaction distances or bond lengths as those of diflubenzuron. Moreover, chitinase inhibition assays are performed to further demonstrate its mode of action. In addition, the anti-bacterial activity of the series of compounds is also tested and the results showed that the series of compounds has moderate biological activity against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc), with inhibition rates of 91%, 92% and 92%, 88% at the concentration of 100 µg/mL, respectively. Our study indicates that B15 can be used as a novel insecticide for crop protection.Graphical

Identifying the Key Role of Plutella xylostella General Odorant Binding Protein 2 in Perceiving a Larval Attractant, (E,E)-2,6-Farnesol.

There is currently a lack of effective olfaction-based techniques to control diamondback moth (DBM) larvae. Identifying behaviorally active odorants for DBM larvae and exploring their recognition mechanisms can provide insights into olfaction-based larval control strategies. Through the two-choice assay, (E,E)-2,6-farnesol (farnesol) was identified as a compound exhibiting significant attractant activity toward DBM larvae, achieving an attraction index of 0.48 ± 0.13. PxylGOBP1 and PxylGOBP2, highly expressed in the antennae of DBM larvae, both showed high affinity toward farnesol. RNAi technology was used to knock down PxylGOBP1 and PxylGOBP2, revealing that the attraction of DBM larvae to farnesol nearly vanished following the knockdown of PxylGOBP2, indicating its critical role in recognizing farnesol. Further investigation into the PxylGOBP2-farnesol interaction revealed the importance of residues like Thr9, Trp37, and Phe118 in PxylGOBP2's binding to farnesol. This research is significant for unveiling the olfactory mechanisms of DBM larvae and developing larval behavior regulation techniques.

Does fungal infection increase the palatability of oilseed rape to insects?

Multiple and simultaneous attacks by pathogens and insect pests frequently occur in nature. Plants respond to biotic stresses by activating distinct defense mechanisms, but little is known about how plants cope with multiple stresses. The focus of this study was the combined interaction of fungal infection caused by Leptosphaeria maculans (synonym Plenodomus lingam) and arthropod infestation by the diamondback moth (Plutella xylostella) in oilseed rape (Brassica napus). We hypothesized that infection by the fungal pathogen L. maculans could alter oilseed rape palatability to P. xylostella-chewing caterpillars. Feeding preference tests were complemented with analyses of defense gene transcription, and levels of glucosinolates (GLSs) and volatile organic compounds (VOCs) in L. maculans-inoculated and non-inoculated (control) leaves to determine possible causes of larval choice. Caterpillars preferred true leaves to cotyledons, hence true leaves were used for further experiments. True leaves inoculated with L. maculans were more palatable to caterpillars over control leaves during the early stage of infection at 3 days post inoculation (dpi), but this preference disappeared in the later stages of infection at 7 dpi. In parallel, genes involved in the salicylic acid and ethylene pathways were up-regulated in L. maculans-inoculated leaves at 3 and 7 dpi; L. maculans increased the level of total aliphatic GLSs, specifically glucobrassicanapin, and decreased the level of glucoiberin at 3 dpi and altered the content of specific VOCs. A group of 55 VOCs with the highest variability between treatments was identified. We suggest that the P. xylostella preference for L. maculans-inoculated leaves in the early stage of disease development could be caused by the underlying mechanisms leading to changes in metabolic composition. Further research should pinpoint the compounds responsible for driving larval preference and evaluate whether the behavior of the adult moths, i.e. the stage that makes the first choice regarding host plant selection in field conditions, correlates with our results on larval host acceptance. © 2024 Society of Chemical Industry.

Design, synthesis, and insecticidal activities of the novel sulfur-containing meta-amide compounds as potential pesticides

The potential risks associated with the high halogen content of typical meta-amide ( m-diamide) insecticidals aroused concerns among researchers. Hoping to make discoveries by introducing sulfur elements with good environmental compatibility, a series of novel sulfur-containing m-amide derivatives C were synthesized through exploration under mild conditions according to the literature. And the structures were confirmed by melting points, 1H NMR, 13C NMR, 19F NMR, and HRMS. It was found that some target compounds C exhibited moderate to high insecticidal activities against Aphis craccivora (38.89%–75.00%) and Plutella xylostella (93.33%−100.00%) at 500 mg.L−1. Especially, the sulfone-containing compound C-3 revealed superior lethality rates against P. xylostella (100%, 12.5 mg.L−1) and A. craccivora (75.00%, 500 mg.L−1), suggesting its potential as a leading compound for further investigation.

Discovery of new N-Phenylamide Isoxazoline derivatives with high insecticidal activity and reduced honeybee toxicity

Isoxazoline is a novel structure with strong potential for controlling agricultural insect pests, but its high toxicity to honeybees limits its development in agriculture. Herein, a series of N-phenylamide isoxazoline derivatives with low honeybee toxicity were designed and synthesized using the intermediate derivatization method. Bioassay results showed that these compounds exhibited good insecticidal activity. Compounds 3b and 3f showed significant insecticidal effects against Plutella xylostella (P. xylostella) with median lethal concentrations (LC50) of 0.06 and 0.07 mg/L, respectively, comparable to that of fluralaner (LC50 = 0.02 mg/L) and exceeding that of commercial insecticide fluxametamide (LC50 = 0.52 mg/L). It is noteworthy that the acute honeybee toxicities of compounds 3b and 3f (LD50 = 1.43 and 1.63 μg/adult, respectively) were significantly reduced to 1/10 of that of fluralaner (LD50 = 0.14 μg/adult), and were adequate or lower than that of fluxametamide (LD50 = 1.14 μg/adult). Theoretical simulation using molecular docking indicates that compound 3b has similar binding modes with fluralaner and a similar optimal docking pose with fluxametamide when binding to the GABA receptor, which may contribute to its potent insecticidal activity and relatively low toxicity to honey bees. This study provides compounds 3b and 3f as potential new insecticide candidates and provides insights into the development of new isoxazoline insecticides exhibiting both high efficacy and environmental safety.

Ligands of HMG-like dorsal switch protein 1 of Spodoptera exigua leads to mortality in diamondback moth, Plutellaxylostella

HMG-like dorsal switch protein 1 (DSP1) is the insect homolog of the high mobility group box 1 (HMGB1) protein of the vertebrates. Previous studies confirmed DSP1 in Spodoptera exigua, Tenebrio molitor, and Aedes albopictus, and were analyzed for their immune roles, survivability, and binding affinity with entomopathogenic bacterial metabolites. The present study aimed to predict, and confirm DSP1 in diamondback moth, Plutella xylostella along with the effect of Spodoptera exigua DSP1 ligands in the survivability of this insect. DSP1 of Plutella xylostella (Px-DSP1) consists of 465 amino acids (AA). Phylogeny analysis showed that Px-DSP1 clustered with other Lepidopteran insects where each insect order clustered separately. Domain analysis showed that like other insects, Px-DSP1 contains two HMG boxes (Box A and Box B), one coiled-coil (CC), five Q-rich low complexity (LC), and an acidic tail (AT). Px-DSP1 was expressed in each developmental stage and tissue. The highest expression was in L4 larvae and fat body tissues. Thermal shift assay (TSA) showed the binding affinity of 3-Ethoxy-4-Methoxyphenol (EMP), Phthalimide (PM), and o-Cyanobenzoic acid (CBA) to rDSP1 of Spodoptera exigua. Mortality bioassay showed that all these metabolites were toxic against P. xylostella larvae. Among these, EMP was more toxic providing more than 65% mortality at 500 ppm concentration. However, PM and CBA also showed more than 60 and 50% mortality, respectively at 500 ppm concentration. We assume that like Se-DSP1, these compounds also bind with Px-DSP1 which leads to the inhibition of DSP1-mediated immunity and impose the mortality of Plutella xylostella larvae.

Exploring the role of the ovary-serine protease gene in the female fertility of the diamondback moth using CRISPR/Cas9.

Oogenesis is a complex pathway necessary for proper female reproduction in insects. Ovary-serine protease (Osp) is a homologous gene of serine protease Nudel (SpNudel) and plays an essential role in the oogenesis and ovary development of Drosophila melanogaster. However, the function of Osp is not determined in Plutella xylostella, a highly destructive pest of cruciferous crops. The PxOsp gene comprises a 5883-bp open-reading frame that encodes a protein consisting of 1994 amino acids, which contain four conserved domains. PxOsp exhibited a high relative expression in adult females with a specific expression in the ovary. Through the utilization of CRISPR/Cas9 technology, homozygous mutants of PxOsp were generated. These homozygous mutant females produced fewer eggs (average of 56 eggs/female) than wild-type (WT) females (average of 97 eggs/female) when crossed with WT males, and these eggs failed to hatch. Conversely, mutant males produced normal progeny when crossed with WT females. The ovarioles in homozygous mutant females were significantly shorter (5.02 mm in length) and contained fewer eggs (average of 3 eggs/ovariole) than WT ovarioles (8.09 mm in length with an average of 8 eggs/ovariole). Moreover, eggs laid by homozygous mutant females were fragile, with irregular shapes, and were unable to maintain structural integrity due to eggshell ruptures. However, no significant differences were observed between WT and mutant individuals regarding developmental duration, pupal weight, and mating behavior. Our study suggesteds that PxOsp plays a vital role in female reproduction, particularly in ovary and egg development. Disrupting PxOsp results in recessive female sterility while leaving the male reproductive capability unaffected. This report represents the first study of a haplosufficient gene responsible for female fertility in lepidopteran insects. Additionally, these findings emphasize PxOsp as a potential target for genetically-based pest management of P. xylostella. © 2024 Society of Chemical Industry.

Eco-Geographical and Botanical Patterns of Resistance to Lepidoptera Insects in Brassica rapa L.

In the context of the widespread expansion of damage by herbivorous pests of Brassica crops, taking into account the requirements for minimizing pesticide pollution of the environment, it is important to have fundamental knowledge of the geographical features of the distribution of pests and about the botanical confinement of plant resistance in order to develop a strategy for creating new Brassica cultivars with complex resistance to insects. The relevance of our work is related to the study of the variability in the degree of resistance of the extensive genetic diversity of Brassica rapa accessions to the main herbivorous pests of Brassica crops in contrasting ecological and geographical zones of the Russian Federation (Arctic, northwestern, and southern zones). We have studied the distribution and food preferences of Lepidoptera insects (diamondback moth Plutella xylostella and cabbage moth Mamestra brassicae) on a set of 100 accessions from the VIR B. rapa collection (Chinese cabbage, pakchoi, wutacai, zicaitai, mizuna, and leaf and root turnips) in the field in three zones of the Russian Federation. We have found that the diamondback moth and cabbage moth are largely harmful in three zones of the European part of the Russian Federation, although the degree of damage to plants by these insects varies by year of cultivation. On average, for the set studied during the two years of the experiment, the degree of plant damage by both pests in the Arctic zone was low and almost low, and in the northwestern and southern zones, it was medium. It was noted that diamondback moth damage was greater in the northwestern zone in both years and in the southern and Arctic zones in 2021, while in 2022, the degree of cabbage moth damage was slightly higher in the southern and Arctic zones. Under the conditions of field diamondback moth damage, the accessions of Chinese cabbage, wutacai, and mizuna turned out to be the most resistant (the damage score was 1.92-1.99), whereas the accessions of wutacai and pakchoi were the most resistant to the cabbage moth (the damage score was 1.62-1.78). A high variability in the degree of resistance of Brassica crops to Lepidoptera insects from complete resistance to susceptibility was revealed. We have identified sources of resistance to insects, including complex resistance in all study areas, among landraces and some modern cultivars of Chinese cabbage, pakchoi, wutacai, and mizuna from Japan and China, as well as European turnips. The highest susceptibility to pests in the studied set was noted in the accession of root turnip "Hinona" (k-1422, USA) (average damage score of 3.24-3.53 points). We were not able to establish the morphological features of resistant plants or the geographical confinement of the origin of resistance of B. rapa crop accessions.

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.

Discovery of New Botanical Insecticides: Identification and Insecticidal Activity of Saponins from Clematis obscura Maxim and Insights into the Stress Response of Acyrthosiphon pisum Harris.

To discover new botanical products-based insecticide candidates, 14 triterpenoid saponins (1-14) including four new ones, obscurosides A-D (1-4), were isolated from Clematis obscura Maxim as potential agrochemicals against Acyrthosiphon pisum Harris and Plutella xylostella (L.). Compounds 1-3 were characterized by a rare ribose substitution at C-3, and 4 was a bidesmoside glycosylated at the rare C-23 and C-28 positions of the oleanane aglycone. Compounds 10 (median antifeeding concentration, AFC50 = 1.10 mg/mL; half-lethal concentration, LC50 = 1.21 mg/mL) and 13 (AFC50 = 1.09 mg/mL, LC50 = 1.37 mg/mL) showed significant insecticidal activities against third larvae of P. xylostella at 72 h. All saponins displayed antifeedant activities against A. pisum with the deterrence index of 0.20-1.00 at 400 μg/mL. Compound 8 showed optimal oral toxicity (LC50 = 50.09 μg/mL) against A. pisum, followed by compounds 1, 5-7, 9, and 14 (LC50 = 90.21-179.25 μg/mL) at 72 h. The shrinkage of the cuticle and the destruction of intestinal structures of microvilli, nucleus, endoplasmic reticulum, and mitochondria were toxic symptoms of 8-treated A. pisum. The significantly declined Chitinase activity in 8-treated A. pisum with an inhibition rate of 79.1% at LC70 (70% lethal concentration) could be the main reason for its significant oral toxicities. Molecular docking revealed favorable affinities of compounds 1 and 8 with group I Chitinase OfChtI (Group I Chitinase from Ostrinia furnacalis) through conventional hydrogen bonds and alkey/π-alkey interactions by different patterns. These results will provide valuable information for the development of novel botanical pesticides for the management of insect pests, especially against A. pisum.

Resistance Mechanism of Plutella xylostella (L.) Associated with Amino Acid Substitutions in Acetylcholinesterase-1: Insights from Homology Modeling, Docking and Molecular Dynamic Simulation.

Plutella xylostella, a destructive crucifer pest, can rapidly develop resistance to most classes of pesticides. This study investigated the molecular resistance mechanisms to chlorpyrifos, an organophosphate pesticide. Two P. xylostella genes, ace1 and ace2, were described. The nucleotide sequence results revealed no variation in ace2, while the resistant strain (Kar-R) had four amino acid alterations in ace1, two of which (A298S and G324A) were previously shown to confer organophosphate resistance in P. xylostella. In the present study, the 3D model structures of both the wild-type (Gu-S) and mutant (Kar-R) of P. xylostella ace1 strains were studied through molecular dynamics (MDs) simulations and molecular docking. Molecular dynamics simulations of RMSD revealed less structural deviation in the ace1 mutant than in its wild-type counterpart. Higher flexibility in the 425-440 amino acid region in the mutant active site (Glu422 and Acyl pocket) increased the active site's entropy, reducing the enzyme's affinity for the inhibitors. Gene expression analysis revealed that the relative transcription levels of ace1 were significantly different in the Kar-R strain compared with the Gu-S strain. This study enhances the understanding of the mechanisms governing ace1's resistance to insecticide and provides essential insights for new insecticides as well as valuable insights into environmentally conscious pest management techniques.

Mass trapping of the diamondback moth (Plutella xylostella L.) by a combination of its sex pheromone and allyl isothiocyanate in cabbage fields in southern Vietnam.

A lure composed of (Z)-11-hexadecenal, (Z)-11-hexadecenyl acetate, and (Z)-11-hexadecen-1-ol at a ratio of 5 : 5 : 1 at a dose of 0.01 mg was optimal for the attraction of the Vietnamese strain of the diamondback moth (DBM). The combination of the sex pheromone with a plant volatile, allyl isothiocyanate, significantly increased the attraction of the pheromone trap. Females were also attracted, but they were only about 2% of all moths captured. In plots with 120-130 traps per ha, mass trapping with the combined lures reduced the DBM larval densities in cabbage fields as effectively as the spraying of insecticides 6 to 8 times. The weekly trap catches indicated that DBM adult densities in the mass-trapping fields were low until 28 days after transplantation, and then were kept to a modest increase until day 49. This field study also shows that the trap catches were well correlated with the DBM larval densities.

Nutritional Status, Sex, and Ambient Temperature Modulate the Wingbeat Frequency of the Diamondback Moth Plutella xylostella.

The diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), is a cosmopolitan horticultural pest that is undergoing a fast, climate-driven range expansion. Its wide geographic distribution, pest status, and high incidence of insecticide resistance are directly tied to long-distance migration. Wingbeat frequency (WBF) is a key aspect of P. xylostella migratory behavior, but has received limited scientific attention. Here, we investigated the effects of environmental parameters, age, adult nutrition, and sex on P. xylostella WBF. Across experimental regimes, WBF ranged from 31.39 Hz to 78.87 Hz. Over a 10-35 °C range, the WBF of both male and female moths increased with temperature up to 62.96 Hz. Though male WBF was unaffected by humidity, females exhibited the highest WBF at 15% relative humidity (RH). WBF was unaffected by adult age, but adult nutrition exerted important impacts. Specifically, the WBF of moths fed honey water (54.66 Hz) was higher than that of water-fed individuals (49.42 Hz). Lastly, males consistently exhibited a higher WBF than females. By uncovering the biological and (nutritional) ecological determinants of diamondback moth flight, our work provides invaluable guidance to radar-based monitoring, migration forecasting, and the targeted deployment of preventative mitigation tactics.

Effect of Brucea javanica Oil on the Toxicity of β-Cypermethrin Emulsifiable Concentrate Formulation.

Enhancing the performance of traditional pesticide formulations by improving their leaf surface wetting capabilities is a crucial approach for maximizing the pesticide efficiency. This study develops an emulsifiable concentrate (EC) of 4.5% β-cypermethrin containing Brucea javanica oil (BJO). The incorporation of BJO aims to improve the leaf-wetting properties of the EC formulation and enhance its insecticidal effectiveness. The droplet size and emulsion characteristics of β-CYP EC emulsion with varying concentrations of the emulsifier were evaluated, and changes after incorporating BJO were assessed to develop the optimal formulation. A comprehensive comparison was conducted among commercial 4.5% β-cypermethrin EC (β-CYP EC-1), 4.5% β-cypermethrin EC with BJO (β-CYP EC-2), and 4.5% β-cypermethrin EC without BJO (β-CYP EC-3). This comparison encompassed various factors including storage stability, insecticidal activity, cytotoxicity, and wetting performance on cabbage leaves. The results indicated that the ideal emulsifier concentration was 15% emulsifier 0201B. β-CYP EC-2 demonstrated superior wetting properties on cabbage leaves (the wetting performance of β-CYP EC-2 emulsion on cabbage leaves is 2.60 times that of the β-CYP EC-1 emulsion), heightened insecticidal activity against the third larvae of Plutella xylostella [diamondback moth (DBM)] [the insecticidal activity of the β-CYP EC-2 emulsion against the third larvae of DBM is 1.93 times that of the β-CYP EC-1 emulsion (12 h)], and more obvious inhibitory effects on the proliferation of DBM embryo cells than the other tested formulations. These findings have significant implications for advancing pest control strategies and promoting sustainable and effective agricultural practices.

Involvement of miR-8510a-3p in response to Cry1Ac protoxin by regulating PxABCG3 in Plutella xylostella

Overuse of insecticides has accelerated the evolution of insecticide resistance and created serious environmental concerns worldwide, thus incentivizing development of alternative methods. Bacillus thuringiensis (Bt) is an insecticidal bacterium that has been developed as a biopesticide to successfully control multiple species of pests. It operates by secreting several insect toxins such as Cry1Ac. However, metabolic resistance based on ATP-binding cassette (ABC) transporters may play a crucial role in the development of metabolic resistance to Bt. Here, we characterized an ABCG gene from the agricultural pest Plutella xylostella (PxABCG3) and found that it was highly expressed in a Cry1Ac-resistant strain, up-regulated after Cry1Ac protoxin treatment. Binding miR-8510a-3p to the coding sequence (CDS) of PxABCG3 was then confirmed by a luciferase reporter assay and RNA immunoprecipitation. miR-8510a-3p agomir delivery markedly reduced PxABCG3 expression in vivo and consequently decreased the tolerance of P. xylostella to Cry1Ac, while reduction of miR-8510a-3p significantly increased PxABCG3 expression, accompanied by an increased tolerance to Cry1Ac. Our results suggest that miR-8510a-3p could potentially be used as a novel molecular target against P. xylostella or other lepidopterans, providing novel insights into developing effective and environmentally friendly pesticides.