Fumigant Activity Research Articles

Level of exposure to pyrethroids and presence of symptoms in workers of a fumigation and pest control company

Pyrethroids are manufactured chemical substances that act at the level of the central nervous system, whose mechanism of action is to interfere with ionic transport in the axon membrane, interfere with neural function and block inhibitory pathways. The use of these substances as insecticides has spread massively worldwide due to their lower persistence and toxicity. The objective: of this research was to associate clinical manifestations with exposure to pyrethroids in workers of the fumigation and pest control company, located in the Sucre municipality, Aragua state during the period of February - June 2024. Materials and methods: It is about of a quantitative approach study with an observational, clinical-epidemiological, analytical, cross-sectional design and with documentary support in a population of 22 workers. Results: The average age was 34.95, 90% of the workers were male, it is relevant that 50% carry out mixing preparation, application and fumigation activities, 100% use personal protective equipment, 54.55% have contact with the pyrethroid, with potential exposure of 54.55% of which 100% of them presented signs and symptoms, and the presence of symptoms with the level of exposure. Conclusion: it is corroborated that occupational exposure to pyrethroids represents a serious risk to the health of workers, because exposure is directly related to the appearance of neurological symptoms.

Exploring termiticidal properties and GC/MS-based chemical profile of Lantana camara (L.)

India accounts for almost 10 % of the worlds' termite species. Odontotermes horni is one of the most important termites, posing significant threats to agricultural and horticultural ecosystems. The persistent nature of synthetic termiticides necessitates the development of alternative control strategies. The present study investigates the phytochemical composition and potential termiticidal and acetylcholinesterase (AChE) inhibitory properties of Lantana camara (L.) leaf against O. horni. Methanolic, ethyl acetate, and aqueous extracts of L. camara (L.) leaves were used to assess their toxicity. The methanolic extract exhibited the highest potency, with an LC50 of 0.98%, followed by ethyl acetate (1.40 %) and water extract (8.81 %). The per cent mortality recorded at 2.5 % concentration for methanol, ethyl acetate, and aqueous extract was 96.20, 78.75 and 21.25, respectively. By fumigant action, the L. camara (L.) leaf extract at a 5% concentration of methanol, ethyl acetate and aqueous extract resulted in 68.75, 42.50 and 26.25 percent mortality, respectively. The methanolic extract showed the highest AChE inhibition (52.39 %), followed by the ethyl acetate (47.00 %) and the aqueous (43.53 %) extracts after 24 hours of exposure. GC-MS analysis of plant volatiles of the L. camara (L.) revealed 196 compounds, including terpenoids, known for termiticidal activity.

A novel encapsulation method for lemongrass essential oil in nanoemulsion and SiO2 nanoparticles against the storage mite Aleuroglyphus ovatus (Acari: Acaridae)

Lemongrass essential oil (LEO), which is extracted from Cymbopogon citratus, has emerged as a promising alternative to traditional synthetic pesticides. In the present study, we fabricated pure LEO and its nanomaterials (nanoemulsion [NE] and SiO2 nanoparticles [NPs]) and investigated their acaricidal effects on Aleuroglyphus ovatus (Acari: Acaridae), a common storage pest mite. A loading capacity (LC) of 57.45% was obtained, showing successful encapsulation of LEO in SiNPs. The contact mortality, fumigant mortality, ovicidal activity, repellent activity, and toxic effects of LEO on A. ovatus were investigated. The median lethal concentration (LC50) values of contact mortality of LEO, LEO-NE, and LEO-SiNPs against adult mites were 0.067, 0.053, and 0.019 mg/cm2, respectively, after 24 h of exposure. Similarly, the corresponding LC50 values of fumigant activity were 0.044, 0.096, and 0.067 mg/cm3, respectively. All products had greater contact and fumigant effects on nymphs and larvae than they did on adults. After 5 days of exposure to the products, LEO-NE and LEO-SiNPs had greater inhibitory effects on hatching than did pure LEO. LEO-SiNPs exhibited a rapid and significant repellent effect at 3 h (82.22%) and were effective even after 24 h (35.56%), indicating their persistent and long-term acaricide activity. A study of toxicity symptom revealed two different manifestations of toxicity in mites after exposure to these products (knock-down type and immobilized type). Taken together, these findings suggest that LEO and its nanomaterials exhibit significant acaricidal activity against A. ovatus.

Bioassays of Fumigant Toxicity and Repulsiveness of Haplophyllum tuberculatum Extracts

Abstract Food grains were severely damaged by stored goods insects. The red flour beetle Tribolium castaneum, the cigarette beetle Lasioderma serricorne and the rice weevil Sitophilus orysae are some of the most destructive pests which attack raw cereals throughout the world. In stored grain mill, fumigation with synthetic fumigants was the most economical tool for managing stored pests. Nevertheless, the application of chemical pesticides caused adverse effects on humans and environment. Chloroform, acetone, methanol and water extracts and essential oil of Haplophyllum tuberculatum aerial parts were tested for their fumigant and repellent effect against adults of the three stored products pests (T. castaneum, L. serricorne and S. oryzae). GC/MS analysis of the essential oil resulted in determination of 19 compounds. The major constituents were β-phellandrene (16.17%), trans-p-menth-2-ene-1-ol, (13.22%) and cis-p-menth-2-ene-1-ol (8.29%). Thus, it seemed that the essential oil had the highest fumigant activity against L. serricorne after 12 h of exposure compared to the two other insects with a LC50 equal to 38.59 µ.l-1 air. The best repellency was observed for the chloroform and methanol extracts against T. castaneum. The respective repellent doses RD50 values were = 0.03 and 0.04 mg.ml-1 after 24 h of exposure. However, after 24 h of exposure acetone extract seems to be more repellent with respective repellent dose values of = 0.14 mg.ml-1 (RD50) against L. serricorne. H. tuberculatum essential oil and extract proved to be effective in control pest infestations in grains and dry food products.

Antifungal effects of three natural branched medium-chain fatty acids and their potential as fumigants against Aspergillus flavus in stored peanut seeds

The contamination of peanuts with aflatoxins predominantly produced by Aspergillus flavus poses a worldwide threat to both food safety and agricultural economies. Antifungal compounds from natural sources may offer a safe and effective alternative strategy to control A. flavus in peanuts. We evaluated the contact and fumigant antifungal effects of three natural branched medium-chain fatty acids (branched-MCFAs), (E)-2-methyl-2-pentenoic acid, 2-methylhexanoic acid, and 2-methylheptanoic acid against A. flavus relative to their straight-chain isomers and sorbic acid a commonly used preservative. In vitro experiments showed that the inhibitory effects of these three branched-MCFAs on A. flavus were stronger than their straight-chain isomers and sorbic acid. In addition, fumigant effects of the branched-MCFAs were more effective than their direct contact inhibitory effects against the growth of A. flavus. 2-Methylhexanoic acid, 2-methylheptanoic acid, and (E)-2-methyl-2-pentenoic acid showed significant fumigant activity, with the minimum inhibitory concentration (MIC) values of 0.10, 0.10, and 0.12 g/l air, respectively. Fumigation of these branched-MCFAs also significantly slowed the growth of A. flavus in peanut seeds, and completely inhibited A. flavus growth at 2.0 g/l air. After 24 h of fumigation exposure to the branched-MCFAs, the fumigated A. flavus on medium or peanut seeds was re-incubated to observe whether the A. flavus could continue to grow, and the results revealed that the in vitro and in vivo minimum fungicidal concentrations (MFC) were 0.15 and 2.5 g/l air, respectively. This study indicated that these three natural branched-MCFAs have strong antifungal fumigation activity with application potential in protecting peanut seeds from A. flavus contamination during storage.

Quantitative structure-insecticidal activity of essential oils on the human head louse (Pediculus humanus capitis)

ABSTRACT In the search for natural and non-toxic products alternatives to synthetic pesticides, the fumigant and repellent activities of 35 essential oils are predicted in the human head louse (Pediculus humanus capitis) through the Quantitative Structure-Activity Relationships (QSAR) theory. The number of constituents of essential oils with weight percentage composition greater than 1% varies from 1 to 15, encompassing up to 213 structurally diverse compounds in the entire dataset. The 27,976 structural descriptors used to characterizing these complex mixtures are calculated as linear combinations of non-conformational descriptors for the components. This approach is considered simple enough to evaluate the effects that changes in the composition of each component could have on the studied bioactivities. The best linear regression models found, obtained through the Replacement Method variable subset selection method, are applied to predict 13 essential oils from a previous study with unknown property data. The results show that the simple methodology applied here could be useful for predicting properties of interest in complex mixtures such as essential oils.

Volatile organic compounds released from entomopathogenic nematode-infected insect cadavers for the biocontrol of Meloidogyne incognita.

Root-knot nematodes (RKNs), Meloidogyne spp., are one of the most destructive polyphagous plant-parasitic nematodes. They pose a serious threat to global food security and are difficult to control. Entomopathogenic nematodes (EPNs) show promise in controlling RKNs. However, it remains unclear whether the volatile organic compounds (VOCs) emitted from EPN-infected cadavers can control RKNs. We investigated the fumigation activity of VOCs released from cadavers infected by five different species of EPNs on RKNs in Petri dishes, and found that VOCs released from Steinernema feltiae (SN strain) and S. carpocapsae (All strain) infected cadavers had a significant lethal effect on second-stage juveniles (J2s) of Meloidogyne incognita. The VOCs released from the cadavers infected with S. feltiae were analyzed using SPME-GC/MS. Dimethyl disulfide (DMDS), tetradecane, pentadecane, and butylated hydroxytoluene (BHT), were selected for a validation experiment with pure compounds. The DMDS compound had significant nematicidal activity and repelled J2s. DMDS also inhibited egg hatching and the invasion of tomato roots by J2s. In a pot experiment, the addition of S. feltiae-infected cadavers and cadavers wrapped with a 400-mesh nylon net also significantly reduced the population of RKNs in tomato roots after 7 days. The number of root knots and eggs was reduced by 58% and 74.34%, respectively, compared to the control. These results suggested that the VOCs emitted by the EPN-infected cadavers affected various developmental stages of M. incognita and thus have the potential to be used in controlling RKNs through multiple methods. © 2024 Society of Chemical Industry.

Influence of molecular descriptors of plant volatilomics on fumigant action against the three major stored product beetle pests.

Plant volatilomics such as essential oils (EOs) and volatile phytochemicals (PCs) are known as potential natural sources for the development of biofumigants as an alternative to conventional fumigant pesticides. This present work was aimed to evaluate the fumigant toxic effect of five selected EOs (cinnamon, garlic, lemon, orange, andpeppermint) and PCs (citronellol, limonene, linalool, piperitone, andterpineol) against the Callosobruchus maculatus, Sitophilus oryzae, and Tribolium castaneum adults. Furthermore, for the estimation of the relationship between molecular descriptors and fumigant toxicity of plant volatiles, quantitative structural activity relationship (QSAR) models were developed using principal component analysis and multiple linear regression. Amongst the tested EOs, garlic EO was found to be the most toxic fumigant. The PCs toxicity analysis revealed that terpineol, limonene, linalool, and piperitone as potential fumigants to C. maculatus (< 20 µL/L air of LC50), limonene and piperitone as potential fumigants to T. castaneum (14.35 and 154.11 µL/L air of LC50, respectively), and linalool and piperitone as potential fumigants to S. oryzae (192.27 and 69.10 µL/L air of LC50, respectively). QSAR analysis demonstrated the role of various molecular descriptors of EOs and PCs on the fumigant toxicity in insect pest species. In specific, dipole and Randic index influence the toxicity in C. maculatus, molecular weight and maximal projection area influence the toxicity in S. oryzae, and boiling point and Dreiding energy influence the toxicity in T. castaneum. The present findings may provide insight of a new strategy to select effective EOs and/or PCs against stored product insect pests.

Insect-resistant activities of Elsholtzia ciliata essential oil and its main components carvone against Tribolium castaneum in different development stages

The main objectives of the present study are to introduce a ecologically safe, and natural compound for controlling the red flour beetle, Tribolium castaneum. This study aims to thoroughly examine the effects of Elsholtzia ciliata essential oil (E. ciliata EO) and its primary components, carvone, on Tribolium castaneum eggs, larvae, pupae, and adults. The study also includes a simulated warehouse test to assess the efficacy of these substances as contact agents, fumigants, repellents, and antifeedants. All of these anti-insect activities were positively correlated with the concentrations of E. ciliata EO and carvone. Firstly, in the contact activity assay, E. ciliata EO and carvone completely inhibited the hatching of eggs and pupae of the T. castaneum at a concentration of 2.5 μL/cm2. The LC50 of E. ciliata EO and carvone were 7.62 and 4.33 μg/adult, respectively, against senior adults (5 weeks old). Secondly, in the fumigant activity assay, 60 mg/L of E. ciliata EO and carvone essentially completely inhibited pupae eclosion. On the other hand, the LD50 of E. ciliata EO and carvone against senior adults (5 weeks old) were 8.72 and 5.02 mg/L, respectively. Thirdly, for T. castaneum adults, at the highest test concentration, the repellent rate of the E. ciliata EO was above 90%. Fourthly, the larvae and adults of the T. castaneum could reach complete antifeedant activity by E. ciliata EO and carvone at the highest test concentrations. Finally, 3000 ppm of carvone was sufficient to kill all the pests in the warehouse in the simulated warehouse test. In conclusion, the results of this study will contribute to the better control of the storage pest, T. castaneum, and the development of environmentally friendly insecticides based on E. ciliata EO and carvone.

Chemical composition, antifungal, antibacterial, and insecticidal activity of Echinophora chrysantha essential oil

This study presents an investigation of the chemical composition and biological activities of the essential oil (EO) extracted from aerial parts of Echinophora chrysantha (EC). Gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of twenty-two components, representing 97.5% of the total oil. Major constituents were determined as α-phellandrene (55.74%), β-phellandrene (17.41%), and p-cymene (8.95%). The EO was screened for antimicrobial and antifungal activity against a panel of bacteria and fungi using a broth micro-dilution and fumigant activity assay, respectively. EO sample exhibited better activity against Listeria monocytogenes, Staphylococcus aureus Enterococcus faecium with 31.25, 31.25, and 62.5 μg/mL MIC values. EOs showed moderate mycelium growth inhibitory activity against Phytophthora infestans (32.9±1.9%), Verticillium dahliae (42.3±1.8%), and Fusarium oxysporum f. sp. lycopersici (53.0±2.9%) at 8 μL/petri concentration. The insecticidal activity of EO was also evaluated against two insects (Rhyzopertha dominica and Tribolium confusum) showing moderate activity with mortality rates of 25.8±0.6% and 37.9±1.2% at a 5% (v/v) concentration. Literature search has not revealed any previous work on the antimicrobial, antifungal, and insecticidal activities of the EO from E. chrysantha. In conclusion, this is the first report describing the biological activities of this plant EOs. Additionally, these findings highlight the practical implications of the utilizing essential oil of EC as a potential natural remedy against a spectrum of microbial threats in both pharmaceutical and food preservation applications.

Efficacy of fumigant compounds from essential oil of feverfew (Chrysanthemum parthenium L.) against maize weevil (Sitophilus zeamais Mots.): Fumigant toxicity test and in-silico study

Post-harvest insects are among the significant problems in the agricultural sector. The most accessible tools available for managing post-harvest arthropod-pests are fumigants because of the convenience of their applications and fast action in disinfecting. This study aimed to examine the fumigant toxicity of essential oil (EO) against maize weevil and identify the specific fumigants among the major components. The EO was extracted from aerial part of Chrysanthemum parthenium L. using Clevenger apparatus and was tested for fumigant toxicity. GC-MS was used to determine the chemical composition of EO. The major components were identified and screened virtually using Auto dock vina 1.2. in PyRx 0.8 platform. Dm AChE PDB ID: 6XYY was used as a target for molecular docking and malathion and pirimiphusmethyl were used as a reference for comparison. From the results of binding affinities, most of the major EO components showed better fumigant activity than the reference fumigants. More specifically 1,6-dioxaspiro[4,4]non-ene, b-farensen, bornyl-tiglate, g-terpinene, p-cymene, bornyl-acetate, bornyl-isovalerate, terpinen-4-ol, trans-chrysanthenyl-acetate and a-phellandrene were found to be effective fumigants against maize weevil. The above findings suggest that the EO of the aerial part of C. parthenium can be a potential candidate for the development of novel natural fumigants for stored products.&#x0D; KEY WORDS: Essential oil, Fumigants, Insecticides, Binding affinity, Maize weevil&#x0D; Bull. Chem. Soc. Ethiop. 2024, 38(2), 457-472. &#x0D; DOI: https://dx.doi.org/10.4314/bcse.v38i2.13

Insecticidal activity, Chemical Constituents of Trachyspermum ammi, Withania coagulans and Murraya koenigii ethanloic extracts against Bemisia tabaci.

Whitefly is one of the most widespread agricultural pests in the world. Essential oils might be used to control this insect in an environmentally responsible way. The fumigant, repellent, and anti-oviposition activity of ethanol-extracted essential oils of Trachyspermum ammi, Withania coagulans, and Murraya koenigii against Bemisia tabaci was investigated in this study. In the experiment, three essential oil concentrations (2.5 mg/mL, 5 mg/mL, and 10 mg/mL) were used. Trachyspermum ammi had the highest percentage of whitefly death in laboratory experiments due to its fumigant toxicity; the same tendency was found in contact toxicity and repellent effect. Mortality percent rises as the concentration of essential oil increases with bioassay time. As the concentration of essential oil grows with bioassay time, so does the mortality rate. The most adult whiteflies escaped from the treated plants' greenhouse due to the highest essential oil concentration. The greatest repellency was found with Trachyspermum ammi essential oil at 10 mg/mL. The essential oil had the greatest anti-oviposition efficacy against whiteflies. Trachyspermum ammi possessed the most potent anti-oviposition deterrent, followed by Withania coagulans in second place. Murraya koenigii finished third with moderate anti-oviposition, which affects the number of eggs produced in comparison to the control. As a consequence, these three oils might be used as an effective and environmentally acceptable bio-insecticide to control B. tabaci.

Volatile organic compounds produced by Paenibacillus polymyxa J2-4 exhibit toxic activity against Meloidogyne incognita.

Root knot nematodes cause great damage to crops worldwide. Due to the negative effects of the application of fumigant and old chemical nematicides, biological nematicides have drawn increasing attention in recent years. Here we tested the fumigant activity of the volatile organic compounds (VOCs) blends emitted from Paenibacillus polymyxa and pure commercial VOCs against M. incognita. In this study, we investigated whether P. polymyxa strain J2-4 could produce VOCs that exhibit nematicidal activity. In vitro assays indicated that J2-4 VOCs were highly toxic to second stage juveniles (J2s) and could inhibit egg hatching. Three-layered pot experiments showed that the number of nematodes that penetrating in cucumber roots was reduced by 69.27% after the application of J2-4 VOCs under greenhouse conditions. We identified 14 volatiles using solid-phase micro-extraction gas chromatography-mass spectrometry. The efficacy of six commercially available VOCs, namely 2-isobutyl-3-methylpyrazine, 2,4-dimethoxybenzaldoxime, 2-dodecanone, 2-tridecanol, 2-tridecanone, and 2-tetradecanol, against M. incognita were examined. Except for 2,4-dimethoxybenzaldoxime, the remaining five VOCs showed strong direct-contact nematicidal activity against J2s of M. incognita, and only 2-isobutyl-3-methylpyrazine showed strong fumigant activity against J2s of M. incognita. In pot experiments, 2-isobutyl-3-methylpyrazine and 2-dodecanone reduced the number of root galls by about 70%, and 2-tridecanone reduced the number of root galls and egg masses by about 63% compared with controls. Paenibacillus polymyxa strain J2-4 exhibited high fumigant activity against M. incognita. Our results provide evidence for the use of J2-4 and its VOCs as biocontrol agents in the management of root-knot nematodes. © 2023 Society of Chemical Industry.

Characterization of secondary metabolites from the leaves of curry leaf (Murraya koenigii L.) essential oils with insecticidal activities against stored product insects

Curry leaf, a significant aromatic shrub belonging to the Rutaceae family, is indigenous to the Indian subcontinent and is widely renowned for its application as a flavor enhancer. Due to specific flavor and fragrance, the leaves of M. koenigii have been recognized for their potential contributions to human health. Curry leaf essential oils have recently received much attention due to their numerous benefits and minimal risk to non-target organisms. This work focused on the comprehensive characterization of secondary metabolites present in the essential oil extracted from curry leaves and aims to evaluate its insecticidal potential in terms of contact, fumigant, and repellent activities against red flour beetle (Tribolium castaneum) and pulse beetle (Callasobruchus maculatus) for first time. Chemical characterization through GC-MS/MS showed that the main chemical compounds within curry leaf essential oil were caryophyllene (28.47%), α-guaiene (13.35%), and α-phellandrene (12.26%). Notably, results from various insecticidal bioassays showed substantial effects upon contact (LC50 at 24 h, 10.56 mg/cm2 for T. castaneum, 20.80 mg/cm2 for C. maculatus) and fumigant toxicities (LC50 at 24 h, 23.93 mg/L air for T. castaneum, 12.96 mg/L air for C. chinensis), alongside repellent activities (at 5 mg/cm2, a mean PR of 90% to T. castaneum and at 5 mg/cm2, C. maculatus demonstrated 80% PR, targeting both insects. Furthermore, a phytotoxicity assessment was performed on stored paddy grains, and neither seedling development nor germination rates were negatively affected. The essential oils extracted from curry leaves exhibit considerable potential as botanical insecticides that are effective against stored-product insects and environmentally benign.

Volatile Organic Compounds of Bacillus pumilus Strain S1-10 Exhibit Fumigant Activity Against Meloidogyne incognita.

Root-knot nematodes (RKNs) are highly specialized parasites that cause significant yield losses worldwide. In this study, we isolated Bacillus pumilus strain S1-10 from the rhizosphere soil of Zingiber officinale Rosc. plants and evaluated its fumigant activity against Meloidogyne incognita. S1-10 exhibited a strong repellent effect on second-stage juveniles (J2s) of M. incognita, and in vitro assays indicated that S1-10 volatile organic compounds (VOCs) suppressed J2 activity and egg hatching. Under greenhouse conditions, 71 and 79% reductions of nematodes and eggs were detected on plants treated with S-10 VOCs compared with controls. Ten VOCs were identified through gas chromatography and mass spectrometry (GC-MS), of which 2-(methylamino)-ethanol (2-ME) had strong fumigant activity against J2s of M. incognita, with an LC50 value of 1.5 mM at 12 h. These results indicate that S1-10 represents a potential novel biocontrol agent for RKNs.

Phytotoxic and Insecticidal Activity of Industrial Hemp (Cannabis sativa L.) Extracts against Plodia interpunctella Hübner—A Potential Sunflower Grain Protectant

The biological activity (contact and contact-digestive toxicity, repellent and fumigant effects, effect on the insect’s development and life cycle parameters) of industrial hemp (Cannabis sativa L.) ethanolic extract was assessed against Plodia interpunctella, the most destructive storage pest of sunflower. Additionally, the study aimed to examine the phytotoxic activity of the extract in order to assess its potential as a sunflower grain protectant. Phytotoxicity assessment was based on the effect on germination energy and seed germination and the activity of antioxidative enzymes, enzymes of the polyphenolic metabolism, and the intensity of lipid peroxidation in sunflower seedlings. The antioxidant capacity and content of phenolic compounds (total phenolics and total tannins) were also measured in seedlings. In the experiments, 70% ethanolic extract of dried flowering buds of industrial hemp (variety Helena) was applied at 0.5%, 1.0% and 2.0% concentrations directly on sunflower seeds. Ethanol solution (70%) was the control. The hemp extract (1% and 2%) revealed medium repellence for P. interpunctella larvae (L3–4) while at 2% concentration it caused 42.5% larval mortality after 72 h. Moreover, the insect’s development was prolonged and fecundity significantly reduced in hemp treatments. The extract did not exhibit fumigant activity. Germination energy and germination of sunflower seeds were stimulated in treatment with 2% hemp extract, while most biochemical parameters of the seedlings were not significantly affected by the hemp extract.

Fumigant activity and transcriptomic analysis of two plant essential oils against the tea green leafhopper, Empoasca onukii Matsuda.

Introduction: The tea green leafhopper, Empoasca (Matsumurasca) onukii Matsuda, R., 1952 (Hemiptera: Cicadellidae), is currently one of the most devastating pests in the Chinese tea industry. The long-term use of chemical pesticides has a negative impact on human health, impeding the healthy and sustainable development of the tea industry in this region. Therefore, there is a need for non-chemical insecticides to control E. onukii in tea plants. The essential oils from plants have been identified for their potential insecticidal ability; however, there is a lack of knowledge regarding the effect of plant essential oils on E. onukii and its gene expression. Methods: In order to address these knowledge gaps, the components of Pogostemon cablin and Cinnamomum camphora essential oils were analyzed in the present study using gas chromatography-mass spectrometry. The fumigation toxicity of two essential oils on E. onukii was tested using sealed conical flasks. In addition, We performed comparative transcriptome analyses of E. onukii treated with or without P. cablin essential oil. Results: The 36-h lethal concentration (LC50) values for E. onukii treated with P. cablin and C. camphora essential oils were 0.474 and 1.204μLmL-1 respectively. Both essential oils exhibited the potential to control E. onukii, but the fumigation activity of P. cablin essential oil was more effective. A total of 2,309 differentially expressed genes were obtained by transcriptome sequencing of E. onukii treated with P. cablin essential oil. Conclusion: Many of differentially expressed genes were found to contain detoxifification genes, indicating that these families may have played an important role when E. onukii was exposed to essential oil stress. We also found differential expression of genes related to redox-related gene families, suggesting the upregulation of genes associated with possible development of drug and stress resistance. This work offers new insights for the prevention and management of E. onukii in the future.

An unexpected explosion while fumigating a grain silo: It wasn't the dust

AbstractLarge‐scale fumigation of grain silos is a strategy to mitigate infestation of the bulk material. A common fumigant precursor for grain processes is aluminum phosphide, which exothermically decomposes in the presence of moisture (from the grain or air) to the toxic fumigant: phosphine gas. To overcome the hazards of exothermic decomposition and phosphine exposure, aluminum phosphide pellets can be metered into the silo's grain feed to distribute them throughout the grain more evenly. This approach decreases the decomposition rate of aluminum phosphide, better distributes heat generation to avoid igniting grain, and sustains a phosphine gas concentration well below the pyrophoric concentration—all while achieving the fumigation objectives. During a fumigation activity, a large explosion occurred within a group of silos at a grain elevator complex. Dust explosions are a common hazard for grain handling facilities, but this incident was caused by the autoignition of a phosphine gas cloud inside the conveyor tunnels. It was only through post‐incident evaluations of the grain flow dynamics and pellet addition activities that a gap between the desired pellet distribution and the incident conditions was identified. As a result, a new insight into bulk grain handling and safe fumigation was developed.

Biological activities of Elsholtzia stauntoni essential oil and its major constituents against Tribolium castaneum larvae and Lasioderma serricorne adults

This study investigated the biological activity of essential oils (EOs) and their main components (caryophyllene and cuminol) against Tribolium castaneum larvae and Lasioderma serricorne adults. EOs were extracted from both flowers and leaves of Elsholtzia stauntoni. The results indicated that the EOs derived from both flowers and leaves, as well as their main components (caryophyllene and cuminol), exhibited contact activities with LD50 values of 35.11, 43.66, 15.44, and 26.05 μg/larva, respectively, against T. castaneum larvae. Moreover, they demonstrated obvious contact toxicities with LD50 values of 14.15, 11.18, 17.81, and 13.91 μg/adult, respectively, against L. serricorne adults. Additionally, EOs from both flowers and leaves exhibited fumigant activities against T. castaneum larvae (LC50 = 24.42 and 62.54 mg/L) and L. serricorne adults (LC50 = 15.26 and 24.29 mg/L). Furthermore, the EOs of flowers and leaves and their main components (caryophyllene and cuminol) remained significantly repellency to T. castaneum larvae and L. serricorne adults within the testing concentration range of 78.63-15.83 nL/cm2 after 12 h of exposure. These findings suggested that the EO from E. stauntoni and its two major components could potentially be developed as a natural insecticide for controlling T. castaneum larvae and L. serricorne adults.

Pulegone, a component of Schizonepeta tenuifolia volatiles can act as an effective fumigant of the rusty grain beetle Cryptolestes ferrugineus

The utilization of new plant-based fumigants is one of the most important green control methods for safe storage and protection of grain. The rusty grain beetle, Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae), is a common stored grain pest that causes a great loss of stored grain every year. This study determined that, Schizonepeta tenuifolia Briq. spike (SS) powder had strong fumigant insecticidal effectiveness against C. ferrugineus. Moreover, the volatile eluates (VEs) of SS extracted with Porapak™ Q adsorbent at a flow rate of 600 mL/min exhibited higher insecticidal activity against C. ferrugineus adults than the larvae; the VEs LC50 of C. ferrugineus adults were 14.93%− 24.83% of those of C. ferrugineus larvae. The temperature, not the age of C. ferrugineus adults, significantly influenced the fumigation effect of SS VEs; at relatively low temperature (15 ℃) the SS VEs showed quicker and more efficient fumigant activity than at a high temperature (30–35 ℃). In addition, S. tenuifolia VEs showed better fumigation effects against Oryzaephilus surinamensis (Coleoptera: Silvanidae) and Sitophilus oryzae (Coleoptera: Curculionidae) compared to Tribolium castaneum (Coleoptera: Tenebrionidae). The four most abundant components of SS volatiles analyzed by GC-MS were pulegone (62.62%), isomenthone (18.34%), 2-isopropyl-2,5-dimethylcyclohexanone (2.45%), and isopulegone (1.32%), in order by their peak area ratio. Toxicity testing of the two compounds with the largest proportion indicated that only pulegone had insecticidal activity against C. ferrugineus adults with a LC50 (8.90 mL/L) at 72 h. Consistent with VEs, temperature also greatly affect the fumigant activity of pulegone and at low temperature (15 ℃) the pulegone showed more quick and effective insecticidal activity against C. ferrugineus adults. We further found that both VEs and pulegone can inhibit carboxylesterase (CarE), peroxidase (POD), and superoxide dismutase (SOD) in vivo and in vitro, especially the inhibition rate of carboxylesterase, which reached 84.87% and 63.82% at 24 h in vivo, which suggested that the fumigant insecticidal activity of SS VEs and pulegone may partly be mediated by affecting the detoxification and metabolism enzyme system of C. ferrugineus. Therefore, both S. tenuifolia and pulegone can be used as botanical fumigant to potentially control stored grain pests.