Fumigant Toxicity Research Articles

Efficacy of <em>Eucalyptus citriodora</em> and <em>Syzygium aromaticum</em> essential oil as insecticidal, antiovipositant, and fumigant against <em>Callosobruchus maculatus</em> F (Coleoptera: Bruchidae)

Callosobruchus maculatus is the most pernicious pest of stored grain worldwide. Even though synthetic insecticides are commonly used to eliminate this insect pest, the negative effect of this pest management method on humans and the environment raises concern among people around the world. This study was done to identify the active ingredient of essential oils in Eucalyptus citriodora and Syzygium aromaticum and to evaluate the effectiveness of those essential oils in controlling C. maculatus. The results of gas chromatography/mass spectrometry analysis indicated that the essential oil extracted from the leaves of S. aromaticum are rich in Eugenol and β caryophyllene as much as 81% and 14.65% consecutively, while E. citriodora oil contains 86% of Citronella. According to the bioassay results, increasing the essential oil concentration from 1% to 3% resulted in a significant increase in insect mortality rate, oviposition deterrence, and fumigant toxicity. Additionally, S. aromaticum has significantly shown a higher insecticidal performance compared to E. citriodora. However, there are no synergistic effects observed on the use of essential oil of both plant species on C. maculatus. These results suggest that S. aromaticum and E. citriodora essential oils could be potential candidates as a natural insecticide in managing C. maculatus in stored products.

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.

Fumigant Toxicity and Repellent Effect of Propolis Oil Against Adults and Third Instar Larvae of Red Flour Beetle Tribolium castaneum (Herbst), (Coleoptera:Tenebrionidae)

Fumigant Toxicity and Repellent Effect of Propolis Oil Against Adults and Third Instar Larvae of Red Flour Beetle Tribolium castaneum (Herbst), (Coleoptera:Tenebrionidae)

Antagonistic, additive and synergistic interactions in the fumigant toxicity of binary mixes of powders of cloves and citrus fruit peels to adults of Callosobruchus maculatus Fabricius (Coleoptera: Chrysomelidae: Bruchinae)

The study evaluated the fumigant toxicity of cloves (Eugenia aromatica Baill.) and citrus peels (Citrus spp.) powders applied singly and binary combinations (1:1 ratio) to the cowpea storage beetle, Callosobruchus maculatus Fabricius under ambient laboratory conditions (28 ± 4°C and 75 ± 10% rh). The powders (singles and mixtures), placed in empty tea bags, were tested at the dosages of 0.0 (control), 0.5, 1.0 1.5 and 2.0 g/20 g of grain in plastic bottles with airtight lids against freshly emerged adult beetles. Adult mortality was observed 24, 48, and 72 h post fumigation. To determine antagonistic, additive and synergistic interactions, corrected mortality data was used to compute co-toxicity factors. Co-toxicity factor for the binary combinations of powders at different dosages at 24 hours indicated antagonistic interaction, ranging from - 40 to -100. Co-toxicity factor at 48 hours ranged from -30 to -90 indicating mainly antagonistic interaction except for Clove + Tangerine, Clove + Lime and Clove + Grape applied at 2.0 g/20 g of grain with -6.7, 0.0, and 6.6 respectively, indicative of additive interaction. Co-toxicity factor at the 0.5 g/20 g of grain dosage at 72 hours ranged from -53.3 to -56.6 indicating antagonistic interaction; at the 1.0 and 1.5 g/20 g ranged from -20 to 6.7 indicating additive interaction; and at the 2.0 g/20 g was 19.7 for Clove and Sweet orange mixture also indicating additive interaction, but 40, 46.7 and 46.7 for Clove and Grape, Clove and Tangerine, and Clove and Lime mixtures, respectively, indicating synergistic interactions.

Exploring the Insecticidal and Repellent Activity of Garlic Essential Oil against Sitophilus oryzae (L.) Infestation in Stored Maize

The potential of garlic essential oil for its insecticidal and repellent properties against the rice weevil, Sitophilus oryzae was investigated through various bioassays. The results of the contact toxicity assay showed that the mortality rates were dependent on the concentration of the garlic essential oil, and its effectiveness increased with time. This was evident from the decreasing median lethal doses (LC50) over the course of the study, ranging from 7.13 µl/ 20g of seeds (1 DAT) to 3.40 µl / 20g of seeds (5 DAT). The highest repellency rate of 88.89 per cent was achieved with a concentration of 6µl over a 4-hour period. This finding was further supported by the negative preference indices, which ranged from -1.0 to -0.1. With regard to fumigant toxicity assay, the LC50 values decreased as the study progressed, ranging from 4.72 µl /96cm3 (1 DAT) to 1.70 µl/96cm3 (5 DAT). Thus, garlic essential oil can be considered as a potent botanica compound on account of its contact, repellent and fumigant toxicity properties against Sitophilus oryzae. The results of this study underscore the potential of garlic essential oil as a promising compound for the management of S. oryzae.

Transcriptome reveals the toxicity difference of dimethyl disulfide by contact and fumigation on Meloidogyne incognita through calcium channel-mediated oxidative phosphorylation

The prevention and control of root-knot nematode disease has been posing a severe challenge worldwide. Fumigant dimethyl disulfide (DMDS) has excellent biological activity against nematodes. However, DMDS displays significant differences in contact and fumigation toxicity on nematodes. The specific regulatory mechanisms of DMDS on nematodes were investigated by characterizing the ultrastructure of nematodes, examining the physiological and biochemical indicators, and conducting transcriptome high-throughput sequencing. As indicated by the results, DMDS fumigation exhibited the biological activity of against M. incognita 121 times higher than DMDS contact. DMDS contact destroyed nematode body wall cells. Besides, DMDS fumigation destroyed the structure of pseudocoelom. DMDS treatment expedited the oxygen consumption of nematode while inhibiting acetylcholinesterase activity. As indicated by the analysis of vital signaling pathways based on transcriptome, DMDS based on the contact mode penetrated directly into the nematode through the body wall and subsequently affected calcium channels in the body wall and muscle, disrupting their structure; it serves as an uncoupling agent to interfere with ATP synthase. Moreover, DMDS based on the fumigation mode entered the body through the respiratory pathway of olfactory perception-oxygen exchange and subsequently affected calcium channels in the nerve; eventually, DMDS acted on complex IV or complex I.

Sesquiterpenes from two Compositae plants as promising inhibitors to nuclear hormone receptor 3 of Tribolium castaneum

Essential oils (EOs) and their volatile secondary metabolites have been proved to be effective on storage pests control, while restricted on the application due to unclear mechanism. Molecular dynamics (MD) simulations and binding free energies analysis provided an effective approach to reveal mechanism on conformational calculation. In this work, the insecticidal and repellent capacities of Praxelis clematidea and Ageratum houstonianum oils and their main components identified by gas chromatography–mass spectrometry (GC–MS) were scientifically measured. Interestingly, P. clematidea oil exhibited strong fumigant toxicity against Tribolium castaneum (LC50 = 7.07 mg/L air). Moreover, two EOs exhibited over 80% repellent rate against T. castaneum at the highest concentration of 78.63 nL/cm2. Furthermore, hundreds of enzymes related to the regulation of biological processes of T. castaneum were screened to explore the underlying molecular mechanism and develop promising insecticides. Besides, top hits were subjected to MD simulations and binding free energies analysis to elucidate complex inter-molecular stability and affinity over simulated time. The results demonstrated that isolongifolene, δ-cadinene, β-caryophyllene and caryophyllene oxide were prioritized as they were establishing conserved and stable interactions with residues of nuclear hormone receptor 3 (TcHR3) of T. castaneum, which suggested that the four sesquiterpenes have potential to be promising insecticides on storage pests control.

Chemical composition and bioactivity of essential oils from Piper nigrum L. and Piper retrofractum Vahl. against Callosobruchus maculatus (F.)

Plants containing substances with insecticidal properties can be used for pest control. Essential oils of Piper nigrum L. and Piper retrofractum Vah. from dried seeds and fresh leaves extracted by hydrodistillation was determined using Gas Chromatography-Mass Spectrometry (GC-MS). The fumigation toxicity and bioactivity bioassay were investigated using vapor-phase test. Experiment was performed under completely randomized design (CRD) with 4 replications. Adult mortality, number of eggs and adult emergence of F1 progeny of C. maculatus were recorded. Chemical compounds of essential oils from dried seeds and fresh leaves of P. nigrum and P. retrofractum were determined at 22-27 components (90.34-93.27%). Major compounds in dried seeds and fresh leaves of P. nigrum and P. retrofractum were alpha-bergamotene, caryophyllene, beta-selinene, germacrene D, naphthalene, undecane, 5-octadecene, cyclohexene, limonene and 2-beta-pinene. Both essential oils contained limonene, linalool, caryophyllene and naphthalene in seeds and leaves. These four components showed insecticidal properties. Essential oils at concentrations of 5 µL/L air P. nigrum and 10 µL/L air P. retrofractum extracted from dried seeds were more effective in oviposition inhibition and adult emergence of C. maculatus than essential oils extracted from fresh leaves. P. nigrum essential oil from dried seeds at a concentration of 5 µL/L air was the highest efficiency of oviposition inhibition with 55.17% and adult emergence inhibition of 71.09% of C. maculatus. This suggested that P. nigrum essential oil extracted from dried seeds could be used for protection on C. maculatus in stored grain.

Exploring insecticidal properties and acetylcholinesterase inhibition by three plant essential oils against the cheese skipper Piophila casei (Diptera: Piophilidae)

Piophila casei is a highly problematic pest in the food industry, specifically ham processing. However, given the specific requirements of the food industry, there is an urgent requirement for environmentally friendly, more efficient and safer approaches to manage the P. casei. This study aimed to assess the fumigant and contact toxicity of three plant essential oils (EOs) against P. casei by examining their impact on P. casei acetylcholinesterase (AChE) activity and investigating the potential mode of action of their primary constituents using molecular docking and molecular dynamics simulations. The results indicate that Mentha canadensis EO exhibited substantial contact toxicity against P. casei, with the LC50 of 2.98 μL/cm2 after 48-h contact with second instar larvae and an IC50 of 4.99 μL/cm2 for inhibiting pupation in third instar larvae over a 5-day period. Moreover, M. canadensis and Jasminum sambac EOs demonstrated their significant fumigant toxicity, with LT50 of 7.06 and 17.55 h, respectively, at an air concentration of 0.5 mL/L. Among the three EOs, M. canadensis EO displayed the most effective inhibition of P. casei AChE activity, while the other two EOs also exhibited certain levels of activity inhibition, shedding light on the insecticidal mechanisms of EOs against P. casei. Additionally, the molecular docking and molecular dynamics simulations were employed to investigate the mechanisms of action and binding capacity of menthol and limonene, the major constituents of M. canadensis EO. The experimental validation verified the efficacy of menthol. Overall, the results demonstrate that M. canadensis EO and its components exhibit remarkable insecticidal properties and high safety profiles, rendering them suitable for insecticide deployment in pest management within the food industry.

The component of the Chamaecyparis obtusa essential oil and insecticidal activity against Tribolium castaneum (Herbst)

Tribolium castaneum (Herbst) is a worldwide grain storage pest controlled by chemical control methods of phosphine fumigation, which results in many hazards, damages human health, makes pests resistant to pesticides, and pollutes the environment. In recent years, the popularity of botanical insecticides has continued to rise, and plant essential oils (EO) are considered potential alternatives for developing insecticides. In the current study, we selected the Chamaecyparis obtusa EO to determine its insecticidal effects and component analysis on T. castaneum. Through gas chromatography-ion mobility spectrometry (GC-IMS) technology, cedrol was the most obvious compound in the signal peak of the volatile components detected in the C. obtusa EO. The results of the bioassay showed that the C. obtusa EO had certain contact activity against T. castaneum, and the LD50 was 52.54 μg/adult. At three concentrations (0.41,1.62, 2.83 uL/cm2), the repellent rates of C. obtusa EO against T. castaneum were all above 80% at 15, 30, 60, and 120 min, respectively, indicating that the repellent effect was strong. Meanwhile, the C. obtusa EO exhibited fumigant toxicity against T. castaneum with LC50 values of 7.09 μg/L air. In addition, C. obtusa EO significantly increased the activity of AChE, CarE, POD, CAT, T-SOD, and chitinase in T. castaneum. Finally, the mechanism of C. obtusa EO on T. castaneum adults was explored based on transcriptome sequencing. We found that the DEGs focused on the chitin metabolic process and some aging genes in T. castaneum. Therefore, C. obtusa EO could be used as potential eco-friendly candidates for stored grain pest management.

Evaluation of the Stability of a 1,8-Cineole Nanoemulsion and Its Fumigant Toxicity Effect against the Pests Tetranychus urticae, Rhopalosiphum maidis and Bemisia tabaci.

Pest control is a main concern in agriculture. Indiscriminate application of synthetic pesticides has caused negative impacts leading to the rapid development of resistance in arthropod pests. Plant secondary metabolites have been proposed as a safer alternative to conventional pesticides. Monoterpenoids have reported bioactivities against important pests; however, due to their high volatility, low water solubility and chemical instability, the application of these compounds has been limited. Nanosystems represent a potential vehicle for the broad application of monoterpenoids. In this study, an 1,8-cineole nanoemulsion was prepared by the low energy method of phase inversion, characterization of droplet size distribution and polydispersity index (PDI) was carried out by dynamic light scattering and stability was evaluated by centrifugation and Turbiscan analysis. Fumigant bioactivity was evaluated against Tetranychus urticae, Rhopalosiphum maidis and Bemisia tabaci. A nanoemulsion with oil:surfactant:water ratio of 0.5:1:8.5 had a droplet size of 14.7 nm and PDI of 0.178. Formulation was stable after centrifugation and the Turbiscan analysis showed no particle migration and a delta backscattering of ±1%. Nanoemulsion exhibited around 50% more bioactivity as a fumigant on arthropods when compared to free monoterpenoid. These results suggest that nanoformulations can provide volatile compounds of protection against volatilization, improving their bioactivity.

Biorational potential of Mentha essential oils of Indian origin: Comparative note on insecticidal efficacy, fumigant persistence, oviposition deterrence of Sitophilus oryzae

Natural compounds have widely gained their acceptance as biorationals for management of storing grain from insect pests. Mentha spp. are commercially important plant genus known for its distinct aroma. The present study is aimed towards the comparative insecticidal activity of four mint essential oils (Mentha arvensis, Mentha citrata, Mentha piperita and Mentha spicata) against rice weevil (Sitophilus oryzae). Further, the GC-MS analysis of mint essential oil’s (EO’s) exhibited diversity in aroma compounds, M. arvensis (menthol 61% and l-menthone 9.11%), M. citrata (linalool 36.74% and linalyl acetate 35.9%), M. piperita (menthol 36.28%, menthone 26.37% and iso-menthone 5.15%) and M. spicata (54.14% of carvone and 20.97% of limonene). Whereas, the M. spicata EO exhibited the strongest toxicity (fumigant and contact) in both with and without food conditions around 100% mortality for 25 μL dose within 24 h of exposure. The LC50 and LD50 values exhibited by M. spicata were 54.07 μL/L and 11.5 μL/100 cm2 respectively. Similarly, the concentrations of 2.5% and 5% of M. spicata EO also exhibited a strong fumigant and contact toxicity against S. oryzae within 24 h as compared to known prophylactic insecticide (0.3% of Deltamethrin). Besides, 100% oviposition deterrence exhibited by all the four mint EO’s and 56% of AChE inhibition is noticed for M. spicata EO. Furthermore, post-treated grains showed no persistence of mint aroma residues and the treated grains retained the seed viability. Thus, on a comparative note, the M. spicata EO possess potential biorational traits for the effective management of stored grain from insect pests.

Extraction and chemical characterisation of agro-waste from turmeric leaves as a source of bioactive essential oils with insecticidal and antioxidant activities

Turmeric (Curcuma longa L.) is a significant crop that has historically been used worldwide as a medicinal plant, spice, food colouring agent, and a significant ingredient in cosmetic industries. After harvesting rhizomes, leaves are considered waste material. This research study aims to extract and chemically characterise the essential oil from the leaves waste of turmeric with an evaluation of different insecticidal, antioxidant, and phytotoxic activities. Subsequently, the contact toxicity, fumigant toxicity, and repellent activity were evaluated against two key stored grain insect species. The gas chromatography-mass spectrometry (GC–MS) characterisation revealed that α-phellandrene (28.95%), 2-carene (16.51%), eucalyptol (10.54%) and terpinolene (10.24%) were the major chemical constituents. The study's findings on the insecticidal effects of essential oils extracted from turmeric leaves revealed noteworthy repellent, contact (at 24 h, LC50 = 6.51 mg/cm2 for Tribolium castaneum and LC50 = 4.74 mg/cm2 for Rhyzopertha dominica) and fumigant toxicities (at 24 h, LC50 = 2.57 mg/L air for T. castaneum and LC50 = 2.83 mg/L air for R. dominica), against two key stored grain insects. In addition, turmeric leaf essential oil showed notable antioxidant activity (IC50 = 10.04 ± 0.03 µg/mL for DPPH assay; IC50 = 14.12 ± 0.21 µg/mL for ABTS assay. Furthermore, a phytotoxicity study was carried out on stored paddy seeds and no toxic effects were found on germination rate and seedling growth. So, it might be expected that the essential oils extracted from the turmeric leaf waste could be valorised and demonstrate their potential as safe botanical insecticides against stored-product insects, with noble antioxidant properties.

Medico-­social and epidemiological aspects of occupational dermatoses incidence among water transport workers (literature review)

Objective — to conduct a comprehensive retrospective study of the medico-social and epidemiological direction regarding the structure, determinants and cause-and-effect relationships between the performance of professional duties and skin diseases in sailors; substantiate proposals for additional measures that will improve the level of health protection of water transport workers of Ukraine to international standards. Materials and methods. The research methods applied in the work were as follows: bibliosemantic, statistical observation, analytical and structural analysis. These methods made it possible to process only valid, complete and up-to-date information, to make correct and thorough conclusions about the nature and regularities of the researched process. Results and discussion. The volume of water transportation of chemicals, goods or foods that were treated with chemicals is increasing every year. Some cargoes on board ships are disinfected, in particular, with the help of toxic fumigants. All fumigants that are used to protect transported goods are a potential health hazard for workers and can cause, among other things, occupational dermatoses.Available data on the study of sanitary-chemical, hygienic and epidemiological parameters of working conditions, living conditions and morbidity of dockers and sailors during transshipment in ports and transportation of bulk freight on ships of the bulk fleet indicate contamination of workplaces with dangerous and harmful substances, which caused damage to the mucous membranes and skin coverings. Conclusions. The mechanisms of health preservation and emergency response readiness constitute a complex scientific and practical problem and require further thorough study, considering the variety of determinants and risk factors in water transport, the differences in their physical and chemical properties, as well as the potential impact on human health and the aquatic environment. Scientifically based proposals have been provided regarding additional measures, the implementation of which will bring the level of health protection of water transport workers of Ukraine closer to international standards. Among the scientific and practical tasks related to the treatment and prevention of skin diseases among water transport workers, the priority is given to the implementation of modern diagnostic algorithms, training of personnel, organization of telemedical consultations, updating the completeness of ship’s first-aid kits in order to provide timely, high-quality emergency medical care as needed.

Determination of fumigant toxicity of single, binary and tertiary mixtures of three essential oils against Frankliniella occidentalis Pergande (Thysanoptera: Thripidae)

Determination of fumigant toxicity of single, binary and tertiary mixtures of three essential oils against Frankliniella occidentalis Pergande (Thysanoptera: Thripidae)

Chemical composition and toxicity of Artemisia herba-alba essential oil against Cydia pomonella L. (Lepidoptera:Tortricidae) under laboratory conditions

The codling moth Cydia pomonella L. (Lepidoptera: Tortricidae) is a destructive pest of apples and pears worldwide. Due to the phytotoxic effect of chemical fumigant on postharvest apple, botanical insecticides are an interesting alternative to synthetic chemical insecticides regarding their low environmental impact. Hence, in the present study, we investigated the chemical composition and fumigant toxicity of Artemisia herba-alba essential oil against the fifth-instar codling moth, under laboratory conditions. In total, 49 compounds were identified by gas chromatography/mass spectrometry. The major constituents determined were dextro-camphor (30.60%), 2,6-dimethyl-1,3,6-heptatriene (26.71%), safranal (7.04%), borneol (3.94%) and eucalyptol (3.47%). A. herba-alba essential oil showed strong larvicidal activity, with minimum lethal concentration LC50 values of 13.49 and 04.45 μl L-1 air at 24 h and 48 h, respectively. The LT50 values at the lowest (1.81 μl L-1 air) and highest oil concentrations (18.18 μl L-1 air) were, in turn, 59.35 to 19.52 h. The obtained results indicated that essential oil of A. herba-alba may have a potential to be developed as a botanical fumigant against the fifth-instar codling moth.

Antifungal Activity of Menthol, Eugenol and Their Combination against Aspergillus ochraceus and Aspergillus niger In Vitro and in Stored Cereals.

Aspergillus ochraceus and Aspergillus niger are spoilage and mycotoxin-producing fungi that can contaminate agricultural commodities and derived products. In the present study, menthol, eugenol, and their combination (mix 1:1) were tested to determine their contact and fumigation toxicity against the two fungi. Menthol, eugenol, and their mixture significantly reduced mycelial growth and spore germination at concentrations from 300 to 600 µg/mL, and the inhibitory effects showed clear dose dependence. The minimum inhibitory concentration (MIC) values against A. ochraceus were 500 µg/mL (menthol), 400 µg/mL (eugenol), and 300 µg/mL (mix 1:1), while the MIC values for A. niger were 500 µg/mL (menthol), 600 µg/mL (eugenol), and 400 µg/mL (mix 1:1). Additionally, the analyzed compounds exhibited more than 50% protection against A. ochraceus and A. niger by fumigation of stored cereal grains (maize, barley, and rice) in sealed containers. The binary mixture of menthol and eugenol showed synergistic effects against both fungi in both in vitro direct contact and stored grain fumigation trials. The results of the present study provide a scientific basis for the application of a combination of natural antifungals in food preservation.

Does access to improved grain storage technology increase farmers' welfare? Experimental evidence from maize farming in Ethiopia

AbstractSeasonal price variability for cereals is two to three times higher in Africa than on the international reference market. Seasonality is even more pronounced when access to appropriate storage and opportunities for price arbitrage are limited. As smallholder farmers typically sell their production after harvest, when prices are low, this leads to lower incomes as well as higher food insecurity during the lean season, when prices are high. One solution to reduce seasonal stress is the use of improved storage technologies. Using data from a randomised controlled trial, in a major maize‐growing region of Western Ethiopia, we study the impact of hermetic bags, a technology that protects stored grain against insect pests, so that the grain can be stored longer. Despite considerable price seasonality—maize prices in the lean season are 36% higher than after harvesting—we find no evidence that hermetic bags improve welfare, except that access to these bags allowed for a marginally longer storage period of maize intended for sale by 2 weeks. But this did not translate into measurable welfare gains as we found no changes in any of our welfare outcome indicators. This ‘near‐null’ effect is due to the fact that maize storage losses in our study region are relatively lower than previous studies suggested—around 10% of the quantity stored—likely because of the widespread use of an alternative to protect maize during storage, for example a cheap but highly toxic fumigant. These findings are important for policies that seek to promote improved storage technologies in these settings.

Toxicity, Ovipositional Behaviour and Electrophysiological Response of Rice Moth <i>Corcyra cephalonica</i> (Stainton) Adults to Essential Oils

Rice moth Corcyra cephalonica (Stainton) is a serious pest on storage commodities. The management of C. cephalonica relies on the use of chemical pesticides. Insecticide resistance and its effect on nontarget demand for compounds that are clean, and green. Essential oils (EOs) viz., Trachyspermum ammi (Ajowan), Piper betle (betel), Eucalyptus citriodora (citridora), Cymbopogan nardus (citronella), Pelargonium graveolens (geranium), Rosmarinus officinalis (rosemary) and Ocimum basilicum (sweet basil) were investigated for their cidal activities against the egg and adult stages of C. cephalonica. On ovicidal action, among the EOs tested P. betle was found to have higher cidal action to eggs (EC50 3.79 mg/ dm3), followed by T. ammi EO (EC50 4.17 mg/ dm3). P. graveolens and P. betle EOs caused the highest fumigant toxicity in adults with the lowest LC50 values (12.58 and 18.01 mg/ dm3). All the EOs tested caused an antennal response in C.cephalonica female adults. Among the Eos, R. officinalis and P. graveolens elicited the highest antennal response in female moths (1.3 mV and 0.84 mV). In the behavioural assay, the female moths showed reduced preference for the oviposition substrate treated with EOs. The desirable cidal, physiological and behavioural response of EOs on C. cephalonica adults makes them a viable alternative to synthetic pesticides.

Fumigant toxicity and behavioral alterations of six plant essential oils against the red fire ant (Solenopsis invicta Buren).

The red imported fire ant (RIFA), Solenopsis invicta Buren (Hymenoptera: Formicidae), is an invasive species that is considered to be among the 100 most dangerous species to human health and the environment. RIFA is currently controlled primarily by chemical insecticides. However, human health concerns and environmental problems require environment friendly, green insect pest control technology. In this study, the HS-SPME-GC/MS method was used to determine the volatile components of six essential oils, namely Illicium verum Burm, Blumea balsamifera (L.) DC., Citrus limon Burm, Acorus tatarinowii Schott, Mosla chinensis Maxim, and Cinnamomum cassia Presl, as well as their fumigation activity against RIFA. D-Limonene was identified as a core volatile in all six essential oils. The effects of volatile substances from essential oils on the fumigation activity and behavior of RIFA workers were studied by closed fumigation method. Except for C. limon essential oil, all other five plant essential oils exhibit excellent fumigation activity under the treatment of a concentration at 10 μL/ cm3 within 24 h. All plant essential oils are capable of causing the death of all red fire ants, while C. limon essential oil exhibited the lowest fumigation activity at 63.25%. Significant reductions in RIFA aggregation, aggressiveness, and gripping abilities were observed with all plant essential oils, and antenna sensilla appeared to bend or break. Moreover, after treating red ant fire ants with essential oil for 24 h, three protective enzyme activities were assessed. All six plant essential oils were shown to have enhanced enzyme activities for superoxide dismutase (SOD), glutathione S-transferase (GST), and catalase (CAT). It has been shown that plant essential oils have the capability of reducing the viability of red fire ants via receptor and behavioral factors, ultimately causing them to die off. As a conclusion, plant oils were demonstrated to be negatively affecting RIFA and providing a green and environmentally sustainable control method in this study.