Insecticidal Activity Of Essential Oil Research Articles

Insecticidal activity of essential oils from six aromatic plants against Aedes aegypti, dengue vector from two localities of Ouagadougou, Burkina Faso

Insecticidal activity of essential oils from six aromatic plants against Aedes aegypti, dengue vector from two localities of Ouagadougou, Burkina Faso

Chemical Composition, Antimicrobial and Insecticidal Activities of Essential Oils of Discarded Perfume Lemon and Leaves (Citrus Limon (L.) Burm. F.) as Possible Sources of Functional Botanical Agents.

Two essential oils were isolated from discarded perfume lemon and leaves (Citrus limon (L.) Burm. F.) by hydro-distillation with good yield (0.044% for perfume lemon and 0.338% for leaves). Their biological activities were evaluated against five selected bacterial strains and Aedes albopictus (Ae. albopictus, Diptera: Culicidae). Chemical composition indicated that both essential oils were rich in essential phytochemicals including hydrocarbons, monoterpenes and sesquiterpene. These constituents revealed some variability among the oils displaying interesting chemotypes (R)-(+)-limonene (12.29–49.63%), citronellal (5.37–78.70%) and citronellol (2.98–7.18%). The biological assessments proved that the two essential oils had similar effect against bacterial (inhibition zones diameter ranging from 7.27 ± 0.06 to 10.37 ± 0.15 mm; MICs and MBCs ranging from 1.6 to 6.4 mg/mL); against Ae. albopictus larvae (LC50 ranging from 384.81 to 395.09 ppm) and adult mosquito (LD50 ranging from 133.059 to 218.962 μg/cm2); the activity of the two chemotypes ((R)-(+)-limonene and citronellal): larvae (LC50 ranging from 267.08 to 295.28 ppm), which were all presented in dose-dependent manners. Through this work, we have showcased that recycling and reusing of agriculture by-products, such as discarded perfume lemon and leaves can produce eco-friendly alternatives in bacterial disinfectants and mosquito control product.

Evaluation of Aphicidal Effect of Essential Oils and Their Synergistic Effect against Myzus persicae (Sulzer) (Hemiptera: Aphididae).

The insecticidal activities of essential oils obtained from black pepper, eucalyptus, rosemary, and tea tree and their binary combinations were investigated against the green peach aphid, Myzus persicae (Aphididae: Hemiptera), under laboratory and glasshouse conditions. All the tested essential oils significantly reduced and controlled the green peach aphid population and caused higher mortality. In this study, black pepper and tea tree pure essential oils were found to be an effective insecticide, with 80% mortality when used through contact application. However, for combinations of essential oils from black pepper + tea tree (BT) and rosemary + tea tree (RT) tested as contact treatment, the mortality was 98.33%. The essential oil combinations exhibited synergistic and additive interactions for insecticidal activities. The combination of black pepper + tea tree, eucalyptus + tea tree (ET), and tea tree + rosemary showed enhanced activity, with synergy rates of 3.24, 2.65, and 2.74, respectively. Essential oils formulation was effective on the mortality of aphids. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed that stability of a mixture of essential oils was not affected by store temperature (15, 25, and 35 °C) and the functional groups were not changed during storage. Based on our results, the essential oils can be used as a commercial insecticide against M. persicae.

Essential Oil from Flowering Tops of Lavandula dentata (L): Chemical Composition, Aantimicrobial, Antioxidant and Insecticidal Activities

In this study, the chemical composition, antioxidant, antimicrobial, and insecticidal activities of essential oil (EO) from Lavandula dentata (L. dentata) flowering tops collected from northern Tunisia were assessed. Forty-three compounds were identified. β-eudesmol (21.178 %), myrtenol (13.023 %), and sabinol (11.021 %) were the main compounds. The antibacterial potential was evaluated against three Gram-positive bacteria and three Gram-negative bacteria. The diameter of inhibition varied between 20.83±0.47 mm and 24.16±0.47 mm. The largest one was found in Salmonella typhimurium, however, the smallest one was found in Bacillus cereus. The minimal inhibition concentration (MIC) varied between 0.1 and 0.6 μg/ml. Furthermore, the antifungal potential was carried out. The mycelial growth of all the treated fungi was significantly different from the control ones (p<0.05), except in the case of P. notatum when treated with a dose of 1.25 mg/ml. Moreover, L. dentata EO was screened for its antioxidant activity using three methods. IC50 values were 113.29± 0.012 mg/ml, 53.029± 0.02 mg/ml, 43.20± 0.004 mg/ml, respectively for the DPPH test, the ABTS test and the reducing power test. The insecticidal activity was tested against adults of two major insect pests namely Rhyzopertha dominica and Sitophilus oryzae using contact, fumigant toxicity, and repellent bioassays. Results revealed that the L. dentata EO exhibited strong fumigant, repellent, and contact properties. For all tests, R. dominica was more sensitive compared to S. oryzae. This study revealed that EO from L. dentata flowering tops could be potentially valorized as a new antibacterial, antifungal, and bioinsecticide product.

Chemical constituents of essential oils from Thymus vulgaris and Cymbopogon citratus and their insecticidal potential against the tomato borer, Tuta absoluta (Lepidoptera: Gelechiidae)

This study aimed to determine the chemical composition and insecticidal activity of essential oils from Thymus vulgaris (thyme) and Cymbopogon citratus (lemongrass) against the devastating pest, Tuta absoluta. Essential oils were extracted by hydrodistillation and chemically analyzed by Gas chromatography coupled to mass spectrometry. Their knockdown (KD50) and larvicidal (LD50) activities were assessed through direct contact and fumigation toxicity assays. The major components of thyme oil were Thymol (21.53%), α-Pinene (Dextro) (17.43%) and o-Cymene (15.37%), while, Neral (34.48%), Geranial (34.37%) and β-Myrcene (12.84%) were prominent in lemongrass oil. Statistical analysis indicated that both oils exhibited similar knockdown and insecticidal efficiencies through direct contact and fumigation routes. The resultant biological parameters for lemongrass and thyme oils were KD50 values of 0.193 µL/mL and 0.592 µL/mL and LD50 values of 0.328 µL/mL and 0.608 µL/mL respectively for contact toxicity and KD50 of 1.290 µL/mL and 2.565 µL/mL and LD50 of 1.479 µL/mL and 3.046 µL/mL for lemongrass and thyme oils respectively for fumigant toxicity. The reference insecticide, Lynx (λ-cyhalothrin 15 g/L + acetamiprid 20 g/L) elicited no mortality through both routes after 4 hours of exposure. Both essential oils prolonged life cycle of insect pest through both routes as compared to the reference insecticide. However, greenhouse and open field trials are required to validate this approach prior to its implementation for T. absoluta control in tomato farms. To our knowledge, this study reports for the first time the insecticidal potential of lemongrass essential oil against T. absoluta.

Insecticidal activity of essential oils of Cupressus arizonica greene and C. sempervirens L. on Tortrix viridana (Lepidotera, Tortricidae)

Tortrix viridana is one of the most important defoliators of oak trees. In 2006 and 2007, this insect caused significant defoliations of oak forests in the Northwestern Tunisia. This work aims at studying the insecticidal activity of essential oils of Cupressus arizonica and C. sempervirens on 3rd, 4th and 5th instars larvae of T. viridana by the contact test. Three different concentrations of essential oils (0.05%, 0.1% and 0.5%) were used to test their contact effectiveness; the Deltamethrin and the ethanol were used as positive and negative controls. Larvicidal activity was determined by measuring the Mean Mortality Time (MMT) to kill 100% of larvae. A total of 28 chemical compounds have been identified from C. arizonica and 20 chemical compounds from C. sempervirens. The difference in MMT of the 3rd instar larva was highly significant between the 3 concentrations of the two tested essential oils, the negative and positive controls. In fact, the concentration (0.5%) was more efficient than the two other concentrations with a MMT=1h31min12s for C. arizonica and 5h11min20s for C. sempervirens. The same results were observed for the 4th (MMT=3h23min24s (Ca) and 4h1min (Cs)) and 5th (MMT= 3h23min24s (Ca) and 4h01min (Cs)) instars. The results revealed that the essential oil of C. arizonica was more effective than C. sempervirens. Therefore, it is recommended to use the essential oil of C. arizonica and not that of C. sempervirens, given its insecticidal efficiency on the 3rd instar larva of T. viridana

Phytochemical Screening and Insecticidal Activities of Essential oil of Mentha x piperita L. (Lamiales: Lamiaceae) and their Enzymatic Properties against Mosquito Culex pipiens L. (Diptera: Culicidae)

Biopesticides from botanicals are nowadays strongly encouraged for use in the program of controlling insect vectors of diseases and other harmful insects. The present study had the objective of determining the chemical composition of the essential oil of Mentha x piperita L. (Lamiaceae). We also evaluated the larvicidal and ovicidal activities of EO against Culex pipiens L. according to the World Health Organization (WHO) protocol. The chemical composition of EO from the aerial parts of peppermint was analyzed by gas chromatography-mass spectrometry GC/MS. The main components were menthol (28.66 %), limonene (19.01 %), and p-cymene (15.82 %). Also, this research found that M. x piperita EO showed larvicidal activity against fourth-instar larvae. Mortalities were recorded after 24, 48, and 72 h of treatment. It has potent larvicidal activity with increasing concentration and exposure time (LC50 values were 448.74; 181.97 and 152.05 ppm). Besides, EO showed excellent ovicidal activity, the results of which indicated that the hatchability of eggs treated with LC50 and LC25 is 18.13 % and 53.67 %, respectively. Furthermore, the study examines the efficacy of this oil on the glutathione S-transferase (GST) and acetylcholinesterase (AChE) activity of Cx. pipiens larvae treated with LC50 and LC90. This experiment has led to neurotoxic activity and stimulation of the detoxification system, as shown by AChE inhibition and GST induction respectively. In conclusion, M. x piperita EO is a natural larvicide and promising ovicide against Cx. pipiens. Therefore, it is recommended for use as a natural biocide in the implementation of effective mosquito control programs.

Insecticidal Activities of Essential Oil of Ocimun Gratissimun in Composite of Modified Saponins-Clay Montmorillonite and Mango Seed Starch Bioplastic

Insecticidal Activities of Essential Oil of Ocimun Gratissimun in Composite of Modified Saponins-Clay Montmorillonite and Mango Seed Starch Bioplastic

Comparative evaluation of insecticidal properties of essential oils of some selected botanicals as bio-pesticides against Cowpea bruchid, Callosobruchus maculatus (Fabricius) [Coleoptera: Chrysomelidae

BackgroundThe insecticidal activities of essential oils from seeds of five botanicals Tetrapleura tetraptera, Annona muricata, and Aframomum melegueta and leaves of Eucalyptus globulus and Ficus exasperata were evaluated as biopesticides against the storage pest of cowpea Callosobruchus maculatus (Fabricius). The oils were applied at the concentration of 1 ml/kg, 3 ml/kg, and 5 ml/kg of cowpea seeds mixed evenly. The experiment was laid out in a completely randomized design. The parameters assessed include the percentage of mortality, oviposition, adult emergence, seeds damaged, weight loss, and germinability capacity of the protected seeds.ResultsThe results from the study showed that the effectiveness of the essential oils was dependent on application rates and time of exposure. In the treated cowpea seeds, A. melegueta essential oil was the most effective with 50% lethal concentration (LC50) value of 2.42 ml/kg and 95% lethal concentration (LC95) value of 4.86 ml/kg when compared to the other treatments as indicated by the application rate which caused 50% and 95% mortality of cowpea beetles. A. melegueta essential oil at the concentration of 5 ml/kg achieved 100% mortality of C. maculatus at 48 h of application. Cowpea seeds treated with 5 ml/kg of E. globulus essential oil significantly reduced (P < 0.05) oviposition compared to the other treatments. Cowpea seeds treated with 5 ml/kg of A. muricata essential oil reduced adult emergence (3.67) and weight loss (0.59). The cowpea seeds treated with essential oils at different concentrations had no significant (P > 0.05) adverse effect on seed germination after 120 days of storage.ConclusionBased on the findings of this study, the essential oils could be explored as an alternative bio-pesticide to synthetic insecticide in the protection of stored cowpea against C. maculatus.

Chemical diversity of essential oils of Myrtaceae species and their insecticidal activity against Rhyzopertha dominica

Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) is one of the main stored grain pests in the world. The present study describes the investigation of the insecticidal activity of essential oils (EOs) extracted from the leaves of twelve Myrtaceae species against this important pest. The essential oils of Eucalyptus resinifera Sm. (Myrtaceae) were the most actives and presented 1,8-cineole (59.3%), p-cymene (12.9%), and α-pinene (9.7%) as the main components. Contact bioassays revealed that the EOs of E. resinifera were less toxic (LD50 = 17.08 μg mg−1 of insect body weight; LD95 = 56.17 μg mg−1) than the commercial insecticide pirimiphos-methyl (LD50 = 0.49 μg mg−1; LD95 = 1.14 μg mg−1) used as positive control. In the fumigation bioassays, however, these EOs were more effective (LC50 = 70.55 μL L−1, LC95 = 266.40 μL L−1) than the commercial insecticide (LC50 = 154.74 μL L−1; LC95 = 334.95 μL L−1). The LT50 on R. dominica adults for the EOs of E. resinifera were 1.75 h and 13.0 h in the contact and fumigation bioassays, respectively. The fumigant effect was due to the terpenoid 1,8-cineole, while the contact effect was caused by the association of the major components of the essential oils of E. resinifera. Thus, the EOs of E. resinifera have potential to be used as an alternative to commercial insecticides in R. dominica management.

Insecticidal activity of essential oils of species from the genus Lippia against Nasutitermes corniger (Motschulsky) (Isoptera: Termitidae)

Lippia is one of the main genera in the family Verbenaceae, with 200 species described. Despite its richness in bioactive molecules, with several scientifically proven applications, there is little information on the insecticidal potential of its species. This study aimed to assess the insecticidal potential of essential oils from the species Lippia thymoides (Martius &amp; Schauer); Lippia lasiocalycina (Schauer) and Lippia insignis (Moldenk) against Nasutitermes corniger (Motschulsky) (Isoptera-Termitidae). Insecticidal activity was evaluated by exposure to a contaminated surface, whereby plastic pots were lined with filter paper and imbibed in 1.5 ml of solution containing essential oils (10 µl/ml), with 10 N. corniger specimens per pot. The mortality count was performed at 24 and 48 h. The LC50 was determined by diluting the essential oils to concentrations of 0, 0.625, 1.25, 2.5, 5.0 and 10 µl/ml, which were chemically analyzed by GC-FID and GC-MS. The data indicated high toxicity for the essential oils for the Lippia species tested. The lowest LC50 (0.46 µl/ml) was recorded for L. lasiocalycina. The most common constituents were β-myrcene and (E)-ocimenone in essential oil of L. lasiocalycina, β-myrcene and limonene for L. insignis, and (E)-caryophyllene and caryophyllene oxide for L. thymoides. The results demonstrate the viability of developing biopesticides for N. corniger control.

Adulticidal Activity of Melaleuca alternifolia (Myrtales: Myrtaceae) Essential Oil With High 1,8-Cineole Content Against Stable Flies (Diptera: Muscidae).

The stable fly, Stomoxys calcitrans (Linnaeus 1758), is a hematophagous fly responsible for causing loss of performance in horses, causing losses in cattle productivity, and impacting the animals' health through the spread of pathogenic microorganisms. The objective of this work was to investigate the insecticidal activity of essential oil obtained from Melaleuca alternifolia (Cheel), presenting high 1,8-cineole content, against S. calcitrans adults. Insecticidal activity was determined using surface application methods and exposure to oil impregnated paper. It was observed that treatments at 25 and 50 μg/cm2 (P < 0.05) present fumigant activity through exposure to the impregnated paper, and in the first 15 min of exposure, the mortality rates obtained for these treatments were, respectively (96.6 ± 3.3% and 100%), equivalent to the positive control. Using the superficial application method, the only treatment concentration presenting adulticidal action was 5% (w/v) (P < 0.05). Respective toxicities LC50 (%, w/v) and LC80 for the impregnated paper method were 1.06 ± 0.02 and 1.47 ± 0.17; for the superficial application method, they were 3.82 ± 0.65 and 5.53 ± 0.74. As demonstrated, M. alternifolia essential oil presents adulticidal potential against S. calcitrans.

Insecticidal activity of essential oils compared with chemical insecticide against stored-grain pest Sitophilus oryzae

Stored-grain pest Sitophilus oryzae causes loss of rice in quantitative and qualitative. Until recently, the most frequent ways used to control insect pest is synthetic chemicals that harmful to human health, causing resistance to the pest, and pollute the environment. An alternative solution is offered by natural insecticide. The aim of the research is to analyze the effect of toxicity of three essential oils compared with a chemical insecticide toward rice weevil (Sitophilus oryzae). Bioassay was carried out by fumigation. The essential oil of Myristica fragrans 40 μL g−1 was the most insecticidal than essential oil of Cymbopogon citratus and Eucalyptus sp. with 100% mortality after 48 h exposure. Chlorpyriphos 2 μL g−1 as chemical insecticide generally used had 100% mortality after 24 h exposure. In spite of natural insecticide had longer time and higher concentration to kill insect pest, but it can be used for integrated management of stored-grain pest rice weevil (Sitophilus oryzae) that more safety for human and environment.

Ecofriendly Approach for the Control of a Common Insect Pest in the Food Industry, Combining Polymeric Nanoparticles and Post-application Temperatures.

One of the most common insect pests is Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), which affects different food commodities. A new effective approach for the management of insect pests is the development of new formulations based on essential oils (EO). However, few works informed about the relationship between insecticidal activity of EO or essential oils loaded polymeric nanoparticles (EOPN) and post-application temperature. In our work, palmarosa [Cymbopogon martinii (Roxb.) Watson], geranium (Geranium maculatum L.), and peppermint (Mentha piperita L.) oils were formulated in a polyethylene glycol 6000 matrix to obtain EOPN. Geranium and palmarosa EOPN had sizes of 259 and 191 nm, respectively; the encapsulation efficiency (EE) was close to 90%, and the samples were monodisperse. The sizes from peppermint EOPN were around 380 nm, with an EE of 72%, and were polidisperse. In a contact toxicity bioassay, the insecticidal effect of the oils was increased by all EOPN, with palmarosa oil being the most toxic. In addition, the oils and their nanoparticles showed a significantly negative temperature coefficient when applied by contact. In a fumigant bioassay, just palmarosa and peppermint EOPN enhanced the oil activity and palmarosa EO and EOPN showed the highest toxic effect. In this case, the EO and EOPN insecticidal activity was unaffected by environmental temperature variation.

Insecticidal activity of essential oil from Cephalotaxus sinensis and its main components against various agricultural pests

Plant essential oils (EOs) could be used as new alternatives of synthetic insecticides due to their environmental friendliness, safety to non-target organisms, and low-level resistance. In this study, the essential oil of Cephalotaxus sinensis (CSEO), an important Chinese medicinal species, showed potent insecticidal activity against Megoura japonica, Plutella xylostella and Sitophilus zeamais in laboratory bioassays; CSEO 20 % emulsifiable concentrate exhibited the control efficacy of 85.67 % against M. japonica after 7 days treatment at concentration of 0.25 % (w/v) in the greenhouse experiment. The GC-MS results showed that the main components of CSEO were α-pinene (37.89 %), β-caryophyllene (16.78 %) and germacrene D (10.79 %). Five active compounds, β-elemene (1), β-caryophyllene (2), β-phellandrene (3) caryophyllene oxide (4) and α-pinene (5) were isolated from CSEO. β-Caryophyllene (2) exhibited highest contact toxicity against M. japonica and P. xylostella, with the median lethal dose (LD50) values of 0.072 μg/adult and 0.32 μg/larva, respectively. α-Pinene (5) showed the highest fumigant toxicity against M. japonica and P. xylostella, with the median lethal concentration (LC50) values of 6.74 and 7.35 mg/L, respectively. Furthermore, β-phellandrene (3) had the potent contact and fumigant toxicity against S. zeamais with the LD50 and LC50 value of 2.19 μg/adult and 3.57 mg/L, respectively. Thus, CSEO and their major components have the potential to be developed as novel botanical insecticides for the control of agricultural pests.

Chemical composition and insecticidal activity of the essential oils of &lt;i&gt;Crateva Adansonii&lt;/i&gt; dc. Leaf on &lt;i&gt;Sitophilus Zeamais&lt;/i&gt; and &lt;i&gt;Callosobrunchus Maculatus&lt;/i&gt;

This study was conducted to determine the insecticidal activity of essential oil of Crateva adansonii against adult S. zeamaise and C. maculatus. The essential oil was obtained from the leaves of the plant using a Clevenger apparatus and analyzed by gas chromatography and mass spectrometry (GC/MS). The experimental data generated from the insecticidal assay results were analysed using statistical tool (ANOVA). GC/MS analysis revealed the presence of 52 compounds but with a low total yield of volatile fractions (0.1%). The major constituents of the oil were n-hexadecanoic acid (palmitic acid) (14.68%), Phytol (14.21%), 9,12-octadecanoic acid (Z,Z)- (linoleic acid)(5.81%), linalool (5.75%). Insecticidal bioassays showed that Crateva adansonii oil had a strong insecticidal activity on adult test insects they were exposed to at different concentrations and periods. An increase in the exposure time from 24 h to 72 h caused increase in mortality from 35.5% to 100% in S. zeamais and 31.1% to 100% in C. maculatus, respectively. According to these results, Crateva adansonii essential oil can be useful as an alternative for beans and maize protection against C. maculatus and S. zeamais.Key words: Insecticidal Bioassays, C. maculatus, S. zeamais, Crateva adansonii, Essential Oil,

O óleo essencial de Pimenta racemosa é eficiente inseticida para controle de Sitophilus spp. (Coleoptera: Curculionidae) em grãos armazenados

Os produtos formulados a partir de plantas possuem uma gama de compostos ativos, dos quais muitos apresentam efeitos inseticidas já comprovados, podendo ser atraentes ou repelentes aos insetos, servindo assim como alternativa no controle das populações de insetos-praga. Assim sendo, o presente estudo objetivou investigar a potencial atividade inseticida de óleos essenciais e métodos de aplicação sobre Sitophilus spp. em grãos de feijão (Phaseolus vulgaris) sob atmosfera controlada. Os óleos essenciais utilizados foram: Cymbopogon citratus (citronela), Cymbopogon nardus (capim-limão) e Pimenta racemosa (pimenta-gim), os quais foram aplicados em dois métodos em grãos de feijão, direta e indiretamente. Constatou-se um efeito inseticida sobre Sitophilus spp. decorrente da aplicação de óleos essenciais em grãos de feijão. Obteve-se maior efeito inseticida no tratamento com óleo essencial de pimenta-gim sendo que a segunda maior mortalidade média foi apresentada pelo óleo de capim limão. Estes resultados demostram que estes dois óleos são eficientes para manejo de Sitophilus spp. nas primeiras 72 horas posteriores a aplicação.

Ocotea porosa: Anatomy and Histochemistry of Leaves and Stems, Chemical Composition, Cytotoxicity and Insecticidal Activities of Essential Oil

Abstract Ocotea porosa (Nees & Mart.) Barroso, commonly known as “imbuia”, “canela-imbuia” or “imbuia-amarela” in Brazil, is a tree of the Southern Atlantic Forest. The present study investigates the anatomy of leaf and stem, volatile oil chemistry, as well as cytotoxicity and insecticidal activities of the essential oil of O. porosa. Species identification was achieved by anatomy features, mainly due to paracytic and anomocytic stomata; non-glandular trichomes; biconvex midrib and petiole with a collateral open arc vascular bundle; presence of a sclerenchymatous layer, starch grains and crystal sand in the stem; and the presence of phenolic compounds in the epidermis, phloem and xylem of the midrib, petiole and stem. The main volatile components of the essential oil were α-pinene (19.71%), β-pinene (13.86%) and bicyclogermacrene (24.62%). Cytotoxicity against human cancer cell (MCF-7), mouse cancer cell (B16F10) and mouse non-tumoral cell (McCoy) was observed as well as insecticidal activity of the essential oil against susceptible ‘Ft. Dix’ bed bugs (Cimex lectularius L.) by topical application.

Composition and Insecticidal Activity of Essential Oil of Bacopa caroliniana and Interactive Effects of Individual Compounds on the Activity.

Bacopa caroliniana (BC) is a perennial creeping herb and popular aquarium plant. This plant is easily cultivated; consequently, it has the potential to be a raw material which is readily available for mass production if it contains useful bioactive substances. The information about the functionality of this plant has been very limited. Therefore, the aims of this research were to analyze the composition of the essential oil (EO) of BC and to study its insecticidal effect on rice weevils. Moreover, the interactive effects of active compounds of the EO on this activity were also investigated. A total of 18 volatile compounds was identified, accounting for ca. 94% of the BC-EO in terms of quantity. Of them, α-terpinolene was the largest compound. The impact of individual volatile compounds on the inhibition of acetylcholine esterase and insecticidal activity were determined. α-Terpinolene exhibited the highest activity on these assays. Both additive and synergistic effects existed in terms of the insecticidal activity. Many compounds found in the BC-EO are widely present in other EOs. Thus, the information obtained from this study is useful for EO-related research, applications in selecting EOs or in seeking the best combination of EOs or individual compounds to achieve efficient insecticidal effects.

Insecticidal activity of the essential oil and polar extracts from Ocimum gratissimum grown in Ivory Coast: Efficacy on insect pests and vectors and impact on non-target species

Ocimum gratissimum L. (white wild basil) is an aromatic herb cultivated in Western Africa for culinary and pest control purposes. The current research evaluated the insecticidal activity of white wild basil essential oil, ethanolic and water extracts against insect pests and vectors, i.e., the tobacco cutworm Spodoptera littoralis, the housefly Musca domestica, and the filariasis vector Culex quinquefasciatus. Furthermore, the toxicity of the essential oil and polar extracts against the non-target earthworm Eisenia fetida was assessed. The chemical profiles of the essential oil and polar extracts were obtained by GC–MS and HPLC-DAD analyses. Acute toxicity experiments were conducted on larvae of C. quinquefasciatus and S. littoralis and adults of M. domestica and E. fetida, to determine the LC50 and LC90 values of the oil and polar extracts. Chronic toxicity was evaluated on S. littoralis feeding on tomato discs treated with essential oil and polar extracts. The essential oil was dominated by thymol (50.0%) and p-cymene (16.8%), whereas ethanolic and aqueous extracts were characterized by carvacrol (13%) and thymol (11%), and shikimic acid (3%) and rosmarinic acid (2%), respectively. The essential oil was significantly more active on target insects than extracts, showing LC50/LD50 of 39.6 mg L−1 on C. quinquefasciatus, 72.2 μg adult−1 on M. domestica and 30.2 μg larva−1 on S. littoralis. Furthermore, the essential oil and ethanolic extract at sublethal doses (10 and 70 μg cm-2, respectively) affected the survival of S. littoralis larvae from the third day on. White wild basil oil LD50,90 at day 5 were 2.8 and 12.3 μg cm-2. Finally, the essential oil and polar extracts were not toxic to E. fetida over the positive control α-cypermethrin. Overall, our study showed that the essential oil of white wild basil is a potential candidate as a functional ingredient in insecticidal formulations to manage agricultural moth pests and insect vectors of public importance.