The insecticidal activity of 120 plant essential oils and control efficacy of six experimental spray formulations (SF) containing the oils (SF-0.25, 0.5, 1, 2.5, 5 and 10% sprays) against both nymph and adult of citrus flatid planthopper, Metcalfa pruinosa, was examined using a direct contact application. Reponses varied according to dose (1000 mg litre-1 and 500 mg litre-1). Based on 24 h exposure in leaf dipping assay at 1000 mg litre-1 strong mortality was observed in more than 19 essential oils among 130 was screened. At 500 mg litre-1 very strong mortality (100%) was observed in cinnamon technical, cinnamon green leaf, cinnamon #500, cassia tree, citronella java and penny royal followed by origanum, thyme white, grape fruit, savory, fennel sweet, aniseed and cinnamon bark (93.3- 80%) showed considerable moratality against nymphs of M. pruinosa. The moderate mortality was found in thyme red, tagette, calamus, lemoneucalptus and geranium (73.3-60%). The other oil has low or very low mortality against M. pruinosa. The oil applied as SF-10% sprays provided 100% mortality against adult M. pruinosa. In particular cinnamon technical showed very strong (>SF-0.5= 100%) effect followed by cinnamon #500 (>SF-2.5=100%), cinnamon green leaf (>SF-2.5=100%) and penny royal (>SF-2.5=100%) respectively. Global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment justify further studies on the active essential oils as potential larvicides for the control of M. pruinosa populations as direct spray with contact action.

We evaluated the larvicidal activity of 20 plant essential oils and components from ajowan (Trachyspermum ammi) and Peru balsam (Myroxylon pereira) oils against Aedes aegypti. Of the 20 plant essential oils, ajowan and Peru balsam oils at 0.1 mg/mL exhibited 100% and 97.5% larval mortality, respectively. At this same concentration, the individual constituents, (+)-camphene, benzoic acid, thymol, carvacrol, benzyl benzonate and benzyl trans-cinnamate caused 100% mortality. The toxicity of blends of constituents identified in 2 active oils indicated that thymol and benzyl benzoate were major contributors to the larvicidal activity of the artificial blend. We also tested the acute toxicity of these 2 active oils and their major constituents against the water flea, Daphnia magna. Peru balsam oil and benzyl trans-cinnamate were the most toxic to D. magna. Two days after the treatment, residues of ajowan and Peru balsalm oils in water were 36.2% and 85.1%, respectively. Less than 50% of benzyl trans-cinnamate and thymol were detected in the water at 2 days after treatment. Our results show that the essential oils of ajowan and Peru balsam and some of their constituents have potential as botanical insecticides against Ae. aegypti mosquito larvae.

Fumigant effects of six plant essential oils (Helichrysum angustifolia, H. gymnocepha, H. splendidum, Arachis Hypogaea (peanut oil), Mentha arvensis (corn mint oil), and Thymus magnus (thyme oil) were tested against the adults of three grain storage insects (Lasioderma serricorne, Sitophilus zeamais, and Tribolium castaneum). Among them, the corn mint oil revealed to have fumigant toxicity against L. serricorne (LD50 = 1.3 ㎕ L-1), S. zeamais (LD50 = 3.6 ㎕ L-1), and T. castaneum (LD50 = 16.2 ㎕ L-1). The chemical constituents of corn mint oil were analyzed using GC-MS as follows: (-)-menthone (15.3%), isomenthone (10.0%), methyl-cetate (5.0%), β-caryophyllene (9.1%), and 1-menthol (48.1%). To enhance the fumigant toxicity, ethyl formate was added. This novel formulations of mixture could find significant differences in terms of their synergistic effects.

The toxicity of 102 plant essential oils against third instars of cecidomyiid gall midge, Camptomyia corticalis, was examined using a vapor-phase mortality bioassay. Results were compared with that of a conventional insecticide dichlorvos. Based on 24 h LC50 values, all essential oils were less toxic than dichlorvos (LC50, 0.027 mg/cm3). The LC50 of caraway seed, armoise, sage (Clary), oreganum, lemongrass, niaouli, spearmint, cassia special, sage (Dalmatian), thyme red, bay, garlic, and pennyroyal essential oil is between 0.55–0.60 mg/cm3. The LC50 of cassia pure, thyme white, cassia redistilled, star anise, peppermint, wintergreen, cinnamon bark, majoram, chamomile romon, eucalyptus, rosemary, cedar wood, pimento berry, savory (summer), lavender, and coriander oil is between 0.61–0.99 mg/cm3. All other essential oils tested exhibited low toxicity to the cecidomyiid larvae (LC50,>0.99 mg/cm3). The active principles of active essential oils were identified by GC-MS analysis. The major active principles are such as pulegone, thujone, camphor, 1,8-cineole, a-pinene, thymol, menthol. At a rate of 5 mg/cm3, pulegone, and thujone, exhibited 100% morality whereas camphor, 1,8-cineole, α-pinene, thymol and menthol showed 90% mortality at 15 mg/cm3. Global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment justify further studies on the essential oils and their constituents described as potential insecticides for the control of the mushroom fly as fumigants with contact action.

We evaluated insecticidal and acetylcholine esterase inhibition activity of 11 Apiaceae plant essential oils and their constituents against male and female adults of Blattella germanica. Of 11 Apiaceae plant essential oils tested, dill (Anethum graveolens), carvi (Carum carvi), and cumin (Cuminum cyminum) essential oils demonstrated > 90 % fumigant toxicity against male adults of German cockroach at 5 mg/filter paper. In contact toxicity test, dill (Anethum graveolens), carvi (Carum carvi), cumin (Cuminum cyminum), and ajowan (Trachyspermum ammi) essential oils produced strong insecticidal activity against male and female adults of German cockroach. Among test compounds, carvone, 1,8-cineole, trans-dihydrocarvone, cuminaldehyde, trans-anethole, p-cymene, and γ-terpinene demonstrated strong fumigant toxicity against male and female adults of B. germanica. In a contact toxicity test, carveol, cuminaldehyde, (S)-(+)-carvone, trans-anethole, thymol, and p-cymene showed the strong contact toxicity against B. germanica male and female adults. IC50 values of α-pinene, carvacrol, and dihydrocarvone against female acetylcholine esterase were 0.28, 0.17, and 0.78 mg/mL, respectively. The toxicity of blends of constituents identified in 4 active oils indicated that carvone, cuminaldehyde, and thymol were major contributors to the fumigant or contact toxicity of the artificial blend.

The larvicidal activity of 12 Apiaceae essential oils and their constituents was evaluated against third instar larvae of mosquitoes, Aedes albopictus. Of the 12 Apiaceae essential oils, Dill (Anethum graveolens), Caraway seed (Carum carvi), Cumin (Cuminum cyminum), Carrot seed (Daucus carota), Parsley (Petroselinum sativum) and Ajowan (Trachyspermum ammi) oils at 0.1 mg/ml exhibited 90% larval mortality after 2 days. Analysis by gas chromatography-mass spectrometry led to identification of 8, 3, 13, 12 compounds, respectively. in the oils of Dill (Anethum graveolens), Caraway seed (Carum carvi), Cumin (Cuminum cyminum), Ajowan (Trachyspermum ammi). The compounds thus identified were tested individually for their larvicidal activities against Aedes albopictus. At this same concentration, the individual constituents tested, α-phellandrene, α-Terpinene, ρ -cymene, (+)-Limonene, γ-Terpinene, Thymol, Carvacrol resulted in 100% mortality after 2 days. At this same concentration, the individual constituents tested, (+)-carvone, cuminaldehyde, neral, trans-anethole resulted in 80% mortality after 2 days.

We evaluated insecticidal activity of 11 Apiaceae plant essential oils and their constituents against rice weevil, Sitophilus oryzae.. Of 11 Apiaceae plant essential oils tested, dill (Anethum graveolens), carvi (Carum carvi), caraway seed (Carum carvi) and cumin (Cuminum cyminum) essential oils demonstrated strong fumigant toxicity against adults of rice weevil. Components of 4 active compounds were analyzed by GC and GC-MS, and fumigant toxicity of individual compound was also tested. Among test compounds, carvone, dihydrocarvone, carveol, linalool oxide, neral, cuminaldehyde, and anethole demonstrated the strong insecticidal activity. The toxicity of blends of constituents identified in 4 active oils indicated that carvone, and cuminaldehyde were major contributors to the fumigant toxicity of the artificial blend.

Six plant essential oils, vanillin, and their mixtures were tested for repellent activities and olfactory responses in a dengue virus vector mosquito, Aedes aegypti. Among the plant essential oils, cassia oil showed complete protection time (CPT) of 75 minutes. CPTs of lemongrass, lemoneucalyptus, xanthoxylum oils, and vanillin were within 30 minutes at 5% (0.21 mg/cm2) tested level, although their CPTs were not comparable to same concentration of DEET that showed 127.5 minutes of CPT. However, their repellency effects were significantly improved in two conditions; improving concentration up to 15% level (0.63 mg/cm2) and addition of vanillin. In bioassays using binary or tertiary mixtures with one or two essential oils with or without vanillin, the composition of 1:3:1 (v/v/w) consisted of lemongrass oil, xanthoxylum oil and vanillin provided 270 min-CPT. As a practical application, the mixture of 1:1:1 formulation containing lemongrass oil, xanthoxylum oil, and vanillin (v/v/w) was enclosed into the Viscopearl, porous cellulose beads that provide gradual release of volatile compounds. Efficiently, more than 90% of repellency for 2 hours was observed in cage and semi-field chamber tests using the formulation. In addition to behavioral assays, we subsequently examined how mosquitoes sense the blends of oils with vanillin by using electroantennogram (EAG) recording. Binary mixture with one oil and vanillin, which extended CPTs, showed no significant patterns of EAG alternation, while tertiary mixtures of oils and vanillin decreased patterns of EAG responses as an increase of vanillin contents in the mixture, implying further potential roles of vanillin as a synergist in mosquito repellency. Based on behavioral and electrophysiological data, cassia, rosemary, lemongrass, xanthoxylum, and lemoneucalyptus oils could provide the high possibility for development of commercial products for useful management strategies to control mosquitoes.

The emulsion and micro-encapsuled formulation from three essential oils, cassia, thyme white and lemon grass were tested for their insecticidal activities against Lycoriella ingenua (Dufour) adults at 0.3% concentration. As a result, the micro-encapsules than emulsion formulation was confirmed to show greater activity. Based on this result, insecticidal activities at several levels of concentration were examined, resulting in more than 80% insecticidal activity after 30 minutes at 0.6% level of cassia formulation. And also, insecticidal activity of three oil-based micro-encapsuled formulations lasted for up to 12 hours at 0.9% concentration. The main ingredients derived from three essential oils were evaluated on the insecticidal activity against Lycoriella ingenua. As a result, in case of thymol from thyme white, it showed more than 80% mortality after over 30 minutes at 0.25%, and in cinnamic aldehyde and citral, exhibited 88% and 82% mortality after 30 minutes at the 0.5% level, respectively. These three compounds were examined for whether the insecticidal activity was maintained depending on being over time. In case of thymol, it maintained good insecticidal activity against Lycoriella ingenua at 0.5% level until 120 hours, while cinnamic aldehyde and citral showed lower activity after 12 hours.

The repellency of 104 plant essential oils to female Aedes aegypti was examined using a cage-distribution assay. Results were compared with those of the conventional mosquito repellent N,N-diethyl-m-toluamide (DEET). Coriander, oreganum, pennyroyal, lemoneucalyptus, and spearmint exhibited high repellency effect (>60 minutes at 50 mg/filter paper), followed by sage, leavander, tarragon, bergamot, and neroli oils which showed moderate effective (< 40 minutes at 50 mg/filter paper (5 cm diameter)). In the light of global efforts to reduce the level of highly toxic synthetic repellents, essential oils described merit further study as potential repellents for the control of mosquito populations.

In the previous study, the plant essential oils such as clove bud , thyme white and garlic oils gave potent toxicity with the range of 1.5 to 4.5×10-3 ul cm-3 of LC50 values against Bemisia tabaci. Based on the bio-assay results, three plant essential oils(clove bud, thyme white and garlic) were applied to 30% emulsion type. The 100, 200 and 400 fold dilution of these emulsions was showed mild toxicity under port scale treatment against Q biotype. At each fold dilution, clove bud showed 44, 26 and 14%, and thyme white produced 44, 39 and 27%, respectively. Of garlic emulsion, its toxicity was evaluated with 27, 26 and 11%, respectively. But, in case of clove bud and thyme white mixture, their toxicity was more good under the mixture than under the single treatment. Mixture with clove bud 200 fold dilution adding to thyme white 200 fold dilution showed potent activity with 86% mortality. And also 200 adding to 400, and 400 to 400 exhibited 61%, 76%, respectively. These essential oil mixtures showed similar strong toxicity against B biotype under port scale test. In particular, the mixture with clove bud 200 fold dilution adding to thyme white 200 fold dilution showed the highest synergistic effect. Toxicity to plants, except the 100 fold dilution of these emulsions was not observed.

Aedes aegypti is a primary vector that transmits dengue and yellow fever around the world. To prevent the spreading and elimination of mosquitoes, insecticides and repellents like DEET (N, N-diethyl-m-methyl benzamide) have been broadly used. Even though DEET is considered as highly effective and proven protection against mosquito, it causes skin irritants and rashes, melts some synthetic plastics, and unpleasant smells. Therefore, there is a trend finding alternative mosquito repellents instead of using DEET. We tested repellent effects with plant essential oils and synergistic effects of those plant essential oils with additional vanillin, comparing them to DEET itself. Some of prepared mixtures showed better repellency than DEET. In addition, we evaluated the differences in the peripheral olfactory responses of Ae.aegypti females using EAG tests (electroantennogram). The aim of this test is to determined how the vanillin within plant essential oils or DEET acts in mosquito’s olfactory organs in aspect of molecular mechanisms. Revealing the novel function and localization of these putative repellent receptors may provide new insight into development of repellent as well as behavioral control agents in the future and contribute to understand the mechanism of processing patterns of repellent receptors in mosquitoes.

Plant essential oils from 26 plant species were tested for their insecticidal activities against the Japanese termite, Reticulitermes speratus Kolbe, using a fumigation bioassay. Responses varied with source, exposure time, and concentration. Among the essential oils tested, strong insecticidal activity was observed with the essential oils of ajowan (Trachyspermum ammi), allspice (Pimenta dioica), caraway (Carum carvi), dill (Anethum graveolens), geranium (Pelargonium graveolens), and litsea (Litsea cubeba). The composition of six essential oils was identified by using gas chromatography-mass spectrometry. The compounds thus identified were tested individually for their insecticidal activities against Japanese termites. Responses varied in a dose-dependent manner for each compound. Phenol compounds exhibited the strongest insecticidal activity among the test compounds further, alcohol and aldehyde groups were more toxic than hydrocarbons. The essential oils and compounds described herein merit further study as potential fumigants for termite control.

The toxicity of 10 plant essential oils to adults of acaricide-susceptible, chlorfenapyr-resistant (CRT-53), fenpropathrin-resistant (FRT-53), pyridaben-resistant (PRT-53), and abamectin-resistant (ART-53) strains of Tetranychus urticae Koch and to female Neoseiulus californicus McGregor was examined using spray or vapor-phase mortality bioassays. In bioassay with the susceptible adults, strong toxicity was produced by lemon eucalyptus, peppermint, citronella Java, thyme red, caraway seed, pennyroyal, and clove leaf essential oils (LC50, 0.0193-0.0327 mg/cm3). The toxicity of these essential oils was almost identical against adults from either of the susceptible and resistant strains, even though CRT-53, FRT-53, PRT-53, and ART-53 adults exhibited high levels of resistance to chlorfenapyr [resistanc ratio (RR), >9140], fenpropathrin (RR, 94), pyridaben (RR, >390), and abamectin (RR,85), respectively. Against female N. californicus was 1.0 to 1.9 times more tolerant than T. urticae to the test essential oils. Thus, these essential oils merit further study as potential acaricides for the control of acaricide-resistant T. urticae populations as fumigants because of their lower toxicity to N. californicus.

One hundred seven plant essential oils were tested for insecticidal activities against Bemisia tabaci B and Q biotype adults, using the fumigation and direct spray methods. In the fumigation assay with the Q biotype adults, garlic oil was the most toxic (1.5×10-3 μl/cm3) on the basis of the LC50 value. Clove leaf, thyme, oregano (origanum), clove bud, savory, cinnamon bark, dabana, vetiver haiti and catnip essential oils also gave potent toxicity with the range of 1.7 to 4.5×10-3 μl/cm3 of LC50 values. These essential oils showed similar strong toxicity against B biotype. Based on the results obtained from fumigation test, nine plant essential oils were selected for the direct spray application at three concentrations (0.5, 0.1 and 0.02%). A litter difference was obtained between B and Q types in mortality to the tested oils. At the 0.5% concentration, they gave considerable mortality of 76 to 100%. At 0.1%, only garlic essential oil produced 96 to 100% mortality, but the others showed less than 76% mortality. Several plant essential oils appear to be candidates for the control of B. tabaci.

The repellency to female Stomoxys calcitrans (L.) of 21 essential oils alone or in combination with Calophyllum inophyllum nut oil (tamanu oil) was examined using a skin bioassay. Results were compared with those following treatment with the commonly used repellent DEET (N,N-diethyl-3-methylbenzamide). As judged by the protection time (PT) to first bite at 0.5 mg cm-2, patchouli (3.67 h) was the most effective essential oil, followed by clove bud, lovage root, clove leaf and thyme white essential oils (3.50-2.12 h). Thyme red, oregano and geranium essential oils exhibited moderate protection time (PT, 1.24-1.11 h). At 0.25 mg cm-2, effective protection time of clove bud, clove leaf and lovage root essential oils was about 1 h. The protection times of DEET were 4.47 and 2.17h at 0.5 and 0.25 mg cm-2 respectively. The remarkable increase in the protection time were produced by binary mixtures of five essential oils (clove bud, clove leaf, thyme white, patchouli and savory) and tamanu oil (0.25:2.0 mg cm-2) compared with those of either the constituted essential oil, tamanu oil or DEET alone, indicating the involvement in synergy. These essential oils, tamanu oil and binary mixtures did not cause any adverse effects on the human volunteers at 0.5 mg cm-2 except savory oil. Thus binary mixtures of essential oils and tamanu oil described merit further study as potential insect repellents for protection from humans and domestic animals from biting and nuisance caused by S. calcitrans.

Commercial plant essential oils from 27 plant species were tested for their nematicidal activities against the pinewood nematode, Bursaphelenchus xylophilus. Good nematicidal activity against B. xylophilus was achieved with essential oils of coriander (Coriandrum sativum), styrax (Liquidamber orientalis) and valerina (Valeriana wallichi). Analysis by gas chromatography-mass spectrometry led to identification of 26, 10 and 4 major compounds from coriander (Coriandrum sativum), styrax (Liquidamber orientalis) and valerina (Valeriana wallichi) oils, respectively. These compounds from three plant essential oils were tested individually for their nematicidal activities against the pine wood nematode. Among compounds, benzaldehyde, trans-cinnamyl alcohol, cis-asarone, octanal, nonanal, decanal, trans-2-decenal, undecanal, dodecanal, decanol, and trans-2-decen-1-ol showed strong nematicidal activity. The essential oils and their described herein merit further study as potential nematicides against the pine wood nematode.

Plant essential oils from twenty plant species were tested for their insecticidal activity against larvae of Lycoriella ingenua using a fumigation bioassay. Good insecticidal activity (>90%) against larvae of L. ingenua was achieved with essential oils of caraway seed (Carum carvi), lemongrass (Cymbopogon citratus), mandarine (Citrus reticulate), nutmeg (Myristica fragrans), cade (Juniperus oxycedrus), spearmint (Mentha spicata), cumin (Cuminum cyminum) and thyme red (Thymus vulgaris) oils at 30×10-3 mg/㎖ air. Among them, caraway seed, spearmint, cumin and thyme red essential oils were highly effective against L. ingenua at 20×10-3 mg/㎖ air. Analysis by gas chromatography-mass spectrometry led to identification of 4, 9, 8 and 17 compounds from caraway seed, spearmint, cumin and thyme red oils, respectively. These compounds were tested individually for their insecticidal activities against larvae of L. ingenua, and compared to the toxicity of dichlorvos. Carvacrol, thymol, linalool, cuminaldehyde, p-cymen, terpinen-4-ol and carvone was effective at 10×10-3 mg/㎖. The insecticidal activity of dichlorvos was 60% at 10×10-3 mg/㎖. Effects of four selected plant essential oils on growth of Pleurotus ostreatus were also investigated.