Contact toxicity of Azadirachta indica (Adr. Juss.), Eucalyptus camaldulensis (Dehn.) and Laurus nobilis (L.) essential oils on mortality cotton aphids,Aphis gossypii Glover (Hem.: Aphididae)

Essential oils from three species of plants comprising three plant families were obtained by Clevenger-type water distillation. The major compounds in these essential oils were identified with GC-MS and their insecticidal activity against adult cotton aphid, Aphis gossypii Glover tested with dosage-mortality bioassays. We examined mortality only for viviparous adults because sizeable aphid populations on cucumber (Cucurbitaceae) hosts are largely produced by these wingless, parthenogenic females. Three of the oils were directly applied to aphid females in randomised blocks at 25?±?2?°C and 60?±?5% R.H. and under a L16:D8 photoperiod. Essential oils were mixed with a non-toxic emulsifying agent, Tween 80. Results show adverse contact effects of essential oils studied in the control of cotton aphid. Probit analysis and LC₅₀ at concentrations at different exposures showed aphids were incapacitated and killed by aliphatic aldehydes, phenols and monocyclic terpenes contained in Azadirachta indica, Eucalyptus camaldulensis and Laurus nobilis. LC₅₀ on cotton aphid, for azadirachtin eucalyptus and laurel essential oils were respectively 5389, 9515 and 13730?ppm. In the current study, efficacy in respect to the contact toxicity (LC₅₀) followed the order: A. indica?>?E. camaldulensis?>?L. nobilis after 24?h treatment. Our results show quantitative and qualitative differences in the chemical composition and insecticidal activities of our essential oils. All oils became insect toxic as concentration increased. According to the results, essential oils of all the three plants have the potential to be employed in the pest management programmes that can be used in protection of greenhouse conditions against cotton aphid.     

Biotic Resource Needs of Specialist Orchid Pollinators

Orchid pollinators have highly varied life histories with complex biotic resource requirements, about which we have limited knowledge. Among the specialist orchid pollinators are insect predators and parasitoids with specific prey types such as aphids and subterranean scarab larvae; oligolectic bees that collect pollen from limited sources such as bellflowers; euglossine bees and butterflies that collect particular plant chemicals for reproduction and self defense; oil-collecting bees that provision their brood cells with floral oils from a few plants; bees that collect rare floral resins to construct their nest and brood cells; moths and butterflies that require specific larval host plants; mosquitos and horse flies that need blood; and fungus gnats and carrion flies tied to fungi and dead animals. Loss of critical biotic resources and relationships can reduce the abundance of orchid pollinators and/or their effectiveness. Protection of large, plant rich, pesticide-free orchid habitats is key to conserving essential pollinator resources.     

八角茴香精油防治蜂螨的蜂群效果研究

本研究在蜂群中测定了八角茴香精油对西方蜜蜂大蜂螨和小蜂螨的杀螨效果。结果表明:应用八角茴香精油一个疗程后,大蜂螨的巢房寄生率由用药前的7.17%下降到1.93%,蜂体寄生率由用药前的4.13%下降到了1%,与氟氯苯氰菊酯组差异不显著;小蜂螨巢房寄生率由用药前的7.65%下降到3.4%,与升华硫组差异不显著;且八角茴香精油不会引起蜂群群势下降。可见,八角茴香精油在防治蜜蜂大、小蜂螨的应用上具有很大潜力。     

印度藏茴香植物精油对温室棉蚜的熏蒸毒性及其成分分析（英文）

【目的】棉蚜Aphis gossypii是世界各地室内和室外果树、蔬菜和观赏植物上最具危害性的害虫之一。这一害虫取食植物汁液,产生蜜露,传播植物病毒,对植物从质和量上产生破坏。为了控制温室中的这一害虫,植物精油可用作化学农药的替代药物。本实验研究了印度藏茴香Carum copticum植物精油对棉蚜成虫的熏蒸毒性。【方法】将研磨的印度藏茴香干种子用改良的挥发油提取器(Clevenger-type apparatus)进行水蒸馏。所有生物测定均在27±2℃,相对湿度65%±5%和光周期16L∶8D条件下进行。研究采用完全随机设计,6个处理(5个不同浓度的精油加对照)。每一浓度3次重复,每一重复20头成虫。【结果】结果表明,棉蚜成蚜接触印度藏茴香精油24 h后出现明显的死亡。该精油对棉蚜成蚜的致死中浓度(LC50)为1.21μL/L空气。棉蚜成蚜的死亡百分率对精油的施用表现出较高的敏感性。精油浓度为1.21μL/L空气时,估计的棉蚜的致死中时(LT50)为11.79 h。这一精油的熏蒸毒性与浓度和接触时间之间具有一定的相关性。GC/MS组分分析结果表明,该精油由18种化合物组成,最重要的是一些化合物引起了熏蒸毒性,如麝香草酚(占50.07%)、γ-萜品烯(占23.99%)和对异丙基苯甲烷(占22.90%)。【结论】本研究结果表明印度藏茴香植物精油对棉蚜具有较好的杀虫效果。印度藏茴香精油对棉蚜产生较大的影响,由于它具有较高的熏蒸毒性潜力,因此可在温室中用于这一害虫的综合治理。     

Effect of essential oils on postharvest decay and quality factors of tomato in vitro and in vivo conditions

For increasing the shelf life and control of devastating fungal pathogen grey mould (Botrytis cinerea), tomato fruits during storage were applied different concentrations of ammi (Carum copticum) and anise (Pimpinella anisum) essential oils. First, antifungal activities of essential oils were tested on artificial growth media. The growth of grey mould was completely inhibited by ammi and anise essential oils at relatively higher concentrations. In second stage, fruits were infected artificially by grey mould spore and then treated with different concentrations of these essential oils. The results of in vivo conditions showed that ammi and anise essential oils applied at all concentrations were increasing the shelf life and inhibited the grey mould growth on tomato fruits completely in comparison to control. Fruits treated with these essential oils had significantly higher total soluble solids (TSS), ascorbic acid, β-carotene and lycopene content compared to control fruits.     

Brood Odor Discrimination Abilities in Hygienic Honey Bees (Apis mellifera L.) Using Proboscis Extension Reflex Conditioning

To understand the effect of abnormal brood odors on the initiation or control of hygienic behavior in honey bees, we employed the associative learning paradigm, proboscis extension reflex conditioning. Bees from two genetic lines(hygienic and non-hygienic) were able to discriminate between high concentrations of two floral odors equally well. Differential discrimination abilities were observed between the two lines when healthy and diseased brood odors were used, with the bees from the hygienic line discriminating between the pair of brood odors better than the non-hygienic bees. These results suggest that hygienic behavior in individual bees is associated with the bees' responses to olfactory stimuli emanating from diseased brood.     

Chemical composition and antimicrobial activity of Citrus essences on honeybee bacterial pathogen <Emphasis Type="Italic">Paenibacillus larvae</Emphasis>, the causal agent of American foulbrood

Antimicrobial properties and chemical composition of four citrus fruit essential oils to control Paenibacillus larvae, the causal agent of American foulbrood disease (AFB) were determined. This honeybee larvae disease occurs throughout the world and is found in many beekeeping areas of Argentina. Citrus fruit essential oils tested were those from grapefruit (Citrus paradisi), sweet orange (Citrus sinensis), mandarin (Citrus nobilis) and lemon (Citrus limon). The components of the essential oils were identified by SPME-GC/MS analysis. The antimicrobial activity of the oils against P. larvae were determined by the broth microdilution method. Two way ANOVA tests for minimum inhibitory concentrations (MICs) data and minimal bactericide concentrations (MBCs) data, indicated significant differences between the strains and the oils tested. The antimicrobial assays showed that the oil of C. paradisi inhibited the bacterial strains at the lowest concentrations tested, MICs and MBCs averages of 385.0 mg/l and 770.0 mg/l, respectively. This property could be attributed to the kind and percentage of the volatile components of the oil, like limonene (69.9%) and myrcene (9.6%). The use of essential oils or their specific volatile components individually against pests related to food provision may represent an alternative scope for the control of this serious disease because it does not leave toxic chemical residues in honey nor in its by products.     

Repellency of essential oils to Frankliniella occidentalis (Thysanoptera: Thripidae) as affected by type of oil and polymer release

Eight essential oils [0.125-1.0% (vol:vol) in acetone] were separately deposited on leaf disks to evaluate their potential to repel western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), adult females. Two of the best-performing essential oils were incorporated into polymer matrices of methyl cellulose or alginate [0.5 or 1% (wt:vol)] to verify the potential of the polymer to extend repellency of oils over time (24-120 h). Results showed that at a concentration of 0.5%, Thymus vulgaris L. (common thyme) and Satureja montana L. (winter savory) were the most repellent essential oils. For these two treatments, no western flower thrips were counted on treated leaf disks 60 min after the start of the test. T. serpyllum and O. compactum also showed repellency values > or = 90% at this concentration. With both the alginate and methyl cellulose polymers, the incorporation of polymers into treatment solutions containing 0.5% concentrations of S. montana and T. serpyllum resulted in higher repellency compared with treatment solutions lacking these polymers for a minimum of 3 d. For the alginate polymer, differences associated with polymer concentrations were most dramatic. High repellency was maintained for 4 d when a 0.5% concentration of the alginate was used in combination with a 0.5% concentration of S. montana. The use of repellent oils with polymers that extend their repellency may prove useful for both pre- and postharvest applications in flower crops.     

Toxic but drank: gustatory aversive compounds induce post-ingestional malaise in harnessed honeybees

Background

Deterrent substances produced by plants are relevant due to their potential toxicity. The fact that most of these substances have an unpalatable taste for humans and other mammals contrasts with the fact that honeybees do not reject them in the range of concentrations in which these compounds are present in flower nectars. Here we asked whether honeybees detect and ingest deterrent substances and whether these substances are really toxic to them.

Results

We show that pairing aversive substances with an odor retards learning of this odor when it is subsequently paired with sucrose. Harnessed honeybees in the laboratory ingest without reluctance a considerable volume (20 µl) of various aversive substances, even if some of them induce significant post-ingestional mortality. These substances do not seem, therefore, to be unpalatable to harnessed bees but induce a malaise-like state that in some cases results in death. Consistently with this finding, bees learning that one odor is associated with sugar, and experiencing in a subsequent phase that the sugar was paired with 20 µl of an aversive substance (devaluation phase), respond less than control bees to the odor and the sugar. Such stimulus devaluation can be accounted for by the malaise-like state induced by the aversive substances.

Conclusion

Our results indicate that substances that taste bitter to humans as well as concentrated saline solutions base their aversive effect on the physiological consequences that their ingestion generates in harnessed bees rather than on an unpalatable taste. This conclusion is only valid for harnessed bees in the laboratory as freely-moving bees might react differently to aversive compounds could actively reject aversive substances. Our results open a new possibility to study conditioned taste aversion based on post-ingestional malaise and thus broaden the spectrum of aversive learning protocols available in honeybees.     

Hygienic behavior in the honey bee (Apis mellifera L.) and the modulatory role of octopamine

Honey bees, Apis mellifera, which perform hygienic behavior, quickly detect, uncap and remove diseased brood from the nest. This behavior, performed by bees 15-20 days old and prior to foraging, is likely mediated by olfactory cues. Because the neuromodulator octopamine (OA) plays a pivotal role in olfactory-based behaviors of honey bees, we examined whether bees bred for hygienic and nonhygienic behavior differed with regard to their OA expression and physiology. We compared the staining intensity of octopamine-immunoreactive (OA-ir) neurons in the deutocerebral region of the brain, medial to the antennal lobes, between hygienic and nonhygienic bees (based on genotype and phenotype). We also tested how the olfactory responses of the two lines, based on electroantennograms (EAGs), were affected by oral administration of OA and of epinastine, a highly specific OA antagonist. Our results revealed that bees expressing hygienic behavior (irrespective of genotype) possessed OA-ir neurons that exhibited more intense labeling than same-aged bees not performing the behavior. In bees bred for nonhygienic behavior, OA significantly increased the EAG response to low concentrations of diseased brood odor. Conversely, in bees bred for hygienic behavior, epinastine significantly reduced the magnitude of the EAG response, a reduction not observed in nonhygienic bees. Our results provide two lines of evidence that OA has the potential to facilitate the detection and response of honey bees to diseased brood. We discuss the contributions of OA for behavioral shaping and its ability to bias the nervous system to express one form of behavior over another.     

Octopamine and tyramine influence the behavioral profile of locomotor activity in the honey bee (Apis mellifera)

The biogenic amines octopamine and tyramine are believed to play a number of important roles in the behavior of invertebrates including the regulation of motor function. To investigate the role of octopamine and tyramine in locomotor behavior in honey bees, subjects were injected with a range of concentrations of octopamine, tyramine, mianserin or yohimbine. Continuous observation of freely moving worker bees was used to examine the effects of these treatments on the amount of time honey bees spent engaged in different locomotor behaviors such as walking, grooming, fanning and flying. All treatments produced significant shifts in behavior. Decreases in time spent walking and increases in grooming or stopped behavior were observed for every drug. However, the pattern of the shift depended on drug, time after injection and concentration. Flying behavior was differentially affected with increases in flying seen in octopamine treated bees, whereas those receiving tyramine showed a decrease in flying. Taken together, these data provide evidence that octopamine and tyramine modulate motor function in the honey bee perhaps via interaction with central pattern generators or through effects on sensory perception.     

Associative learning and discrimination of motion cues in the harnessed honeybee Apis mellifera L.

We previously studied a conditioning paradigm to associate the proboscis extension reflex (PER) with monochromatic light (conditioned stimulus; CS) in harnessed honeybees. Here, we established a novel conditioning paradigm to associate the PER with a motion cue generated using graphics interchange format (GIF) animations with a speed of 12 mm/s speed and a frame rate of 25 Hz as the CS, which were projected onto a screen consisting of a translucent circular cone that largely covered the visual field of the harnessed bee using two liquid crystal projectors. The acquisition rate reached a plateau at approximately 40% after seven trials, indicating that the bees were successfully conditioned with the motion cue. We demonstrated four properties of the conditioning paradigm. First, the acquisition rate was enhanced by antennae deprivation, suggesting that sensory input from the antennae interferes with the visual associative learning. Second, bees conditioned with a backward-direction motion cue did not respond to the forward-direction, suggesting that bees can discriminate the two directions in this paradigm. Third, the bees can retain memory for motion cue direction for 48 h. Finally, the acquisition rate did not differ significantly between foragers and nurse bees. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Insecticidal and Repellent Activity of Siparuna guianensis Aubl. (Negramina) against Aedes aegypti and Culex quinquefasciatus

This study investigated the toxic effects of essential oils isolated from Siparuna guianensis against Aedes aegypti, Culex quinquefasciatus (eggs, larvae, pupae, and adult) and Aedes albopictus (C6/36) cells. The oviposition-deterring activity, egg viability, and repellence activity in the presence of different essential oils concentrations were determined. The essential oils showed high toxicity to all developmental stages of A. aegypti and C. quinquefasciatus. Furthermore, the oils also showed high repellent activity towards the adult stage of mosquitoes (0.025 to 0.550 μg/cm2 skin conferred 100% repellence up to 120 min) and in contact with cultured insect cells (C6/36) induced death possibly by necrosis. The results presented in this work show the potential of S. guianensis essential oils for the development of an alternative and effective method for the natural control of mosquitoes in homes and urban areas.     

Locomotory behavior of flightless Harmonia axyridis Pallas (Col., Coccinellidae)

To improve the efficiency of the ladybeetle Harmonia axyridis as a biological control agent against aphids, a flightless population was produced by feeding adults with a mutagen and selecting their progeny for non-flying but otherwise morphologically normal individuals. The inability to fly could result from a change in their flying behavior compared with control adults. Flight duration was very much shorter, wing beat frequency and more particularly the amplitude of the wing beats were clearly lower. More time was spent on the other components of flight behavior such as wing rotation, wing immobility and wing folding. The sequence of these patterns differed slightly mainly due to changes in their frequency. The locomotory behavior was not modified by the mutation, which only affected the wing muscles. The searching behavior of mutant adults differed from that of control adults only in that they took longer to encounter and ingest aphids. As this difference is not important, it should be possible to use this flightless population in biological control programs.     

Repellent effectiveness of seven plant essential oils,sunflower oil and natural insecticides against horn flies on pastured dairy cows and heifers

Plant essential oils (basil, geranium, balsam fir, lavender, lemongrass, peppermint, pine and tea tree), mixed with either sunflower oil or ethyl alcohol, were applied at 5% concentrations to the sides of Holstein cattle. Pastured cattle treated with essential oils diluted in sunflower oil had less flies than the untreated control for a 24‐h period. However, the essential oil treatments were not significantly different than the carrier oil alone. Barn‐held heifers treated with essential oils and sunflower oil alone had significantly less flies than the untreated control for up to 8 h after treatment. Basil, geranium, lavender, lemongrass and peppermint repelled more flies than sunflower oil alone for a period ranging from 1.5 to 4 h after treatments applied to heifers. All essential oils repelled > 75% of the flies on the treated area for 6 and 8 h on pastured cows and indoor heifers, respectively. Geranium, lemongrass and peppermint stayed effective for a longer duration. Essential oils mixed with ethyl alcohol demonstrated less repellence than when mixed with the carrier oil. Safer's soap, natural pyrethrins without piperonyl butoxide and ethyl alcohol alone were not efficient at repelling flies. Essential oils could be formulated for use as fly repellents in livestock production.     

Antimicrobial activities of various essential oils against foodborne pathogenic or spoilage moulds

The use of essential oils in the food industry, as natural sanitizing agents, requires the definition of optimal conditions. The aim of the present work was to evaluate some antimicrobial activity parameters as mycelial growth inhibition, minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of six essential oils against Aspergillus niger, Aspergillus terreus,Chaetomium globosum, Penicillium chrysogenum, Penicillium pinophilum, Trichoderma harzianum and Trichoderma viride. The antimicrobial activity of essential oils was monitored by the macrodiluition technique. The mycelial growth inhibition, fungistatic and fungicidal concentrations were recorded for each strain that showed sensitivity to the essential oils. The essential oils of catnip, cinnamon, tea tree and thyme essential oils exhibited a large spectrum antimicrobial activities; those of clary sage and laurel inhibited the mycelial growth in a few fungal strains. The essential oils of cinnamon and thyme had the lowest MIC and MFC values against all the fungi assayed, followed by catnip, tea tree, clary sage and laurel. The use of these natural products rather than, the currently used antifungal chemicals, may be of interest given that: i) essential oils are of natural origin which means they are safer for human health and the environment and ii) there is less chance that the pathogenic microorganisms will develop resistance.     

The influence of essential oils on human attention. I: alertness

Scientific research on the effects of essential oils on human behavior lags behind the promises made by popular aromatherapy. Nearly all aspects of human behavior are closely linked to processes of attention, the basic level being that of alertness, which ranges from sleep to wakefulness. In our study we measured the influence of essential oils and components of essential oils [peppermint, jasmine, ylang-ylang, 1,8-cineole (in two different dosages) and menthol] on this core attentional function, which can be experimentally defined as speed of information processing. Substances were administered by inhalation; levels of alertness were assessed by measuring motor and reaction times in a reaction time paradigm. The performances of the six experimental groups receiving substances (n = 20 in four groups, n = 30 in two groups) were compared with those of corresponding control groups receiving water. Between-group analysis, i.e. comparisons between experimental groups and their respective control groups, mainly did not reach statistical significance. However, within-group analysis showed complex correlations between subjective evaluations of substances and objective performance, indicating that effects of essentials oils or their components on basic forms of attentional behavior are mainly psychological.     

Efficacy of plant essential oils on post-harvest control of rot caused by Botrytis cinerea on kiwi fruits

Antifungal activity of the essential oils of Carum carvi and Pimpinella anisum against Botrytis cinerea fruit rot of key kiwi fruit was studied. In vitro experiments, antifungal activities of essential oils were tested on potato dextrose agar media. Results of an in vitro experiment showed that these essential oils, at all applied concentrations, inhibited grey mould growth. Black caraway essential oil at concentrations of 600 and 800?μL?L^?1 inhibited germination spores of grey mould. Then, the fruits were artificially inoculated with a suspension at 1?×?10⁵?conidia/ml and then treated with different concentrations of these essential oils. The results of in vivo conditions showed that black caraway and anise essential oils applied at all concentrations were increasing the shelf life and inhibited the grey mould growth on kiwi fruits completely in comparison to control. The result showed that black caraway and anise oils at a concentration of 800?μL?L^?1 had higher total soluble solids, ascorbic acid, titrable acidity and antioxidant content compared to untreated fruits.     

Effects of nanostructured essential oils against subterranean termites (Coptotermes gestroi)

Currently, the control of termites is mainly carried out with the use of chemical pesticides, which although effective, pose risks to the environment and to human beings. An alternative to using such chemical pesticides is natural products such as essential oils in insecticidal action. Despite the fact of being effective, essential oils are unstable, poorly soluble in water, and degrade from the action of light, oxygen even at moderate temperatures. Thus, the nanostructuring of essential oils could circumvent such problems and ensure its effectiveness. The following study aimed to assess for the first time the effects of nanostructured systems of essential oils of Cymbopogon flexuosus, Eucalyptus globulus and Melaleuca alternifolia in subterranean termites (Coptotermes gestroi). The results showed that the solid lipid nanoparticles of M. alternifolia have both repellent and insecticide action. The following study showed that nanostructuring of essential oils with insecticidal action is a promising tool in the fight against termites.     

Identification of Bioactive Compounds against Aedes aegypti (Diptera: Culicidae) by Bioassays and in Silico Assays

Most of the hematophagous insects act as disease vectors, including Aedes aegypti, responsible for transmitting some of the most critical arboviruses globally, such as Dengue. The use of repellents based on natural products is a promising alternative for personal protection compared to industrial chemical repellents. In this study, the repellent effect of essential oils extracted from Lippia thymoides, Lippia alba, Cymbopogon winterianus, and Eucalyptus globulus leaves was evaluated. Essential oils used showed repellent activity against Ae. aegypti in laboratory bioassays, obtaining protection rates above 70 % from 3.75 mg/mL and higher concentration for all analyzed oils. GC/MS identified 57 constituents, which were used in the ligand-based pharmacophore model to expose compounds with requirements for repellents that modulate mosquitoes behavior through odorant-binding protein 1 Ae. aegypti. Ligand-based pharmacophore model approach results suggested that repellent activity from C. winterianus, L. alba, and L. thymoides essential oils’ metabolites is related to Citronelal (QFIT=26.77), Citronelol (QFIT=11.29), Citronelol acetate (QFIT=52.22) and Geranil acetate (QFIT=10.28) with synergistic or individual activity. E. globulus essential oil's repellent activity is associated with Ledol (0.94 %; QFIT=41.95). Molecular docking was applied to understand the binding mode and affinity of the essential oils’ data set at the protein binding site. According to molecular docking, Citronelol (ChemPLP=60.98) and geranyl acetate (ChemPLP=60.55) were the best-classified compounds compared to the others and they can be explored to develop new repellents.