Insecticidal and feeding deterrent activities of essential oils in the cabbage looper,Trichoplusia ni (Lepidoptera: Noctuidae)

Ten essential oils were tested against the cabbage looper, Trichoplusia ni larvae for contact, residual and fumigant toxicities and feeding deterrent effects. Against third instar T. ni, Syzygium aromaticum (LD₅₀ = 47.8 μg/larva), Thymus vulgaris (LD₅₀ = 52.0 μg/larva) (the two positive controls) and Cinnamomum glanduliferum (LD₅₀ = 76.0 μg/larva) were the most toxic via topical application. Litsea pungens (LD₅₀ = 87.1 μg/larva), Ilex purpurea (LD₅₀ = 94.0 μg/larva), Cinnamomum cassia (LD₅₀ = 101.5 μg/larva) and Litsea cubeba (LD₅₀ = 112.4 μg/larva) oils were equitoxic. Thymus vulgaris (LC₅₀ = 4.8 mg/ml) and S. aromaticum (LC₅₀ = 6.0 mg/ml) oils were the most toxic in residual bioassays. Cymbopogon citratus (LC₅₀ = 7.7 mg/ml) and C. cassia (LC₅₀ = 8.5 mg/ml) oils were equitoxic followed by Cymbopogon nardus (LC₅₀ = 10.1 mg/ml) in this bioassay. The remaining five oils showed little or no residual effects. In a fumigation bioassay, L. cubeba (LC₅₀ = 16.5 μl/l) and I. purpurea (LC₅₀ = 22.2 μl/l) oils were the most toxic. Cinnamomum glanduliferum (LC₅₀ = 29.7 μl/l) and Sabina vulgaris (LC₅₀ = 31.2 μl/l) oils were equitoxic. Interestingly, S. aromaticum did not exhibit any fumigant toxicity. Cymbopogon citratus, C. nardus and C. cassia strongly deterred feeding by third instar T. ni (DC₅₀s = 26.9, 33.8 and 39.6 μg/cm², respectively) in a leaf disc choice bioassay. The different responses of T. ni larvae to the oils in different bioassays suggest that these essential oils exhibit different modes of action. Based on their comparable efficacy with essential oils already used as active ingredients in many commercial insecticides (i.e. clove oil and thyme oil), some of these essential oils may have potential as botanical insecticides against T. ni.     

Sublethal effects of chlordimeform on chemical communication and other reproductive behaviors in the female cabbage looper moth (Lepidoptera: Noctuidae)

Insecticides can affect the complex coordination of activities associated with reproduction through their sublethal impact on the nervous system. Our objective was to document the effects of a sublethal dose (1% mortality) of chlordimeform on reproductive events in the female cabbage looper moth, Trichoplusia ni. A significantly higher percentage of females treated with chlordimeform initiated calling at some time during the scotophase. Chlordimeform stimulated pheromone emission early in the scotophase. However, late in the scotophase pheromone emission was significantly lower in chlordimeform-treated females when compared with control females. Overall, a lower amount of pheromone was detected in glands of chlordimeform-treated females. This effect was significant only during the second half of the scotophase. We suggest that chlordimeform stimulates pheromone transport to the gland surface and calling behavior resulting in depletion of pheromone reserves over the course of the scotophase. Chlordimeform also decreased the mating success of males. Oviposition and egg hatch were also affected by chlordimeform. Mated females treated with chlordimeform laid significantly fewer eggs than acetone-treated females. In addition, hatchability of eggs laid by mated female T. ni treated with chlordimeform was significantly lower than for eggs laid by control females.     

Circadian changes in melatonin in the nervous system and hemolymph of the cabbage looper moth,Trichoplusia ni

Quantitative levels of melatonin and 5-hydroxytryptamine were measured over the scotophase in the protocerebrum, subesophageal ganglion, optic lobes, thoracic ganglia, and hemolymph of adult male cabbage looper moths, Trichoplusia ni, using HPLC with electrochemical detection. Melatonin levels were very low (s < 1 pmol) or undetectable during the photophase, but increased in all tissues during the dark. Lowest mean levels in the dark were observed in the optic lobes (0.3 to 0.7 pmols). Maximal mean levels in the protocerebrum (5.2 pmols) occurred in the early part of the scotophase, but in all other tissues (2.8 in the subesophageal ganglion; 9.5 in thoracic ganglia) and hemolymph (18 pg/l) maximal mean levels were observed later in the dark. Levels of 5-hydroxytryptamine in each tissue, in contrast, were higher than melatonin levels in the photophase, and in the protocerebrum and thoracic ganglia decreased during the dark, but in the optic lobes and subesophageal ganglion remained unchanged. Further, decreases in 5-hydroxytryptamine during the dark were significantly lower than the increased levels of melatonin, suggesting that active synthesis of 5-hydroxytryptamine was occurring. In a second experiment, when measured from individuals in three different photoperiods (618, 1212, 186 lightdark) maximum mean melatonin levels in the brain (protocerebral and subesophageal ganglia) peaked within the first 1.5 h of the dark and remained at measurable levels for the duration of the dark. In a third experiment, levels of melatonin in the brain and thoracic ganglia displayed rhythmicity in continuous dark conditions but not in continuous light, when compared with profiles obtained in a normal light dark regime.Abbreviations CNS Central nervous system - HPLC-ECD high performance liquid chromatography with electrochemical detection - MEL melatonin - 5HT 5-hydroxytryptamine - N-ac-SHT N-acetyl-5-hydroxytryptamine     

Environmental factors affecting chemical variability of essential oils in Thymus piperella L.

Environmental factors affecting essential oils variability in Thymus piperella L. are studied. The relationship between the bioclimatics index and edaphic factors with three chemotypes is determined through the application of multivariate analysis (CANOCO) and other statistical processes to both ecological and the essential oil data set components. Chemotype p-cymene γ-terpinene carvacrol shows a positive relationship with the aridity index (I_a) and Altitude. The p-cymene thymol chemotype is related to factors affecting water balance in both the soils and plants. The influence of climatic factors over p-cymene carvacrol is less evident. The compound p-cymene, common to the three chemical groups and the most abundant of all, presents positive correlation with the organic matter in the soil.     

Properties of the Δ11-desaturase enzyme used in cabbage looper moth sex pheromone biosynthesis

The biosynthesis of a large number of sex pheromone components of various moth species can be explained by invoking a Δ 11-desaturation of common fatty acids. A Δ11-desaturase system from Trichoplusia ni, the cabbage looper moth, is identified and partially purified. Some of its properties are defined and compared with those of the ubiquitous Δ-9 desaturase enzyme. Similarities between the two systems include subcellular location (microsomal), substrate specificity (16- and 18-carbon acids), and lack of sensitivity to carbon monoxide, while differences include cofactor preference (NADH rather than NADPH), sensitivity to cyanide ion, pH optimum (7.4-7.8 vs 6.8-7.2), and location in the organism (in the pheromone gland compared to generally distributed). The effects of insect age were also investigated.     

Effects of infection with a granulosis virus on larval growth, development and ecdysteroid production in the cabbage looper, Trichoplusia ni

ABSTRACT. Granulosis virus-infected Trichoplusia ni (Hûbner) larvae exhibited an increased larval life span with no supernumerary moult and no pupation. Weight gain was not affected. Insects infected shortly after hatching were slower in reaching the fourth and fifth stadia than were control insects. Haemolymph ecdysteroid titres were lower in virus-infected insects than control insects, but these differences were only significant ( P <0.05) in the fifth stadium. Electron microscopic examination of the pro thoracic glands revealed extensive granulosis virus infection, and glands from virus-infected insects produced no RIA-detectable ecdysteroids in vitro. Injection of 20-OII-ecdysone into virus-infected larvae at various concentrations and times did not induce pupation.     

Functional organization of the macroglomerular complex related to behaviourally expressed olfactory redundancy in male cabbage looper moths

Abstract. The neurophysiological bases for behaviourally expressed olfactory redundancy in the sex pheromone communication system of the cabbage looper moth, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae), were examined by coupling the cut-sensillum extracellular recording technique with a highly specific neuronal marking method for moth peripheral receptors. In seventy-two antennal sensilla, axonal pathways of cobalt-stained neurones could be traced into the male-specific macroglomerular complex in the antennal lobe. In T. ni males this comprises five glomeruli, two of which are subdivided into morphologically, and in some instances functionally identifiable, regions. Axonal arborizations of forty-eight neurones (single stainings) showed high fidelity (98%) for containment within a specific glomerulus or glomerular subdivision, and the neuropil targeted seemed to be related to the specificity of a neurone to a particular female-emitted sex pheromone component (27-12:Ac, Z7-14:Ac, Z9-14:Ac, 12:Ac, 11–12:Ac, Z5-12:Ac), or to a behavioural antagonist (Z7-12:OH). Double (twenty-one) and multiple stainings (three) showed axons projecting into two or more glomeruli, respectively, with 100% fidelity for the component-specific glomerulus or glomerular subdivision to be targeted. We suggest that the potential for a single minor component to cross-stimulate two or more neurones within a sensillum may enable partial blends to continue to provide sensory input into all of the pheromone-processing glomeruli of the complex. Our interpretation is that redundancy occurs at the receptor level on neighbouring dendrites, and thus allows various four-component partial blends to evoke full pheromone-mediated behaviour.     

Effects of natural and synthetic neuroactive substances on the growth and feeding of cabbage looper, Trichoplusia ni

In this study we investigated the effects of two naturally occurring beta-carboline alkaloids and two synthetic tricyclic antidepressants on the growth and food consumption of fifth instar larvae of the cabbage looper, Trichoplusia ni Hübner (Lepidoptera: Noctuidae). In artificial diets at high concentrations (3,000 ppm), harmane, amitriptyline, and imipramine reduce growth and feeding; harmane reduced feeding consistently at a lower concentration (200 ppm). In animals other than insects, beta-carboline alkaloids inhibit monoamine oxidase (MAO) activity and thus affect rates of disposition of serotonin and other monoamine neurotransmitters. Because brain serotonin levels are associated with variation in rates of carbohydrate and protein intake in insects, the effects of beta-carboline alkaloid ingestion on dietary self-selection behavior were examined. Choosing between diets lacking carbohydrate but containing protein and diets lacking protein but containing carbohydrate, larvae consumed a greater proportion of diet containing protein but lacking carbohydrate in the presence of harmane than in its absence. These results are consistent with beta-carboline alkaloid-mediated persistence of serotonin in the brain due to MAO inhibition. Alternatively, these results could reflect alkaloid-mediated peripheral inhibition of sucrose taste receptors influencing ingestive behaviors. That beta-carboline alkaloid ingestion is associated with changes in feeding behavior is consistent with a possible defensive role for these compounds in plant foliage.     

Effect of essential oils on pathogenic and biofilm-forming Vibrio parahaemolyticus strains

Abstract

In this study, the effect of three essential oils (EOs) – clove oil (CO), thyme oil (TO), and garlic oil (GO), which are generally recognized as safe – on the planktonic growth, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), motility, biofilm formation, and quorum sensing (QS) of Vibrio parahaemolyticus was investigated. All three EOs showed bacteriostatic activity, with MICs in the range 0.02%–0.09% (v/v). CO and TO completely controlled planktonic growth at 0.28% and 0.08% (v/v), which is four times their MIC (4?×?MIC), after 10?min, whereas GO completely controlled growth at 0.36% (v/v) (4?×?MIC) after treatment for 20?min. V. parahaemolyticus motility was significantly reduced by all three EOs at 4?×?MIC (0.28% for CO, 0.08% for TO, and 0.36% for GO), whereas QS was controlled and biofilm formation reduced by all three EOs at 8?×?MIC (0.56% for CO, 0.16% for TO, and 0.72% for GO) after 30?min of treatment. These results suggest that CO, TO, and GO have a significant inhibitory effect on V. parahaemolyticus cells in biofilm sand thus represent a promising strategy for improving food safety. These results provide the evidence required to encourage further research into the practical use of the proposed EOs in food preparation processes.     

Effect of sealing and Tween 80 on the antifungal susceptibility testing of essential oils

Concentrations of essential oils showing high volatility decreased substantially in broth and agar media when incubated under open conditions. The decrease in the half life was from 0.7 to 38 hr in broth medium at 27 C. When evaporation was prevented by sealing, MIC values against Aspergillus fumigatus, Candida albicans and Trichophyton mentagrophytes by broth or agar dilution assay were lowered two to eight-fold, as compared with those obtained under open conditions. Addition of Tween 80 caused a rise of the MICs against A. fumigatus by two to four-fold in broth dilution assay, but little affected the MICs in agar dilution assay.     

粤北阴香不同器官中精油成分研究

采用水蒸汽同步蒸馏法分别对采自粤北的阴香的果、叶、枝条提取精油,并用气质联用仪对所提取的精油进行了成分分析和鉴定。共鉴定了41种成分,主要成分为龙脑（68．5％～73．8％）、芳香醇、丁子香烯、橙花叔醇、榄香烯、柠檬醛、莰烯、葑醇、愈创烯、香叶烯、枞萜、萜品醇、蒎烯等。阴香不同器官（果、叶、枝）中的精油成分及所占比例均有差异。     

The effect of host plant species on performance and movement behaviour of the cabbage looper Trichoplusia ni and their potential influences on infection by Autographa californica multiple nucleopolyhedrovirus

• 1 Cabbage loopers Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) are serious pests in greenhouses growing tomatoes, cucumbers and bell peppers. A potential microbial control, now in development, is the broad host‐range virus Autographa californica multiple nucleopolyhedrovirus (AcMNPV).
• 2 The relationships between the three host plants and the feeding behaviour, larval movement and performance of cabbage looper larvae that might relate to their interaction with AcMNPV applications were investigated.
• 3 Larvae reared on cucumber plants consumed approximately ten‐fold more leaf area than larvae reared on pepper plants and almost five‐fold more than larvae reared on tomato plants. This could influence the amount of AcMNPV consumed if it were used as a microbial spray because increased consumption can be associated with increased probability of infection. Survival from neonate to pupa also varied, with the greatest being on cucumber, followed by tomato and pepper plants. Larvae fed cucumber were approximately four‐fold heavier than larvae fed tomato and over 15‐fold heavier than larvae fed pepper plants.
• 4 The distribution of larvae on plants in commercial greenhouses where a single crop was being grown also varied with food plant with 73% being found on the bottom and middle portions of tomato plants and 87% occurring in the top portions of pepper plants. Larvae tended to be distributed on the middle portion of cucumber plants, the lower portion of tomato plants and the top portion of pepper plants. Larval movement did not vary between AcMNPV‐infected and uninfected controls.
• 5 It is predicted that the higher leaf area consumption and location of larvae in the middle portion of cucumber plants may make them more susceptible to viral sprays. Furthermore, given their greater survival than larvae fed tomato and pepper, there may be a greater need for virus applications.

     

Modulatory effects of octopamine and serotonin on male sensitivity and periodicity of response to sex pheromone in the cabbage looper moth,Trichoplusia ni

The pheromone-mediated flight behavior of male cabbage looper moths in a sustained-flight tunnel and random activity exhibited during scotophase were observed after males were treated with octopamine or serotonin (5 hydroxytryptamine). Octopamine induced a hypersensitivity to the olfactory signal, resulting in a significant lowering of the pheromone dose that elicited peak levels of response. Octopamine, however, did not affect the circadian rhythmicity of response to pheromone. In contrast, serotonin disrupted the circadian rhythmicity of response, resulting in a high percentage of males exhibiting random activity and response to pheromone throughout the entire 8 h scotophase instead of during the normal peak period during the latter part of the scotophase. Serotonin did not effect a decrease in the dose of pheromone eliciting peak response. In addition, at the highest dosages tested octopamine and serotonin induced opposite postures associated with a paralysis that occurred when males attempted to take flight to the pheromone.     

Yield,chemical composition,and bioactivity of essential oils from 12 species of Eucalyptus on Aedes aegypti larvae

The insecticidal activity of essential oils from 12 species of Eucalyptus (Myrtaceae) was evaluated on larvae of Aedes aegypti (L.) (Diptera: Culicidae), the most important vector of dengue and yellow fever in the Americas. Oils were obtained by hydrodistillation and their chemical composition was determined by gas chromatography coupled to mass spectrometry; yields ranged from 0.2 to 2.5%. Essential oils were mainly composed of 1,8‐cineole, α‐pinene, α‐phellandrene, β‐phellandrene, γ‐terpinene, 4‐terpineol, α‐terpineol, p‐cymene, and spathulenol. Larvicidal effects were tested on susceptible third or fourth stage Ae. aegypti larvae, determining median lethal concentration (LC₅₀) and median effective concentration (EC₅₀). Essential oils from Eucalyptus dunnii (Maiden), Eucalyptus gunnii (Hook), Eucalyptus tereticornis (Smith), Eucalyptus camaldulensis (Dehn), and Eucalyptus saligna (Smith) showed the best larvicidal activities with LC₅₀ values of 25.2, 21.1, 22.1, 26.8, and 22.2, respectively. No significant differences were observed between LC₅₀ and EC₅₀ values of the same oil. Regression analysis revealed a significant relationship between total essential oil yields and 1,8‐cineole concentration. Significant relationships were also revealed between larval mortality and the concentration of 1,8‐cineole and p‐cymene. This indicated that Eucalyptus species with high oil yields have higher 1,8‐cineole concentrations and lower p‐cymene concentrations and have less effect on Ae. aegypti. Our results suggest the potential of controlled crossing methods to obtain Eucalyptus trees with chemical profiles having enhanced activity against this mosquito.     

Effect of a nuclepolyhedrovirus of Autographa californica expressing the enhancin gene of Trichoplusia ni granulovirus on T. ni larvae

A recombinant Autographa californica nucleopolyhedrovirus (AcMNPV) strain showing higher virulence against Trichoplusia ni larvae than the wild-type virus was developed. The 'enhancin' (VEF) gene of T. ni granulovirus (TnGV) and the AcMNPV polyhedrin gene were cloned into the baculovirus transfer vector pAcUW31. This plasmid and AcMNPV BacPAK6 DNA were co-transfected into the BTI-Tn5B1-4 cell line. A recombinant AcMNPV strain (BacVEFPol) was purified, amplified, and bioassayed against T. ni first instar larvae. Its estimated LC₅₀ (0.184 OB/mm²) was 2.18 times lower than the LC₅₀ estimated for the wild-type AcMNPV (0.402 OB/mm²). Likewise, an LT₅₀ of 67.7 h was estimated for the recombinant AcMNPV strain while the LT₅₀ of wild-type AcMNPV was estimated at 81.9 h. This indicates a 17.4% reduction of the time required to kill the larvae. The higher virulence of the recombinant strain, evidenced by its LC₅₀ and LT₅₀ values being lower than those of the wild-type strain, indicates that the VEF protein is expressed properly and may be occluded in the OBs.     

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.     

Variations in the essential oils of Tanacetum vulgare

The essential oil content of Hungarian samples of Tanacetum vulgare varies from 0.02 to 0.66% and exhibits a heterogeneous distribution indicating genetic variation. The rotatory power of the essential oil is also widely divergent and plants containing laevo-rotatory essential oils mainly occur in large numbers in the region east of the Tisza. The essential oil composition of wild plants remained constant during their cultivation. 26 different chemoforms have been found so far in Hungary. Individuals and populations containing artemisia ketone and umbellulone as their main components are the most frequent.     

The inhibitory effect of essential oils on herpes simplex virus type-1 replication in vitro

The antiviral effect of 12 essential oils on herpes simplex virus type-1 (HSV-1) replication was examined in vitro. The replication ability of HSV-1 was suppressed by incubation of HSV-1 with 1% essential oils at 4 C for 24 hr. Especially, lemongrass completely inhibited the viral replication even at a concentration of 0.1%, and its antiviral activity was dependent on the concentrations of the essential oil. When Vero cells were treated with the essential oil before or after viral adsorption, no antiviral activity was found, which suggests that the antiviral activity of essential oils including lemongrass may be due to the direct interaction with virions.     

Changeability in Retama raetam essential oils chemical composition,antioxidant and antimicrobial properties as affected by the physiological stage

Abstract

Retama raetam essential oils (EOs) composition and biological activities were assessed during three developmental periods. The essential oil yield varied significantly among the developmental stages and the optimal was detected at the fresh fruiting stage (0.34%). In addition, EOs composition varied significantly (p < 0.05) according to the different developmental stages. In fact, 2-Methoxy-4-vinylphenol, linalool, and 1-octen-3-ol were the main compounds in the vegetative, flowering, and the fresh fruiting stages, respectively. Developmental stage had also a strong effect on EOs antioxidant and antimicrobial activities. In fact, during the fresh fruiting stage, IC₅₀ and EC₅₀ values of the antioxidant assays were 2 to 3 times inferior to all others stages. Concerning the determination of the diameter of inhibition, a slight to high antimicrobial activity was revealed against 12 bacteria and 4 yeasts. Once again, EOs from the fresh fruiting stage had higher bactericidal effect than those from the flowering and vegetative ones (IZ varied from 10 to 13 mm). The results of this investigation showed for the first time the high accumulation of EOs at the early stages of fruit development making the fresh fruiting optimal stage for the extraction of powerful antioxidant and antimicrobial EOs.     

The antimicrobial activity of four commercial essential oils in combination with conventional antimicrobials

Aims:  Due to the emergence of multi-drug resistance, alternatives to conventional antimicrobial therapy are needed. This study aims to investigate the in vitro pharmacological interactions between essential oils (considered valuable as natural therapeutic treatments) and conventional antimicrobials (ciprofloxacin/amphotericin B) when used in combination.
Methods and Results:  Interactions of the essential oils ( Melaleuca alternifolia , Thymus vulgaris , Mentha piperita and Rosmarinus officinalis ) when combined with ciprofloxacin against Staphylococcus aureus indicate mainly antagonistic profiles. When tested against Klebsiella pneumoniae the isobolograms show antagonistic, synergistic and additive interactions depending on the combined ratio. The R. officinalis/ ciprofloxacin combination against K. pneumoniae displayed the most favourable synergistic pattern. The interactions of M. alternifolia (tea tree), T.   vulgaris (thyme), M. piperita (peppermint) and R. officinalis (rosemary) essential oils with amphotericin B indicate mainly antagonistic profiles when tested against Candida albicans.
Conclusion:  While a number of interactions show complete antagonism, others show varied (synergistic, additive and/or antagonistic) interactions, thus the efficacy is dependent on the ratio in which the two components co-exist.
Significance and Impact of the Study:  The predominant antagonistic interactions noted here, suggests that some natural therapies containing essential oils should be used with caution when combined with antibiotics.