Antonios Michaelakis

Coactivity of sulfide ingredients: a new perspective of the larvicidal activity of garlic essential oil against mosquitoes

BACKGROUND The activity of several garlic oil ingredients against Culex pipiens L. larvae was studied. In addition to diallyl sulfide (DS) and diallyl disulfide (DDS), the garlic oils used included one essential oil (EO) and two semi-synthetic garlic essential oils (SSGEO1 and SSGEO2), which resulted from the enrichment of EO with DS and DDS standards respectively. The oils were compared with respect to their toxicity. RESULTS The chemical composition of the tested oils was evaluated by means of gas chromatography-mass spectrometry. Experimental data from the tested samples revealed high toxicity. In detail, DDS (6.09 mg L(-1)) was the most active, followed by SSGEO2 (7.05 mg L(-1)) and EO (8.01 mg L(-1)), while SSGEO1 and DS were relatively inactive. CONCLUSION The addition of DDS to EO did not change the toxic effect of the essential oil, whereas the presence of DS in excess produced an enriched essential oil with low toxicity. Furthermore, the antagonistic effect of DS and DDS against the other components of EO was shown by the application of two equations obtained from the literature. Their larvicidal performances were correlated, for the first time, with their detailed chemical composition. Data analysis strongly indicated the toxicity of the other EO sulfur ingredients.

A Study on Distribution and Seasonal Abundance of Aedes albopictus (Diptera: Culicidae) Population in Athens, Greece

ABSTRACT In September 2008, Aedes (Stegomyia) albopictus (Skuse 1894), a mosquito of great medical importance, was reported for the first time in a district of Athens, Greece. The following year, its distribution and population abundance over time around its first detection site was investigated. A network of 50 ovitraps was established in a surrounding area of 25 km2 and monitored for 17 mo from 17 August 2009 through 31 December 2010. Weekly servicing of the ovitraps and subsequent laboratory treatment of the collected mosquito eggs, revealed that Ae. albopictus is the dominant container breeding Aedes species and is widespread in the entire study area. The seasonal monitoring showed that this mosquito is continuously active from mid spring until the end of December with a considerably high oviposition activity recorded during summer and fall. Moreover, comparison of its activity during late August and end of December, between the two consecutive surveillance years, indicated a significant increase of population abundance the second year. The current study suggests the necessity of setting up in the city of Athens an integrated surveillance program in a greater scale for Asian tiger mosquitos effective control.

Essential oils of Satureja species: insecticidal effect on Culex pipiens larvae (Diptera: Culicidae).

The chemical composition of the essential oils of the wild growing plants of Greek S. spinosa L., S. parnassica subsp. parnassica Heldr.& Sart ex Boiss., S. thymbra and S. montana were determined by GC and GC/MS analysis. The larvicidal activities of the essential oils were assayed against Culex pipiens biotype molestus. The analytical data indicated that various monoterpene hydrocarbons and phenolic monoterpenes constitute the major constituents of the oils, but their concentration varied greatly among the oils examined. The bioassay results indicated that the oils possess significant larvicidal activities and represent an inexpensive source of natural substances mixture that exhibit potentials for use to control the mosquito larvae.

Evaluation of naturally occurring curcuminoids and related compounds against mosquito larvae

The three curcuminoid components commonly isolated from Curcuma longa, curcumin (1), demethoxycurcumin (2), and bis-demethoxycurcumin (3) were separated and isolated from a commercially available turmeric extract product in high purity and sufficient amounts. Three more derivatives of curcumin, the di-O-demethylcurcumin (4), di-O-methylcurcumin (5) and the di-O-acetylcurcumin (6) were also synthesized and characterized. All six compounds were evaluated for their larvicidal effect against the mosquito Culex pipiens. Curcumin (1) exhibited highly potent larvicidal activity with LC(50) value of 19.07mgL(-1). Moreover, di-O-demethylcurcumin (4), was found to be equally active with LC(50) value of 12.42mgL(-1). Based on the LC(90) values of the two compounds, di-O-demethylcurcumin (4) was the most active of all, resulting in an LC(90) value of 29.40mgL(-1), almost half of the LC(90) value 61.63mgL(-1) found for compound 1. The rest of the compounds were inactive at concentrations even as high as 150mgL(-1) indicating a dependence of the larvicidal activity upon the substitution patent and the presence of aromatic hydroxyl and methoxy moieties. These results show for the first time the potential of this valuable natural product regarding its use as vector control agent.

Essential Oils of Umbelliferae (Apiaceae) Family Taxa as Emerging Potent Agents for Mosquito Control

Warm-humid areas around the globe constitute the cradle of humanity, providing their inhabitants the most favorable environments for living and agricultural production. In this “Garden of Eden”, which spreads within the globe’s temperate and tropical zones, is also thriving an annoying but dangerous daemon, the mosquito. This little devil constitutes the main vector of malaria and human encephalitis, both infectious diseases that account as major threats of public health (Becker et al., 2003). Recently, these threats have been spread to a broader geographical area, as a consequence of their vectors (Aedes sp., Anopheles sp. and Culex sp.) introduction into metropolitan areas of northern hemisphere, such as Chicago (Tedesco et al., 2010), New York (Peterson et al., 2006) and Paris (Delaunay et al., 2009). Since mosquito breeding habitats in both urban and rural areas are man-made (Imbahale et al., 2010), there are several restrictions limiting the efforts towards the development of an integrated vector management system. Todate, the history of evolutions of malaria vector interventions is directly connected with the mosquito control tools development, concerning either environmental modifications/manipulations or their chemical and/or biological control (Kilama, 2009).

Prolonged slow release of (Z)-11-hexadecenyl acetate employing polyurea microcapsules

Abstract:  The potential use of polyurea microcapsules, as ‘release carriers’ for insect pheromones, has been demonstrated. (Z)‐11‐hexadecenyl acetate (Z11‐16:Ac), the major sex pheromone component of several Noctuidae species, was used as the model molecule. The coating materials ability to release the pheromone was initially studied by the solid‐phase micro‐extraction technique. Polyurea microcapsules released Z11‐16:Ac relatively slowly, with a duration of approximately 1 month, as it was determined under both laboratory and semi‐field conditions. Preliminary laboratory bioassays revealed a satisfactory attraction of Sesamia males, at doses of 50 and 500 mg of dried microcapsules containing the aforementioned pheromone. Almost all male insects tested initiated flight and among them 40.2–49.4% successfully contacted the pheromone source. The preparation of polyurea microcapsules needs further refinement as to increase release duration; nevertheless, these results demonstrate strong potential for the future use of polyurea microcapsules as part of integrated insect control programmes.

Volatile Secondary Metabolite Pattern of Callus Cultures of Chamomilla recutita

Abstract The effects of various plant growth regulators and culture conditions on the production of volatile secondary metabolites from callus cultures of Chamomile (Chamomilla recutita) inflorescence were investigated and the most efficient conditions were determined. The essential oil composition was assayed by GC-MS analysis and found to contain chamomillol, gossonorol, cubenol, α-cadinol, (-)-α-bisabolol, 1-azulenethanol acetate and (-)-α-bisabolol acetate.

Toxicity of plant essential oil vapours to aphid pests and their coccinellid predators

Abstract The comparative toxicity of five essential oil vapours was tested against four aphid species, the black bean aphid Aphis fabae, the pea aphid Acyrthosiphon pisum, the chrysanthemum aphid Macrosiphoniella sanborni, the green peach aphid Myzus persicae and on two of the most common coccinellid predators, the seven-spotted ladybird Coccinella septempunctata and the two-spotted ladybird Adalia bipunctata. All essential oils were highly toxic to the aphid species tested with LC50 and LC99 values ranging between 0.17 and 1.92 and 0.44 and 4.83 µL/L air, respectively, depending on the aphid species and on the essential oil. Coccinellid predators were also highly susceptible to the essential oil vapours and the selective toxicity ratio varied depending on aphid species, coccinellid predator and essential oil. The possibilities for the utililization of essential oils as aphicides, especially in IPM programmes in glasshouses are discussed with regard to the present findings.

Lures for red palm weevil trapping systems: aggregation pheromone and synthetic kairomone.

BACKGROUND The optimisation of the lure is essential for the implementation of trapping systems to control insect pests. In this work, the response of the red palm weevil (RPW), Rhynchophorus ferrugineus Olivier, to increasing emission rates of its aggregation pheromone (ferrugineol) and the efficacy of a convenient synthetic kairomone based on fermentation odours (ethyl acetate and ethanol) have been evaluated in different years and locations along the Mediterranean basin. RESULTS In general, although capture data and emission had noticeable variability among locations, significantly fewer RPW were captured in pyramidal Picusan® traps with the lowest ferrugineol emission rates tested (0.6-3.8 mg day-1 ). Captures increased rapidly with ferrugineol emission up to 4-5 mg day-1 ; then, higher emission rates did not improve or reduce captures, up to the highest emission rate tested of 50.9 mg day-1 . Thus, there is no evidence of an optimum release rate corresponding to a maximum of RPW catches. Traps baited with the synthetic kairomone (1:3 ethyl acetate/ethanol) captured 1.4-2.2 times more total weevils than traps baited only with ferrugineol. Moreover, in most of the locations, the synthetic blend was at least as effective as the local coattractants used (plant material + molasses). CONCLUSIONS Ferrugineol emission rate can vary in a wide range without significantly affecting RPW response. Coattractants based on fermenting compounds, ethyl acetate and ethanol, are able to improve the attractant level of ferrugineol and could be employed to replace non-standardised natural kairomones in RPW trapping systems after further optimisation of their proportions and doses.

Main Arthropod Pests of Citrus Culture and Pest Management in Greece

The key arthropod pests in the citrus producing areas in Greece comprise the Mediterranean fruit fly Ceratitis capitata, the California red scale Aonidiella aurantii and the citrus mealybug Planococcus citri. Outbreaks of the whiteflies Aleurothrixus floccosus and Dialeurodes citri, the scales Ceroplastes rusci and Saissetia oleae as well as the Tetranychidae mites Panonychus citri and Tetranychus urticae and the Eriophyiidae mites Aculops pelekassi and Aceria sheldoni may occur locally. The citrus leafminer Phyllocnistis citrella, aphids (Aphis spiraecola, A. gossypii, Toxoptera aurantii) and thrips (Heliothrips haemorrhoidalis, Pezothrips kellyanus) are of minor importance. The problems due to major and minor citrus pests and control measures in Greece are reviewed and Integrated Pest Management (IPM) strategies are recommended.