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Insecticidal effect of oregano (Origanum vulgare L. ssp. hirtum Ietswaart) on bean weevil (Acanthoscelides obtectus Say)
Published June 6, 2001
84-88.

The effectiveness of drug plant and of essential oil of oregano (Origanum vulgare L. ssp. hirtum Ietswaart) against the adults and egg hatching of bean weevil (Acanthoscelides obtectus Say) was studied in laboratory trials in order to screen for a new potential insecticide in the control of this granary pest ...of beans. The adult mortality as well as oviposition and hatching capabilities were evaluated after 6 days of treatment of beans cv. `Berggold' (55 g) in Petri dishes by powdered drug (0.33 g, 0.66 g, 1.0 g and 2.0 g) and by equivalent amounts of essential oil (5 ill, 10 15 ill and 30 ill). Oregano essential oil showed both fumigant and contact toxicities to bean weevil, the later being more potent. When considering fumigant toxicity, insecticidal effect (mortality rate 82.5%) was observed 6 days after application of high concentrations of oregano essential oil (150 Al per 55 g of beans). When considering contact toxicity, both oregano drug plant and essential oil at all tested concentrations significantly increased the bean weevils' mortality rates with comparison to the controls. Also, egg laying and hatching were inhibited after treatment of bean weevil with powdered drug plant or with essential oil at all tested concentrations. Insecticidal effect of drug plants issuing from two different stocks depended on their essential oil contents. Essential oils (5 pi, 15 pi and 30 IA per 55 g of beans) induced 100% mortality of bean weevil population when applied directly to the surface of beans (55 g) in Petri dishes. The content of essential oil in oregano and oregano-based preparations for insecticidal use is proposed as a parameter for quality control purposes.

 

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Evaluation of essential oils by gas-chromatography and a new method: "electronic nose"
Published March 21, 2001
85-89.

The chemical quality of the essential oils is determined by their composition as well as by the complex aroma features. For the evaluation of odour and aroma, sensory tests are practised, especially for applications such as aromatherapy, food industry or perfumery. In the recent studies we investigated eight Mentha origins (populations... of Mentha iperita, M. spicata and M. arvensis) of our genebank collection using a new and effective instrumental sensory evaluation method parallelly with the usual GC analysis.

The results show that the examined mint clones possess different essential oil accumulation levels and special flavour characteristics, too. The GC analysis of the essential oil revealed characteristic differences at both inter- and intraspecific level in the proportion of mentol, menthon, carvon, limonene, menthyl acetate and in two not identified monoterpenes.

In the sensory tests the special complex aroma enables a reliable distinction with a single exception among the populations by the help of the "electronic nose" equipment. The distinction among the samples based on the sensor signals of the instrument — evaluated by multivariate methods — shows a close relation with the detected monoterpene components of the essential oil.

 

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Effect of different treatments to bacterial canker (Clavibacter michiganensis subsp. michiganensis), bacterial speck (Pseudomonas syringae pv. tomato) in tomato, and bacterial spot (Xanthomonas campestris pv. vesicatoria) in pepper
Published May 15, 2007
49-53.

In ecological farming systems farmers can't use chemicals against pests. In ecological plant protection the aim is to prevent diseases; if it is not possible the use of allowed materials are permitted. Until now there haven't been enough effective and environmental friendly materials for seed treatment in organic farming. Seed borne diseases of... tomato and pepper can cause serious losses in yield, so finding appropriate inhibitors has a great importance. Different materials were tested against these bacterial strains for seed treatment in this study. In vitro trials have shown that vinegar, cider vinegar, red wine vinegar and white wine vinegar have inhibiting effect against the causative agent of bacterial canker (Clavibacter michiganensis subsp. michiganensis), bacterial speck (Pseudomonas syringae pv. tomato) of tomato. These materials also have inhibiting impact on the causative agent of bacterial spot of pepper (Xanthomonas campestris pv. vesicatoria). Seed treatment with (natural alkaline material) sodium hydrogen carbonate (NaHCO3) had no effect on the examined bacterial strains. Among examined essential oils cinnamon oil seemed to be the most effective, but all oils decreased the germination ability. Thyme and savory teas were effective against Pseudomonas syringae pv. tomato. Other examined materials had insufficient bactericide impact (sucrose, NaCI, ethanol, valerian extract, peppermint tea). The germination test has shown that examined vinegar types don't decrease germination ability.

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Evaluation of supercritical plant extracts on volatile and non volatile biologically active lipophil components
Published June 6, 2001
78-83.

Authors dealt more than ten years with the analysis of supercritical extracts. For extraction (SFE) carbon dioxide was used as supercritical solvent. Fractionation of extracts was carried out by releasing the separations pressure at two stages. The extracts were collected as separate samples successively in time.

The traditional extract...ions were carried out with steam distillation or by using n-hexane and ethanol in Soxhlet apparatus. For the analysis of volatile compounds GC, GC-MS; of non volatile compounds TLC-densitometry and spectroscopic methods were used.

The following general characteristics were established comparing the composition of steam distillated oils with that of volatile SFE fractions. The SFE fractions were richer in monoterpene-esters and poorer in alcohols than the essential oils prepared by traditional way (clary sage, lavandel). Regarding the distributi,n of the monoterpene and sesquiterpene compounds, the SFE fractions contained sesquiterpene hydrocarbon in higher percentage than the distillated oils (e.g. 13-caryophyllene in Salvia fruticosa, (3-caryophyllene, y­muurolene, y-cadinene in Ochnum basilicum). Further the proportion of sesquiterpenes increased in SFE fractions collected successively in time.Significant difference was remarkable in respect of the optical rotationability of lovage oil and SFE fraction which was probably caused by the different ratio between the two ligustilid enantiomers. It was verified in some cases that a part of mono- and sesquiterpenes were present originally in a bounded form (glycosides) in plants. Therefore they appeared in essential oil fractions only after previous acidic treatment (Thymus, Origanum species). During the supercritical extraction the azulenogene sesquiterpene lactones did not transform to azulenes (in chamomile, yarrow), but the non volatile SFE fractions of some Asteraceae plant contained sesquiterpene--lacton of unchanged structure in high quantity (e.g. cnicin in blessed thistle, parthenolide in feverfew). Authors obtained also SFE fractions which were rich in triterpenoids and phytosterols (marigold, common dandelion).

 

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