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  • Author or Editor: S. F. Fahim x
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The chemical composition of essential oil extracted from leaves of the medicinal plant Mentha longifolia (L.) Huds growing in Egypt, were determined through Gas Chromatography/Mass Spectrometry ( GC/MS). The analyses revealed that the major component of M. longifolia was Monterpene ketone (piperitone oxide). Mentha longifolia was potent for the pest Tetranychus urticae Koch with a significant increase in repellency. In addition, it exhibited strong oviposition deterrence to the pest based on a 99.4% reduction of the total number of eggs on leaf discs treated with the oil. The LC50 values of M. longifolia against eggs, nymphs and females of T. urticae by fumigant application, were 2.95, 3.47, 3.74 μL / L, while the LC90 values were 8.99, 9.41, 11.01 μL/ L, respectively.

The toxicity of M. longifolia oil by fumigant application to females and eggs of 3 predatory phytoseiid mites was tested. Neoseiulus californicus (McGregor) is extremely insusceptible to M. longifolia oil than the pest T. urticae and both phytoseiid mites, Neoseiuls barkeri (Hughes) and Typhlodromips swirskii (Athias Henriot) under laboratory conditions. When both stages of tested predatory mites, exposed to fumigant of LC50 and LC90 μL/L values reported on T. urticae, female’s mortality of N. californicus was lesser than that reported on N. barkeri and T. swirskii.

These show that the fumigant toxicity of M. longifolia oil has the highest lethal activity to the pest T. urticae and the least to the predatory mite N. californicus. Results indicated that the mode of delivery of the essential oil was largely a result of action in the vapor phase via respiratory system. Data was suggested that M. longifolia oil have the potential agent to be used in the maintainable management of T. urticae combined with N. californicus.

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The toxicity of Melissa officinalis L. essential oil and its formulation (Melissacide) were evaluated against eggs and females of two predatory phytoseiid mites, Typhlodromips swirskii (Athias Henriot) and Neoseiulus barkeri (Hughes), using direct spray. Results indicate that both tested materials were potent on predatory females than egg stage. Typhlodromips swirskii was proved to be more sensitive to the oil and formulation than N. barkeri.

Females mortality were (62-100%) in T. swirskii, and (46-69%) in N. barkeri, when both predatory mites were sprayed with LC50 and LC90 of the oil and Melissacide reported on Tetranychus urticae Koch. Females of both predators were suffered from reduction in food consumption when sprayed with two sublethal concentrations of Melissacide, while insignificant differences reported in daily number of eggs deposited by females of T. swirskii, when sprayed with its LC25 value of Melissacide and control.

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The deterrent and toxicity effects of Melissa officinalis L. essential oil on Tetranychus urticae Koch were studied under laboratory conditions. Leaf discs treated with increasing concentrations of lemon balm oil showed high percentage of repellency (64–86%), respectively. The oviposition deterrent indices (ODI) of Melissa oil was ranged (74–94%) for T. urticae at concentration (0.3–1%). The direct contact application of M. officinalis oil proved to be the most toxic application on various stages of T. urticae compared to leaf dipping, fumigation and systemic applications. Oil formulation (Melissacide) was shown to be the effective one against T. urticae nymphs, females and eggs (LC50 = 0.03, 0.03 and 0.04%) compared to Melissa oil.The toxicity of M. officinalis oil and Melissacide by direct spray to females and eggs of the predatory mite Neoseiulus californicus (McGregor) was tested. The predator N. californicus is extremely less sensitive to Melissa oil and Melissacide than the pest T. urticae in the laboratory. When N. californicus was sprayed with (LC50 and LC90 values reported on T. urticae), females mortalities ranged between 8.5–13%, respectively. Melissacide is non-persistent in the environment due to its volatile nature. No phytotoxicity was observed in bean plant after four weeks of Melissacide treatment.Results obtained chemically from M. officinalis oil, may suggest that the higher percentage of benzene, 1(1,5dimethyl-4hexenyl)4methyl (= α-curcumene), caryophyllene oxide, ëCadinol and cedrene of the oil could be responsible for the toxic effect.

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