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The repellency and toxicity effects of essential oils from the Libyan plants Salvadora persica and Rosmarinus officinalis against nymphs of Ixodes ricinus

Elmhalli, Fawzeia, Garboui, Samira S., Borg-Karlson, Anna-Karin, Mozūraitis, Raimondas, Baldauf, Sandra L., Grandi, Giulio
Experimental & applied acarology 2019 v.77 no.4 pp. 585-599
Ixodes ricinus, Rosmarinus officinalis, Salvadora persica, acarology, acetone, alpha-pinene, beta-pinene, bioassays, cineole, essential oils, exposure duration, gas chromatography-mass spectrometry, leaves, lethal concentration 50, mortality, nymphs, oils, rosemary, tick control, ticks, toxicity
Essential oils extracted from the leaves of Libyan Rosemary (Rosmarinus officinalis L.), and Miswak (Salvadora persica L.) were evaluated for their acaricidal and repellent effects on Ixodes ricinus L. nymphs (Acari: Ixodidae) using a bioassay based on an ‘open filter paper method’. Rosmarinus officinalis leaf essential oil diluted to 0.5 and 1 µl/cm² in acetone exhibited, respectively, 20 and 100% tick mortality after about 5 h of exposure. A total of 50 and 95% of I. ricinus nymphs were killed by direct contact with the oil when exposed to lethal concentrations (LC) of 0.7 µl/cm² (LC₅₀) and 0.95 µl/cm² (LC₉₅), respectively. The LC₅₀ (0.5 µl/cm²) was reached before the end of the first 24 h of exposure time (ET), as tick mortality at 24 h was 60%. Salvadora persica leaf essential oil at 1 µl/cm² showed a significant repellency effect against I. ricinus nymphs at 1.5 h ET. A 95% repellency was observed at a repellent concentration (RC₉₅) of 1 µl/cm² of S. persica, but no significant mortality was recorded at this dose of S. persica oil. Gas chromatography–mass spectrometry analyses showed that the main monoterpenes in both oils were 1,8-cineol, α-pinene, and β-pinene, although in markedly different proportions. These results suggest that essential oils have substantial potential as alternative approaches for I. ricinus tick control.