Medical and Veterinary Entomology (2014) 28, 253-256

W.P. Mayeku, N.I. Omollo, O.J. Odalo and A. Hassanali (2014)
Chemical composition and mosquito repellency of essential oil of Conyza newii propagated in different geographical locations of Kenya
Medical and Veterinary Entomology 28 (3), 253-256
Abstract: Previously, essential oil of Conyza newii (Asterale: Asteracea, Oliv. and Hiern) growing in the northern part of West Pokot (35°E, 1°N) of Kenya was shown to be highly repellent [RD₅₀ = 8.9 × 10^-5 mg/cm², 95% confidence interval (CL)] to Anopheles gambiae s.s. Fumigant toxicity of the oil to the mosquito was also demonstrated. The major constituents of the oil were found to be monoterpenoids, including (S)-(-)-perillyl alcohol, (S)-(-)-perillaldehyde, geraniol, (R)-(+)-limonene, trans-β-ocimene and 1,8-cineol. In this study, the chemical composition and repellency of essential oils of the plant seedlings collected from West Pokot (35°E, 1°N) and propagated in seven different geographical regions of Kenya [West Pokot (35°E, 1°N), Kilome (37°E, 1°S), Naivasha (36°E, 0°), Webuye (34°E, 1°N), Nyakach (34°E, 0°), Kericho (35°E, 0°) and Nairobi (36°E, 1°S)] were compared. There were significant variations (P < 0.01, 95% CL) in the relative proportions of the six constituents and this was reflected in the repellency of the essential oils (P < 0.01, 95% CL). Higher repellency of the oil was associated with greater proportions of (S)-(-) perillyl alcohol, (S)-(-)-perillaldehyde and geraniol, and lower repellency was associated with an increased proportion of (R)-(+)-limonene. The results suggest significant epigenetic (chemotypic) variations in the repellency and composition of C. newii essential oils growing in different regions of Kenya.
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Database assignments for author(s): Ahmed Hassanali

Research topic(s) for pests/diseases/weeds:
control - general

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Anopheles gambiae