Repellence and Larvicidal Efficacy of Some Selected Plant Oils and Extracts Against Adult Anopheles Arabiensis (Patton) and Larvae of Aedes Aegypti (Linnaeous) (Culicidae: Diptera) Under Laboratory Conditions

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Addis Ababa University


Insecticides and repellent chemicals are among the major tools of controlling disease vectors. In this study, the knock-down, adultcidal and repellence activities of crude ethyl alcohol extracts of the leaves of spearmint (Mentha spicata) and rosemary (Rosemarinus officinalis) were tested against the larval and adult stages of malaria vector Anopheles arabiensis. The larvacidal effect of seed powder of neem (Azadrichiata indica) was evaluated under laboratory condition against the fourth instar larvae of Aedes aegypti. Extracts of M. spicata and R. officinalis caused moderate knock-down and mortality activity after 1 h and 24 h of exposure, respectively, but higher repellency effects at 1 h. M. spicata caused average percent knock-down, mortality and repellency effects ranging from 8 to 32%, 0 to 28% and 95 to 97%, respectively at six different concentrations used. Whilst R. officinalis induced between 0 and 36%, 0 and 32% and 63 and 74% mean percent knock-down, mortality and repellency effects, in that order. Adult mosquito mortality increased with increasing concentration of the extracts but there was no significant variation among all concentrations of extracts of both plants used (P>0.05), except 0.1 and 1 percent concentrations which were significant (P<0.05). M. spicata showed much superior average percent repellency. No significant variation was shown on repellency effect among the different concentrations (P>0.05). A significantly higher repellency effect was observed in the different concentrations of extracts of R. officinalis (P<0.05) as compared to the control. The mean percent larval mortality against A. agypti caused by seed powder of A. indica at concentration of 5g/250ml was 58% at 24 h and 81% at 48 h. There was no significant difference in larval mortality between 24 and 48 h of exposure (P>0.05). In conclusion, M. spicata and R. officinalis can’t be considered as sources of potential adulticides based on WHO standards as their extracts failed to produce >60% mortality but can be regarded as potential sources of viii repellents against An. arabiensis. Besides, A. indica could be a potential source of larvicides against the larvae of Ae. aegypti. Keywords: Adulticides, Anopheles arabiesnis, Aedes agepti, Larvicides, Plant extracts



Adulticides, Anopheles Arabiesnis, Aedes Agepti, Larvicides, Plant Extracts