Repellence and larvicidal effects of some selected plant extracts against adult Anopheles arabiensis and Aedes aegypti larvae under laboratory conditions

Abstract

Insecticides and repellent chemicals are used to control the exposure to disease vectors. In this study, the repellence activity of ethanol extracts of the leaves of spearmint (Mentha spicata) and rosemary (Rosemarinus officinalis) was evaluated against the adult stages of female Anopheles arabiensis. In addition, the larvacidal effect of seed powder of neem (Azadrichiata indica) was evaluated against the 4th instar larvae of Aedes aegypti under laboratory condition. M. spicata caused average percent repellence effects ranging from 95 to 97% at six different concentrations whilst, R. officinalis induced between 63 and 74%. One-way analysis of variance (ANOVA) revealed that there was no significant difference in the repellence effect among the different concentrations of M. spicata extracts used against An. arabiensis (F = 0.848; P = 0.542). In contrast, statistically significant variation in the repellence effects were observed among the different concentrations of ethanolic extracts of R. officinalis against An. arabiensis females (F = 3.609; P = 0.032). The mean percent larval mortality against Ae. aegypti caused by the seed powder of A. indica at a concentration of 5 g/250 mL 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 (t = 2.328; P = 0.145). In conclusion, ethanolic extracts of M. spicata and R. officinalis could be used as potential sources of repellents against An. arabiensis. Besides, A. indica seed powder could be a potential source of larvicides against the larvae of Ae. Aegypti.