Bioefficacy of Catharanthus roseus (L.) G. Don (Apocyanaceae) and Hyptis suaveolens (L.) Poit (Lamiaceae) ethanolic aerial extracts on the larval instars of the dengue and chikungunya vector Aedes aegypti Linnaeus 1762 (Diptera: Culicidae)

Abstract

Extensive use of synthetic and chemical insecticides has resulted in environmental hazards and also in development of physiological resistance among vector mosquito species. Plant products are considered to be a potential alternative approach as they are environmentally safe, target specific and biodegradable. In the present study, the bioefficacy of ethanolic extract of Catharanthus roseus and Hyptis suaveolens aerial parts were tested on the first, second, third and fourth instar larvae of Aedes aegypti at concentrations of 100, 200, 300, 400 and 500mg/L. Larval mortality was observed after 24 hours and the corresponding LC50 values were 68.36, 99.93, 101.24 and 114.93mg/L and mortality recorded in terms of percentage were 96.86, 93.52, 95.19% and 98.53 at 500mg/L and for Hyptis suaveolens, it was 22.91, 28.30, 35.64 and 36.82mg/L and 96.86, 95.19, 98.53 and 98.53% at 500mg/L respectively. Further investigations are needed to elucidate the larvicidal activity against a wide range of mosquito species and also the active ingredient(s) of the extract responsible for larvicidal activity should be identified.