Pupicidal Activity of Ethanol and Water Extracts of <i>Phytolacca dodecandra </i> on <i> Anopheles gambiae</i> (Diptera Culicidae) Pupae

Abstract

Pupae are an integral part of Anopheles gambiae life history and a tool that effectively targets them is likely to impact on malaria vector density. In this study we evaluated pupicidal activities of crude ethanol and water extracts of Phytolacca dodecandra (L’ Herit) on An. gambiae (Diptera: Culicidae) under laboratory condition. Individual early pupae of An. gambiae mosquitoes were exposed to concentrations of 40, 20, 10, 5, 2.5 mgs/100 ml of mature green fruits and leaves of the shoot and midsection of P. dodecandra in containers measuring 6 cm top × 5.7 cm bottom × 3.5 cm height. P. dodecandra was sourced from Eldoret (highland) and Nyando (lowland). Extraction of P. dodecandra bioactives was done using 80% ethanol and distilled water. Extracts of Neem leaves and untreated rain water were used as positive and negative controls respectively. WHO, 2005 mortality threshold of >80% was used to determine the effectiveness of the extracts as pupicide 24 hours post exposure. Mortality of exposed pupae was dose dependent. Concentrations of 20 mgs/100 mls and higher and 40 mgs/ 100mls of mature green fruits from Nyando and Eldoret met the mortality threshold respectively. Extracts of P. dodecandra from Nyando was more potent than that from Eldoret as was water compared to ethanol extracts. Positive (Neem) control killed < 80% of exposed pupae. It was concluded that crude extracts of P. dodecandra are potent as pupicide against An. gambiae mosquitoes and is a likely alternative to synthetic insecticides against An. gambiae in future.