Adulticidal and repellent activities of some botanical oils against malaria mosquito: Anopheles gambiae (Diptera: Culicidae)

The study is undertaken to determine the adulticidal efficacy and repellent activity of different solvent extracts of Ocimum caninum, Ocimum gratissimum, Chromolaena odorata and Datura stramonium against adult Anopheles gambiae. The extracts showed adulticidal activity at LC50 (0.82-4.58 mg/l) and LC90 (2.38-8.33 mg/l). The highest mortality was observed in Ocimum gratissimum and Datura stramonium with the LC50 and LC90 values of 2.35 mg/l, 4.75 ml/l and 0.82 mg/l, 2.38 mg/l respectively. Meanwhile, the lowest adulticidal activity was recorded in Chromolaena odorata with the lowest LC50 (4.52 mg/l) and LC90 (8.32 mg/l). The repellent efficacy was determined against the mosquitoes at five concentrations viz 1.0, 2.0, 3.0, 4.0 and 5.0 mg/l under laboratory condition (28 ± 2 °C, 75 ± 5% RH, 12L: 12D photoperiod). The results showed complete protections of 90 min for Ocimum caninum, 120 min for Ocimum gratissimum, 30 min for Chromolaena odorata and 120 min for Datura stramonium at 5 mg/l of the extracts respectively. It was observed that D. stramonium and O. gratissimum provided highest protection (120 min) against Anopheles gambiae while the least protection (30 s) was observed in Chromolaena odorata at 5 mg/l. The results of the study showed that all the crude extracts with the exception of Chromolaena odorata were potential botanicals for confirming protection on the exposed parts of human body against Anopheles gambiae for at least 90 min and as such can be included in integrated vector management to reduce malaria infection in endemic areas.