Bioefficacy of Leaf Extracts of two underutilized ferns, Azolla pinnata and Polystichum acrostichoides against Malaria Vector, Anopheles gambiae Giles [Diptera: Culicidae

Abstract

The bioefficacy of Azolla pinnata and Polystichum acrostichoides leaf extracts were evaluated in the laboratory against the immature stages (larvae and pupae) and adults of Anopheles gambiae at a relative humidity of 75±5% and an ambient temperature of 28 ±2°C. The efficacy of the extracts was evaluated in a standard bioassay at different concentration of 15mg/L, 30mg/L, 60mg/L, 120mg/L and 240mg/L using standard methods were tested. The effects of various concentrations of the plant extracts (A. pinnata and P. acrostichoides) used in this study were significantly different (p<0.05) in efficacy on An. gambiae larvae. The mortality rate of An. gambiae caused by the tested plants’ extracts were concentration-dependent. The larvicidal efficacies of A. pinnata and P. acrostichoides at concentrations of 15mg/L, 30mg/L, 60mg/L, 120mg/L and 240mg/L were 40%, 55%, 70%, 95% and 100%, and 27.25%, 42.5%, 57.25%, 85% and 100% after 24 hours exposure, respectively. Pupa mortality of An. gambiae exhibited by the highest concentration of A. pinnata and P. acrostichoides were 100% and 90% respectively after 24 hours exposure. The mortality of the adults caused by the highest used concentration was 70% and 57.5% for A. pinnata and P. acrostichoides respectively after 24 hours exposure. The Probit model analysis revealed that A. pinnata extract was the most effective due to its low lethal concentrations to cause 50% (LC50) and 90% (LC90) mortality of malaria vector (An. gambiae) larvae, pupa and adult. Results from this current study indicate the potentials of A. pinnata leaf extract as a mosquito insecticidal agent.