Toxicity of Smoke from Pelletized Leaf Powder and Essential Oil of Hyptis suaveolens (L.) Poit (Wild Spikenard) Against Anopheles gambiae (Giles, 1902) (Diptera; Culicidae)
NJE Vol. 34: 61-68, 2018
Ajelara, K. O., Denloye, A. A., Alafia, A. O., Awusinu, K., Bajulaiye, A. A. and Muse, W. A.
Abstract: Mosquitoes are the most important single group of insect vectors of the causative parasites of several diseases including malaria, dengue and filariasis for which cheap, safe, locally available and environmentally benign control measures are being sought. This study aimed at determining the toxicity of smoke from pelletized leaf powder and essential oil of Hyptis suaveolens (L) against third instar larvae and 0-2 day old adult Anopheles gambiae respectively in the laboratory. Test larvae were exposed to various concentrations ranging from 0ppm (control) through 50 to 500ppm of leaf essential oil at ambient laboratory temperature (25±10C) in standard bioassay for 96 hrs using Complete Randomized Block Design. Larval mortality was recorded at 24, 48, 72 and 96 hours of exposure. For exposure to pellets, 0-2 day old adult test insects were exposed to smoke from smoldering pellets having concentrations: 0% (Control), 20, 40, 60, 80 and 100% in glass fumigation chamber where the test smoke and insects were contained. Data from quantal responses were subjected to Probit analyses for determination of lethal concentration values. Results showed that essential oil and smoke from smoldering pellet were toxic to both larvae and adults at all concentrations respectively. The computed 24 hr-LC50 of test essential oil against larvae is 1448 ppm; 48 hr-LC50 551.47 ppm, 72 hrs LC50 is 187.43 ppm and 96 hours LC50 is 142.10 ppm, respectively. The insecticidal pellet LC50 at 30, 60, 90 and 120 minutes values were 107.79%, 69.56%, 31.27% and 22.15%, respectively. The results show that H. suaveolens could be exploited as a plant based insecticide for the control of Anopheles mosquitoes and suggests the need for further work including field studies.
Keywords: Anopheles gambiae, Hyptis suaveolens, Quantal response, Probit analysis, Biopesticide