Toxicity of <i>Sargassum wightii</i> to the Malaria Vector <i>Anopheles stephensi</i> Liston (Diptera: Culicidae)

Abstract

Seaweed based pesticides exhibit mosquitocidal properties and are found to be effective, biodegradable and non-toxic to non-target organisms. Sargassum wightii Greville butanol and ethanol extracts were tested for its toxicity against the second and third instar larvae of Anopheles stephensi Liston in the present study. One hundred percent larval mortality was observed in the second instar of An. stephensi by the ethanol extract at the highest concentration of 500 mg/ l after 24 hours of exposure. The LC50 values of S. wightii butanol and ethanol extracts were 107.03 and 89.67 mg/ l, against the second instar of An. stephensi; and 132.56 and 92.00 mg/ l against the third instar of An. stephensi respectively. Phytochemical analysis of S. wightii extracts revealed presence of alkaloids, carbohydrates, fatty acids, flavonoids, phenols, proteins, tannins and terpenes. Larval mortality of second and third instars of An. stephensi can be attributed to the major compounds present in S. wightii revealed by GC-MS analysis, viz., ethyl salicylate, methyl salicylate, ethyl palmitate, palmitic acid, oleic acid, phytolin and diethyl phthalate. The present study accentuates S. wightii butanol and ethanol extracts to cause lethal effects to the second and third instar larvae of An. stephensi.