Comparative evaluation of the effect of phytochemicals of garlic (<em>Allium sativum</em>) ethanolic extract against <em>Aedes albopictus</em> and <em>Culex quinquefasciatus</em> mosquitoes in Sri Lanka

Abstract

Botanical extracts offer sustainable and eco-friendly alternatives to synthetic insecticides for managing insect pests, including mosquitoes. This research focuses on the potential of ethanolic garlic extract as a larvicide against Aedes albopictus and Culex quinquefasciatus mosquito species in Sri Lanka. Third to early fourth instar larvae were exposed to six concentrations of ethanolic garlic extract (ranging from 5 to 250 ppm) for 72 hours to assess efficacy. The experiment, repeated four times with controls, monitored daily mortalities. Lethal concentrations required to eliminate 50% (LC50) and 90% (LC90) of larvae at 24, 48, and 72 hours were determined through regression analysis. A phytochemical analysis was conducted to assess the compounds present in the garlic extract. Positive correlations were observed between garlic concentration and mortality percentages during each exposure period for both Ae. albopictus and Cu. quinquefasciatus larvae. LC50 values for Ae. albopictus larvae were 45.5 ppm, 28.0 ppm, and 14.4 ppm at 24, 48, and 72 hours respectively, with corresponding LC90 values of 140.0 ppm, 91.0 ppm, and 42.9 ppm. For Cu. quinquefasciatus larvae, LC50 values were 26.3 ppm, 9.4 ppm, and 4.4 ppm, while LC90 values were 169.8 ppm, 30.7 ppm, and 17.6 ppm for the same exposure periods. The garlic ethanolic extract retained its flavonoids, saponins, and reducing sugars even after a year of extraction, as revealed by phytochemical analysis. The study underscores the potent toxicity of garlic extract against mosquito larvae, with LC50 values below 50 ppm. These findings highlight the potential of garlic extracts as effective larvicides for combating mosquito vectors, contributing to environmentally friendly pest management strategies.