Evaluation of pyriproxyfen against Aedes aegypti and Aedes albopictus from Penang, Malaysia

Aedes aegypti and Aedes albopictus mosquitoes are the primary vectors of tropical diseases, including dengue fever (DHF), chikungunya, and Zika, particularly in tropical regions such as Malaysia. Vector control efforts are now increasingly focused on biological and environmentally friendly approaches, one of which is using insect growth regulator (IGR)-based insecticides such as pyriproxyfen. Pyriproxyfen works by disrupting the metamorphosis process of mosquito larvae into adults without causing direct death, but it is effective in inhibiting the emergence of adult mosquitoes by more than 90%, depending on the dose and environmental conditions. This study evaluated the concentration-dependent effects of pyriproxyfen on laboratory and field populations of Aedes spp. Laboratory strains exhibited 100% adult mortality at 1.04 ppm (Ae. aegypti) and 1.08 ppm (Ae. albopictus), whereas field populations required 1.15 - 1.71 ppm depending on locality. LC₅₀ values were lowest in laboratory strains (0.267 ppm for Ae. aegypti and 0.236 ppm for Ae. albopictus), while field strains ranged from 0.326 to 0.571 ppm. LC₉₅ values followed a similar trend, with 1.026 ppm (Ae. aegypti) and 1.107 ppm (Ae. albopictus) in laboratory strains. Inhibition of emergence (IE%) was high in laboratory strains, reaching 97.89% at 0.50 ppm in Ae. aegypti and 63.54% at 0.50 ppm in Ae. albopictus. Field populations required higher concentrations for similar suppression, with IE% ranging from 17.68 - 98.23% in Ae. aegypti and 13.14- 98.24% in Ae. albopictus, peaking at 1.50 ppm. From this finding, it is suggested that pyriproxyfen effectively inhibits adult emergence in both laboratory and field populations, with laboratory strains more sensitive at lower concentrations and field strains responding at higher doses. These results provide strong evidence for pyriproxyfen as an effective, adaptive, and sustainable component of integrated vector management in Malaysia.