Methoxyfenozide as a potent insect growth regulator: Disruption of growth, development and chitin synthesis in <i>Aedes aegypti</i> for sustainable vector control

Aedes aegypti is a major vector of arboviral diseases such as dengue, chikungunya, Zika, and yellow fever. Traditional chemical insecticides have led to widespread insecticide resistance and posed risks to non-target organisms and the environment. Insect growth regulators (IGRs) offer a promising alternative by disrupting mosquito development rather than inducing immediate lethality. The present study evaluated the efficacy of methoxyfenozide, a non-steroidal ecdysteroid agonist, in disrupting the development and chitin synthesis of Ae. aegypti larvae to explore its potential as a mosquito control agent. Larvicidal activity, inhibition of adult emergence, and effects on chitin synthesis were assessed using standard bioassays and biochemical quantification techniques. Lethal concentrations and emergence inhibition dosages were determined using probit analysis. Methoxyfenozide exhibited dose-dependent larvicidal activity, with respective LC50 and LC90 values of 6.326 mg/L and 115.615 mg/L after 24 hours, and 4.180 mg/L and 119.100 mg/L after 48 hours, indicating a delayed action. The compound significantly inhibited adult emergence (p < 0.05), exhibiting an IE90 value of 1.209 mg/L. Morphological abnormalities, such as arrested moulting and structural deformities, were also observed. Biochemical analysis revealed a substantial reduction in chitin content in methoxyfenozide-treated larvae, with a greater decrease observed after longer treatment durations and at higher dosages. The study revealed that methoxyfenozide effectively disrupted Ae. aegypti development, inhibited both larval survival and adult emergence, as well as impeded chitin content deposition. The effective mode of action and minimal toxicity to non-target species highlight its potential for inclusion in integrated vector management strategies.