Emergence inhibition and stage-specific mortality of chitin-synthesis inhibitors (novaluron, triflumuron, and lufenuron) against Aedes aegypti, a dengue vector

Abstract

Chitin-synthesis inhibitor (CSI) insect growth regulators (IGRs) are increasingly used in mosquito control due to their ability to disrupt insect development rather than induce rapid mortality. This study assessed the larvicidal activity, emergence inhibition, and the relative efficacy and stage-specific activity of three CSI compounds (novaluron, triflumuron, and lufenuron) against Aedes aegypti under laboratory conditions. Third-instar larvae were exposed to concentrations ranging from 0.05 to 6.25 µg/L, and larval mortality was recorded at 24, 48, and 72 hours, while adult emergence inhibition was used to estimate EI₅₀ and EI₉₀ values.
No larval mortality was observed at 24 hours across all treatments, and mortality remained low at 72 hours, reaching a maximum of 11.67 ± 3.51% for novaluron, 8.33 ± 1.53% for lufenuron, and 6.33 ± 2.08% for triflumuron at the highest concentration. In contrast, all compounds demonstrated strong, concentration-dependent emergence inhibition, achieving 100% inhibition at 6.25 µg/L. Lufenuron exhibited the highest potency with the lowest EI₅₀ (0.122 µg/L) and EI₉₀ (1.638 µg/L), followed by novaluron (EI₅₀ = 0.156 µg/L; EI₉₀ = 1.903 µg/L) and triflumuron (EI₅₀ = 0.228 µg/L; EI₉₀ = 2.040 µg/L). Stage-specific mortality analysis further demonstrated compound-specific differences in the timing and developmental stage at which mortality occurred. Lufenuron predominantly affected earlier larval stages, whereas novaluron showed greater effects during the pupal stage, and triflumuron exhibited a more distributed pattern across larval and pupal stages. These findings highlight that reliance on short-term larval mortality alone may underestimate the efficacy of chitin-synthesis inhibitor IGRs. In contrast, emergence inhibition and stage-specific mortality provide a more biologically relevant and informative assessment of their activity. Among the tested compounds, lufenuron exhibited the highest potency, supporting its potential application in mosquito control programs.