Effect of treatment using Carica papaya seed extract with Ag–TiO₂ nanocomposite on the mortality of Aedes aegypti larvae

The incidence and mortality rate of dengue hemorrhagic fever (DHF) in Indonesia have continued to increase. However, the insecticidal control of the vector of DHF, Aedes aegypti (yellow fever mosquito), has resulted the development of insecticide resistance. The aim of this study was to evaluate the effects, singly and in combination, of two components with proven larvicidal activity, namely, the Ag–TiO₂ nanocomposite and Carica papaya seed extract, on the mortality of A. aegypti larvae. This experimental study was categorized into the control and three intervention groups: 1) papaya seed extract at concentrations of 0, 2, 4, 6, 8, and 10 ppm; 2) Ag–TiO₂ at concentrations of 0, 5,10,15, 20, and 25 ppm; and 3) mixture of Ag–TiO₂ and C. papaya seed extract 50% and 90% lethal concentration. After 24 h exposure, the 50% lethal concentration and the 90% lethal concentration were determined for the Ag–TiO₂ nanocomposite (5.19 ppm and 10.87 ppm, respectively) and the C. papaya seed extract (25.98 ppm and 44.30 ppm, respectively). Significant differences were detected among Ag–TiO₂ concentrations and mixture-group concentrations (p < 0.05). Significant positive correlations were detected between larval mortality and Ag–TiO₂ concentrations and mixture group concentrations (r = 0.812, p = 0.001 and r = 0.343, p < 0.001, respectively). Changes in the visual appearance of dead larvae following treatment with nanocomposites and/or seed extract included damage to the abdominal segments, increased transparency of the abdomen, and reduced brush numbers. Therefore, the addition of the nanocomposite Ag–TiO₂ to C. papaya seed extract increased the larvicidal effectiveness of the seed extract against A. aegypti larvae.