Mosquito larvicidal assay
The results of present study revealed that the synthesized silver nanoparticles using aqueous extract of D. denudatum exhibited potent anti-mosquito activity by killing all the exposed second instar larvae of A. aegypti within 48 h exposure period (Fig. 5). However lower concentrations of silver nanoparticle was not much effective as it knock down only 50% of larval population. Susceptibility of A. aegypti larvae to silver nanoparticle increases when exposure time extended to 48 h. The LC50 values of DdAgNPs are 96 ppm (24 h) and 9.6 ppm (48 h) against second instar larvae of A. aegypti. Recent years green synthesized silver nanoparticles gained much attention due to its high larvicidal potency and less toxic to the environment. Rajkumar and Rahuman, [25] reported that synthesized silver nanoparticle using Eclipta prostrata extract showed 100% larval mortality with LC50 values of 4.56 and 5.14 ppm for Culex quinquefasciatus and Anopheles subpictus, respectively. Patil et al. [26] reported that, the LC50 values for second and fourth larval instars of A. aegypti after 24 h exposure of synthesized Ag NPs using Plumeria rubra latex were 1.49, 1.82 ppm, respectively. The potent larvicidal activity noticed in DdAgNPs against dengue vector A. aegypti suggested that it could be used as a possible bio-insecticide in mosquito control programs.