Aedes aegypti is a primary vector of dengue and
chikungunya. The use of synthetic insecticides to control
Aedes populations often leads to high operational costs and
adverse non-target effects. Botanical extracts have been proposed
for rapid extracellular synthesis of mosquitocidal nanoparticles,
but their impact against predators of mosquito larvae
has not been well studied. We propose a single-step method
for the biosynthesis of silver nanoparticles (AgNP) using the
extract of Artemisia vulgaris leaves as a reducing and stabilizing
agent. AgNP were characterized by UV–vis spectroscopy,
Fourier transform infrared spectroscopy (FTIR), scanning
electron microscopy (SEM), energy-dispersive X-ray
spectroscopy (EDX), and X-ray diffraction (XRD). SEM
and XRD showed that AgNP were polydispersed, crystalline,
irregularly shaped, with a mean size of 30–70 nm. EDX confirmed
the presence of elemental silver. FTIR highlighted that
the functional groups from plant metabolites capped AgNP,
stabilizing them over time.We investigated the mosquitocidal
properties of A. vulgaris leaf extract and green-synthesized
AgNP against larvae and pupae of Ae. aegypti. We also evaluated
the predatory efficiency of Asian bullfrog tadpoles,
Hoplobatrachus tigerinus, against larvae of Ae. aegypti, under
laboratory conditions and in an aquatic environment treated
with ultra-low doses of AgNP. AgNP were highly toxic to Ae.
aegypti larval instars (I–IV) and pupae, with LC50 ranging
from 4.4 (I) to 13.1 ppm (pupae). In the lab, the mean number
of prey consumed per tadpole per day was 29.0 (I), 26.0 (II),
21.4 (III), and 16.7 (IV). After treatment with AgNP, the mean
number of mosquito prey per tadpole per day increased to 34.2
(I), 32.4 (II), 27.4 (III), and 22.6 (IV). Overall, this study
highlights the importance of a synergistic approach based on
biocontrol agents and botanical nano-insecticides for mosquito
control. |
