Abstract:
Climate changes including global warming make the world a safer breeding place
for mosquitoes. Application of larvicide is a successful precaution method to reduce
mosquitoes before emerging into adults. Identifying phytochemical properties is a
cheap and environmentally safe technique. In this view, the study attempts to find
out the toxic effect of aqueous leaf extract of E. agallocha on brackish fish (E.
suratensis) and mosquito larvae (Aedes aegypti) under laboratory conditions.
Mosquito larvae and brackish fish from the lagoon were reared separately at 25-
27°C and 75-85% relative humidity. Five replicates with ten mosquito larvae and
five replicates with six brackish fish in each were maintained. Aqueous leaf extract
of E. agallocha at four concentrations 0.0625 g/ml, 0.125 g/ml, 0.25 g/ml, and 0.5
g/ml with lagoon water (control) were tested against fourth instar larvae and
brackish fish separately. After 24 hrs of treatments, the number of dead larvae and
fish were counted. All concentrations of the leaf extracts applied were able to cause
significant (p<0.0001) mortality on the larva of mosquito and brackish fish. The
highest larval mortality (80%) and brackish fish mortality (100%) were recorded
from 0.5 g/ml while the least (48%) for larvae and (16.67%) for fish mortality were
obtained by 0.0625 g/ml. Concentrations less than 0.0625 g/ml of leaf extracts were
suitable for selective fish harvest by making them daze and mortality increases with
the increase of concentration of leaf extract. Excoecaria agallocha leaf extract
founds to be an effective replacement for synthetic larvicides while it is toxic for
brackish fish
