Larvicidal efficacy of the crude leaf extracts of eucalyptus Camaldulensis Dehn (Myrtales: Myrtaceae) against the mosquito larvae of Culex Quinquefasciatus say (Diptera: Culicidae)

Abstract

Eucalyptus camaldulensis was assayed to evaluate the larvicidal efficacy of its
leaf extracts against the 3rd instar larvae of Culex quinquefasciatus at five dose
concentrations (viz. 0.25, 0.50, 0.75, 1.0, 1.25, 1.5, 2.0, 2.5 and 3.0) in five solvents
(viz. chloroform, ethanol, di-chloromethane, acetone and water) based extracts
after 24 hrs exposure. Among all the extracts the shade dried chloroform based
leaf extracts showed the highest larvicidal efficacy (viz. 42.67, 56.67, 68.0, 92.67
and 100%) at low dose concentrations of 0.25, 0.50, 0.75, 1.0 and 1.25,
respectively while the sun dried water based leaf extracts showed the lowest
larvicidal efficacy (viz. 21.33, 30.67, 48.67, 58.0 and 74.0%) at high dose
concentrations of 1.0, 1.5, 2.0, 2.5 and 3.0, respectively among the ten different
experimental conditions. The relative potency of ten types of crude leaf extracts
of E. camaldulensis against the mosquito larvae are shown as follows in
decreasing order on the basis of LC50 value : Shade dried chloroform based leaf
extract (0.356 mg/ml) > sun dried chloroform based leaf extract (0.400 mg/ml) >
shade dried di-chloromethane based leaf extract (0.411 mg/ml) > sun dried dichloromethane
based leaf extract (0.579 mg/ml) > shade dried ethanol based leaf
extract (0.736 mg/ml) > sun dried ethanol based leaf extract (0.817 mg/ml) > shade
dried acetone based leaf extract (1.000 mg/ml) > sun dried acetone based leaf
extract (1.251 mg/ml) > shade dried water based leaf extract (1.807 mg/ml) > Sun
dried water based leaf extract (2.020 mg/ml).The effectiveness of the shade dried
leaf extracts was shown higher than the sun dried leaf extracts under comparable
condition. No mortality was observed in control treatment. The study revealed
that these leaf extracts have the potency to consider as an effective larvicidal
agent. It is an alternative source for developing a novel larvicide for controlling
the mosquito species.